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https://github.com/wader/fq.git
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7c5215347d
Remove bitio.Buffer layer. bitio.Buffer was a kitchen sink layer with helpers now it's just a buffer and most functions have been moved to decode instead. bitio package now only have primitive types and functions simialar to standard library io and bytes packages. Make nearly eveything internally use bitio.Bit* interfaces so that slicing work correctly this will also make it possible to start experimenting with more complicated silcing helpers, ex things like: breplace(.header.bitrate; 123) to get a new buffer with bitrate changed.
126 lines
3.0 KiB
Go
126 lines
3.0 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/format/registry"
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"github.com/wader/fq/pkg/decode"
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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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registry.MustRegister(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 filesystem (MS-DOS, OS/2, NT/Win32)",
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1: "Amiga",
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2: "VMS (or OpenVMS)",
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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 filesystem (OS/2, NT)",
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7: "Macintosh",
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8: "Z-System",
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9: "CP/M",
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10: " TOPS-20",
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11: " NTFS filesystem (NT)",
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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, in interface{}) interface{} {
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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") // TODO: unix time
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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.MustCopyBits(crc32W, d.MustClone(uncompressedBR))
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d.FieldU32("crc32", d.ValidateUBytes(crc32W.Sum(nil)), scalar.Hex)
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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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