prometheus/chunkenc/bstream.go
Simon Pasquier 597202ae43 Remove more unused code
Signed-off-by: Simon Pasquier <spasquie@redhat.com>
2019-01-07 14:45:17 +01:00

201 lines
4.6 KiB
Go

// Copyright 2017 The Prometheus Authors
// Licensed 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.
// The code in this file was largely written by Damian Gryski as part of
// https://github.com/dgryski/go-tsz and published under the license below.
// It received minor modifications to suit Prometheus's needs.
// Copyright (c) 2015,2016 Damian Gryski <damian@gryski.com>
// All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
// * Redistributions of source code must retain the above copyright notice,
// this list of conditions and the following disclaimer.
//
// * Redistributions in binary form must reproduce the above copyright notice,
// this list of conditions and the following disclaimer in the documentation
// and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
package chunkenc
import "io"
// bstream is a stream of bits.
type bstream struct {
stream []byte // the data stream
count uint8 // how many bits are valid in current byte
}
func newBReader(b []byte) bstream {
return bstream{stream: b, count: 8}
}
func (b *bstream) bytes() []byte {
return b.stream
}
type bit bool
const (
zero bit = false
one bit = true
)
func (b *bstream) writeBit(bit bit) {
if b.count == 0 {
b.stream = append(b.stream, 0)
b.count = 8
}
i := len(b.stream) - 1
if bit {
b.stream[i] |= 1 << (b.count - 1)
}
b.count--
}
func (b *bstream) writeByte(byt byte) {
if b.count == 0 {
b.stream = append(b.stream, 0)
b.count = 8
}
i := len(b.stream) - 1
// fill up b.b with b.count bits from byt
b.stream[i] |= byt >> (8 - b.count)
b.stream = append(b.stream, 0)
i++
b.stream[i] = byt << b.count
}
func (b *bstream) writeBits(u uint64, nbits int) {
u <<= (64 - uint(nbits))
for nbits >= 8 {
byt := byte(u >> 56)
b.writeByte(byt)
u <<= 8
nbits -= 8
}
for nbits > 0 {
b.writeBit((u >> 63) == 1)
u <<= 1
nbits--
}
}
func (b *bstream) readBit() (bit, error) {
if len(b.stream) == 0 {
return false, io.EOF
}
if b.count == 0 {
b.stream = b.stream[1:]
if len(b.stream) == 0 {
return false, io.EOF
}
b.count = 8
}
d := (b.stream[0] << (8 - b.count)) & 0x80
b.count--
return d != 0, nil
}
func (b *bstream) ReadByte() (byte, error) {
return b.readByte()
}
func (b *bstream) readByte() (byte, error) {
if len(b.stream) == 0 {
return 0, io.EOF
}
if b.count == 0 {
b.stream = b.stream[1:]
if len(b.stream) == 0 {
return 0, io.EOF
}
return b.stream[0], nil
}
if b.count == 8 {
b.count = 0
return b.stream[0], nil
}
byt := b.stream[0] << (8 - b.count)
b.stream = b.stream[1:]
if len(b.stream) == 0 {
return 0, io.EOF
}
// We just advanced the stream and can assume the shift to be 0.
byt |= b.stream[0] >> b.count
return byt, nil
}
func (b *bstream) readBits(nbits int) (uint64, error) {
var u uint64
for nbits >= 8 {
byt, err := b.readByte()
if err != nil {
return 0, err
}
u = (u << 8) | uint64(byt)
nbits -= 8
}
if nbits == 0 {
return u, nil
}
if nbits > int(b.count) {
u = (u << uint(b.count)) | uint64((b.stream[0]<<(8-b.count))>>(8-b.count))
nbits -= int(b.count)
b.stream = b.stream[1:]
if len(b.stream) == 0 {
return 0, io.EOF
}
b.count = 8
}
u = (u << uint(nbits)) | uint64((b.stream[0]<<(8-b.count))>>(8-uint(nbits)))
b.count -= uint8(nbits)
return u, nil
}