120 lines
2.6 KiB
Go
120 lines
2.6 KiB
Go
// Copyright 2015, Joe Tsai. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE.md file.
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// Package brotli implements the Brotli compressed data format,
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// described in RFC 7932.
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package brotli
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import (
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"fmt"
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"github.com/dsnet/compress/internal/errors"
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)
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func errorf(c int, f string, a ...interface{}) error {
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return errors.Error{Code: c, Pkg: "brotli", Msg: fmt.Sprintf(f, a...)}
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}
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// errWrap converts a lower-level errors.Error to be one from this package.
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// The replaceCode passed in will be used to replace the code for any errors
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// with the errors.Invalid code.
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//
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// For the Reader, set this to errors.Corrupted.
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// For the Writer, set this to errors.Internal.
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func errWrap(err error, replaceCode int) error {
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if cerr, ok := err.(errors.Error); ok {
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if errors.IsInvalid(cerr) {
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cerr.Code = replaceCode
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}
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err = errorf(cerr.Code, "%s", cerr.Msg)
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}
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return err
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}
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var (
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errClosed = errorf(errors.Closed, "")
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errCorrupted = errorf(errors.Corrupted, "")
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errInvalid = errorf(errors.Invalid, "")
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errUnaligned = errorf(errors.Invalid, "non-aligned bit buffer")
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)
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var (
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reverseLUT [256]uint8
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)
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func init() {
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initLUTs()
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}
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func initLUTs() {
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initCommonLUTs()
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initPrefixLUTs()
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initContextLUTs()
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initDictLUTs()
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}
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func initCommonLUTs() {
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for i := range reverseLUT {
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b := uint8(i)
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b = (b&0xaa)>>1 | (b&0x55)<<1
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b = (b&0xcc)>>2 | (b&0x33)<<2
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b = (b&0xf0)>>4 | (b&0x0f)<<4
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reverseLUT[i] = b
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}
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}
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// neededBits computes the minimum number of bits needed to encode n elements.
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func neededBits(n uint32) (nb uint) {
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for n--; n > 0; n >>= 1 {
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nb++
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}
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return
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}
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// reverseUint32 reverses all bits of v.
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func reverseUint32(v uint32) (x uint32) {
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x |= uint32(reverseLUT[byte(v>>0)]) << 24
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x |= uint32(reverseLUT[byte(v>>8)]) << 16
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x |= uint32(reverseLUT[byte(v>>16)]) << 8
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x |= uint32(reverseLUT[byte(v>>24)]) << 0
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return x
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}
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// reverseBits reverses the lower n bits of v.
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func reverseBits(v uint32, n uint) uint32 {
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return reverseUint32(v << (32 - n))
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}
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func allocUint8s(s []uint8, n int) []uint8 {
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if cap(s) >= n {
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return s[:n]
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}
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return make([]uint8, n, n*3/2)
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}
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func allocUint32s(s []uint32, n int) []uint32 {
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if cap(s) >= n {
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return s[:n]
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}
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return make([]uint32, n, n*3/2)
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}
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func extendSliceUints32s(s [][]uint32, n int) [][]uint32 {
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if cap(s) >= n {
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return s[:n]
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}
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ss := make([][]uint32, n, n*3/2)
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copy(ss, s[:cap(s)])
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return ss
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}
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func extendDecoders(s []prefixDecoder, n int) []prefixDecoder {
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if cap(s) >= n {
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return s[:n]
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}
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ss := make([]prefixDecoder, n, n*3/2)
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copy(ss, s[:cap(s)])
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return ss
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}
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