/
bit.go
60 lines (52 loc) · 1021 Bytes
/
bit.go
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package lz4
import (
"bufio"
"hash"
"io"
"github.com/vova616/xxhash"
)
type bitReader struct {
n uint32
bits uint
err error
h hash.Hash32
r io.ByteReader
}
// newBitReader returns a new bitReader reading from r. If r is not
// already an io.ByteReader, it will be converted via a bufio.Reader.
func newBitReader(r io.Reader) bitReader {
br, ok := r.(io.ByteReader)
if !ok {
br = bufio.NewReader(r)
}
return bitReader{
r: br,
h: xxhash.New(0),
}
}
func (br *bitReader) ReadBits(bits uint) (uint32, error) {
for bits > br.bits {
b, err := br.r.ReadByte()
br.h.Write([]byte{b})
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
if err != nil {
br.err = err
return 0, br.err
}
br.n <<= 8
br.n |= uint32(b)
br.bits += 8
}
n := (br.n >> (br.bits - bits)) & ((1 << bits) - 1)
br.bits -= bits
return n, nil
}
func (br *bitReader) ReadBit() (bool, error) {
n, err := br.ReadBits(1)
return n != 0, err
}
func (br *bitReader) Sum32() uint32 {
return br.h.Sum32()
}