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79 lines
1.7 KiB
Go
79 lines
1.7 KiB
Go
// Copyright 2017 Hajime Hoshi
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package bits
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type Bits struct {
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vec []byte
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bitPos int
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bytePos int
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}
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func New(vec []byte) *Bits {
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return &Bits{
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vec: vec,
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}
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}
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func Append(bits *Bits, buf []byte) *Bits {
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return New(append(bits.vec, buf...))
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}
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func (b *Bits) Bit() int {
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if len(b.vec) <= b.bytePos {
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// TODO: Should this return error?
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return 0
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}
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tmp := uint(b.vec[b.bytePos]) >> (7 - uint(b.bitPos))
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tmp &= 0x01
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b.bytePos += (b.bitPos + 1) >> 3
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b.bitPos = (b.bitPos + 1) & 0x07
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return int(tmp)
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}
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func (b *Bits) Bits(num int) int {
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if num == 0 {
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return 0
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}
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if len(b.vec) <= b.bytePos {
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// TODO: Should this return error?
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return 0
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}
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bb := make([]byte, 4)
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copy(bb, b.vec[b.bytePos:])
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tmp := (uint32(bb[0]) << 24) | (uint32(bb[1]) << 16) | (uint32(bb[2]) << 8) | (uint32(bb[3]))
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tmp <<= uint(b.bitPos)
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tmp >>= (32 - uint(num))
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b.bytePos += (b.bitPos + num) >> 3
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b.bitPos = (b.bitPos + num) & 0x07
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return int(tmp)
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}
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func (b *Bits) BitPos() int {
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return b.bytePos<<3 + b.bitPos
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}
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func (b *Bits) SetPos(pos int) {
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b.bytePos = pos >> 3
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b.bitPos = pos & 0x7
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}
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func (b *Bits) LenInBytes() int {
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return len(b.vec)
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}
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func (b *Bits) Tail(offset int) []byte {
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return b.vec[len(b.vec)-offset:]
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}
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