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mirror of https://github.com/wader/fq.git synced 2024-12-25 22:34:14 +03:00
fq/format/gzip/gzip.go

137 lines
3.3 KiB
Go

package gz
// https://tools.ietf.org/html/rfc1952
// TODO: test name, comment etc
// TODO: verify isize?
import (
"bytes"
"compress/flate"
"hash/crc32"
"io"
"github.com/wader/fq/format"
"github.com/wader/fq/format/registry"
"github.com/wader/fq/pkg/bitio"
"github.com/wader/fq/pkg/decode"
)
var probeFormat []*decode.Format
func init() {
registry.MustRegister(&decode.Format{
Name: format.GZIP,
Description: "gzip compression",
Groups: []string{format.PROBE},
DecodeFn: gzDecode,
Dependencies: []decode.Dependency{
{Names: []string{format.PROBE}, Formats: &probeFormat},
},
})
}
const delfateMethod = 8
var osNames = map[uint64]string{
0: "FAT filesystem (MS-DOS, OS/2, NT/Win32)",
1: "Amiga",
2: "VMS (or OpenVMS)",
3: "Unix",
4: "VM/CMS",
5: "Atari TOS",
6: "HPFS filesystem (OS/2, NT)",
7: "Macintosh",
8: "Z-System",
9: "CP/M",
10: " TOPS-20",
11: " NTFS filesystem (NT)",
12: " QDOS",
13: " Acorn RISCOS",
}
func gzDecode(d *decode.D, in interface{}) interface{} {
d.FieldValidateUTF8("identification", "\x1f\x8b")
compressionMethod := d.FieldUFn("compression_method", func() (uint64, decode.DisplayFormat, string) {
n := d.U8()
if n == delfateMethod {
return n, decode.NumberDecimal, "deflate"
}
return n, decode.NumberDecimal, "unknown"
})
hasHeaderCRC := false
hasExtra := false
hasName := false
hasComment := false
d.FieldStructFn("flags", func(d *decode.D) {
d.FieldBool("text")
hasHeaderCRC = d.FieldBool("header_crc")
hasExtra = d.FieldBool("extra")
hasName = d.FieldBool("name")
hasComment = d.FieldBool("comment")
d.FieldU3("reserved")
})
d.FieldU32LE("mtime") // TODO: unix time
switch compressionMethod {
case delfateMethod:
d.FieldUFn("extra_flags", func() (uint64, decode.DisplayFormat, string) {
n := d.U8()
switch n {
case 2:
return n, decode.NumberDecimal, "slow"
case 4:
return n, decode.NumberDecimal, "fast"
default:
return n, decode.NumberDecimal, "unknown"
}
})
default:
d.FieldU8("extra_flags")
}
d.FieldStringMapFn("os", osNames, "unknown", d.U8, decode.NumberDecimal)
if hasExtra {
// TODO:
xLen := d.FieldU16("xlen")
d.FieldBitBufLen("extra_fields", int64(xLen*8))
}
if hasName {
d.FieldStrNullTerminated("name")
}
if hasComment {
d.FieldStrNullTerminated("comment")
}
if hasHeaderCRC {
d.FieldU16LE("header_crc")
}
compressedLen := d.BitsLeft() - ((4 + 4) * 8) // len-(crc32+isize)
compressedBB := d.FieldBitBufLen("compressed", compressedLen)
var calculatedCRC32 []byte
switch compressionMethod {
case delfateMethod:
deflateR := flate.NewReader(compressedBB)
uncompressed := &bytes.Buffer{}
crc32W := crc32.NewIEEE()
if _, err := decode.Copy(d, io.MultiWriter(uncompressed, crc32W), deflateR); err != nil {
d.Invalid(err.Error())
}
calculatedCRC32 = crc32W.Sum(nil)
uncompressedBB := bitio.NewBufferFromBytes(uncompressed.Bytes(), -1)
dv, _, _ := d.FieldTryFormatBitBuf("uncompressed", uncompressedBB, probeFormat, nil)
if dv == nil {
d.FieldRootBitBuf("uncompressed", uncompressedBB)
}
default:
d.FieldBitBufLen("compressed", compressedLen)
}
if calculatedCRC32 != nil {
d.FieldChecksumLen("crc32", 32, calculatedCRC32, decode.LittleEndian)
} else {
d.FieldU32LE("crc32")
}
d.FieldU32LE("isize")
return nil
}