Merge branch 'wader_master' into postgres

2024-11-23 09:56:07 +03:00 · 2022-10-05 19:39:35 +03:00 · 2022-10-05 19:39:35 +03:00 · 6588e1dd88
commit 6588e1dd88
parent e57c3b980b 8997faa2d7
66 changed files with 4365 additions and 1208 deletions
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@ -7,7 +7,7 @@ on:
  pull_request:

 env:
-  GOLANGCILINT_VERSION: 1.49.0
+  GOLANGCILINT_VERSION: 1.50.0

 jobs:
  lint:
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@ -154,14 +154,18 @@
        "tfhd",
        "tfra",
        "tmpl",
+        "toactual",
        "toarray",
        "toboolean",
        "tobytes",
        "tobytesrange",
+        "todescription",
        "toimage",
        "tojson",
        "tojvalue",
+        "topath",
        "torepr",
+        "tosym",
        "tovalue",
        "toxml",
        "toxmlentities",
--- a/CHANGES.md
+++ b/CHANGES.md
@ -1,3 +1,178 @@
+# 0.0.10
+
+## Changes
+
+- Add `bplist` Apple Binary Property List decoder. Thanks David McDonald @dgmcdona #427
+- Add `markdown` decoder. #422
+- Fix panic when interrupting (ctrl-c) JSON output (`fq tovalue file ` etc), #440
+- Fix issue using `debug` (and some other native go iterator functions) inside `path(...)`, which is used by assign (`... = ...`) expressions etc. #439
+- Fix issue and also make `toactual` and `tosym` work more similar to `tovalue`. #432
+- Fix issue with unknown fields (gaps found after decoding) where one continuous gap could end up split into two of more unknown fields. #431
+- More format documentation and also nicer help output. Also now all documentation is in markdown format. #430 #422
+  ```
+  # or help(matroska) in the REPL
+  $ fq -h matroska
+  matroska: Matroska file decoder
+
+  Decode examples
+  ===============
+
+    # Decode file as matroska
+    $ fq -d matroska . file
+    # Decode value as matroska
+    ... | matroska
+
+  Lookup element using path
+  =========================
+
+    $ fq 'matroska_path(".Segment.Tracks[0)")' file.mkv
+
+  Get path to element
+  ===================
+
+    $ fq 'grep_by(.id == "Tracks") | matroska_path' file.mkv
+
+  References
+  ==========
+  - https://tools.ietf.org/html/draft-ietf-cellar-ebml-00
+  - https://matroska.org/technical/specs/index.html
+  - https://www.matroska.org/technical/basics.html
+  - https://www.matroska.org/technical/codec_specs.html
+  - https://wiki.xiph.org/MatroskaOpus
+  ```
+
+## Decoder changes
+
+- `ar` Allow empty integer strings. For example owner id can be an empty string. #428
+- `bitcoin_blkdat` Assert that there is a header. As the format is part of the probe group this speeds up probing. #402
+- `bplist` Add Apple Binary Property List decoder.
+  ```sh
+  $ fq '.objects.entries[0] | .key, .value' Info.plist
+      │00 01 02 03 04 05 06 07 08 09│0123456789│.objects.entries[0].key{}:
+  0x32│               5c            │     \    │  type: "ascii_string" (5) (ASCII encoded string)
+  0x32│               5c            │     \    │  size_bits: 12
+      │                             │          │  size: 12
+  0x32│                  43 46 42 75│      CFBu│  value: "CFBundleName"
+  0x3c│6e 64 6c 65 4e 61 6d 65      │ndleName  │
+      │00 01 02 03 04 05 06 07 08 09│0123456789│.objects.entries[0].value{}:
+  0x1ea│         5f                  │   _      │  type: "ascii_string" (5) (ASCII encoded string)
+  0x1ea│         5f                  │   _      │  size_bits: 15
+  0x1ea│            10               │    .     │  large_size_marker: 1 (valid)
+  0x1ea│            10               │    .     │  exponent: 0
+  0x1ea│               18            │     .    │  size_bigint: 24
+      │                             │          │  size: 24
+  0x1ea│                  41 70 70 6c│      Appl│  value: "AppleProResCodecEmbedded"
+  0x1f4│65 50 72 6f 52 65 73 43 6f 64│eProResCod│
+  0x1fe│65 63 45 6d 62 65 64 64 65 64│ecEmbedded│
+  ```
+  - Supports `torepr`
+  ```sh
+  $ fq torepr.CFBundleName Info.plist
+  "AppleProResCodecEmbedded"
+  ```
+- `elf`
+  - More robust decoding when string tables are missing. #417<br>
+    ```sh
+    # extract entry opcodes and disassemble with ndisasm
+    $ fq -n '"f0VMRgIBAQAAAAAAAAAAAAIAPgABAAAAeABAAAAAAABAAAAAAAAAAAAAAAAAAAAAAAAAAEAAOAABAAAAAAAAAAEAAAAFAAAAAAAAAAAAAAAAAEAAAAAAAAAAQAAAAAAAAAAAAAEAAAAAAAAAAQAAAAAAIAAAAAAAsDxmvwYADwU=" | frombase64 | . as $b | elf | $b[.header.entry-.program_headers[0].vaddr:]' \
+    | ndisasm -b 64 -
+    00000000  B03C              mov al,0x3c
+    00000002  66BF0600          mov di,0x6
+    00000006  0F05              syscall
+    ```
+  - Now decodes program header notes. #421
+- `markdown` Add decoder. Is used in fq to render CLI help. #422
+  ```sh
+  # array with all level 1 and 2 headers
+  $ fq -d markdown '[.. | select(.type=="heading" and .level<=2)?.children[0]]' README.md
+  [
+    "fq",
+    "Usage",
+    "Presentations",
+    "Install",
+    "TODO and ideas",
+    "Development and adding a new decoder",
+    "Thanks and related projects",
+    "License"
+  ]
+  ```
+- `matroska` Add support for sample lacing. Used by FLAC samples etc. #404
+- `mp4` More codec names and also use official names from mp4ra.org. #424<br>
+  ```sh
+  # show details of first two track in file
+  $ fq -o line_bytes=10 '.tracks[0,1]' big_buck_bunny.mp4
+          │00 01 02 03 04 05 06 07 08 09│0123456789│.tracks[0]{}: track
+  0x00910a│20 68 10 01 a0 40 0e 20 8c 1b│ h...@. ..│  samples[0:1295]:
+  0x009114│c2 2b 99 09 84 42 60 a8 c4 60│.+...B`..`│
+  *       │until 0x541697.7 (5473678)   │          │
+          │                             │          │  id: 1
+          │                             │          │  data_format: "mp4a" (MPEG-4 Audio)
+          │00 01 02 03 04 05 06 07 08 09│0123456789│.tracks[1]{}: track
+  0x00a5e6│                           00│         .│  samples[0:1440]:
+  0x00a5f0│00 00 0c 06 00 07 8b 71 b0 00│.......q..│
+  0x00a5fa│00 03 00 40 80 00 00 00 15 06│...@......│
+  *       │until 0x540959.7 (5464939)   │          │
+          │                             │          │  id: 2
+          │                             │          │  data_format: "avc1" (Advanced Video Coding)
+
+  ```
+- `html` Handle leading doc type and processing directives. #414
+
+## Changelog
+
+* a77cec92 Added documentation and tests, fixed bad date parsing
+* d784db69 Adds support for Apple Binary Plist, version 00
+* 5711f290 Code fixes from PR, still need to add tests and testdata
+* 6b04f2de Documentation cleanup
+* bcccde23 Fixes and embeds documentation
+* ebae938d Fixes bug in integer parsing
+* 368d183b Size check on nBits to save memory
+* 84ca1010 Update docker-golang from 1.19.0 to 1.19.1
+* c47c3866 Update github-go-version from 1.19.0, 1.19.0, 1.19.0 to 1.19.1
+* 816169b6 Update github-golangci-lint to 1.50.0 from 1.49.0
+* 21f2980e Update make-golangci-lint to 1.50.0 from 1.49.0
+* 5f619940 adds function for decoding fixed sized arrays
+* f08f44f1 ar: Integer strings might be empty
+* 004406de bitcoin_blkdat,bitcoin_block: Make sure there is a header if blkdat
+* 421b2b30 bplist: Fix unknown field for singletons and add torepr tests
+* 16b01211 bplist: Make torepr convert to values
+* fe64530e csv: Add tsv and header example
+* cb3dc802 decode,tar: Add scalar description and Try* helpers
+* a6429ffe decode: Remove RangeSorted flag as we can decide on array/struct instead
+* a468684a deps: Manual update ones not using bump
+* a7a101ca doc,help: Nicer format help and move help tests into each format
+* 725ab1b1 doc,html,xml: Add more documentation and examples
+* abd19ed8 doc: Fix format sections a bit
+* 0fdc03a4 doc: Fix some incorrect example prompts
+* 5382d46a elf: Basic program header notes decoding
+* 12105d8c elf: Treat missing string tables as empty to be more robust
+* 3deceeeb fixes from PR comments
+* 226a9a3e generics: Use more from x/exp
+* 404b1704 gojq: Update fq fork
+* 376f0ebb gojq: Update rebased fq fork
+* 87b2c6c1 help,doc: Use markdown for format documentation again
+* 8016352b html: Handle html with leading doctype etc
+* 768df301 interp,decode: For struct use map to lookup field
+* c4219d69 interp: Fix interrupt panic for cli eval
+* 00ee10a1 interp: Make to{actual,sym} behave similar to tovalue
+* 00a50662 markdown: Add decoder
+* 7749e1b5 matroska: Add proper lacing support
+* 20a15372 mp4: Fix data_format typo
+* 2655ba09 mp4: More codec names (from mp4ra.org)
+* 7cd43b49 perfomance: increase performance by map usage
+* 6a6fec54 range,decode: Use own range sort impl to speed up a bit
+* 0f35fe48 ranges,decode: Correctly skip empty ranges when adding unknown fields
+* ea81efec readline: Update rebased fq fork
+* 369f4016 removed unneccessary type conversions
+* 3198602d removed unused return type
+* 7d865343 sortex: Package with type safe sort helpers
+* 808202fa test: Skip go test with -race by default
+* 12836abe updates fqtest
+* 1e47f4f2 updates tests post integer-bug fix
+* 3d8ea1de updates torepr for data type
+* 1385b5d0 wasm: Add some documentation
+* d6316d5c wav: Decode smpl chunk
+
 # 0.0.9

 ## Changes
--- a/2
+++ b/2
@ -69,7 +69,7 @@ gogenerate:
 lint:
 # bump: make-golangci-lint /golangci-lint@v([\d.]+)/ git:https://github.com/golangci/golangci-lint.git|^1
 # bump: make-golangci-lint link "Release notes" https://github.com/golangci/golangci-lint/releases/tag/v$LATEST
-	go run github.com/golangci/golangci-lint/cmd/golangci-lint@v1.49.0 run
+	go run github.com/golangci/golangci-lint/cmd/golangci-lint@v1.50.0 run

 .PHONY: depgraph.svg
 depgraph.svg:
--- a/README.md
+++ b/README.md
@ -51,6 +51,7 @@ bitcoin_blkdat,
 [bitcoin_block](doc/formats.md#bitcoin_block),
 bitcoin_script,
 bitcoin_transaction,
+[bplist](doc/formats.md#bplist),
 bsd_loopback_frame,
 [bson](doc/formats.md#bson),
 bzip2,
--- a/doc/formats.md
+++ b/doc/formats.md
@ -27,6 +27,7 @@
 |[`bitcoin_block`](#bitcoin_block) |Bitcoin&nbsp;block                                                                       |<sub>`bitcoin_transaction`</sub>|
 |`bitcoin_script`                  |Bitcoin&nbsp;script                                                                      |<sub></sub>|
 |`bitcoin_transaction`             |Bitcoin&nbsp;transaction                                                                 |<sub>`bitcoin_script`</sub>|
+|[`bplist`](#bplist)               |Apple&nbsp;Binary&nbsp;Property&nbsp;List                                                |<sub></sub>|
 |`bsd_loopback_frame`              |BSD&nbsp;loopback&nbsp;frame                                                             |<sub>`inet_packet`</sub>|
 |[`bson`](#bson)                   |Binary&nbsp;JSON                                                                         |<sub></sub>|
 |`bzip2`                           |bzip2&nbsp;compression                                                                   |<sub>`probe`</sub>|
@ -119,7 +120,7 @@
 |`inet_packet`                     |Group                                                                                    |<sub>`ipv4_packet` `ipv6_packet`</sub>|
 |`ip_packet`                       |Group                                                                                    |<sub>`icmp` `icmpv6` `tcp_segment` `udp_datagram`</sub>|
 |`link_frame`                      |Group                                                                                    |<sub>`bsd_loopback_frame` `ether8023_frame` `sll2_packet` `sll_packet`</sub>|
-|`probe`                           |Group                                                                                    |<sub>`adts` `ar` `avro_ocf` `bitcoin_blkdat` `bzip2` `elf` `flac` `gif` `gzip` `jpeg` `json` `jsonl` `macho` `macho_fat` `matroska` `mp3` `mp4` `mpeg_ts` `ogg` `pcap` `pcapng` `png` `tar` `tiff` `toml` `wasm` `wav` `webp` `xml` `yaml` `zip`</sub>|
+|`probe`                           |Group                                                                                    |<sub>`adts` `ar` `avro_ocf` `bitcoin_blkdat` `bplist` `bzip2` `elf` `flac` `gif` `gzip` `jpeg` `json` `jsonl` `macho` `macho_fat` `matroska` `mp3` `mp4` `mpeg_ts` `ogg` `pcap` `pcapng` `png` `tar` `tiff` `toml` `wasm` `wav` `webp` `xml` `yaml` `zip`</sub>|
 |`tcp_stream`                      |Group                                                                                    |<sub>`dns_tcp` `rtmp`</sub>|
 |`udp_payload`                     |Group                                                                                    |<sub>`dns`</sub>|

@ -260,6 +261,46 @@ Decode value as bitcoin_block
 ... | bitcoin_block({has_header:false})
 ```

+## bplist
+
+### Show full decoding
+```sh
+$ fq -d bplist dv Info.plist
+```
+
+### Timestamps
+Timestamps in Apple Binary Property Lists are encoded as Cocoa Core Data
+timestamps, where the raw value is the floating point number of seconds since
+January 1, 2001. By default, `fq` will render the raw floating point value. In
+order to get the raw value or string description, use the `todescription`
+function, you can use the `tovalue` and `todescription` functions:
+
+```sh
+$ fq 'torepr.SomeTimeStamp | tovalue' Info.plist
+685135328
+
+$ fq 'torepr.SomeTimeStamp | todescription' Info.plist
+"2022-09-17T19:22:08Z"
+```
+
+
+### Get JSON representation
+```sh
+$ fq torepr com.apple.UIAutomation.plist
+{
+  "UIAutomationEnabled": true
+}
+```
+
+### Authors
+- David McDonald
+[@dgmcdona](https://github.com/dgmcdona)
+
+### References
+- http://fileformats.archiveteam.org/wiki/Property_List/Binary
+- https://medium.com/@karaiskc/understanding-apples-binary-property-list-format-281e6da00dbd
+- https://opensource.apple.com/source/CF/CF-550/CFBinaryPList.c
+
 ## bson

 ### Convert represented value to JSON
@ -832,7 +873,7 @@ Elements are arrays of the shape `["#text": "body text", "attr_name", {key: "att

 ```sh
 # decode as array
-✗ echo '<a><b/><b>bbb</b><c attr="value">ccc</c></a>' | fq -d xml -o array=true
+$ echo '<a><b/><b>bbb</b><c attr="value">ccc</c></a>' | fq -d xml -o array=true
 [
  "a",
  null,
--- a/doc/formats.svg
+++ b/doc/formats.svg
--- a/doc/usage.md
+++ b/doc/usage.md
@ -372,8 +372,8 @@ unary uses input and if more than one argument all as arguments ignoring the inp
  - `parents` output parents of value
  - `topath` path of value. Use `path_to_expr` to get a string representation.
  - `tovalue`, `tovalue($opts)` symbolic value if available otherwise actual value
-  - `toactual` actual value (decoded etc)
-  - `tosym` symbolic value (mapped etc)
+  - `toactual`, `toactual($opts)` actual value (usually the decoded value)
+  - `tosym`, `tosym($opts)` symbolic value (mapped etc)
  - `todescription` description of value
  - `torepr` convert decode value into what it reptresents. For example convert msgpack decode value
  into a value representing its JSON representation.
--- a/format/all/all.fqtest
+++ b/format/all/all.fqtest
@ -4,6 +4,7 @@ $ fq -n _registry.groups.probe
  "ar",
  "avro_ocf",
  "bitcoin_blkdat",
+  "bplist",
  "bzip2",
  "elf",
  "flac",
@ -56,6 +57,7 @@ bitcoin_blkdat       Bitcoin blk.dat
 bitcoin_block        Bitcoin block
 bitcoin_script       Bitcoin script
 bitcoin_transaction  Bitcoin transaction
+bplist               Apple Binary Property List
 bsd_loopback_frame   BSD loopback frame
 bson                 Binary JSON
 bzip2                bzip2 compression
--- a/format/all/all.go
+++ b/format/all/all.go
@ -11,6 +11,7 @@ import (
 	_ "github.com/wader/fq/format/avro"
 	_ "github.com/wader/fq/format/bencode"
 	_ "github.com/wader/fq/format/bitcoin"
+	_ "github.com/wader/fq/format/bplist"
 	_ "github.com/wader/fq/format/bson"
 	_ "github.com/wader/fq/format/bzip2"
 	_ "github.com/wader/fq/format/cbor"
--- a/format/bitcoin/bitcoin_block.go
+++ b/format/bitcoin/bitcoin_block.go
@ -4,6 +4,7 @@ package bitcoin

 import (
 	"fmt"
+	"time"

 	"github.com/wader/fq/format"
 	"github.com/wader/fq/pkg/decode"
@ -62,7 +63,7 @@ func decodeBitcoinBlock(d *decode.D, in interface{}) interface{} {
 			d.FieldU32("version", scalar.ActualHex)
 			d.FieldRawLen("previous_block_hash", 32*8, rawHexReverse)
 			d.FieldRawLen("merkle_root", 32*8, rawHexReverse)
-			d.FieldU32("time", scalar.DescriptionActualUUnixTime)
+			d.FieldU32("time", scalar.DescriptionUnixTimeFn(scalar.S.TryActualU, time.RFC3339))
 			d.FieldU32("bits", scalar.ActualHex)
 			d.FieldU32("nonce", scalar.ActualHex)
 		})
--- a/format/bplist/bplist.go
+++ b/format/bplist/bplist.go
@ -0,0 +1,236 @@
+package bplist
+
+import (
+	"embed"
+	"math"
+	"math/big"
+	"time"
+
+	"github.com/wader/fq/format"
+	"github.com/wader/fq/pkg/decode"
+	"github.com/wader/fq/pkg/interp"
+	"github.com/wader/fq/pkg/scalar"
+)
+
+//go:embed bplist.jq bplist.md
+var bplistFS embed.FS
+
+func init() {
+	interp.RegisterFormat(decode.Format{
+		Name:        format.BPLIST,
+		ProbeOrder:  format.ProbeOrderBinUnique,
+		Description: "Apple Binary Property List",
+		Groups:      []string{format.PROBE},
+		DecodeFn:    bplistDecode,
+		Functions:   []string{"torepr"},
+	})
+	interp.RegisterFS(bplistFS)
+}
+
+const (
+	elementTypeNullOrBoolOrFill = 0x00
+	elementTypeInt              = 0x01
+	elementTypeReal             = 0x02
+	elementTypeDate             = 0x03
+	elementTypeData             = 0x04
+	elementTypeASCIIString      = 0x05
+	elementTypeUnicodeString    = 0x06
+	elementTypeUID              = 0x08
+	elementTypeArray            = 0x0a
+	elementTypeSet              = 0x0c
+	elementTypeDict             = 0x0d
+)
+
+const (
+	null      = 0x00
+	boolFalse = 0x08
+	boolTrue  = 0x09
+)
+
+var elementTypeMap = scalar.UToScalar{
+	elementTypeNullOrBoolOrFill: {Sym: "singleton", Description: "Singleton value (null/bool)"},
+	elementTypeInt:              {Sym: "int", Description: "Integer"},
+	elementTypeReal:             {Sym: "real", Description: "Floating Point Number"},
+	elementTypeDate:             {Sym: "date", Description: "Date, 4 or 8 byte float"},
+	elementTypeData:             {Sym: "data", Description: "Binary data"},
+	elementTypeASCIIString:      {Sym: "ascii_string", Description: "ASCII encoded string"},
+	elementTypeUnicodeString:    {Sym: "unicode_string", Description: "Unicode string"},
+	elementTypeUID:              {Sym: "uid", Description: "UID"},
+	elementTypeArray:            {Sym: "array", Description: "Array"},
+	elementTypeSet:              {Sym: "set", Description: "Set"},
+	elementTypeDict:             {Sym: "dict", Description: "Dictionary"},
+}
+
+var cocoaTimeEpochDate = time.Date(2001, time.January, 1, 0, 0, 0, 0, time.UTC)
+
+// decodes the number of bits required to store the following object
+func decodeSize(d *decode.D, sms ...scalar.Mapper) uint64 {
+	n := d.FieldU4("size_bits")
+	if n != 0x0f {
+		return n
+	}
+
+	d.FieldU4("large_size_marker", d.AssertU(0b0001))
+
+	// get the exponent value
+	n = d.FieldU4("exponent")
+
+	// calculate the number of bytes encoding the size
+	n = 1 << n
+
+	// decode that many bytes as big endian
+	n = d.FieldUFn(
+		"size_bigint",
+		func(d *decode.D) uint64 {
+			v := d.UBigInt(int(n * 8))
+			d.AssertBigIntRange(big.NewInt(1), big.NewInt(math.MaxInt64))
+			return v.Uint64()
+		}, sms...)
+
+	return n
+}
+
+func decodeItem(d *decode.D, p *plist) {
+	m := d.FieldU4("type", elementTypeMap)
+	switch m {
+	case elementTypeNullOrBoolOrFill:
+		d.FieldU4("value", scalar.UToScalar{
+			null:      scalar.S{Sym: nil},
+			boolTrue:  scalar.S{Sym: true},
+			boolFalse: scalar.S{Sym: false},
+		})
+	case elementTypeInt:
+		n := d.FieldUFn("size", func(d *decode.D) uint64 {
+			return 1 << d.U4()
+		})
+		if n*8 <= 64 {
+			d.FieldU("value", int(n*8))
+		} else {
+			d.FieldUBigInt("value", int(n))
+		}
+	case elementTypeReal:
+		n := decodeSize(d)
+		d.FieldValueU("size", n)
+		d.FieldF("value", int(n))
+	case elementTypeDate:
+		n := 1 << decodeSize(d, d.AssertU(4, 8))
+		d.FieldValueU("size", uint64(n))
+		d.FieldF("value", n*8, scalar.DescriptionTimeFn(scalar.S.TryActualF, cocoaTimeEpochDate, time.RFC3339))
+	case elementTypeData:
+		n := decodeSize(d)
+		d.FieldValueU("size", n)
+		d.FieldRawLen("value", int64(n*8))
+	case elementTypeASCIIString:
+		n := decodeSize(d)
+		d.FieldValueU("size", n)
+		d.FieldUTF8("value", int(n))
+	case elementTypeUnicodeString:
+		n := decodeSize(d)
+		d.FieldValueU("size", n)
+		d.FieldUTF16("value", int(n))
+	case elementTypeUID:
+		n := decodeSize(d)
+		d.FieldValueU("size", n)
+		d.FieldUBigInt("value", int(n)).Uint64()
+	case elementTypeArray:
+		n := decodeSize(d)
+		d.FieldValueU("size", n)
+		d.FieldStructNArray("entries", "entry", int64(n),
+			func(d *decode.D) {
+				idx := d.FieldU8("object_index")
+				decodeReference(d, p, idx)
+			})
+	case elementTypeSet:
+		n := decodeSize(d)
+		d.FieldValueU("size", n)
+		d.FieldStructNArray("entries", "entry", int64(n),
+			func(d *decode.D) {
+				idx := d.FieldU8("object_index")
+				decodeReference(d, p, idx)
+			})
+	case elementTypeDict:
+		n := decodeSize(d)
+		d.FieldValueU("size", n)
+		d.FieldStructNArray("entries", "entry", int64(n),
+			func(d *decode.D) {
+				var ki, vi uint64
+				ki = d.FieldU8("key_index")
+				d.SeekRel(int64((n-1)*p.t.objRefSize)*8, func(d *decode.D) {
+					vi = d.FieldU8("value_index")
+				})
+				d.FieldStruct("key", func(d *decode.D) {
+					decodeReference(d, p, ki)
+				})
+				d.FieldStruct("value", func(d *decode.D) {
+					decodeReference(d, p, vi)
+				})
+			})
+	default:
+		d.Errorf("unknown type marker: %d", m)
+	}
+}
+
+func decodeReference(d *decode.D, p *plist, idx uint64) {
+	if idx > uint64(len(p.o)) {
+		// prevent a panic
+		d.Errorf("index %d out of bounds for object table size %d", idx, len(p.o))
+		return
+	}
+
+	d.SeekAbs(int64(p.o[idx]*8), func(d *decode.D) {
+		decodeItem(d, p)
+	})
+}
+
+type trailer struct {
+	offTblOffSize    uint64
+	objRefSize       uint64
+	nObjects         uint64
+	topObjectOffset  uint64
+	offsetTableStart uint64
+}
+
+type plist struct {
+	t trailer
+	o []uint64
+}
+
+func bplistDecode(d *decode.D, _ any) any {
+	d.FieldStruct("header", func(d *decode.D) {
+		d.FieldUTF8("magic", 6, d.AssertStr("bplist"))
+		d.FieldUTF8("version", 2, d.AssertStr("00"))
+	})
+
+	p := new(plist)
+
+	d.SeekAbs(d.Len()-32*8, func(d *decode.D) {
+		d.FieldStruct("trailer", func(d *decode.D) {
+			d.FieldU40("unused")
+			d.FieldS8("sort_version")
+			p.t.offTblOffSize = d.FieldU8("offset_table_offset_size", d.AssertURange(1, 8))
+			p.t.objRefSize = d.FieldU8("object_reference_size", d.AssertURange(1, 8))
+			p.t.nObjects = d.FieldU64("object_count")
+			p.t.topObjectOffset = d.FieldU64("top_object_offset")
+			p.t.offsetTableStart = d.FieldU64("offset_table_start")
+		})
+	})
+
+	d.SeekAbs(int64(p.t.offsetTableStart*8), func(d *decode.D) {
+		i := uint64(0)
+		d.FieldArrayLoop("offset_table",
+			func() bool { return i < p.t.nObjects },
+			func(d *decode.D) {
+				off := d.FieldU("element", 8*int(p.t.offTblOffSize))
+				p.o = append(p.o, off)
+				i++
+			},
+		)
+	})
+
+	d.FieldStruct("objects",
+		func(d *decode.D) {
+			decodeReference(d, p, 0)
+		})
+
+	return nil
+}
--- a/format/bplist/bplist.jq
+++ b/format/bplist/bplist.jq
@ -0,0 +1,30 @@
+def _bplist_torepr:
+  def _f:
+    ( if .type == "singleton" then .value | tovalue
+      elif .type == "int" then .value | tovalue
+      elif .type == "real" then .value | tovalue
+      elif .type == "date" then .value | tovalue
+      elif .type == "data" then .value | tovalue
+      elif .type == "ascii_string" then .value | tovalue
+      elif .type == "unicode_string" then .value | tovalue
+      elif .type == "uid" then .value | tovalue
+      elif .type == "array" then
+        ( .entries
+        | map(_f)
+        )
+      elif .type == "set" then
+        ( .entries
+        | map(_f)
+        )
+      elif .type == "dict" then
+        ( .entries
+        | map({key: (.key | _f), value: (.value | _f)})
+        | from_entries
+        )
+      else  error("unknown type: \(.type)")
+      end
+     );
+  ( .objects
+  | _f
+  );
+
--- a/format/bplist/bplist.md
+++ b/format/bplist/bplist.md
@ -0,0 +1,37 @@
+### Show full decoding
+```sh
+$ fq d Info.plist
+```
+
+### Timestamps
+Timestamps in Apple Binary Property Lists are encoded as Cocoa Core Data
+timestamps, where the raw value is the floating point number of seconds since
+January 1, 2001. By default, `fq` will render the raw floating point value. In
+order to get the raw value or string description, use the `todescription`
+function, you can use the `tovalue` and `todescription` functions:
+
+```sh
+$ fq 'torepr.SomeTimeStamp | tovalue' Info.plist
+685135328
+
+$ fq 'torepr.SomeTimeStamp | todescription' Info.plist
+"2022-09-17T19:22:08Z"
+```
+
+
+### Get JSON representation
+```sh
+$ fq torepr com.apple.UIAutomation.plist
+{
+  "UIAutomationEnabled": true
+}
+```
+
+### Authors
+- David McDonald
+[@dgmcdona](https://github.com/dgmcdona)
+
+### References
+- http://fileformats.archiveteam.org/wiki/Property_List/Binary
+- https://medium.com/@karaiskc/understanding-apples-binary-property-list-format-281e6da00dbd
+- https://opensource.apple.com/source/CF/CF-550/CFBinaryPList.c
--- a/format/bplist/testdata/Info.plist
+++ b/format/bplist/testdata/Info.plist
--- a/format/bplist/testdata/bplist.fqtest
+++ b/format/bplist/testdata/bplist.fqtest
--- a/format/bplist/testdata/com.apple.UIAutomation.plist
+++ b/format/bplist/testdata/com.apple.UIAutomation.plist
--- a/format/format.go
+++ b/format/format.go
@ -45,6 +45,7 @@ const (
 	BITCOIN_BLOCK       = "bitcoin_block"
 	BITCOIN_SCRIPT      = "bitcoin_script"
 	BITCOIN_TRANSACTION = "bitcoin_transaction"
+	BPLIST              = "bplist"
 	BSD_LOOPBACK_FRAME  = "bsd_loopback_frame"
 	BSON                = "bson"
 	BZIP2               = "bzip2"
--- a/format/gzip/gzip.go
+++ b/format/gzip/gzip.go
@ -8,6 +8,7 @@ import (
 	"compress/flate"
 	"hash/crc32"
 	"io"
+	"time"

 	"github.com/wader/fq/format"
 	"github.com/wader/fq/pkg/decode"
@ -74,7 +75,7 @@ func gzDecode(d *decode.D, _ any) any {
 		hasComment = d.FieldBool("comment")
 		d.FieldU3("reserved")
 	})
-	d.FieldU32("mtime", scalar.DescriptionActualUUnixTime)
+	d.FieldU32("mtime", scalar.DescriptionUnixTimeFn(scalar.S.TryActualU, time.RFC3339))
 	switch compressionMethod {
 	case delfateMethod:
 		d.FieldU8("extra_flags", deflateExtraFlagsNames)
--- a/format/mp4/boxes.go
+++ b/format/mp4/boxes.go
@ -210,7 +210,7 @@ func decodeLang(d *decode.D) string {

 // Quicktime time seconds in January 1, 1904 UTC
 var quicktimeEpochDate = time.Date(1904, time.January, 4, 0, 0, 0, 0, time.UTC)
-var quicktimeEpoch = scalar.DescriptionActualUTime(quicktimeEpochDate, time.RFC3339)
+var quicktimeEpoch = scalar.DescriptionTimeFn(scalar.S.TryActualU, quicktimeEpochDate, time.RFC3339)

 func decodeFieldMatrix(d *decode.D, name string) {
 	d.FieldStruct(name, func(d *decode.D) {
--- a/format/mp4/mp4.go
+++ b/format/mp4/mp4.go
@ -271,7 +271,7 @@ func mp4Tracks(d *decode.D, ctx *decodeContext) {
 					}
 				}

-				d.FieldValueStr("data_foramt", trackSDDataFormat, dataFormatNames)
+				d.FieldValueStr("data_format", trackSDDataFormat, dataFormatNames)

 				switch trackSDDataFormat {
 				case "lpcm",
--- a/format/mp4/testdata/aac.fqtest
+++ b/format/mp4/testdata/aac.fqtest
@ -429,4 +429,4 @@ $ fq -d mp4 dv aac.mp4
 0x290|b4                                             |.               |          [1]: raw bits byte_align 0x290.6-0x290.7 (0.2)
 0x290|   70                                          | p              |          [2]: raw bits data 0x291-0x291.7 (1)
     |                                               |                |      id: 1 0x59d-NA (0)
-     |                                               |                |      data_foramt: "mp4a" (MPEG-4 Audio) 0x59d-NA (0)
+     |                                               |                |      data_format: "mp4a" (MPEG-4 Audio) 0x59d-NA (0)
--- a/format/mp4/testdata/av1.fqtest
+++ b/format/mp4/testdata/av1.fqtest
@ -341,4 +341,4 @@ $ fq -d mp4 dv av1.mp4
 0x0050|f6 0a 4f ae f3 fe ec e7 30 4f 3f 13 9c 75 c9 6a|..O.....0O?..u.j|            data: raw bits 0x50-0x11bf.7 (4464)
 *     |until 0x11bf.7 (4464)                          |                |
      |                                               |                |      id: 1 0x14b2-NA (0)
-      |                                               |                |      data_foramt: "av01" (AV1 video) 0x14b2-NA (0)
+      |                                               |                |      data_format: "av01" (AV1 video) 0x14b2-NA (0)
--- a/format/mp4/testdata/avc.fqtest
+++ b/format/mp4/testdata/avc.fqtest
@ -514,4 +514,4 @@ $ fq -d mp4 dv avc.mp4
 0x00d50|79 0a ff 01 f9 2d 04 d3 29 fe 4d 76 42 26 f6 cd|y....-..).MvB&..|
 *      |until 0xd80.7 (51)                             |                |
       |                                               |                |      id: 1 0x10e0-NA (0)
-       |                                               |                |      data_foramt: "avc1" (Advanced Video Coding) 0x10e0-NA (0)
+       |                                               |                |      data_format: "avc1" (Advanced Video Coding) 0x10e0-NA (0)
--- a/format/mp4/testdata/dash.fqtest
+++ b/format/mp4/testdata/dash.fqtest
@ -348,7 +348,7 @@ $ fq -d mp4 dv dash_audio_init.mp4
     |                                               |                |  tracks[0:1]: 0x330-NA (0)
     |                                               |                |    [0]{}: track 0x330-NA (0)
     |                                               |                |      id: 1 0x330-NA (0)
-     |                                               |                |      data_foramt: "mp4a" (MPEG-4 Audio) 0x330-NA (0)
+     |                                               |                |      data_format: "mp4a" (MPEG-4 Audio) 0x330-NA (0)
     |                                               |                |      samples[0:0]: 0x330-NA (0)
 $ fq -d mp4 dv dash_audio_1.m4s
     |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|.{}: dash_audio_1.m4s (mp4) 0x0-0x4eb.7 (1260)
@ -491,7 +491,7 @@ $ fq -d mp4 dv dash_audio_1.m4s
 *    |until 0x4e6.7 (193)                            |                |
 0x4e0|                     01 18 81 b4 70|           |       ....p|   |        [5]: raw bits sample 0x4e7-0x4eb.7 (5)
     |                                               |                |      id: 1 0x4ec-NA (0)
-     |                                               |                |      data_foramt: "unknown" 0x4ec-NA (0)
+     |                                               |                |      data_format: "unknown" 0x4ec-NA (0)
 $ fq -d mp4 dv dash_video_init.mp4
      |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|.{}: dash_video_init.mp4 (mp4) 0x0-0x332.7 (819)
      |                                               |                |  boxes[0:2]: 0x0-0x332.7 (819)
@ -886,7 +886,7 @@ $ fq -d mp4 dv dash_video_init.mp4
      |                                               |                |  tracks[0:1]: 0x333-NA (0)
      |                                               |                |    [0]{}: track 0x333-NA (0)
      |                                               |                |      id: 1 0x333-NA (0)
-      |                                               |                |      data_foramt: "avc1" (Advanced Video Coding) 0x333-NA (0)
+      |                                               |                |      data_format: "avc1" (Advanced Video Coding) 0x333-NA (0)
      |                                               |                |      samples[0:0]: 0x333-NA (0)
 $ fq -d mp4 dv dash_video_1.m4s
      |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|.{}: dash_video_1.m4s (mp4) 0x0-0x1fd0.7 (8145)
@ -1001,4 +1001,4 @@ $ fq -d mp4 dv dash_video_1.m4s
 0x1720|53 23 af ff f2 50 06 7f 30 02 17 55 d4 5a 6f db|S#...P..0..U.Zo.|
 *     |until 0x1fd0.7 (end) (2240)                    |                |
      |                                               |                |      id: 1 0x1fd1-NA (0)
-      |                                               |                |      data_foramt: "unknown" 0x1fd1-NA (0)
+      |                                               |                |      data_format: "unknown" 0x1fd1-NA (0)
--- a/format/mp4/testdata/decode_samples.fqtest
+++ b/format/mp4/testdata/decode_samples.fqtest
@ -14,4 +14,4 @@ $ fq -o decode_samples=false -d mp4 '.tracks | dv' aac.mp4
 0x280|                                       01 18 81|             ...|      [3]: raw bits sample 0x28d-0x291.7 (5)
 0x290|b4 70                                          |.p              |
     |                                               |                |    id: 1 0x59d-NA (0)
-     |                                               |                |    data_foramt: "mp4a" (MPEG-4 Audio) 0x59d-NA (0)
+     |                                               |                |    data_format: "mp4a" (MPEG-4 Audio) 0x59d-NA (0)
--- a/format/mp4/testdata/flac.fqtest
+++ b/format/mp4/testdata/flac.fqtest
@ -372,4 +372,4 @@ $ fq -d mp4 dv flac.mp4
 0x280|                     00                        |       .        |          byte_align: 0 (valid) 0x287.2-0x287.7 (0.6)
 0x280|                        82 cb                  |        ..      |          footer_crc: "82cb" (raw bits) (valid) 0x288-0x289.7 (2)
     |                                               |                |      id: 1 0x543-NA (0)
-     |                                               |                |      data_foramt: "fLaC" (Fres Lossless Audio Codec) 0x543-NA (0)
+     |                                               |                |      data_format: "fLaC" (Fres Lossless Audio Codec) 0x543-NA (0)
--- a/format/mp4/testdata/fragmented.fqtest
+++ b/format/mp4/testdata/fragmented.fqtest
@ -1167,7 +1167,7 @@ $ fq -d mp4 dv fragmented.mp4
 0x02240|86 f8 14 d8 53 23 af ff f2 50 06 7f 30 02 17 55|....S#...P..0..U|
 *      |until 0x2af4.7 (2234)                          |                |
       |                                               |                |      id: 1 0x2bb4-NA (0)
-       |                                               |                |      data_foramt: "avc1" (Advanced Video Coding) 0x2bb4-NA (0)
+       |                                               |                |      data_format: "avc1" (Advanced Video Coding) 0x2bb4-NA (0)
       |                                               |                |    [1]{}: track 0x13e0-0x2bb3.7 (6100)
       |                                               |                |      samples[0:6]: 0x13e0-0x2af9.7 (5914)
       |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|        [0][0:4]: sample (aac_frame) 0x13e0-0x14ad.7 (206)
@ -1270,4 +1270,4 @@ $ fq -d mp4 dv fragmented.mp4
 0x02af0|                        b4                     |        .       |          [1]: raw bits byte_align 0x2af8.6-0x2af8.7 (0.2)
 0x02af0|                           70                  |         p      |          [2]: raw bits data 0x2af9-0x2af9.7 (1)
       |                                               |                |      id: 2 0x2bb4-NA (0)
-       |                                               |                |      data_foramt: "mp4a" (MPEG-4 Audio) 0x2bb4-NA (0)
+       |                                               |                |      data_format: "mp4a" (MPEG-4 Audio) 0x2bb4-NA (0)
--- a/format/mp4/testdata/hevc.fqtest
+++ b/format/mp4/testdata/hevc.fqtest
@ -636,4 +636,4 @@ $ fq -d mp4 dv hevc.mp4
 0x0040|fd a9 78 83 ff fb 75 6c 0b 3f ff 94 ce 7f aa fe|..x...ul.?......|
 *     |until 0x880.7 (2127)                           |                |
      |                                               |                |      id: 1 0x149b-NA (0)
-      |                                               |                |      data_foramt: "hev1" (High Efficiency Video Coding) 0x149b-NA (0)
+      |                                               |                |      data_format: "hev1" (High Efficiency Video Coding) 0x149b-NA (0)
--- a/format/mp4/testdata/in24.fqtest
+++ b/format/mp4/testdata/in24.fqtest
@ -280,4 +280,4 @@ $ fq dv in24.mp4
     |                                               |                |  tracks[0:1]: 0x3ec-NA (0)
     |                                               |                |    [0]{}: track 0x3ec-NA (0)
     |                                               |                |      id: 1 0x3ec-NA (0)
-     |                                               |                |      data_foramt: "in24" 0x3ec-NA (0)
+     |                                               |                |      data_format: "in24" 0x3ec-NA (0)
--- a/format/mp4/testdata/lpcm.fqtest
+++ b/format/mp4/testdata/lpcm.fqtest
@ -271,4 +271,4 @@ $ fq dv lpcm.mp4
     |                                               |                |  tracks[0:1]: 0x512-NA (0)
     |                                               |                |    [0]{}: track 0x512-NA (0)
     |                                               |                |      id: 1 0x512-NA (0)
-     |                                               |                |      data_foramt: "lpcm" 0x512-NA (0)
+     |                                               |                |      data_format: "lpcm" 0x512-NA (0)
--- a/format/mp4/testdata/mp3.fqtest
+++ b/format/mp4/testdata/mp3.fqtest
@ -506,4 +506,4 @@ $ fq -d mp4 dv mp3.mp4
 *    |until 0x29d.7 (188)                            |                |
     |                                               |                |          crc_calculated: "c36b" (raw bits) 0x29e-NA (0)
     |                                               |                |      id: 1 0x565-NA (0)
-     |                                               |                |      data_foramt: "mp4a" (MPEG-4 Audio) 0x565-NA (0)
+     |                                               |                |      data_format: "mp4a" (MPEG-4 Audio) 0x565-NA (0)
--- a/format/mp4/testdata/mpeg2.fqtest
+++ b/format/mp4/testdata/mpeg2.fqtest
@ -356,4 +356,4 @@ $ fq -d mp4 dv mpeg2.mp4
 0x0040|00 00 00 00 01 b8 00 08 00 40 00 00 01 00 00 0f|.........@......|
 *     |until 0x1fa5.7 (8046)                          |                |
      |                                               |                |      id: 1 0x22a9-NA (0)
-      |                                               |                |      data_foramt: "mp4v" (MPEG-4 Visual) 0x22a9-NA (0)
+      |                                               |                |      data_format: "mp4v" (MPEG-4 Visual) 0x22a9-NA (0)
--- a/format/mp4/testdata/opus.fqtest
+++ b/format/mp4/testdata/opus.fqtest
@ -353,4 +353,4 @@ $ fq -d mp4 dv opus.mp4
 0x120|02 cc 49 57 27 d4 a3 83 e9 53 33 fe 45 62 33 33|..IW'....S3.Eb33|
 *    |until 0x196.7 (120)                            |                |
     |                                               |                |      id: 1 0x439-NA (0)
-     |                                               |                |      data_foramt: "Opus" (Opus audio coding) 0x439-NA (0)
+     |                                               |                |      data_format: "Opus" (Opus audio coding) 0x439-NA (0)
--- a/format/mp4/testdata/stz2.fqtest
+++ b/format/mp4/testdata/stz2.fqtest
@ -463,4 +463,4 @@ $ fq -d mp4 'dv' stz2.mp4
 *    |until 0x4f5.7 (188)                            |                |
     |                                               |                |          crc_calculated: "c36b" (raw bits) 0x4f6-NA (0)
     |                                               |                |      id: 1 0x530-NA (0)
-     |                                               |                |      data_foramt: "mp4a" (MPEG-4 Audio) 0x530-NA (0)
+     |                                               |                |      data_format: "mp4a" (MPEG-4 Audio) 0x530-NA (0)
--- a/format/mp4/testdata/vorbis.fqtest
+++ b/format/mp4/testdata/vorbis.fqtest
@ -383,4 +383,4 @@ $ fq -d mp4 dv vorbis.mp4
 0x0130|f2 81 46 bb c2 48 52 08 27 b8 83 10 ca 08 b1 a7|..F..HR.'.......|
 *     |until 0x1dc.7 (174)                            |                |
      |                                               |                |      id: 1 0x1189-NA (0)
-      |                                               |                |      data_foramt: "mp4a" (MPEG-4 Audio) 0x1189-NA (0)
+      |                                               |                |      data_format: "mp4a" (MPEG-4 Audio) 0x1189-NA (0)
--- a/format/mp4/testdata/vp9.fqtest
+++ b/format/mp4/testdata/vp9.fqtest
@ -336,4 +336,4 @@ $ fq -d mp4 dv vp9.mp4
 0x0040|f9 be 8f e7 71 ff 5f 97 ef c3 f9 7e 37 b0 7e ad|....q._....~7.~.|
 *     |until 0x1563.7 (5424)                          |                |
      |                                               |                |      id: 1 0x184f-NA (0)
-      |                                               |                |      data_foramt: "vp09" (VP9 video) 0x184f-NA (0)
+      |                                               |                |      data_format: "vp09" (VP9 video) 0x184f-NA (0)
--- a/format/prores/testdata/prores_frame.fqtest
+++ b/format/prores/testdata/prores_frame.fqtest
@ -325,4 +325,4 @@ $ fq -d mp4 dv prores_frame.mov
 0x00c0|40 00 00 6b 7d 00 2d 30 05 a7 05 df 00 25 05 6c|@..k}.-0.....%.l|          picture_data: raw bits 0xc0-0x6c3c.7 (27517)
 *     |until 0x6c3c.7 (27517)                         |                |
      |                                               |                |      id: 1 0x6eff-NA (0)
-      |                                               |                |      data_foramt: "ap4h" (Apple ProRes 4444) 0x6eff-NA (0)
+      |                                               |                |      data_format: "ap4h" (Apple ProRes 4444) 0x6eff-NA (0)
--- a/format/tar/tar.go
+++ b/format/tar/tar.go
@ -5,6 +5,7 @@ package tar

 import (
 	"bytes"
+	"time"

 	"github.com/wader/fq/format"
 	"github.com/wader/fq/pkg/decode"
@ -53,7 +54,7 @@ func tarDecode(d *decode.D, _ any) any {
 					d.Fatalf("could not decode size")
 				}
 				size := int64(sizeS.SymU()) * 8
-				d.FieldUTF8NullFixedLen("mtime", 12, scalar.TrySymUParseUint(8), scalar.DescriptionSymUUnixTime)
+				d.FieldUTF8NullFixedLen("mtime", 12, scalar.TrySymUParseUint(8), scalar.DescriptionUnixTimeFn(scalar.S.TrySymU, time.RFC3339))
 				d.FieldUTF8NullFixedLen("chksum", 8, scalar.TrySymUParseUint(8))
 				d.FieldUTF8("typeflag", 1, mapTrimSpaceNull)
 				d.FieldUTF8("linkname", 100, mapTrimSpaceNull)
--- a/format/wav/wav.go
+++ b/format/wav/wav.go
@ -157,6 +157,34 @@ func decodeChunk(d *decode.D, expectedChunkID string, stringData bool) {
 		"fact": func(d *decode.D) {
 			d.FieldU32("sample_length")
 		},
+		"smpl": func(d *decode.D) {
+			d.FieldU32("manufacturer")
+			d.FieldU32("product")
+			d.FieldU32("sample_period")
+			d.FieldU32("midi_unity_note")
+			d.FieldU32("midi_pitch_fraction")
+			d.FieldU32("smpte_format")
+			d.FieldU32("smpte_offset")
+			numSampleLoops := int(d.FieldU32("number_of_sample_loops"))
+			samplerDataBytes := int(d.FieldU32("sampler_data_bytes"))
+			d.FieldArray("samples_loops", func(d *decode.D) {
+				for i := 0; i < numSampleLoops; i++ {
+					d.FieldStruct("sample_loop", func(d *decode.D) {
+						d.FieldUTF8("id", 4)
+						d.FieldU32("type", scalar.UToSymStr{
+							0: "forward",
+							1: "forward_backward",
+							2: "backward",
+						})
+						d.FieldU32("start")
+						d.FieldU32("end")
+						d.FieldU32("fraction")
+						d.FieldU32("number_of_times")
+					})
+				}
+			})
+			d.FieldRawLen("sampler_data", int64(samplerDataBytes)*8)
+		},
 	}

 	trimChunkID := d.FieldStrFn("id", func(d *decode.D) string {
--- a/format/xml/testdata/help_xml.fqtest
+++ b/format/xml/testdata/help_xml.fqtest
@ -78,7 +78,7 @@ Elements are arrays of the shape ["#text": "body text", "attr_name", {key: "attr


  # decode as array
-  ✗ echo '<a><b/><b>bbb</b><c attr="value">ccc</c></a>' | fq -d xml -o array=true
+  $ echo '<a><b/><b>bbb</b><c attr="value">ccc</c></a>' | fq -d xml -o array=true
  [
    "a",
    null,
--- a/format/xml/xml.md
+++ b/format/xml/xml.md
@ -60,7 +60,7 @@ Elements are arrays of the shape `["#text": "body text", "attr_name", {key: "att

 ```sh
 # decode as array
-✗ echo '<a><b/><b>bbb</b><c attr="value">ccc</c></a>' | fq -d xml -o array=true
+$ echo '<a><b/><b>bbb</b><c attr="value">ccc</c></a>' | fq -d xml -o array=true
 [
  "a",
  null,
--- a/fq.go
+++ b/fq.go
@ -6,7 +6,7 @@ import (
 	"github.com/wader/fq/pkg/interp"
 )

-const version = "0.0.9"
+const version = "0.0.10"

 func main() {
 	cli.Main(interp.DefaultRegistry, version)
--- a/go.mod
+++ b/go.mod
@ -4,9 +4,9 @@ go 1.18

 require (
 	// fork of github.com/itchyny/gojq, see github.com/wader/gojq fq branch
-	github.com/wader/gojq v0.12.1-0.20220822132002-64fe65a68424
+	github.com/wader/gojq v0.12.1-0.20220929141349-8874f5c7907c
 	// fork of github.com/chzyer/readline, see github.com/wader/readline fq branch
-	github.com/wader/readline v0.0.0-20220704090837-31be50517a56
+	github.com/wader/readline v0.0.0-20220928125628-732951d41240
 )

 require (
@ -27,7 +27,7 @@ require (

 	// has no tags
 	// go get -d github.com/gomarkdown/markdown@master && go mod tidy
-	github.com/gomarkdown/markdown v0.0.0-20220627144906-e9a81102ebeb
+	github.com/gomarkdown/markdown v0.0.0-20220905174103-7b278df48cfb

 	// has no tags yet
 	// bump-disabled: gomod-gopacket /github\.com\/gopacket\/gopacket v(.*)/ https://github.com/gopacket/gopacket.git|^1
@ -52,15 +52,15 @@ require (

 	// has no tags
 	// go get -d golang.org/x/crypto@master && go mod tidy
-	golang.org/x/crypto v0.0.0-20220817201139-bc19a97f63c8
+	golang.org/x/crypto v0.0.0-20220926161630-eccd6366d1be

 	// has no tags
 	// go get -d golang.org/x/exp@master && go mod tidy
-	golang.org/x/exp v0.0.0-20220722155223-a9213eeb770e
+	golang.org/x/exp v0.0.0-20220927162542-c76eaa363f9d

 	// has no tags
 	// go get -d golang.org/x/net@master && go mod tidy
-	golang.org/x/net v0.0.0-20220812174116-3211cb980234
+	golang.org/x/net v0.0.0-20220927171203-f486391704dc

 	// bump: gomod-golang/text /golang\.org\/x\/text v(.*)/ https://github.com/golang/text.git|^0
 	// bump: gomod-golang/text command go get -d golang.org/x/text@v$LATEST && go mod tidy
@ -74,9 +74,9 @@ require (
 )

 require (
-	github.com/itchyny/timefmt-go v0.1.3 // indirect
+	github.com/itchyny/timefmt-go v0.1.4 // indirect
 	github.com/mitchellh/reflectwalk v1.0.2 // indirect
 	github.com/niemeyer/pretty v0.0.0-20200227124842-a10e7caefd8e // indirect
-	golang.org/x/sys v0.0.0-20220811171246-fbc7d0a398ab // indirect
+	golang.org/x/sys v0.0.0-20220829200755-d48e67d00261 // indirect
 	gopkg.in/check.v1 v1.0.0-20200227125254-8fa46927fb4f // indirect
 )
--- a/go.sum
+++ b/go.sum
@ -4,12 +4,12 @@ github.com/creasty/defaults v1.6.0 h1:ltuE9cfphUtlrBeomuu8PEyISTXnxqkBIoQfXgv7BS
 github.com/creasty/defaults v1.6.0/go.mod h1:iGzKe6pbEHnpMPtfDXZEr0NVxWnPTjb1bbDy08fPzYM=
 github.com/golang/snappy v0.0.4 h1:yAGX7huGHXlcLOEtBnF4w7FQwA26wojNCwOYAEhLjQM=
 github.com/golang/snappy v0.0.4/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=
-github.com/gomarkdown/markdown v0.0.0-20220627144906-e9a81102ebeb h1:5b/eFaSaKPFG9ygDBaPKkydKU5nFJYk08g9jPIVogMg=
-github.com/gomarkdown/markdown v0.0.0-20220627144906-e9a81102ebeb/go.mod h1:JDGcbDT52eL4fju3sZ4TeHGsQwhG9nbDV21aMyhwPoA=
+github.com/gomarkdown/markdown v0.0.0-20220905174103-7b278df48cfb h1:7h+tPfwoUE+qLvWYmsvKSiRlXv6WGorb6PUKaZUclwc=
+github.com/gomarkdown/markdown v0.0.0-20220905174103-7b278df48cfb/go.mod h1:JDGcbDT52eL4fju3sZ4TeHGsQwhG9nbDV21aMyhwPoA=
 github.com/gopacket/gopacket v0.0.0-20220819214934-ee81b8c880da h1:AAwDU9N39fQNYUtg270aiU6N7U2ZVsGZKiRwsCMsWEo=
 github.com/gopacket/gopacket v0.0.0-20220819214934-ee81b8c880da/go.mod h1:DlRRfaM/QjAu2ADqraIure1Eif0HpNL8hmyVQ+qci5Y=
-github.com/itchyny/timefmt-go v0.1.3 h1:7M3LGVDsqcd0VZH2U+x393obrzZisp7C0uEe921iRkU=
-github.com/itchyny/timefmt-go v0.1.3/go.mod h1:0osSSCQSASBJMsIZnhAaF1C2fCBTJZXrnj37mG8/c+A=
+github.com/itchyny/timefmt-go v0.1.4 h1:hFEfWVdwsEi+CY8xY2FtgWHGQaBaC3JeHd+cve0ynVM=
+github.com/itchyny/timefmt-go v0.1.4/go.mod h1:nEP7L+2YmAbT2kZ2HfSs1d8Xtw9LY8D2stDBckWakZ8=
 github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
 github.com/kr/text v0.1.0 h1:45sCR5RtlFHMR4UwH9sdQ5TC8v0qDQCHnXt+kaKSTVE=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
@ -23,19 +23,19 @@ github.com/niemeyer/pretty v0.0.0-20200227124842-a10e7caefd8e h1:fD57ERR4JtEqsWb
 github.com/niemeyer/pretty v0.0.0-20200227124842-a10e7caefd8e/go.mod h1:zD1mROLANZcx1PVRCS0qkT7pwLkGfwJo4zjcN/Tysno=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/wader/gojq v0.12.1-0.20220822132002-64fe65a68424 h1:4SZxNA1ti22+TemKXy5H2qyFPPqi5X55vtyjmOnLsqk=
-github.com/wader/gojq v0.12.1-0.20220822132002-64fe65a68424/go.mod h1:HM2cB+ANeJ4kBhxQp/4cNKewKjvYHACuCpBneQBgHkg=
-github.com/wader/readline v0.0.0-20220704090837-31be50517a56 h1:MEvdJFQfJD9D5nH2C5aXW+jWGcU1YmL8fJWIDsXvrJw=
-github.com/wader/readline v0.0.0-20220704090837-31be50517a56/go.mod h1:Zgz8IJWvJoe7NK23CCPpC109XMCqJCpUhpHcnnA4XaM=
-golang.org/x/crypto v0.0.0-20220817201139-bc19a97f63c8 h1:GIAS/yBem/gq2MUqgNIzUHW7cJMmx3TGZOrnyYaNQ6c=
-golang.org/x/crypto v0.0.0-20220817201139-bc19a97f63c8/go.mod h1:IxCIyHEi3zRg3s0A5j5BB6A9Jmi73HwBIUl50j+osU4=
-golang.org/x/exp v0.0.0-20220722155223-a9213eeb770e h1:+WEEuIdZHnUeJJmEUjyYC2gfUMj69yZXw17EnHg/otA=
-golang.org/x/exp v0.0.0-20220722155223-a9213eeb770e/go.mod h1:Kr81I6Kryrl9sr8s2FK3vxD90NdsKWRuOIl2O4CvYbA=
-golang.org/x/net v0.0.0-20220812174116-3211cb980234 h1:RDqmgfe7SvlMWoqC3xwQ2blLO3fcWcxMa3eBLRdRW7E=
-golang.org/x/net v0.0.0-20220812174116-3211cb980234/go.mod h1:YDH+HFinaLZZlnHAfSS6ZXJJ9M9t4Dl22yv3iI2vPwk=
+github.com/wader/gojq v0.12.1-0.20220929141349-8874f5c7907c h1:aQz+gw5Xe2x++st4HBIaMHPPTIyPtESG2HMZJmOaRkc=
+github.com/wader/gojq v0.12.1-0.20220929141349-8874f5c7907c/go.mod h1:/+WKHSfP8sgyJDXeD9VjxlGjExGfjPUy0zm/Zy3Ind0=
+github.com/wader/readline v0.0.0-20220928125628-732951d41240 h1:fqNaldd6kVsMNGXLXH4TtB1kJtaPQOzGwqNYgswIM94=
+github.com/wader/readline v0.0.0-20220928125628-732951d41240/go.mod h1:Zgz8IJWvJoe7NK23CCPpC109XMCqJCpUhpHcnnA4XaM=
+golang.org/x/crypto v0.0.0-20220926161630-eccd6366d1be h1:fmw3UbQh+nxngCAHrDCCztao/kbYFnWjoqop8dHx05A=
+golang.org/x/crypto v0.0.0-20220926161630-eccd6366d1be/go.mod h1:IxCIyHEi3zRg3s0A5j5BB6A9Jmi73HwBIUl50j+osU4=
+golang.org/x/exp v0.0.0-20220927162542-c76eaa363f9d h1:3wgmvnqHUJ8SxiNWwea5NCzTwAVfhTtuV+0ClVFlClc=
+golang.org/x/exp v0.0.0-20220927162542-c76eaa363f9d/go.mod h1:cyybsKvd6eL0RnXn6p/Grxp8F5bW7iYuBgsNCOHpMYE=
+golang.org/x/net v0.0.0-20220927171203-f486391704dc h1:FxpXZdoBqT8RjqTy6i1E8nXHhW21wK7ptQ/EPIGxzPQ=
+golang.org/x/net v0.0.0-20220927171203-f486391704dc/go.mod h1:YDH+HFinaLZZlnHAfSS6ZXJJ9M9t4Dl22yv3iI2vPwk=
 golang.org/x/sys v0.0.0-20220627191245-f75cf1eec38b/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20220811171246-fbc7d0a398ab h1:2QkjZIsXupsJbJIdSjjUOgWK3aEtzyuh2mPt3l/CkeU=
-golang.org/x/sys v0.0.0-20220811171246-fbc7d0a398ab/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.0.0-20220829200755-d48e67d00261 h1:v6hYoSR9T5oet+pMXwUWkbiVqx/63mlHjefrHmxwfeY=
+golang.org/x/sys v0.0.0-20220829200755-d48e67d00261/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/text v0.3.7 h1:olpwvP2KacW1ZWvsR7uQhoyTYvKAupfQrRGBFM352Gk=
 golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
--- a/internal/colorjson/encoder.go
+++ b/internal/colorjson/encoder.go
@ -1,8 +1,8 @@
-// This is gojq:s cli/encoder.go extract to be reusable and non-global color config
+// Package colorjson is gojq:s cli/encoder.go extract to be reusable and have non-global color config
 // TODO: possible gojq can export it?
 //
 // The MIT License (MIT)
-// Copyright (c) 2019-2021 itchyny
+// Copyright (c) 2019-2022 itchyny
 //
 // Permission is hereby granted, free of charge, to any person obtaining a copy
 // of this software and associated documentation files (the "Software"), to deal
@ -21,23 +21,17 @@
 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
-//
-
-// skip errcheck to keep code similar to gojq version
-//
-//nolint:errcheck
 package colorjson

 import (
-	"bufio"
+	"bytes"
 	"fmt"
 	"io"
 	"math"
 	"math/big"
+	"sort"
 	"strconv"
 	"unicode/utf8"
-
-	"golang.org/x/exp/slices"
 )

 type Colors struct {
@ -53,13 +47,14 @@ type Colors struct {
 }

 type Encoder struct {
-	w       *bufio.Writer
-	wErr    error
+	out    io.Writer
+	w      *bytes.Buffer
+	tab    bool
+	indent int
+	depth  int
+	buf    [64]byte
+
 	color   bool
-	tab     bool
-	indent  int
-	depth   int
-	buf     [64]byte
 	valueFn func(v any) any
 	colors  Colors
 }
@ -67,6 +62,7 @@ type Encoder struct {
 func NewEncoder(color bool, tab bool, indent int, valueFn func(v any) any, colors Colors) *Encoder {
 	// reuse the buffer in multiple calls of marshal
 	return &Encoder{
+		w:       new(bytes.Buffer),
 		color:   color,
 		tab:     tab,
 		indent:  indent,
@ -75,16 +71,22 @@ func NewEncoder(color bool, tab bool, indent int, valueFn func(v any) any, color
 	}
 }

-func (e *Encoder) Marshal(v any, w io.Writer) error {
-	e.w = bufio.NewWriter(w)
-	e.encode(v)
-	if e.wErr != nil {
-		return e.wErr
-	}
-	return e.w.Flush()
+func (e *Encoder) flush() error {
+	_, err := e.out.Write(e.w.Bytes())
+	e.w.Reset()
+	return err
 }

-func (e *Encoder) encode(v any) {
+func (e *Encoder) Marshal(v interface{}, w io.Writer) error {
+	e.out = w
+	err := e.encode(v)
+	if ferr := e.flush(); ferr != nil && err == nil {
+		err = ferr
+	}
+	return err
+}
+
+func (e *Encoder) encode(v interface{}) error {
 	switch v := v.(type) {
 	case nil:
 		e.write([]byte("null"), e.colors.Null)
@ -102,18 +104,26 @@ func (e *Encoder) encode(v any) {
 		e.write(v.Append(e.buf[:0], 10), e.colors.Number)
 	case string:
 		e.encodeString(v, e.colors.String)
-	case []any:
-		e.encodeArray(v)
-	case map[string]any:
-		e.encodeMap(v)
+	case []interface{}:
+		if err := e.encodeArray(v); err != nil {
+			return err
+		}
+	case map[string]interface{}:
+		if err := e.encodeMap(v); err != nil {
+			return err
+		}
 	default:
 		if e.valueFn != nil {
 			v = e.valueFn(v)
 		} else {
-			panic(fmt.Sprintf("invalid value: %#+v", v))
+			panic(fmt.Sprintf("invalid type: %[1]T (%[1]v)", v))
 		}
-		e.encode(v)
+		return e.encode(v)
 	}
+	if e.w.Len() > 8*1024 {
+		return e.flush()
+	}
+	return nil
 }

 // ref: floatEncoder in encoding/json
@ -144,37 +154,38 @@ func (e *Encoder) encodeFloat64(f float64) {

 // ref: encodeState#string in encoding/json
 func (e *Encoder) encodeString(s string, color []byte) {
-	if e.color {
-		e.w.Write(color)
+	if color != nil {
+		e.setColor(e.w, color)
 	}
 	e.w.WriteByte('"')
 	start := 0
 	for i := 0; i < len(s); {
 		if b := s[i]; b < utf8.RuneSelf {
-			if ']' <= b && b <= '~' || '#' <= b && b <= '[' || b == ' ' || b == '!' {
+			if ' ' <= b && b <= '~' && b != '"' && b != '\\' {
 				i++
 				continue
 			}
 			if start < i {
 				e.w.WriteString(s[start:i])
 			}
-			e.w.WriteByte('\\')
 			switch b {
-			case '\\', '"':
-				e.w.WriteByte(b)
+			case '"':
+				e.w.WriteString(`\"`)
+			case '\\':
+				e.w.WriteString(`\\`)
 			case '\b':
-				e.w.WriteByte('b')
+				e.w.WriteString(`\b`)
 			case '\f':
-				e.w.WriteByte('f')
+				e.w.WriteString(`\f`)
 			case '\n':
-				e.w.WriteByte('n')
+				e.w.WriteString(`\n`)
 			case '\r':
-				e.w.WriteByte('r')
+				e.w.WriteString(`\r`)
 			case '\t':
-				e.w.WriteByte('t')
+				e.w.WriteString(`\t`)
 			default:
 				const hex = "0123456789abcdef"
-				e.w.WriteString("u00")
+				e.w.WriteString(`\u00`)
 				e.w.WriteByte(hex[b>>4])
 				e.w.WriteByte(hex[b&0xF])
 			}
@ -198,40 +209,39 @@ func (e *Encoder) encodeString(s string, color []byte) {
 		e.w.WriteString(s[start:])
 	}
 	e.w.WriteByte('"')
-	if e.color {
-		e.w.Write(e.colors.Reset)
+	if color != nil {
+		e.setColor(e.w, e.colors.Reset)
 	}
 }

-func (e *Encoder) encodeArray(vs []any) {
+func (e *Encoder) encodeArray(vs []interface{}) error {
 	e.writeByte('[', e.colors.Array)
 	e.depth += e.indent
 	for i, v := range vs {
-		if e.wErr != nil {
-			return
-		}
-
 		if i > 0 {
 			e.writeByte(',', e.colors.Array)
 		}
 		if e.indent != 0 {
 			e.writeIndent()
 		}
-		e.encode(v)
+		if err := e.encode(v); err != nil {
+			return err
+		}
 	}
 	e.depth -= e.indent
 	if len(vs) > 0 && e.indent != 0 {
 		e.writeIndent()
 	}
 	e.writeByte(']', e.colors.Array)
+	return nil
 }

-func (e *Encoder) encodeMap(vs map[string]any) {
+func (e *Encoder) encodeMap(vs map[string]interface{}) error {
 	e.writeByte('{', e.colors.Object)
 	e.depth += e.indent
 	type keyVal struct {
 		key string
-		val any
+		val interface{}
 	}
 	kvs := make([]keyVal, len(vs))
 	var i int
@ -239,12 +249,10 @@ func (e *Encoder) encodeMap(vs map[string]any) {
 		kvs[i] = keyVal{k, v}
 		i++
 	}
-	slices.SortFunc(kvs, func(a, b keyVal) bool { return a.key < b.key })
+	sort.Slice(kvs, func(i, j int) bool {
+		return kvs[i].key < kvs[j].key
+	})
 	for i, kv := range kvs {
-		if e.wErr != nil {
-			return
-		}
-
 		if i > 0 {
 			e.writeByte(',', e.colors.Object)
 		}
@ -256,82 +264,65 @@ func (e *Encoder) encodeMap(vs map[string]any) {
 		if e.indent != 0 {
 			e.w.WriteByte(' ')
 		}
-		e.encode(kv.val)
+		if err := e.encode(kv.val); err != nil {
+			return err
+		}
 	}
 	e.depth -= e.indent
 	if len(vs) > 0 && e.indent != 0 {
 		e.writeIndent()
 	}
 	e.writeByte('}', e.colors.Object)
+	return nil
 }

 func (e *Encoder) writeIndent() {
 	e.w.WriteByte('\n')
 	if n := e.depth; n > 0 {
 		if e.tab {
-			const tabs = "\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t"
-			for n > len(tabs) {
-				e.w.Write([]byte(tabs))
-				n -= len(tabs)
-			}
-			e.w.Write([]byte(tabs)[:n])
+			e.writeIndentInternal(n, "\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t")
 		} else {
-			const spaces = "                                                                "
-			for n > len(spaces) {
-				e.w.Write([]byte(spaces))
-				n -= len(spaces)
+			e.writeIndentInternal(n, "                                ")
+		}
+	}
+}
+
+func (e *Encoder) writeIndentInternal(n int, spaces string) {
+	if l := len(spaces); n <= l {
+		e.w.WriteString(spaces[:n])
+	} else {
+		e.w.WriteString(spaces)
+		for n -= l; n > 0; n, l = n-l, l*2 {
+			if n < l {
+				l = n
 			}
-			e.w.Write([]byte(spaces)[:n])
+			e.w.Write(e.w.Bytes()[e.w.Len()-l:])
 		}
 	}
 }

 func (e *Encoder) writeByte(b byte, color []byte) {
-	if e.wErr != nil {
-		return
-	}
 	if color == nil {
-		if err := e.w.WriteByte(b); err != nil {
-			e.wErr = err
-		}
+		e.w.WriteByte(b)
 	} else {
-		if e.color {
-			if _, err := e.w.Write(color); err != nil {
-				e.wErr = err
-			}
-		}
-		if err := e.w.WriteByte(b); err != nil {
-			e.wErr = err
-		}
-		if e.color {
-			if _, err := e.w.Write(e.colors.Reset); err != nil {
-				e.wErr = err
-			}
-		}
+		e.setColor(e.w, color)
+		e.w.WriteByte(b)
+		e.setColor(e.w, e.colors.Reset)
 	}
 }

 func (e *Encoder) write(bs []byte, color []byte) {
-	if e.wErr != nil {
-		return
-	}
 	if color == nil {
-		if _, err := e.w.Write(bs); err != nil {
-			e.wErr = err
-		}
+		e.w.Write(bs)
 	} else {
-		if e.color {
-			if _, err := e.w.Write(color); err != nil {
-				e.wErr = err
-			}
-		}
-		if _, err := e.w.Write(bs); err != nil {
-			e.wErr = err
-		}
-		if e.color {
-			if _, err := e.w.Write(e.colors.Reset); err != nil {
-				e.wErr = err
-			}
-		}
+		e.setColor(e.w, color)
+		e.w.Write(bs)
+		e.setColor(e.w, e.colors.Reset)
+	}
+}
+
+func (e *Encoder) setColor(buf *bytes.Buffer, color []byte) {
+	if e.color {
+		buf.Write(color)
 	}
 }
--- a/pkg/decode/decode.go
+++ b/pkg/decode/decode.go
@ -688,11 +688,15 @@ func (d *D) trySeekAbs(pos int64, fns ...func(d *D)) (int64, error) {
 	return pos, nil
 }

-// SeekRel seeks relative to current bit position
+// TrySeekRel seeks relative to current bit position. If one or more functions is
+// passed, the original seek position will be restored after decoding.
 func (d *D) TrySeekRel(delta int64, fns ...func(d *D)) (int64, error) {
 	return d.trySeekAbs(d.Pos()+delta, fns...)
 }

+// SeekRel seeks relative to current bit position. If one or more functions is
+// passed, the original seek position will be restored after decoding. Panics if
+// an error occurs while seeking.
 func (d *D) SeekRel(delta int64, fns ...func(d *D)) int64 {
 	n, err := d.trySeekAbs(d.Pos()+delta, fns...)
 	if err != nil {
@ -701,7 +705,8 @@ func (d *D) SeekRel(delta int64, fns ...func(d *D)) int64 {
 	return n
 }

-// SeekAbs seeks to absolute position
+// TrySeekAbs seeks to absolute position. If one or more functions is passed,
+// the original seek position will be restored after decoding.
 func (d *D) TrySeekAbs(pos int64, fns ...func(d *D)) (int64, error) {
 	return d.trySeekAbs(pos, fns...)
 }
@ -798,6 +803,15 @@ func (d *D) FieldStructArrayLoop(name string, structName string, condFn func() b
 	})
 }

+// FieldStructNArray decodes an array of elements with a known count.
+func (d *D) FieldStructNArray(name string, structName string, count int64, fn func(d *D)) *D {
+	return d.FieldArray(name, func(d *D) {
+		for i := int64(0); i < count; i++ {
+			d.FieldStruct(structName, fn)
+		}
+	})
+}
+
 func (d *D) FieldArrayLoop(name string, condFn func() bool, fn func(d *D)) *D {
 	return d.FieldArray(name, func(d *D) {
 		for condFn() {
--- a/pkg/interp/decode.go
+++ b/pkg/interp/decode.go
@ -289,7 +289,7 @@ func (i *Interp) _decode(c any, format string, opts decodeOpts) any {
 		}
 	}

-	return makeDecodeValueOut(dv, formatOutMap)
+	return makeDecodeValueOut(dv, decodeValueValue, formatOutMap)
 }

 func valueKey(name string, a, b func(name string) any) any {
@ -326,11 +326,19 @@ func toValue(optsFn func() Options, v any) (any, bool) {
 	}
 }

-func makeDecodeValue(dv *decode.Value) any {
-	return makeDecodeValueOut(dv, nil)
+type decodeValueKind int
+
+const (
+	decodeValueValue decodeValueKind = iota
+	decodeValueActual
+	decodeValueSym
+)
+
+func makeDecodeValue(dv *decode.Value, kind decodeValueKind) any {
+	return makeDecodeValueOut(dv, kind, nil)
 }

-func makeDecodeValueOut(dv *decode.Value, out any) any {
+func makeDecodeValueOut(dv *decode.Value, kind decodeValueKind, out any) any {
 	switch vv := dv.V.(type) {
 	case *decode.Compound:
 		if vv.IsArray {
@ -338,7 +346,18 @@ func makeDecodeValueOut(dv *decode.Value, out any) any {
 		}
 		return NewStructDecodeValue(dv, out, vv)
 	case *scalar.S:
-		switch vv := vv.Value().(type) {
+		// TODO: rethink value/actual/sym handling
+		var vvv any
+		switch kind {
+		case decodeValueValue:
+			vvv = vv.Value()
+		case decodeValueActual:
+			vvv = vv.Actual
+		case decodeValueSym:
+			vvv = vv.Sym
+		}
+
+		switch vvv := vvv.(type) {
 		case bitio.ReaderAtSeeker:
 			// is lazy so that in situations where the decode value is only used to
 			// create another binary we don't have to read and create a string, ex:
@ -349,11 +368,11 @@ func makeDecodeValueOut(dv *decode.Value, out any) any {
 					IsScalar: true,
 					Fn: func() (gojq.JQValue, error) {
 						buf := &bytes.Buffer{}
-						vvC, err := bitio.CloneReader(vv)
+						vvvC, err := bitio.CloneReader(vvv)
 						if err != nil {
 							return nil, err
 						}
-						if _, err := bitioex.CopyBits(buf, vvC); err != nil {
+						if _, err := bitioex.CopyBits(buf, vvvC); err != nil {
 							return nil, err
 						}
 						return gojqex.String([]rune(buf.String())), nil
@ -364,42 +383,42 @@ func makeDecodeValueOut(dv *decode.Value, out any) any {
 			}
 		case bool:
 			return decodeValue{
-				JQValue:         gojqex.Boolean(vv),
+				JQValue:         gojqex.Boolean(vvv),
 				decodeValueBase: decodeValueBase{dv: dv},
 			}
 		case int:
 			return decodeValue{
-				JQValue:         gojqex.Number{V: vv},
+				JQValue:         gojqex.Number{V: vvv},
 				decodeValueBase: decodeValueBase{dv: dv},
 			}
 		case int64:
 			return decodeValue{
-				JQValue:         gojqex.Number{V: big.NewInt(vv)},
+				JQValue:         gojqex.Number{V: big.NewInt(vvv)},
 				decodeValueBase: decodeValueBase{dv: dv},
 			}
 		case uint64:
 			return decodeValue{
-				JQValue:         gojqex.Number{V: new(big.Int).SetUint64(vv)},
+				JQValue:         gojqex.Number{V: new(big.Int).SetUint64(vvv)},
 				decodeValueBase: decodeValueBase{dv: dv},
 			}
 		case float64:
 			return decodeValue{
-				JQValue:         gojqex.Number{V: vv},
+				JQValue:         gojqex.Number{V: vvv},
 				decodeValueBase: decodeValueBase{dv: dv},
 			}
 		case string:
 			return decodeValue{
-				JQValue:         gojqex.String(vv),
+				JQValue:         gojqex.String(vvv),
 				decodeValueBase: decodeValueBase{dv: dv},
 			}
 		case []any:
 			return decodeValue{
-				JQValue:         gojqex.Array(vv),
+				JQValue:         gojqex.Array(vvv),
 				decodeValueBase: decodeValueBase{dv: dv},
 			}
 		case map[string]any:
 			return decodeValue{
-				JQValue:         gojqex.Object(vv),
+				JQValue:         gojqex.Object(vvv),
 				decodeValueBase: decodeValueBase{dv: dv},
 			}
 		case nil:
@ -409,11 +428,11 @@ func makeDecodeValueOut(dv *decode.Value, out any) any {
 			}
 		case *big.Int:
 			return decodeValue{
-				JQValue:         gojqex.Number{V: vv},
+				JQValue:         gojqex.Number{V: vvv},
 				decodeValueBase: decodeValueBase{dv: dv},
 			}
 		default:
-			panic(fmt.Sprintf("unreachable vv %#+v", vv))
+			panic(fmt.Sprintf("unreachable vv %#+v", vvv))
 		}
 	default:
 		panic(fmt.Sprintf("unreachable dv %#+v", dv))
@ -482,37 +501,29 @@ func (dvb decodeValueBase) JQValueKey(name string) any {
 	case "_name":
 		return dv.Name
 	case "_root":
-		return makeDecodeValue(dv.Root())
+		return makeDecodeValue(dv.Root(), decodeValueValue)
 	case "_buffer_root":
 		// TODO: rename?
-		return makeDecodeValue(dv.BufferRoot())
+		return makeDecodeValue(dv.BufferRoot(), decodeValueValue)
 	case "_format_root":
 		// TODO: rename?
-		return makeDecodeValue(dv.FormatRoot())
+		return makeDecodeValue(dv.FormatRoot(), decodeValueValue)
 	case "_parent":
 		if dv.Parent == nil {
 			return nil
 		}
-		return makeDecodeValue(dv.Parent)
+		return makeDecodeValue(dv.Parent, decodeValueValue)
 	case "_actual":
-		switch vv := dv.V.(type) {
+		switch dv.V.(type) {
 		case *scalar.S:
-			jv, ok := gojqex.ToGoJQValue(vv.Actual)
-			if !ok {
-				return fmt.Errorf("can't convert actual value jq value %#+v", vv.Actual)
-			}
-			return jv
+			return makeDecodeValue(dv, decodeValueActual)
 		default:
 			return nil
 		}
 	case "_sym":
-		switch vv := dv.V.(type) {
+		switch dv.V.(type) {
 		case *scalar.S:
-			jv, ok := gojqex.ToGoJQValue(vv.Sym)
-			if !ok {
-				return fmt.Errorf("can't convert sym value jq value %#+v", vv.Actual)
-			}
-			return jv
+			return makeDecodeValue(dv, decodeValueSym)
 		default:
 			return nil
 		}
@ -642,19 +653,19 @@ func (v ArrayDecodeValue) JQValueIndex(index int) any {
 	if index < 0 {
 		return nil
 	}
-	return makeDecodeValue((v.Compound.Children)[index])
+	return makeDecodeValue((v.Compound.Children)[index], decodeValueValue)
 }
 func (v ArrayDecodeValue) JQValueSlice(start int, end int) any {
 	vs := make([]any, end-start)
 	for i, e := range (v.Compound.Children)[start:end] {
-		vs[i] = makeDecodeValue(e)
+		vs[i] = makeDecodeValue(e, decodeValueValue)
 	}
 	return vs
 }
 func (v ArrayDecodeValue) JQValueEach() any {
 	props := make([]gojq.PathValue, len(v.Compound.Children))
 	for i, f := range v.Compound.Children {
-		props[i] = gojq.PathValue{Path: i, Value: makeDecodeValue(f)}
+		props[i] = gojq.PathValue{Path: i, Value: makeDecodeValue(f, decodeValueValue)}
 	}
 	return props
 }
@ -680,7 +691,7 @@ func (v ArrayDecodeValue) JQValueHas(key any) any {
 func (v ArrayDecodeValue) JQValueToGoJQ() any {
 	vs := make([]any, len(v.Compound.Children))
 	for i, f := range v.Compound.Children {
-		vs[i] = makeDecodeValue(f)
+		vs[i] = makeDecodeValue(f, decodeValueValue)
 	}
 	return vs
 }
@ -711,7 +722,7 @@ func (v StructDecodeValue) JQValueKey(name string) any {
 	}
 	if v.Compound.ByName != nil {
 		if f, ok := v.Compound.ByName[name]; ok {
-			return makeDecodeValue(f)
+			return makeDecodeValue(f, decodeValueValue)
 		}
 	}

@ -720,7 +731,7 @@ func (v StructDecodeValue) JQValueKey(name string) any {
 func (v StructDecodeValue) JQValueEach() any {
 	props := make([]gojq.PathValue, len(v.Compound.Children))
 	for i, f := range v.Compound.Children {
-		props[i] = gojq.PathValue{Path: f.Name, Value: makeDecodeValue(f)}
+		props[i] = gojq.PathValue{Path: f.Name, Value: makeDecodeValue(f, decodeValueValue)}
 	}
 	return props
 }
@ -752,7 +763,7 @@ func (v StructDecodeValue) JQValueHas(key any) any {
 func (v StructDecodeValue) JQValueToGoJQ() any {
 	vm := make(map[string]any, len(v.Compound.Children))
 	for _, f := range v.Compound.Children {
-		vm[f.Name] = makeDecodeValue(f)
+		vm[f.Name] = makeDecodeValue(f, decodeValueValue)
 	}
 	return vm
 }
--- a/pkg/interp/decode.jq
+++ b/pkg/interp/decode.jq
@ -56,8 +56,10 @@ def decode: decode(options.decode_format; {});
 def topath: _decode_value(._path);
 def tovalue($opts): _tovalue(options($opts));
 def tovalue: _tovalue(options({}));
-def toactual: _decode_value(._actual);
-def tosym: _decode_value(._sym);
+def toactual($opts): _decode_value(._actual) | tovalue($opts);
+def toactual: toactual({});
+def tosym($opts): _decode_value(._sym) | tovalue($opts);
+def tosym: tosym({});
 def todescription: _decode_value(._description);

 # TODO: rename?
--- a/pkg/interp/init.jq
+++ b/pkg/interp/init.jq
@ -135,6 +135,9 @@ def _cli_repl_error($_):
  _eval_error("compile"; "repl can only be used from interactive repl");
 def _cli_slurp_error(_):
  _eval_error("compile"; "slurp can only be used from interactive repl");
+# TODO: rewrite query to reuse _display_default_opts value? also _repl_display
+def _cli_display:
+  display(_display_default_opts);
 # _cli_eval halts on compile errors
 def _cli_eval($expr; $opts):
  eval(
@ -145,7 +148,7 @@ def _cli_eval($expr; $opts):
        repl: "_cli_repl_error",
        slurp: "_cli_slurp_error"
      },
-      catch_query: _query_func("_cli_eval_on_expr_error")
+      catch_query: _query_func("_cli_eval_on_expr_error"),
    };
    _cli_eval_on_error;
    _cli_eval_on_compile_error
@ -235,7 +238,6 @@ def _main:
          )
        else
          ( _cli_last_expr_error(null) as $_
-          | _display_default_opts as $default_opts
          | _cli_eval(
              $opts.expr;
              ( $eval_opts
@ -248,9 +250,11 @@ def _main:
                    else _query_func("inputs")
                    end
                  )
+              # call display in sub eval so it can be interrupted
+              # for repl case value will used as input to _repl instead
+              | .output_query = _query_func("_cli_display")
              )
            )
-          | display($default_opts)
          )
        end;
        # finally
--- a/pkg/interp/repl.jq
+++ b/pkg/interp/repl.jq
@ -227,7 +227,7 @@ def _repl_eval($expr; on_error; on_compile_error):
        },
      # input to repl is always array of values to iterate
      input_query: (_query_ident | _query_iter), # .[]
-      # each input should be evaluted separatel like with cli, so catch and just print errors
+      # each input should be evaluted separately like cli file args, so catch and just print errors
      catch_query: _query_func("_repl_on_expr_error"),
      # run display in sub eval so it can be interrupted
      output_query: _query_func("_repl_display")
--- a/pkg/interp/testdata/value_array.fqtest
+++ b/pkg/interp/testdata/value_array.fqtest
@ -1,5 +1,5 @@
 $ fq -i -d mp3 . test.mp3
-mp3> .headers | ., tovalue, type, length?
+mp3> .headers | ., tovalue, toactual, tosym, type, length?
    |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|.headers[0:1]:
    |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|
 0x00|49 44 33 04 00 00 00 00 00 23 54 53 53 45 00 00|ID3......#TSSE..|  [0]{}: header (id3v2)
@ -40,6 +40,8 @@ mp3> .headers | ., tovalue, type, length?
    "version": 4
  }
 ]
+null
+null
 "array"
 1
 mp3> .headers[0] | ., type, length?
@ -149,6 +151,10 @@ mp3> .headers._name | ., type, length?
 "headers"
 "string"
 7
+mp3> .headers._actual | ., type, length?
+null
+"null"
+0
 mp3> .headers._sym | ., type, length?
 null
 "null"
@ -169,14 +175,12 @@ mp3> .headers._bits | ., type, length?
 *   |until 0x2c.7 (45)                              |                |
 "string"
 360
-mp3> 
 mp3> .headers._bytes | ., type, length?
    |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|
 0x00|49 44 33 04 00 00 00 00 00 23 54 53 53 45 00 00|ID3......#TSSE..|.: raw bits 0x0-0x2c.7 (45)
 *   |until 0x2c.7 (45)                              |                |
 "string"
 45
-mp3> 
 mp3> .headers._error | ., type, length?
 null
 "null"
--- a/pkg/interp/testdata/value_boolean.fqtest
+++ b/pkg/interp/testdata/value_boolean.fqtest
@ -1,8 +1,10 @@
 $ fq -i -d mp3 . test.mp3
-mp3> .headers[0].flags.unsynchronisation | ., tovalue, type, length?
+mp3> .headers[0].flags.unsynchronisation | ., tovalue, toactual, tosym, type, length?
   |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|
 0x0|               00                              |     .          |.headers[0].flags.unsynchronisation: false
 false
+false
+null
 "boolean"
 mp3> .headers[0].flags.unsynchronisation[0] | ., type, length?
 error: expected an array but got: boolean
@ -52,8 +54,13 @@ mp3> .headers[0].flags.unsynchronisation._name | ., type, length?
 "unsynchronisation"
 "string"
 17
+mp3> .headers[0].flags.unsynchronisation._actual | ., type, length?
+   |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|
+0x0|               00                              |     .          |.headers[0].flags.unsynchronisation: false
+"boolean"
 mp3> .headers[0].flags.unsynchronisation._sym | ., type, length?
-null
+   |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|
+0x0|               00                              |     .          |.headers[0].flags.unsynchronisation: false
 "null"
 0
 mp3> .headers[0].flags.unsynchronisation._description | ., type, length?
@ -74,13 +81,11 @@ mp3> .headers[0].flags.unsynchronisation._bits | ., type, length?
 0x0|               00                              |     .          |.: raw bits 0x5-0x5 (0.1)
 "string"
 1
-mp3> 
 mp3> .headers[0].flags.unsynchronisation._bytes | ., type, length?
   |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|
 0x0|               00                              |     .          |.: raw bits 0x5-0x5 (0.1)
 "string"
 0
-mp3> 
 mp3> .headers[0].flags.unsynchronisation._error | ., type, length?
 null
 "null"
--- a/pkg/interp/testdata/value_json_array.fqtest
+++ b/pkg/interp/testdata/value_json_array.fqtest
@ -1,7 +1,9 @@
 $ fq -i -n '"[]" | json'
-json> (.) | ., tovalue, type, length?
+json> (.) | ., tovalue, toactual, tosym, type, length?
 []
 []
+[]
+null
 "array"
 0
 json> (.)[0] | ., type, length?
@ -65,6 +67,10 @@ json> (.)._name | ., type, length?
 ""
 "string"
 0
+json> (.)._actual | ., type, length?
+[]
+"array"
+0
 json> (.)._sym | ., type, length?
 null
 "null"
@ -82,13 +88,11 @@ json> (.)._bits | ., type, length?
 0x0|5b 5d|                                         |[]|             |.: raw bits 0x0-0x1.7 (2)
 "string"
 16
-json> 
 json> (.)._bytes | ., type, length?
   |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|
 0x0|5b 5d|                                         |[]|             |.: raw bits 0x0-0x1.7 (2)
 "string"
 2
-json> 
 json> (.)._error | ., type, length?
 null
 "null"
--- a/pkg/interp/testdata/value_json_object.fqtest
+++ b/pkg/interp/testdata/value_json_object.fqtest
@ -1,7 +1,9 @@
 $ fq -i -n '"{}" | json'
-json> (.) | ., tovalue, type, length?
+json> (.) | ., tovalue, toactual, tosym, type, length?
 {}
 {}
+{}
+null
 "object"
 0
 json> (.)[0] | ., type, length?
@ -55,6 +57,10 @@ json> (.)._name | ., type, length?
 ""
 "string"
 0
+json> (.)._actual | ., type, length?
+{}
+"object"
+0
 json> (.)._sym | ., type, length?
 null
 "null"
@ -72,13 +78,11 @@ json> (.)._bits | ., type, length?
 0x0|7b 7d|                                         |{}|             |.: raw bits 0x0-0x1.7 (2)
 "string"
 16
-json> 
 json> (.)._bytes | ., type, length?
   |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|
 0x0|7b 7d|                                         |{}|             |.: raw bits 0x0-0x1.7 (2)
 "string"
 2
-json> 
 json> (.)._error | ., type, length?
 null
 "null"
--- a/pkg/interp/testdata/value_null.fqtest
+++ b/pkg/interp/testdata/value_null.fqtest
@ -1,8 +1,10 @@
 $ fq -i -d mp3 . test.mp3
-mp3> .headers[0].padding | ., tovalue, type, length?
+mp3> .headers[0].padding | ., tovalue, toactual, tosym, type, length?
    |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|
 0x20|         00 00 00 00 00 00 00 00 00 00         |   ..........   |.headers[0].padding: raw bits (all zero)
 "<10>AAAAAAAAAAAAAA=="
+"<10>AAAAAAAAAAAAAA=="
+null
 "string"
 10
 mp3> .headers[0].padding[0] | ., type, length?
@ -65,8 +67,14 @@ mp3> .headers[0].padding._name | ., type, length?
 "padding"
 "string"
 7
+mp3> .headers[0].padding._actual | ., type, length?
+    |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|
+0x20|         00 00 00 00 00 00 00 00 00 00         |   ..........   |.headers[0].padding: raw bits (all zero)
+"string"
+10
 mp3> .headers[0].padding._sym | ., type, length?
-null
+    |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|
+0x20|         00 00 00 00 00 00 00 00 00 00         |   ..........   |.headers[0].padding: raw bits (all zero)
 "null"
 0
 mp3> .headers[0].padding._description | ., type, length?
@ -86,13 +94,11 @@ mp3> .headers[0].padding._bits | ., type, length?
 0x20|         00 00 00 00 00 00 00 00 00 00         |   ..........   |.: raw bits 0x23-0x2c.7 (10)
 "string"
 80
-mp3> 
 mp3> .headers[0].padding._bytes | ., type, length?
    |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|
 0x20|         00 00 00 00 00 00 00 00 00 00         |   ..........   |.: raw bits 0x23-0x2c.7 (10)
 "string"
 10
-mp3> 
 mp3> .headers[0].padding._error | ., type, length?
 null
 "null"
--- a/pkg/interp/testdata/value_number.fqtest
+++ b/pkg/interp/testdata/value_number.fqtest
@ -1,8 +1,10 @@
 $ fq -i -d mp3 . test.mp3
-mp3> .headers[0].version | ., tovalue, type, length?
+mp3> .headers[0].version | ., tovalue, toactual, tosym, type, length?
   |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|
 0x0|         04                                    |   .            |.headers[0].version: 4
 4
+4
+null
 "number"
 4
 mp3> .headers[0].version[0] | ., type, length?
@ -53,8 +55,14 @@ mp3> .headers[0].version._name | ., type, length?
 "version"
 "string"
 7
+mp3> .headers[0].version._actual | ., type, length?
+   |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|
+0x0|         04                                    |   .            |.headers[0].version: 4
+"number"
+4
 mp3> .headers[0].version._sym | ., type, length?
-null
+   |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|
+0x0|         04                                    |   .            |.headers[0].version: 4
 "null"
 0
 mp3> .headers[0].version._description | ., type, length?
@ -74,13 +82,11 @@ mp3> .headers[0].version._bits | ., type, length?
 0x0|         04                                    |   .            |.: raw bits 0x3-0x3.7 (1)
 "string"
 8
-mp3> 
 mp3> .headers[0].version._bytes | ., type, length?
   |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|
 0x0|         04                                    |   .            |.: raw bits 0x3-0x3.7 (1)
 "string"
 1
-mp3> 
 mp3> .headers[0].version._error | ., type, length?
 null
 "null"
--- a/pkg/interp/testdata/value_object.fqtest
+++ b/pkg/interp/testdata/value_object.fqtest
@ -1,5 +1,5 @@
 $ fq -i -d mp3 . test.mp3
-mp3> .headers[0].flags | ., tovalue, type, length?
+mp3> .headers[0].flags | ., tovalue, toactual, tosym, type, length?
   |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|.headers[0].flags{}:
 0x0|               00                              |     .          |  unsynchronisation: false
 0x0|               00                              |     .          |  extended_header: false
@ -11,6 +11,8 @@ mp3> .headers[0].flags | ., tovalue, type, length?
  "unsynchronisation": false,
  "unused": 0
 }
+null
+null
 "object"
 4
 mp3> .headers[0].flags[0] | ., type, length?
@ -69,6 +71,10 @@ mp3> .headers[0].flags._name | ., type, length?
 "flags"
 "string"
 5
+mp3> .headers[0].flags._actual | ., type, length?
+null
+"null"
+0
 mp3> .headers[0].flags._sym | ., type, length?
 null
 "null"
@ -90,13 +96,11 @@ mp3> .headers[0].flags._bits | ., type, length?
 0x0|               00                              |     .          |.: raw bits 0x5-0x5.7 (1)
 "string"
 8
-mp3> 
 mp3> .headers[0].flags._bytes | ., type, length?
   |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|
 0x0|               00                              |     .          |.: raw bits 0x5-0x5.7 (1)
 "string"
 1
-mp3> 
 mp3> .headers[0].flags._error | ., type, length?
 null
 "null"
--- a/pkg/interp/testdata/value_string.fqtest
+++ b/pkg/interp/testdata/value_string.fqtest
@ -1,8 +1,10 @@
 $ fq -i -d mp3 . test.mp3
-mp3> .headers[0].magic | ., tovalue, type, length?
+mp3> .headers[0].magic | ., tovalue, toactual, tosym, type, length?
   |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|
 0x0|49 44 33                                       |ID3             |.headers[0].magic: "ID3" (valid)
 "ID3"
+"ID3"
+null
 "string"
 3
 mp3> .headers[0].magic[0] | ., type, length?
@ -65,8 +67,14 @@ mp3> .headers[0].magic._name | ., type, length?
 "magic"
 "string"
 5
+mp3> .headers[0].magic._actual | ., type, length?
+   |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|
+0x0|49 44 33                                       |ID3             |.headers[0].magic: "ID3" (valid)
+"string"
+3
 mp3> .headers[0].magic._sym | ., type, length?
-null
+   |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|
+0x0|49 44 33                                       |ID3             |.headers[0].magic: "ID3" (valid)
 "null"
 0
 mp3> .headers[0].magic._description | ., type, length?
@ -86,13 +94,11 @@ mp3> .headers[0].magic._bits | ., type, length?
 0x0|49 44 33                                       |ID3             |.: raw bits 0x0-0x2.7 (3)
 "string"
 24
-mp3> 
 mp3> .headers[0].magic._bytes | ., type, length?
   |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|0123456789abcdef|
 0x0|49 44 33                                       |ID3             |.: raw bits 0x0-0x2.7 (3)
 "string"
 3
-mp3> 
 mp3> .headers[0].magic._error | ., type, length?
 null
 "null"
--- a/pkg/interp/testdata/value_t.fqtest.tmpl
+++ b/pkg/interp/testdata/value_t.fqtest.tmpl
@ -1,6 +1,5 @@
-/test.mp3:
 $ CMD
-PROMPT> EXPR | ., tovalue, type, length?
+PROMPT> EXPR | ., tovalue, toactual, tosym, type, length?
 PROMPT> EXPR[0] | ., type, length?
 PROMPT> EXPR[-1000] | ., type, length?
 PROMPT> EXPR[1000] | ., type, length?
@ -21,7 +20,8 @@ PROMPT> EXPR._start | ., type, length?
 PROMPT> EXPR._stop | ., type, length?
 PROMPT> EXPR._len | ., type, length?
 PROMPT> EXPR._name | ., type, length?
-PROMPT> EXPR._symbol | ., type, length?
+PROMPT> EXPR._actual | ., type, length?
+PROMPT> EXPR._sym | ., type, length?
 PROMPT> EXPR._description | ., type, length?
 PROMPT> EXPR._path | ., type, length?
 PROMPT> EXPR._bits | ., type, length?
--- a/pkg/interp/testdata/value_t.fqtest.tmpl.sh
+++ b/pkg/interp/testdata/value_t.fqtest.tmpl.sh
@ -1,10 +1,10 @@
 #!/bin/sh
-sed 's/CMD/fq -i -d mp3 . \/test.mp3/g' <value_t.fqtest.tmpl | sed 's/EXPR/.headers/g' | sed 's/PROMPT/mp3/g' >value_array.fqtest
-sed 's/CMD/fq -i -d mp3 . \/test.mp3/g' <value_t.fqtest.tmpl | sed 's/EXPR/.headers[0].flags.unsynchronisation/g' | sed 's/PROMPT/mp3/g' >value_boolean.fqtest
-sed 's/CMD/fq -i -d mp3 . \/test.mp3/g' <value_t.fqtest.tmpl | sed 's/EXPR/.headers[0].padding/g' | sed 's/PROMPT/mp3/g' >value_null.fqtest
-sed 's/CMD/fq -i -d mp3 . \/test.mp3/g' <value_t.fqtest.tmpl | sed 's/EXPR/.headers[0].version/g' | sed 's/PROMPT/mp3/g' >value_number.fqtest
-sed 's/CMD/fq -i -d mp3 . \/test.mp3/g' <value_t.fqtest.tmpl | sed 's/EXPR/.headers[0].flags/g' | sed 's/PROMPT/mp3/g' >value_object.fqtest
-sed 's/CMD/fq -i -d mp3 . \/test.mp3/g' <value_t.fqtest.tmpl | sed 's/EXPR/.headers[0].magic/g' | sed 's/PROMPT/mp3/g' >value_string.fqtest
+sed 's/CMD/fq -i -d mp3 . test.mp3/g' <value_t.fqtest.tmpl | sed 's/EXPR/.headers/g' | sed 's/PROMPT/mp3/g' >value_array.fqtest
+sed 's/CMD/fq -i -d mp3 . test.mp3/g' <value_t.fqtest.tmpl | sed 's/EXPR/.headers[0].flags.unsynchronisation/g' | sed 's/PROMPT/mp3/g' >value_boolean.fqtest
+sed 's/CMD/fq -i -d mp3 . test.mp3/g' <value_t.fqtest.tmpl | sed 's/EXPR/.headers[0].padding/g' | sed 's/PROMPT/mp3/g' >value_null.fqtest
+sed 's/CMD/fq -i -d mp3 . test.mp3/g' <value_t.fqtest.tmpl | sed 's/EXPR/.headers[0].version/g' | sed 's/PROMPT/mp3/g' >value_number.fqtest
+sed 's/CMD/fq -i -d mp3 . test.mp3/g' <value_t.fqtest.tmpl | sed 's/EXPR/.headers[0].flags/g' | sed 's/PROMPT/mp3/g' >value_object.fqtest
+sed 's/CMD/fq -i -d mp3 . test.mp3/g' <value_t.fqtest.tmpl | sed 's/EXPR/.headers[0].magic/g' | sed 's/PROMPT/mp3/g' >value_string.fqtest

 sed "s/CMD/fq -i -n '\"[]\" | json'/g" <value_t.fqtest.tmpl | sed 's/EXPR/(.)/g' | sed 's/PROMPT/json/g' >value_json_array.fqtest
 sed "s/CMD/fq -i -n '\"{}\" | json'/g" <value_t.fqtest.tmpl | sed 's/EXPR/(.)/g' | sed 's/PROMPT/json/g' >value_json_object.fqtest
--- a/pkg/ranges/ranges.go
+++ b/pkg/ranges/ranges.go
@ -73,6 +73,14 @@ func Gaps(total Range, ranges []Range) []Range {
 	for i := 0; i < len(ranges); {
 		madded = false
 		m = ranges[i]
+
+		// skip empty ranges
+		if m.Len == 0 {
+			i++
+			madded = true
+			continue
+		}
+
 		j := i + 1
 		for ; j < len(ranges); j++ {
 			if m.Start <= ranges[j].Start && m.Stop()+1 >= ranges[j].Start {
@ -91,10 +99,15 @@ func Gaps(total Range, ranges []Range) []Range {
 			break
 		}
 	}
+
 	if !madded {
 		merged = append(merged, m)
 	}

+	if len(merged) == 0 {
+		return []Range{total}
+	}
+
 	gaps := make([]Range, 0, len(merged))
 	if merged[0].Start != total.Start {
 		gaps = append(gaps, Range{Start: 0, Len: merged[0].Start})
--- a/pkg/ranges/ranges_test.go
+++ b/pkg/ranges/ranges_test.go
@ -27,6 +27,13 @@ func TestRangeGaps(t *testing.T) {
 		{"0:10", "1:1 2:5 8:1", "0:1 9:1"},
 		{"0:10", "1:1 2:8 8:2", "0:1"},
 		{"0:10", "0:4 2:8 8:2", ""},
+
+		// handle empty ranges
+		{"0:12", "4:4 8:0", "0:4 8:4"},
+		{"0:12", "0:0 4:4", "0:4 8:4"},
+		{"0:12", "0:0 4:4 8:0", "0:4 8:4"},
+		{"0:12", "0:0 0:0 4:4 8:0 8:0", "0:4 8:4"},
+		{"0:12", "8:0", "0:12"},
 	}
 	for _, tC := range testCases {
 		t.Run(fmt.Sprintf("%v_%v_%v", tC.total, tC.ranges, tC.expected), func(t *testing.T) {
--- a/pkg/scalar/scalar.go
+++ b/pkg/scalar/scalar.go
@ -14,6 +14,7 @@ import (

 	"github.com/wader/fq/internal/bitioex"
 	"github.com/wader/fq/pkg/bitio"
+	"golang.org/x/exp/constraints"
 )

 //go:generate sh -c "cat scalar_gen.go.tmpl | go run ../../dev/tmpl.go ../decode/types.json | gofmt > scalar_gen.go"
@ -246,40 +247,48 @@ func (m BytesToScalar) MapScalar(s S) (S, error) {
 	return s, nil
 }

-// TODO: nicer api, use generics
+// TODO: nicer api, use generic, many generic Try function somehow?
+
+func mapFn[T any](tryVFn func(S) (T, bool), vFn func(S) T, fn func(s S, v T) S) Mapper {
+	return Fn(func(s S) (S, error) {
+		var v T
+		var ok bool
+		if tryVFn != nil {
+			v, ok = tryVFn(s)
+			if !ok {
+				return s, nil
+			}
+		} else {
+			v = vFn(s)
+		}
+		return fn(s, v), nil
+	})
+}
+
+func TryMapFn[T any](epoch time.Time, format string, vFn func(S) (T, bool), fn func(s S, v T) S) Mapper {
+	return mapFn(vFn, nil, fn)
+}
+
+func MapFn[T any](epoch time.Time, format string, vFn func(S) T, fn func(s S, v T) S) Mapper {
+	return mapFn(nil, vFn, fn)
+}

 var unixTimeEpochDate = time.Date(1970, time.January, 1, 0, 0, 0, 0, time.UTC)

-func DescriptionActualUTime(epoch time.Time, format string) Mapper {
-	return Fn(func(s S) (S, error) {
-		s.Description = epoch.Add(time.Second * time.Duration(s.ActualU())).Format(format)
-		return s, nil
+func DescriptionFn[T any](vFn func(S) (T, bool), fn func(v T) string) Mapper {
+	return mapFn(vFn, nil, func(s S, v T) S {
+		s.Description = fn(v)
+		return s
 	})
 }

-func DescriptionSymUTime(epoch time.Time, format string) Mapper {
-	return Fn(func(s S) (S, error) {
-		s.Description = epoch.Add(time.Second * time.Duration(s.SymU())).Format(format)
-		return s, nil
+// TODO: scalar types constraints
+func DescriptionTimeFn[T constraints.Integer | constraints.Float](vFn func(S) (T, bool), epoch time.Time, format string) Mapper {
+	return DescriptionFn(vFn, func(v T) string {
+		return epoch.Add(time.Duration(v) * time.Second).Format(format)
 	})
 }

-var DescriptionActualUUnixTime = DescriptionActualUTime(unixTimeEpochDate, time.RFC3339)
-var DescriptionSymUUnixTime = DescriptionSymUTime(unixTimeEpochDate, time.RFC3339)
-
-func DescriptionActualSTime(epoch time.Time, format string) Mapper {
-	return Fn(func(s S) (S, error) {
-		s.Description = epoch.Add(time.Second * time.Duration(s.ActualS())).Format(format)
-		return s, nil
-	})
+func DescriptionUnixTimeFn[T constraints.Integer | constraints.Float](vFn func(S) (T, bool), format string) Mapper {
+	return DescriptionTimeFn(vFn, unixTimeEpochDate, format)
 }
-
-func DescriptionSymSTime(epoch time.Time, format string) Mapper {
-	return Fn(func(s S) (S, error) {
-		s.Description = epoch.Add(time.Second * time.Duration(s.SymS())).Format(format)
-		return s, nil
-	})
-}
-
-var DescriptionActualSUnixTime = DescriptionActualSTime(unixTimeEpochDate, time.RFC3339)
-var DescriptionSymSUnixTime = DescriptionSymSTime(unixTimeEpochDate, time.RFC3339)
--- a/pkg/scalar/scalar_gen.go
+++ b/pkg/scalar/scalar_gen.go
@ -10,11 +10,17 @@ import (

 // Type BigInt

+// TryActualBigInt try assert actual value is a BigInt and return result
+func (s S) TryActualBigInt() (*big.Int, bool) {
+	v, ok := s.Actual.(*big.Int)
+	return v, ok
+}
+
 // ActualBigInt asserts actual value is a BigInt and returns it
 func (s S) ActualBigInt() *big.Int {
-	v, ok := s.Actual.(*big.Int)
+	v, ok := s.TryActualBigInt()
 	if !ok {
-		panic(fmt.Sprintf("failed to type assert s.Actual %v as *big.Int", s.Actual))
+		panic(fmt.Sprintf("failed to type assert s.Actual %v (%T) as *big.Int", s.Actual, s.Actual))
 	}
 	return v
 }
@ -29,13 +35,19 @@ func (fn ActualBigIntFn) MapScalar(s S) (S, error) {

 // SymBigInt asserts symbolic value is a BigInt and returns it
 func (s S) SymBigInt() *big.Int {
-	v, ok := s.Sym.(*big.Int)
+	v, ok := s.TrySymBigInt()
 	if !ok {
-		panic(fmt.Sprintf("failed to type assert s.Sym %v as *big.Int", s.Sym))
+		panic(fmt.Sprintf("failed to type assert s.Sym %v (%T) as *big.Int", s.Sym, s.Sym))
 	}
 	return v
 }

+// TrySymBigInt try assert symbolic value is a BigInt and return result
+func (s S) TrySymBigInt() (*big.Int, bool) {
+	v, ok := s.Sym.(*big.Int)
+	return v, ok
+}
+
 // SymBigIntFn map sym BigInt using f
 type SymBigIntFn func(a *big.Int) *big.Int

@ -46,11 +58,17 @@ func (f SymBigIntFn) MapScalar(s S) (S, error) {

 // Type BitBuf

+// TryActualBitBuf try assert actual value is a BitBuf and return result
+func (s S) TryActualBitBuf() (bitio.ReaderAtSeeker, bool) {
+	v, ok := s.Actual.(bitio.ReaderAtSeeker)
+	return v, ok
+}
+
 // ActualBitBuf asserts actual value is a BitBuf and returns it
 func (s S) ActualBitBuf() bitio.ReaderAtSeeker {
-	v, ok := s.Actual.(bitio.ReaderAtSeeker)
+	v, ok := s.TryActualBitBuf()
 	if !ok {
-		panic(fmt.Sprintf("failed to type assert s.Actual %v as bitio.ReaderAtSeeker", s.Actual))
+		panic(fmt.Sprintf("failed to type assert s.Actual %v (%T) as bitio.ReaderAtSeeker", s.Actual, s.Actual))
 	}
 	return v
 }
@ -65,13 +83,19 @@ func (fn ActualBitBufFn) MapScalar(s S) (S, error) {

 // SymBitBuf asserts symbolic value is a BitBuf and returns it
 func (s S) SymBitBuf() bitio.ReaderAtSeeker {
-	v, ok := s.Sym.(bitio.ReaderAtSeeker)
+	v, ok := s.TrySymBitBuf()
 	if !ok {
-		panic(fmt.Sprintf("failed to type assert s.Sym %v as bitio.ReaderAtSeeker", s.Sym))
+		panic(fmt.Sprintf("failed to type assert s.Sym %v (%T) as bitio.ReaderAtSeeker", s.Sym, s.Sym))
 	}
 	return v
 }

+// TrySymBitBuf try assert symbolic value is a BitBuf and return result
+func (s S) TrySymBitBuf() (bitio.ReaderAtSeeker, bool) {
+	v, ok := s.Sym.(bitio.ReaderAtSeeker)
+	return v, ok
+}
+
 // SymBitBufFn map sym BitBuf using f
 type SymBitBufFn func(a bitio.ReaderAtSeeker) bitio.ReaderAtSeeker

@ -82,11 +106,17 @@ func (f SymBitBufFn) MapScalar(s S) (S, error) {

 // Type Bool

+// TryActualBool try assert actual value is a Bool and return result
+func (s S) TryActualBool() (bool, bool) {
+	v, ok := s.Actual.(bool)
+	return v, ok
+}
+
 // ActualBool asserts actual value is a Bool and returns it
 func (s S) ActualBool() bool {
-	v, ok := s.Actual.(bool)
+	v, ok := s.TryActualBool()
 	if !ok {
-		panic(fmt.Sprintf("failed to type assert s.Actual %v as bool", s.Actual))
+		panic(fmt.Sprintf("failed to type assert s.Actual %v (%T) as bool", s.Actual, s.Actual))
 	}
 	return v
 }
@ -101,13 +131,19 @@ func (fn ActualBoolFn) MapScalar(s S) (S, error) {

 // SymBool asserts symbolic value is a Bool and returns it
 func (s S) SymBool() bool {
-	v, ok := s.Sym.(bool)
+	v, ok := s.TrySymBool()
 	if !ok {
-		panic(fmt.Sprintf("failed to type assert s.Sym %v as bool", s.Sym))
+		panic(fmt.Sprintf("failed to type assert s.Sym %v (%T) as bool", s.Sym, s.Sym))
 	}
 	return v
 }

+// TrySymBool try assert symbolic value is a Bool and return result
+func (s S) TrySymBool() (bool, bool) {
+	v, ok := s.Sym.(bool)
+	return v, ok
+}
+
 // SymBoolFn map sym Bool using f
 type SymBoolFn func(a bool) bool

@ -118,11 +154,17 @@ func (f SymBoolFn) MapScalar(s S) (S, error) {

 // Type F

+// TryActualF try assert actual value is a F and return result
+func (s S) TryActualF() (float64, bool) {
+	v, ok := s.Actual.(float64)
+	return v, ok
+}
+
 // ActualF asserts actual value is a F and returns it
 func (s S) ActualF() float64 {
-	v, ok := s.Actual.(float64)
+	v, ok := s.TryActualF()
 	if !ok {
-		panic(fmt.Sprintf("failed to type assert s.Actual %v as float64", s.Actual))
+		panic(fmt.Sprintf("failed to type assert s.Actual %v (%T) as float64", s.Actual, s.Actual))
 	}
 	return v
 }
@ -137,13 +179,19 @@ func (fn ActualFFn) MapScalar(s S) (S, error) {

 // SymF asserts symbolic value is a F and returns it
 func (s S) SymF() float64 {
-	v, ok := s.Sym.(float64)
+	v, ok := s.TrySymF()
 	if !ok {
-		panic(fmt.Sprintf("failed to type assert s.Sym %v as float64", s.Sym))
+		panic(fmt.Sprintf("failed to type assert s.Sym %v (%T) as float64", s.Sym, s.Sym))
 	}
 	return v
 }

+// TrySymF try assert symbolic value is a F and return result
+func (s S) TrySymF() (float64, bool) {
+	v, ok := s.Sym.(float64)
+	return v, ok
+}
+
 // SymFFn map sym F using f
 type SymFFn func(a float64) float64

@ -154,11 +202,17 @@ func (f SymFFn) MapScalar(s S) (S, error) {

 // Type S

+// TryActualS try assert actual value is a S and return result
+func (s S) TryActualS() (int64, bool) {
+	v, ok := s.Actual.(int64)
+	return v, ok
+}
+
 // ActualS asserts actual value is a S and returns it
 func (s S) ActualS() int64 {
-	v, ok := s.Actual.(int64)
+	v, ok := s.TryActualS()
 	if !ok {
-		panic(fmt.Sprintf("failed to type assert s.Actual %v as int64", s.Actual))
+		panic(fmt.Sprintf("failed to type assert s.Actual %v (%T) as int64", s.Actual, s.Actual))
 	}
 	return v
 }
@ -173,13 +227,19 @@ func (fn ActualSFn) MapScalar(s S) (S, error) {

 // SymS asserts symbolic value is a S and returns it
 func (s S) SymS() int64 {
-	v, ok := s.Sym.(int64)
+	v, ok := s.TrySymS()
 	if !ok {
-		panic(fmt.Sprintf("failed to type assert s.Sym %v as int64", s.Sym))
+		panic(fmt.Sprintf("failed to type assert s.Sym %v (%T) as int64", s.Sym, s.Sym))
 	}
 	return v
 }

+// TrySymS try assert symbolic value is a S and return result
+func (s S) TrySymS() (int64, bool) {
+	v, ok := s.Sym.(int64)
+	return v, ok
+}
+
 // SymSFn map sym S using f
 type SymSFn func(a int64) int64

@ -190,11 +250,17 @@ func (f SymSFn) MapScalar(s S) (S, error) {

 // Type Str

+// TryActualStr try assert actual value is a Str and return result
+func (s S) TryActualStr() (string, bool) {
+	v, ok := s.Actual.(string)
+	return v, ok
+}
+
 // ActualStr asserts actual value is a Str and returns it
 func (s S) ActualStr() string {
-	v, ok := s.Actual.(string)
+	v, ok := s.TryActualStr()
 	if !ok {
-		panic(fmt.Sprintf("failed to type assert s.Actual %v as string", s.Actual))
+		panic(fmt.Sprintf("failed to type assert s.Actual %v (%T) as string", s.Actual, s.Actual))
 	}
 	return v
 }
@ -209,13 +275,19 @@ func (fn ActualStrFn) MapScalar(s S) (S, error) {

 // SymStr asserts symbolic value is a Str and returns it
 func (s S) SymStr() string {
-	v, ok := s.Sym.(string)
+	v, ok := s.TrySymStr()
 	if !ok {
-		panic(fmt.Sprintf("failed to type assert s.Sym %v as string", s.Sym))
+		panic(fmt.Sprintf("failed to type assert s.Sym %v (%T) as string", s.Sym, s.Sym))
 	}
 	return v
 }

+// TrySymStr try assert symbolic value is a Str and return result
+func (s S) TrySymStr() (string, bool) {
+	v, ok := s.Sym.(string)
+	return v, ok
+}
+
 // SymStrFn map sym Str using f
 type SymStrFn func(a string) string

@ -226,11 +298,17 @@ func (f SymStrFn) MapScalar(s S) (S, error) {

 // Type U

+// TryActualU try assert actual value is a U and return result
+func (s S) TryActualU() (uint64, bool) {
+	v, ok := s.Actual.(uint64)
+	return v, ok
+}
+
 // ActualU asserts actual value is a U and returns it
 func (s S) ActualU() uint64 {
-	v, ok := s.Actual.(uint64)
+	v, ok := s.TryActualU()
 	if !ok {
-		panic(fmt.Sprintf("failed to type assert s.Actual %v as uint64", s.Actual))
+		panic(fmt.Sprintf("failed to type assert s.Actual %v (%T) as uint64", s.Actual, s.Actual))
 	}
 	return v
 }
@ -245,13 +323,19 @@ func (fn ActualUFn) MapScalar(s S) (S, error) {

 // SymU asserts symbolic value is a U and returns it
 func (s S) SymU() uint64 {
-	v, ok := s.Sym.(uint64)
+	v, ok := s.TrySymU()
 	if !ok {
-		panic(fmt.Sprintf("failed to type assert s.Sym %v as uint64", s.Sym))
+		panic(fmt.Sprintf("failed to type assert s.Sym %v (%T) as uint64", s.Sym, s.Sym))
 	}
 	return v
 }

+// TrySymU try assert symbolic value is a U and return result
+func (s S) TrySymU() (uint64, bool) {
+	v, ok := s.Sym.(uint64)
+	return v, ok
+}
+
 // SymUFn map sym U using f
 type SymUFn func(a uint64) uint64

--- a/pkg/scalar/scalar_gen.go.tmpl
+++ b/pkg/scalar/scalar_gen.go.tmpl
@ -11,11 +11,17 @@ import (
 {{- range $name, $t := $.types }}
 	// Type {{$name}}

+	// TryActual{{$name}} try assert actual value is a {{$name}} and return result
+	func (s S) TryActual{{$name}}() ({{$t.go_type}}, bool) {
+		v, ok := s.Actual.({{$t.go_type}})
+		return v, ok
+	}
+
 	// Actual{{$name}} asserts actual value is a {{$name}} and returns it
 	func (s S) Actual{{$name}}() {{$t.go_type}} {
-		v, ok := s.Actual.({{$t.go_type}})
+		v, ok := s.TryActual{{$name}}()
 		if !ok {
-			panic(fmt.Sprintf("failed to type assert s.Actual %v as {{$t.go_type}}", s.Actual))
+			panic(fmt.Sprintf("failed to type assert s.Actual %v (%T) as {{$t.go_type}}", s.Actual, s.Actual))
 		}
 		return v
 	}
@ -30,13 +36,19 @@ import (

 	// Sym{{$name}} asserts symbolic value is a {{$name}} and returns it
 	func (s S) Sym{{$name}}() {{$t.go_type}} {
-		v, ok := s.Sym.({{$t.go_type}})
+		v, ok := s.TrySym{{$name}}()
 		if !ok {
-			panic(fmt.Sprintf("failed to type assert s.Sym %v as {{$t.go_type}}", s.Sym))
+			panic(fmt.Sprintf("failed to type assert s.Sym %v (%T) as {{$t.go_type}}", s.Sym, s.Sym))
 		}
 		return v
 	}

+	// TrySym{{$name}} try assert symbolic value is a {{$name}} and return result
+	func (s S) TrySym{{$name}}() ({{$t.go_type}}, bool) {
+		v, ok := s.Sym.({{$t.go_type}})
+		return v, ok
+	}
+
 	// Sym{{$name}}Fn map sym {{$name}} using f
 	type Sym{{$name}}Fn func(a {{$t.go_type}}) {{$t.go_type}}