Small performance improvement

v2/bitstream/DefaultInputBitStream.go

@@ -64,7 +64,7 @@ func NewDefaultInputBitStream(stream io.ReadCloser, bufferSize uint) (*DefaultIn
 // ReadBit returns the next bit
 func (this *DefaultInputBitStream) ReadBit() int {
 	if this.availBits == 0 {
-		this.pullCurrent() // Panic if stream is closed
+		this.current, this.availBits = this.pull() // Panic if stream is closed
 	}
 
 	this.availBits--
@@ -88,7 +88,7 @@ func (this *DefaultInputBitStream) ReadBits(count uint) uint64 {
 	// Not enough spots available in 'current'
 	count -= this.availBits
 	res := this.current & (0xFFFFFFFFFFFFFFFF >> (64 - this.availBits))
-	this.pullCurrent()
+	this.current, this.availBits = this.pull()
 	return (res << count) | this.ReadBits(count) // handle this.availBits < count (at EOS)
 }
 
@@ -110,7 +110,7 @@ func (this *DefaultInputBitStream) ReadArray(bits []byte, count uint) uint {
 	// Byte aligned cursor ?
 	if this.availBits&7 == 0 {
 		if this.availBits == 0 {
-			this.pullCurrent()
+			this.current, this.availBits = this.pull()
 		}
 
 		// Empty this.current
@@ -153,7 +153,7 @@ func (this *DefaultInputBitStream) ReadArray(bits []byte, count uint) uint {
 			v0 := this.current
 
 			if this.position+32 > this.maxPosition {
-				this.pullCurrent()
+				this.current, this.availBits = this.pull()
 
 				if this.availBits < r {
 					panic("No more data to read in the bitstream")
@@ -182,7 +182,7 @@ func (this *DefaultInputBitStream) ReadArray(bits []byte, count uint) uint {
 
 		for remaining >= 64 {
 			v := this.current
-			this.pullCurrent()
+			this.current, this.availBits = this.pull()
 
 			if this.availBits < r {
 				panic("No more data to read in the bitstream")
@@ -246,8 +246,8 @@ func (this *DefaultInputBitStream) HasMoreToRead() (bool, error) {
 	return err == nil, err
 }
 
-// Pull 64 bits of current value from buffer.
-func (this *DefaultInputBitStream) pullCurrent() {
+// Pull 64 bits from buffer.
+func (this *DefaultInputBitStream) pull() (uint64, uint) {
 	if this.position > this.maxPosition {
 		if _, err := this.readFromInputStream(len(this.buffer)); err != nil {
 			panic(err)
@@ -257,7 +257,7 @@ func (this *DefaultInputBitStream) pullCurrent() {
 	if this.position+7 > this.maxPosition {
 		// End of stream: overshoot max position => adjust bit index
 		shift := uint(this.maxPosition-this.position) << 3
-		this.availBits = shift + 8
+		avail := shift + 8
 		val := uint64(0)
 
 		for this.position <= this.maxPosition {
@@ -266,12 +266,11 @@ func (this *DefaultInputBitStream) pullCurrent() {
 			shift -= 8
 		}
 
-		this.current = val
+		return val, avail
 	} else {
 		// Regular processing, buffer length is multiple of 8
-		this.current = binary.BigEndian.Uint64(this.buffer[this.position : this.position+8])
-		this.availBits = 64
 		this.position += 8
+		return binary.BigEndian.Uint64(this.buffer[this.position-8 : this.position]), 64
 	}
 
 }

v2/bitstream/DefaultOutputBitStream.go

@@ -62,9 +62,10 @@ func NewDefaultOutputBitStream(stream io.WriteCloser, bufferSize uint) (*Default
 
 // WriteBit writes the least significant bit of the input integer. Panics if the bitstream is closed
 func (this *DefaultOutputBitStream) WriteBit(bit int) {
-	if this.availBits <= 1 { // availBits = 0 if stream is closed => force pushCurrent() => panic
-		this.current |= uint64(bit & 1)
-		this.pushCurrent()
+	if this.availBits <= 1 { // availBits = 0 if stream is closed => force push() => panic
+		this.push(this.current | uint64(bit&1))
+		this.current = 0
+		this.availBits = 64
 	} else {
 		this.availBits--
 		this.current |= (uint64(bit&1) << this.availBits)
@@ -84,9 +85,9 @@ func (this *DefaultOutputBitStream) WriteBits(value uint64, count uint) uint {
 	if count >= this.availBits {
 		// Not enough spots available in 'current'
 		remaining := count - this.availBits
-		this.pushCurrent()
+		this.push(this.current)
 		this.current = value << (64 - remaining)
-		this.availBits -= remaining
+		this.availBits = 64 - remaining
 	} else {
 		this.availBits -= count
 	}
@@ -172,8 +173,8 @@ func (this *DefaultOutputBitStream) WriteArray(bits []byte, count uint) uint {
 
 			for remaining >= 64 {
 				val := binary.BigEndian.Uint64(bits[start:])
-				this.current |= (val >> r)
-				this.pushCurrent()
+				this.push(this.current | (val >> r))
+				this.availBits = 64
 				this.current = val << a
 				start += 8
 				remaining -= 64
@@ -197,11 +198,9 @@ func (this *DefaultOutputBitStream) WriteArray(bits []byte, count uint) uint {
 	return count
 }
 
-// Push 64 bits of current value into buffer.
-func (this *DefaultOutputBitStream) pushCurrent() {
-	binary.BigEndian.PutUint64(this.buffer[this.position:this.position+8], this.current)
-	this.availBits = 64
-	this.current = 0
+// Push 64 bits into buffer.
+func (this *DefaultOutputBitStream) push(val uint64) {
+	binary.BigEndian.PutUint64(this.buffer[this.position:this.position+8], val)
 	this.position += 8
 
 	if this.position >= len(this.buffer)-8 {