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package bitio
// TODO: NewBuffer with []byte arg to save on alloc
import (
"io"
)
// Buffer is a bitio.Reader and bitio.Writer providing a bit buffer.
// Similar to bytes.Buffer.
type Buffer struct {
buf []byte
bufBits int64
bitsOff int64
}
func (b *Buffer) Len() int64 { return b.bufBits - b.bitsOff }
func (b *Buffer) Reset() {
b.bufBits = 0
b.bitsOff = 0
}
// Bits return unread bits in buffer
func (b *Buffer) Bits() ([]byte, int64) {
l := b.Len()
buf := make([]byte, BitsByteCount(l))
copyBufBits(buf, 0, b.buf, b.bitsOff, l, true)
return buf, b.bufBits
}
func (b *Buffer) WriteBits(p []byte, nBits int64) (n int64, err error) {
tBytes := BitsByteCount(b.bufBits + nBits)
if tBytes > int64(len(b.buf)) {
if tBytes <= int64(cap(b.buf)) {
b.buf = b.buf[:tBytes]
} else {
buf := make([]byte, tBytes, tBytes*2)
copy(buf, b.buf)
b.buf = buf
}
}
copyBufBits(b.buf, b.bufBits, p, 0, nBits, true)
b.bufBits += nBits
return nBits, nil
}
func (b *Buffer) empty() bool { return b.bufBits <= b.bitsOff }
func (b *Buffer) ReadBits(p []byte, nBits int64) (n int64, err error) {
if b.empty() {
b.Reset()
if nBits == 0 {
return 0, nil
}
return 0, io.EOF
}
c := nBits
left := b.Len()
if c > left {
c = left
}
copyBufBits(p, 0, b.buf, b.bitsOff, c, true)
b.bitsOff += c
return c, nil
}
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