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126 lines
2.9 KiB
Go
126 lines
2.9 KiB
Go
package gz
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// https://tools.ietf.org/html/rfc1952
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// TODO: test name, comment etc
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// TODO: verify isize?
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import (
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"compress/flate"
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"hash/crc32"
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"io"
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"github.com/wader/fq/format"
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"github.com/wader/fq/pkg/decode"
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"github.com/wader/fq/pkg/interp"
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"github.com/wader/fq/pkg/scalar"
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)
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var probeFormat decode.Group
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func init() {
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interp.RegisterFormat(decode.Format{
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Name: format.GZIP,
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Description: "gzip compression",
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Groups: []string{format.PROBE},
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DecodeFn: gzDecode,
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Dependencies: []decode.Dependency{
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{Names: []string{format.PROBE}, Group: &probeFormat},
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},
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})
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}
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const delfateMethod = 8
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var compressionMethodNames = scalar.UToSymStr{
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delfateMethod: "deflate",
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}
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var osNames = scalar.UToSymStr{
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0: "fat",
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1: "amiga",
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2: "vms",
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3: "unix",
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4: "vm_cms",
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5: "atari_tOS",
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6: "hpfs",
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7: "Mmcintosh",
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8: "z_system",
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9: "cpm",
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10: "tops_20",
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11: "ntfs",
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12: "qdos",
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13: "acorn_riscos",
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}
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var deflateExtraFlagsNames = scalar.UToSymStr{
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2: "slow",
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4: "fast",
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}
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func gzDecode(d *decode.D, _ any) any {
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d.Endian = decode.LittleEndian
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d.FieldRawLen("identification", 2*8, d.AssertBitBuf([]byte("\x1f\x8b")))
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compressionMethod := d.FieldU8("compression_method", compressionMethodNames)
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hasHeaderCRC := false
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hasExtra := false
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hasName := false
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hasComment := false
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d.FieldStruct("flags", func(d *decode.D) {
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d.FieldBool("text")
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hasHeaderCRC = d.FieldBool("header_crc")
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hasExtra = d.FieldBool("extra")
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hasName = d.FieldBool("name")
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hasComment = d.FieldBool("comment")
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d.FieldU3("reserved")
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})
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d.FieldU32("mtime", scalar.DescriptionActualUUnixTime)
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switch compressionMethod {
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case delfateMethod:
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d.FieldU8("extra_flags", deflateExtraFlagsNames)
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default:
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d.FieldU8("extra_flags")
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}
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d.FieldU8("os", osNames)
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if hasExtra {
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// TODO:
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xLen := d.FieldU16("xlen")
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d.FieldRawLen("extra_fields", int64(xLen*8))
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}
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if hasName {
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d.FieldUTF8Null("name")
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}
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if hasComment {
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d.FieldUTF8Null("comment")
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}
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if hasHeaderCRC {
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// TODO: validate
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d.FieldRawLen("header_crc", 16, scalar.RawHex)
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}
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var rFn func(r io.Reader) io.Reader
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switch compressionMethod {
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case delfateMethod:
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// bitio.NewIOReadSeeker implements io.ByteReader so that deflate don't do own
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// buffering and might read more than needed messing up knowing compressed size
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rFn = func(r io.Reader) io.Reader { return flate.NewReader(r) }
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}
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if rFn != nil {
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readCompressedSize, uncompressedBR, dv, _, _ := d.TryFieldReaderRangeFormat("uncompressed", d.Pos(), d.BitsLeft(), rFn, probeFormat, nil)
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if uncompressedBR != nil {
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if dv == nil {
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d.FieldRootBitBuf("uncompressed", uncompressedBR)
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}
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d.FieldRawLen("compressed", readCompressedSize)
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crc32W := crc32.NewIEEE()
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// TODO: cleanup clone
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d.CopyBits(crc32W, d.CloneReadSeeker(uncompressedBR))
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d.FieldU32("crc32", d.ValidateUBytes(crc32W.Sum(nil)), scalar.ActualHex)
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d.FieldU32("isize")
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}
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}
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return nil
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}
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