stream/mts/psi.go: added more to AddDescriptor and added signature for edistDesc

stream/mts/encoder.go

@@ -252,7 +252,6 @@ func (e *Encoder) ccFor(pid int) byte {
 func updateMeta(b []byte) error {
 	var p psi.PSIBytes
 	p = b
-	// TODO: get length of meta data and format appropriately
 	m := meta.Format()
 	p.AddDescriptor(psi.MetadataTag, len(m), m)
 	return nil

stream/mts/psi/psi.go

@@ -26,6 +26,12 @@ LICENSE
 
 package psi
 
+import (
+	"errors"
+
+	"github.com/Comcast/gots/psi"
+)
+
 const (
 	PacketSize = 184 // packet size of a psi.
 )
@@ -68,11 +74,39 @@ const (
 	crcSize          = 4
 )
 
+const (
+	SectionLenIdx1 = 2
+	SectionLenIdx2 = 3
+)
+
+const (
+	SectionLenMask1 = 0x03
+)
+
 const MetadataTag = 0x26
 
 type PSIBytes []byte
 
-func (p *PSIBytes) AddDescriptor(tag, len int, data []byte) {
+func (p *PSIBytes) AddDescriptor(tag int, data []byte) error {
+	// first check that we actually have table syntax section
+	// NB: if table syntax section doesn't exist (unlikely I think) then we could
+	// just add it
+
+	// Check that this is actually a PMT
+	if psi.TableID(*p) != pmtID {
+		return errors.New("trying to add descriptor, but not pmt")
+	}
+
+	if !p.editDesc(tag, data) {
+
+	}
+	// if exists update
+	// otherwise add
+	return nil
+}
+
+func (p *PSIBytes) editDesc(tag int, data []byte) bool {
+	return true
 }
 
 // Program specific information