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