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mirror of https://github.com/wader/fq.git synced 2024-12-23 05:13:30 +03:00
fq/format/ape/apev2.go
Mattias Wadman 8e0dde03d0 decode: Support multiple format args and some rename and refactor
This will allow passing both cli options and format options to sub decoder.
Ex: pass keylog option to a tls decoder when decoding a pcap.
Ex: pass decode options to a format inside a http body inside a pcap.

Add ArgAs method to lookup argument based on type. This also makes the format
decode function have same signature as sub decoders in the decode API.

This change decode.Format a bit:
DecodeFn is now just func(d *D) any
DecodeInArg renamed to DefaultInArg
2023-02-18 21:38:51 +01:00

76 lines
1.8 KiB
Go

package ape
// http://wiki.hydrogenaud.io/index.php?title=APE_Tags_Header
import (
"github.com/wader/fq/format"
"github.com/wader/fq/pkg/decode"
"github.com/wader/fq/pkg/interp"
)
var imageFormat decode.Group
func init() {
interp.RegisterFormat(decode.Format{
Name: format.APEV2,
Description: "APEv2 metadata tag",
DecodeFn: apev2Decode,
Dependencies: []decode.Dependency{
{Names: []string{format.IMAGE}, Group: &imageFormat},
},
})
}
func apev2Decode(d *decode.D) any {
d.Endian = decode.LittleEndian
headerFooterFn := func(d *decode.D, name string) uint64 {
var tagCount uint64
d.FieldStruct(name, func(d *decode.D) {
d.FieldUTF8("preamble", 8, d.StrAssert("APETAGEX"))
d.FieldU32("version")
d.FieldU32("tag_size")
tagCount = d.FieldU32("item_count")
d.FieldU32("flags")
d.FieldRawLen("reserved", 64, d.BitBufIsZero())
})
return tagCount
}
tagCount := headerFooterFn(d, "header")
if tagCount > 1000 {
d.Fatalf("too many tags %d", tagCount)
}
d.FieldArray("tags", func(d *decode.D) {
for i := uint64(0); i < tagCount; i++ {
d.FieldStruct("tag", func(d *decode.D) {
itemSize := d.FieldU32("item_size")
var binaryItem bool
d.FieldStruct("item_flags", func(d *decode.D) {
d.FieldU6("unused0")
binaryItem = d.FieldBool("binary")
d.FieldU25("unused1")
})
keyLen := d.PeekFindByte(0, -1)
d.FieldUTF8("key", int(keyLen))
d.FieldU8("key_terminator")
if binaryItem {
d.FramedFn(int64(itemSize)*8, func(d *decode.D) {
d.FieldUTF8Null("filename")
// assume image if binary
d.FieldFormatOrRaw("value", imageFormat, nil)
})
} else {
d.FieldUTF8("value", int(itemSize))
}
})
}
})
// TODO: check footer flag
headerFooterFn(d, "footer")
return nil
}