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