Merged in field-reader (pull request #222)

codec/h264/h264dec/read.go: fieldReader type.

codec/h264/h264dec/parse.go

@@ -36,6 +36,87 @@ const (
 	naMbPartPredMode
 )
 
+// fieldReader provides methods for reading bool and int fields from a
+// bits.BitReader with a sticky error that may be checked after a series of
+// parsing read calls.
+type fieldReader struct {
+	e  error
+	br *bits.BitReader
+}
+
+// newFieldReader returns a new fieldReader.
+func newFieldReader(br *bits.BitReader) fieldReader {
+	return fieldReader{br: br}
+}
+
+// readBitsInt returns an int from reading n bits from br. If we have an error
+// already, we do not continue with the read.
+func (r fieldReader) readBits(n int) uint64 {
+	if r.e != nil {
+		return 0
+	}
+	var b uint64
+	b, r.e = r.br.ReadBits(n)
+	return b
+}
+
+// readUe parses a syntax element of ue(v) descriptor, i.e. an unsigned integer
+// Exp-Golomb-coded element using method as specified in section 9.1 of ITU-T
+// H.264 and return as an int. The read does not happen if the fieldReader
+// has a non-nil error.
+func (r fieldReader) readUe() int {
+	if r.e != nil {
+		return 0
+	}
+	var i int
+	i, r.e = readUe(r.br)
+	return i
+}
+
+// readTe parses a syntax element of te(v) descriptor i.e, truncated
+// Exp-Golomb-coded syntax element using method as specified in section 9.1
+// and returns as an int. The read does not happen if the fieldReader
+// has a non-nil error.
+func (r fieldReader) readTe(x uint) int {
+	if r.e != nil {
+		return 0
+	}
+	var i int
+	i, r.e = readTe(r.br, x)
+	return i
+}
+
+// readSe parses a syntax element with descriptor se(v), i.e. a signed integer
+// Exp-Golomb-coded syntax element, using the method described in sections
+// 9.1 and 9.1.1 and returns as int. The read does not happen if the fieldReader
+// has a non-nil error.
+func (r fieldReader) readSe() int {
+	if r.e != nil {
+		return 0
+	}
+	var i int
+	i, r.e = readSe(r.br)
+	return i
+}
+
+// readMe parses a syntax element of me(v) descriptor, i.e. mapped
+// Exp-Golomb-coded element, using methods described in sections 9.1 and 9.1.2
+// and returns as int. The read does not happen if the fieldReader has a
+// non-nil error.
+func (r fieldReader) readMe(chromaArrayType uint, mpm mbPartPredMode) int {
+	if r.e != nil {
+		return 0
+	}
+	var i uint
+	i, r.e = readMe(r.br, chromaArrayType, mpm)
+	return int(i)
+}
+
+// err returns the fieldReader's error e.
+func (r fieldReader) err() error {
+	return r.e
+}
+
 // readUe parses a syntax element of ue(v) descriptor, i.e. an unsigned integer
 // Exp-Golomb-coded element using method as specified in section 9.1 of ITU-T H.264.
 //