96 lines
2.4 KiB
Go
96 lines
2.4 KiB
Go
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package astits
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import (
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"github.com/pkg/errors"
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)
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// PIDs
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const (
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PIDPAT = 0x0 // Program Association Table (PAT) contains a directory listing of all Program Map Tables.
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PIDCAT = 0x1 // Conditional Access Table (CAT) contains a directory listing of all ITU-T Rec. H.222 entitlement management message streams used by Program Map Tables.
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PIDTSDT = 0x2 // Transport Stream Description Table (TSDT) contains descriptors related to the overall transport stream
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PIDNull = 0x1fff // Null Packet (used for fixed bandwidth padding)
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)
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// Data represents a data
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type Data struct {
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EIT *EITData
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FirstPacket *Packet
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NIT *NITData
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PAT *PATData
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PES *PESData
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PID uint16
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PMT *PMTData
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SDT *SDTData
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TOT *TOTData
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}
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// parseData parses a payload spanning over multiple packets and returns a set of data
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func parseData(ps []*Packet, prs PacketsParser, pm programMap) (ds []*Data, err error) {
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// Use custom parser first
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if prs != nil {
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var skip bool
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if ds, skip, err = prs(ps); err != nil {
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err = errors.Wrap(err, "astits: custom packets parsing failed")
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return
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} else if skip {
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return
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}
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}
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// Reconstruct payload
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var l int
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for _, p := range ps {
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l += len(p.Payload)
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}
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var payload = make([]byte, l)
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var c int
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for _, p := range ps {
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c += copy(payload[c:], p.Payload)
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}
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// Parse PID
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var pid = ps[0].Header.PID
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// Parse payload
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if pid == PIDCAT {
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// Information in a CAT payload is private and dependent on the CA system. Use the PacketsParser
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// to parse this type of payload
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} else if isPSIPayload(pid, pm) {
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var psiData *PSIData
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if psiData, err = parsePSIData(payload); err != nil {
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err = errors.Wrap(err, "astits: parsing PSI data failed")
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return
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}
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ds = psiData.toData(ps[0], pid)
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} else if isPESPayload(payload) {
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d, err := parsePESData(payload)
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if err == nil {
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ds = append(ds, &Data{
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FirstPacket: ps[0],
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PES: d,
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PID: pid,
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})
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}
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}
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return
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}
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// isPSIPayload checks whether the payload is a PSI one
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func isPSIPayload(pid uint16, pm programMap) bool {
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return pid == PIDPAT || // PAT
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pm.exists(pid) || // PMT
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((pid >= 0x10 && pid <= 0x14) || (pid >= 0x1e && pid <= 0x1f)) //DVB
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}
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// isPESPayload checks whether the payload is a PES one
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func isPESPayload(i []byte) bool {
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// Packet is not big enough
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if len(i) < 3 {
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return false
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}
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// Check prefix
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return uint32(i[0])<<16|uint32(i[1])<<8|uint32(i[2]) == 1
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}
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