mirror of https://github.com/stashapp/stash.git
64 lines
1.6 KiB
Go
64 lines
1.6 KiB
Go
package astits
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import (
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"fmt"
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"github.com/asticode/go-astikit"
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)
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const (
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patSectionEntryBytesSize = 4 // 16 bits + 3 reserved + 13 bits = 32 bits
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)
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// PATData represents a PAT data
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// https://en.wikipedia.org/wiki/Program-specific_information
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type PATData struct {
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Programs []*PATProgram
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TransportStreamID uint16
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}
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// PATProgram represents a PAT program
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type PATProgram struct {
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ProgramMapID uint16 // The packet identifier that contains the associated PMT
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ProgramNumber uint16 // Relates to the Table ID extension in the associated PMT. A value of 0 is reserved for a NIT packet identifier.
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}
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// parsePATSection parses a PAT section
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func parsePATSection(i *astikit.BytesIterator, offsetSectionsEnd int, tableIDExtension uint16) (d *PATData, err error) {
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// Create data
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d = &PATData{TransportStreamID: tableIDExtension}
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// Loop until end of section data is reached
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for i.Offset() < offsetSectionsEnd {
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// Get next bytes
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var bs []byte
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if bs, err = i.NextBytesNoCopy(4); err != nil {
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err = fmt.Errorf("astits: fetching next bytes failed: %w", err)
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return
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}
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// Append program
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d.Programs = append(d.Programs, &PATProgram{
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ProgramMapID: uint16(bs[2]&0x1f)<<8 | uint16(bs[3]),
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ProgramNumber: uint16(bs[0])<<8 | uint16(bs[1]),
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})
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}
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return
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}
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func calcPATSectionLength(d *PATData) uint16 {
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return uint16(4 * len(d.Programs))
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}
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func writePATSection(w *astikit.BitsWriter, d *PATData) (int, error) {
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b := astikit.NewBitsWriterBatch(w)
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for _, p := range d.Programs {
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b.Write(p.ProgramNumber)
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b.WriteN(uint8(0xff), 3)
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b.WriteN(p.ProgramMapID, 13)
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}
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return len(d.Programs) * patSectionEntryBytesSize, b.Err()
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}
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