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mirror of https://github.com/wader/fq.git synced 2024-12-24 22:05:31 +03:00
fq/format/ogg/ogg_page.go

58 lines
1.9 KiB
Go

package ogg
import (
"bytes"
"github.com/wader/fq/format"
"github.com/wader/fq/format/registry"
"github.com/wader/fq/pkg/crc"
"github.com/wader/fq/pkg/decode"
)
func init() {
registry.MustRegister(&decode.Format{
Name: format.OGG_PAGE,
Description: "OGG page",
DecodeFn: pageDecode,
})
}
func pageDecode(d *decode.D, in interface{}) interface{} {
p := format.OggPageOut{}
startPos := d.Pos()
// TODO: validate bits left
d.FieldValidateUTF8("capture_pattern", "OggS")
d.FieldValidateUFn("stream_structure_version", 0, d.U8)
d.FieldU5("unused_flags")
p.IsLastPage = d.FieldBool("last_page")
p.IsFirstPage = d.FieldBool("first_page")
p.IsContinuedPacket = d.FieldBool("continued_packet")
d.FieldU64LE("absolute_granule_position")
p.StreamSerialNumber = uint32(d.FieldU32LE("stream_serial_number"))
p.SequenceNo = uint32(d.FieldU32LE("page_sequence_no"))
d.FieldU32LE("page_checksum")
pageSegments := d.FieldU8("page_segments")
var segmentTable []uint64
d.FieldArrayFn("segment_table", func(d *decode.D) {
for i := uint64(0); i < pageSegments; i++ {
segmentTable = append(segmentTable, d.FieldU8("segment_size"))
}
})
d.FieldArrayFn("segments", func(d *decode.D) {
for _, ss := range segmentTable {
p.Segments = append(p.Segments, d.FieldBitBufLen("segment", int64(ss)*8))
}
})
endPos := d.Pos()
pageChecksum := d.FieldMustRemove("page_checksum")
pageCRC := &crc.CRC{Bits: 32, Table: crc.Poly04c11db7Table}
decode.MustCopy(d, pageCRC, d.BitBufRange(startPos, pageChecksum.Range.Start-startPos)) // header before checksum
decode.MustCopy(d, pageCRC, bytes.NewReader([]byte{0, 0, 0, 0})) // zero checksum bits
decode.MustCopy(d, pageCRC, d.BitBufRange(pageChecksum.Range.Stop(), endPos-pageChecksum.Range.Stop())) // rest of page
d.FieldChecksumRange("page_checksum", pageChecksum.Range.Start, pageChecksum.Range.Len, pageCRC.Sum(nil), decode.LittleEndian)
return p
}