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reader.go
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reader.go
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// Licensed to Apache Software Foundation (ASF) under one or more contributor
// license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright
// ownership. Apache Software Foundation (ASF) licenses this file to you under
// the Apache License, Version 2.0 (the "License"); you may
// not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. See the License for the
// specific language governing permissions and limitations
// under the License.
package encoding
import (
"io"
)
// Reader reads bits from buffer.
type Reader struct {
in io.ByteReader
cache byte
len byte
}
// NewReader crate bit reader.
func NewReader(in io.ByteReader) *Reader {
return &Reader{
in: in,
}
}
// ReadBool reads a bit, 1 returns true, 0 returns false.
func (r *Reader) ReadBool() (bool, error) {
if r.len == 0 {
b, err := r.in.ReadByte()
if err != nil {
return false, err
}
r.cache = b
r.len = 8
}
r.len--
b := r.cache & 0x80
r.cache <<= 1
return b != 0, nil
}
// ReadBits read number of bits.
func (r *Reader) ReadBits(numBits int) (uint64, error) {
var result uint64
for ; numBits >= 8; numBits -= 8 {
b, err := r.ReadByte()
if err != nil {
return 0, err
}
result = (result << 8) | uint64(b)
}
for ; numBits > 0; numBits-- {
byt, err := r.ReadBool()
if err != nil {
return 0, err
}
result <<= 1
if byt {
result |= 1
}
}
return result, nil
}
// ReadByte reads a byte.
func (r *Reader) ReadByte() (byte, error) {
if r.len == 0 {
b, err := r.in.ReadByte()
if err != nil {
return b, err
}
r.cache = b
return b, err
}
b, err := r.in.ReadByte()
if err != nil {
return b, err
}
result := r.cache | b>>r.len
r.cache = b << (8 - r.len)
return result, nil
}
// Reset resets the reader to read from a new slice.
func (r *Reader) Reset() {
r.len = 0
r.cache = 0
}