psi: wrote read func for pat, pmt, desc and started writing for essd

stream/mts/psi/psi.go

@@ -21,6 +21,10 @@ const (
 	PMTTableID = 0x02
 )
 
+const (
+	timestampDescTag = 234
+)
+
 // Program specific information
 type PSI struct {
 	Pf  byte   // Point field
@@ -59,7 +63,7 @@ type PMT struct {
 	Pcrpid uint16 // Program clock reference pid
 	Pil    uint16 // Program info length
 	Pd     []Desc // Program descriptors
-	Essd   []ESSD // Elementary stream specific data
+	Essd   ESSD   // Elementary stream specific data
 }
 
 // Elementary stream specific data
@@ -113,17 +117,68 @@ func readTSS(data []byte, p *PSI) *TSS {
 	pos++
 	tss.Lsn = data[pos]
 	pos++
-	if p.Tid == PATTableID {
-		tss.Sd = readPAT(data, &tss)
-	} else if p.Tid == PMTTableID {
-		tss.Sd = readPMT(data, &tss)
-	} else {
+	switch p.Tid {
+	case PATTableID:
+		tss.Sd = readPAT(data[pos:], &tss)
+	case PMTTableID:
+		tss.Sd = readPMT(data[pos:], &tss)
+	default:
 		panic("Can't yet deal with tables that are not PAT or PMT")
 	}
+	return &tss
+}
 
+func readPAT(data []byte, p *TSS) *PAT {
+	pat := PAT{}
+	pos := 0
+	pat.Pn = uint16(data[pos])<<8 | uint16(data[pos+1])
+	pos += 2
+	pat.Pmpid = uint16(data[pos]&0x1f)<<8 | uint16(data[pos+1])
+	return &pat
+}
+
+func readPMT(data []byte, p *TSS) *PAT {
+	pmt := PMT{}
+	pos := 0
+	pmt.Pcrpid = uint16(data[pos]&0x1f)<<8 | uint16(data[pos+1])
+	pos += 2
+	pmt.Pil = uint16(data[pos]&0x03)<<8 | uint16(data[pos+1])
+	pos += 2
+	if pmt.Pil != 0 {
+		pmt.Pd = readDescs(data[pos:], int(pmt.Pil))
+	}
+	pos += int(pmt.Pil)
+	// TODO Read ES stuff
+	pmt.Essd = readEssd(data[pos:])
 	return nil
 }
 
+// readDescs reads provides a slice of Descs given a byte slice that represents Descs
+// and the no of bytes that the descs accumilate
+func readDescs(data []byte, descLen int) (o []Desc) {
+	pos := 0
+	o = make([]Desc, 1)
+	o[0].Dt = data[pos]
+	pos++
+	o[0].Dl = data[pos]
+	pos++
+	o[0].Dd = make([]byte, o[0].Dl)
+	for i := 0; i < int(o[0].Dl); i++ {
+		o[0].Dd[i] = data[pos]
+		pos++
+	}
+	if 2+len(o[0].Dd) != descLen {
+		panic("No support for reading more than one descriptor")
+	}
+	return
+}
+
+func readEssd(data []byte) *ESSD {
+	essd := ESSD{}
+	pos := 0
+	essd.St = data[pos]
+}
+
 // Bytes outputs a byte slice representation of the PSI
 func (p *PSI) Bytes() []byte {
 	l := 1 + len(p.Pfb)
@@ -177,9 +232,7 @@ func (p *PMT) Bytes() []byte {
 	for _, d := range p.Pd {
 		out = append(out, d.Bytes()...)
 	}
-	for _, e := range p.Essd {
-		out = append(out, e.Bytes()...)
-	}
+	out = append(out, p.Essd.Bytes()...)
 	return out
 }
 
@@ -206,18 +259,18 @@ func (e *ESSD) Bytes() []byte {
 	return out
 }
 
-func boolToByte(b bool) byte {
+func boolToByte(b bool) (o byte) {
 	if b {
-		return 0x01
+		o = 0x01
 	}
-	return 0x00
+	return
 }
 
-func byteToBool(b byte) bool {
-	if b == 0 {
-		return false
+func byteToBool(b byte) (o bool) {
+	if b != 0 {
+		o = true
 	}
-	return true
+	return
 }
 
 func crc32_MakeTable(poly uint32) *crc32.Table {