mirror of
https://github.com/wader/fq.git
synced 2024-12-23 21:31:33 +03:00
62 lines
2.0 KiB
Go
62 lines
2.0 KiB
Go
package ogg
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import (
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"bytes"
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"github.com/wader/fq/format"
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"github.com/wader/fq/pkg/bitio"
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"github.com/wader/fq/pkg/checksum"
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"github.com/wader/fq/pkg/decode"
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"github.com/wader/fq/pkg/interp"
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"github.com/wader/fq/pkg/scalar"
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)
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func init() {
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interp.RegisterFormat(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, _ any) any {
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p := format.OggPageOut{}
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startPos := d.Pos()
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d.Endian = decode.LittleEndian
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d.FieldUTF8("capture_pattern", 4, d.AssertStr("OggS"))
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d.FieldU8("version", d.AssertU(0))
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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.FieldU64("granule_position")
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p.StreamSerialNumber = uint32(d.FieldU32("bitstream_serial_number"))
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p.SequenceNo = uint32(d.FieldU32("page_sequence_no"))
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d.FieldU32("crc", scalar.ActualHex)
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pageSegments := d.FieldU8("page_segments")
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var segmentTable []uint64
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d.FieldArray("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.FieldArray("segments", func(d *decode.D) {
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for _, ss := range segmentTable {
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bs := d.ReadAllBits(d.FieldRawLen("segment", int64(ss)*8))
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p.Segments = append(p.Segments, bs)
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}
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})
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endPos := d.Pos()
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pageChecksumValue := d.FieldGet("crc")
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pageCRC := &checksum.CRC{Bits: 32, Table: checksum.Poly04c11db7Table}
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d.Copy(pageCRC, bitio.NewIOReader(d.BitBufRange(startPos, pageChecksumValue.Range.Start-startPos))) // header before checksum
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d.Copy(pageCRC, bytes.NewReader([]byte{0, 0, 0, 0})) // zero checksum bits
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d.Copy(pageCRC, bitio.NewIOReader(d.BitBufRange(pageChecksumValue.Range.Stop(), endPos-pageChecksumValue.Range.Stop()))) // rest of page
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_ = pageChecksumValue.TryScalarFn(d.ValidateUBytes(pageCRC.Sum(nil)))
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return p
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}
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