183 lines
3.3 KiB
Go
183 lines
3.3 KiB
Go
// Copyright 2017 The Prometheus Authors
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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 chunks
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import "io"
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// bstream is a stream of bits.
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type bstream struct {
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stream []byte // the data stream
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count uint8 // how many bits are valid in current byte
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}
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func newBReader(b []byte) *bstream {
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return &bstream{stream: b, count: 8}
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}
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func newBWriter(size int) *bstream {
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return &bstream{stream: make([]byte, 0, size), count: 0}
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}
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func (b *bstream) clone() *bstream {
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d := make([]byte, len(b.stream))
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copy(d, b.stream)
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return &bstream{stream: d, count: b.count}
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}
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func (b *bstream) bytes() []byte {
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return b.stream
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}
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type bit bool
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const (
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zero bit = false
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one bit = true
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)
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func (b *bstream) writeBit(bit bit) {
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if b.count == 0 {
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b.stream = append(b.stream, 0)
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b.count = 8
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}
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i := len(b.stream) - 1
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if bit {
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b.stream[i] |= 1 << (b.count - 1)
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}
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b.count--
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}
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func (b *bstream) writeByte(byt byte) {
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if b.count == 0 {
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b.stream = append(b.stream, 0)
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b.count = 8
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}
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i := len(b.stream) - 1
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// fill up b.b with b.count bits from byt
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b.stream[i] |= byt >> (8 - b.count)
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b.stream = append(b.stream, 0)
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i++
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b.stream[i] = byt << b.count
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}
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func (b *bstream) writeBits(u uint64, nbits int) {
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u <<= (64 - uint(nbits))
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for nbits >= 8 {
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byt := byte(u >> 56)
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b.writeByte(byt)
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u <<= 8
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nbits -= 8
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}
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for nbits > 0 {
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b.writeBit((u >> 63) == 1)
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u <<= 1
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nbits--
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}
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}
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func (b *bstream) readBit() (bit, error) {
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if len(b.stream) == 0 {
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return false, io.EOF
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}
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if b.count == 0 {
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b.stream = b.stream[1:]
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if len(b.stream) == 0 {
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return false, io.EOF
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}
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b.count = 8
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}
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d := (b.stream[0] << (8 - b.count)) & 0x80
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b.count--
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return d != 0, nil
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}
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func (b *bstream) ReadByte() (byte, error) {
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return b.readByte()
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}
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func (b *bstream) readByte() (byte, error) {
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if len(b.stream) == 0 {
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return 0, io.EOF
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}
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if b.count == 0 {
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b.stream = b.stream[1:]
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if len(b.stream) == 0 {
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return 0, io.EOF
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}
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return b.stream[0], nil
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}
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if b.count == 8 {
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b.count = 0
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return b.stream[0], nil
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}
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byt := b.stream[0] << (8 - b.count)
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b.stream = b.stream[1:]
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if len(b.stream) == 0 {
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return 0, io.EOF
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}
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// We just advanced the stream and can assume the shift to be 0.
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byt |= b.stream[0] >> b.count
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return byt, nil
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}
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func (b *bstream) readBits(nbits int) (uint64, error) {
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var u uint64
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for nbits >= 8 {
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byt, err := b.readByte()
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if err != nil {
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return 0, err
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}
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u = (u << 8) | uint64(byt)
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nbits -= 8
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}
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if nbits == 0 {
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return u, nil
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}
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if nbits > int(b.count) {
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u = (u << uint(b.count)) | uint64((b.stream[0]<<(8-b.count))>>(8-b.count))
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nbits -= int(b.count)
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b.stream = b.stream[1:]
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if len(b.stream) == 0 {
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return 0, io.EOF
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}
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b.count = 8
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}
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u = (u << uint(nbits)) | uint64((b.stream[0]<<(8-b.count))>>(8-uint(nbits)))
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b.count -= uint8(nbits)
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return u, nil
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}
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