mirror of
https://github.com/wader/fq.git
synced 2024-10-27 12:19:52 +03:00
60 lines
2.0 KiB
Go
60 lines
2.0 KiB
Go
package ogg
|
|
|
|
// https://xiph.org/ogg/doc/framing.html
|
|
|
|
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(pageCRC, d.BitBufRange(startPos, pageChecksum.Range.Start-startPos)) // header before checksum
|
|
decode.MustCopy(pageCRC, bytes.NewReader([]byte{0, 0, 0, 0})) // zero checksum bits
|
|
decode.MustCopy(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
|
|
}
|