first commit

util/bits/golomb_reader.go

@@ -0,0 +1,65 @@
+package bits
+
+import (
+	"io"
+)
+
+type GolombBitReader struct {
+	R    io.Reader
+	buf  [1]byte
+	left byte
+}
+
+func (self *GolombBitReader) ReadBit() (res uint, err error) {
+	if self.left == 0 {
+		if _, err = self.R.Read(self.buf[:]); err != nil {
+			return
+		}
+		self.left = 8
+	}
+	self.left--
+	res = uint(self.buf[0]>>self.left) & 1
+	return
+}
+
+func (self *GolombBitReader) ReadBits(n int) (res uint, err error) {
+	for i := 0; i < n; i++ {
+		var bit uint
+		if bit, err = self.ReadBit(); err != nil {
+			return
+		}
+		res |= bit << uint(n-i-1)
+	}
+	return
+}
+
+func (self *GolombBitReader) ReadExponentialGolombCode() (res uint, err error) {
+	i := 0
+	for {
+		var bit uint
+		if bit, err = self.ReadBit(); err != nil {
+			return
+		}
+		if !(bit == 0 && i < 32) {
+			break
+		}
+		i++
+	}
+	if res, err = self.ReadBits(i); err != nil {
+		return
+	}
+	res += (1 << uint(i)) - 1
+	return
+}
+
+func (self *GolombBitReader) ReadSE() (res uint, err error) {
+	if res, err = self.ReadExponentialGolombCode(); err != nil {
+		return
+	}
+	if res&0x01 != 0 {
+		res = (res + 1) / 2
+	} else {
+		res = -res / 2
+	}
+	return
+}