stream/mts/psi: changed HasDescriptor to also return index of descriptor in psi. Wrote func called SetProgInfoLen to set the program info length in a pmt. Started writing deleteDescriptor func to get rid of a descriptor.

stream/mts/psi/descriptor_test.go

@@ -128,7 +128,7 @@ func TestHasDescriptor(t *testing.T) {
 	p := PSIBytes(tstPsi3.Bytes())
 
 	// Try getting descriptor that exists
-	got := p.HasDescriptor(LocationDescTag)
+	_, got := p.HasDescriptor(LocationDescTag)
 	want := []byte{
 		LocationDescTag,
 		LocationDataSize,
@@ -141,7 +141,7 @@ func TestHasDescriptor(t *testing.T) {
 
 	// Try getting descriptor that doesnt exist
 	const fakeTag = 236
-	got = p.HasDescriptor(fakeTag)
+	_, got = p.HasDescriptor(fakeTag)
 	want = nil
 
 	if !bytes.Equal(got, want) {
@@ -151,7 +151,7 @@ func TestHasDescriptor(t *testing.T) {
 	// Try getting descriptor from psi that has no descriptors
 	p = PSIBytes(tstPsi2.Bytes())
 
-	got = p.HasDescriptor(LocationDescTag)
+	_, got = p.HasDescriptor(LocationDescTag)
 	want = nil
 
 	if !bytes.Equal(got, want) {
@@ -219,6 +219,10 @@ func TestCreateDescriptor(t *testing.T) {
 	}
 }
 
+func TestDeleteDescriptor(t *testing.T) {
+
+}
+
 func TestUpdateDescriptor(t *testing.T) {
 
 }

stream/mts/psi/psi.go

@@ -245,7 +245,7 @@ func (p *PSIBytes) AddDescriptor(tag int, data []byte) error {
 		return errors.New("trying to add descriptor, but not pmt")
 	}
 
-	desc := p.HasDescriptor(tag)
+	_, desc := p.HasDescriptor(tag)
 	if desc == nil {
 		p.createDescriptor(tag, data)
 		return nil
@@ -258,17 +258,17 @@ func (p *PSIBytes) ProgramInfoLen() int {
 	return int((((*p)[ProgramInfoLenIdx1] & ProgramInfoLenMask1) << 8) | (*p)[ProgramInfoLenIdx2])
 }
 
-func (p *PSIBytes) HasDescriptor(tag int) Descriptor {
+func (p *PSIBytes) HasDescriptor(tag int) (int, Descriptor) {
 	descs := p.descriptors()
 	if descs == nil {
-		return nil
+		return -1, nil
 	}
 	for i := 0; i < len(descs); i += 2 + int(descs[i+1]) {
 		if int(descs[i]) == tag {
-			return descs[i : i+2+int(descs[i+1])]
+			return i, descs[i : i+2+int(descs[i+1])]
 		}
 	}
-	return nil
+	return -1, nil
 }
 
 func (p *PSIBytes) descriptors() []byte {
@@ -283,8 +283,10 @@ func (p *PSIBytes) createDescriptor(tag int, data []byte) {
 	// Calculate the new descriptors index and length.
 	newDescIdx := DescriptorsIdx + curProgLen
 	newDescLen := dataLen + 2
+
 	// Copy data down from newDescIdx to create room for the new descriptor.
 	copy((*p)[newDescIdx+newDescLen:], (*p)[newDescIdx:newDescIdx+newDescLen])
+
 	// Set the tag, data len and data of the new desriptor.
 	(*p)[newDescIdx] = byte(tag)
 	(*p)[newDescIdx+1] = byte(dataLen)
@@ -294,9 +296,7 @@ func (p *PSIBytes) createDescriptor(tag int, data []byte) {
 	// TODO: put this in function set program info length
 	addedLen := dataLen + 2
 	newProgInfoLen := curProgLen + addedLen
-	(*p)[ProgramInfoLenIdx1] &= 0xff ^ ProgramInfoLenMask1
-	(*p)[ProgramInfoLenIdx1] |= byte(newProgInfoLen>>8) & ProgramInfoLenMask1
-	(*p)[ProgramInfoLenIdx2] = byte(newProgInfoLen)
+	p.SetProgInfoLen(newProgInfoLen)
 
 	// set section length
 	// TODO: put this in func set program info length
@@ -306,6 +306,7 @@ func (p *PSIBytes) createDescriptor(tag int, data []byte) {
 	(*p)[SyntaxSecLenIdx2] = byte(newSyntaxSectionLen)
 }
 
+// TODO: make this safer. If no padding, does this index out of range ?
 func (p *PSIBytes) trimPadding() []byte {
 	sectionLength := SyntaxSecLenFrom(*p)
 	paddingIdx := (4 + sectionLength)
@@ -313,6 +314,22 @@ func (p *PSIBytes) trimPadding() []byte {
 	return o
 }
 
+func (p *PSIBytes) SetProgInfoLen(l int) {
+	// TODO: check if pmt first
+	(*p)[ProgramInfoLenIdx1] &= 0xff ^ ProgramInfoLenMask1
+	(*p)[ProgramInfoLenIdx1] |= byte(l>>8) & ProgramInfoLenMask1
+	(*p)[ProgramInfoLenIdx2] = byte(l)
+}
+
+func (p *PSIBytes) deleteDescriptor(tag int) error {
+	if i, desc := p.HasDescriptor(tag); desc != nil {
+		descLen := len(desc)
+		newProgInfoLen := p.ProgramInfoLen() - descLen
+		p.SetProgInfoLen(newProgInfoLen)
+	}
+	return errors.New("Descriptor doesn't exist")
+}
+
 func (d *Descriptor) update(data []byte) {
 	if len(data) > int((*d)[1]) {
 		// TODO: implement resizing of descriptor