stream/mts/psi/psi.go: checking that we have enough space in psi before creating descriptor

stream/mts/psi/psi.go

@@ -52,6 +52,8 @@ const (
 	pmtID = 0x02
 )
 
+const TotalSyntaxSecLen = 180
+
 // Consts relating to time description
 const (
 	TimeDescTag  = 234
@@ -251,8 +253,8 @@ func (p *PSIBytes) AddDescriptor(tag int, data []byte) error {
 
 	i, desc := p.HasDescriptor(tag)
 	if desc == nil {
-		p.createDescriptor(tag, data)
-		return nil
+		err := p.createDescriptor(tag, data)
+		return err
 	}
 
 	oldDescLen := desc.len()
@@ -308,9 +310,12 @@ func (p *PSIBytes) HasDescriptor(tag int) (int, Descriptor) {
 // createDescriptor creates a descriptor in a psi given a tag and data. It does so
 // by resizing the psi, shifting existing data down and copying in new descriptor
 // in new space.
-func (p *PSIBytes) createDescriptor(tag int, data []byte) {
+func (p *PSIBytes) createDescriptor(tag int, data []byte) error {
 	curProgLen := p.ProgramInfoLen()
 	oldSyntaxSectionLen := SyntaxSecLenFrom(*p)
+	if TotalSyntaxSecLen-(oldSyntaxSectionLen+2+len(data)) <= 0 {
+		return errors.New("Not enough space in psi to create descriptor.")
+	}
 	dataLen := len(data)
 	newDescIdx := DescriptorsIdx + curProgLen
 	newDescLen := dataLen + 2
@@ -332,6 +337,8 @@ func (p *PSIBytes) createDescriptor(tag int, data []byte) {
 	newSyntaxSectionLen := int(oldSyntaxSectionLen) + addedLen
 	p.setSectionLen(newSyntaxSectionLen)
 	UpdateCrc((*p)[1:])
+
+	return nil
 }
 
 // setProgInfoLen sets the program information length in a psi with a pmt.