common/bitutil: fix decompression corner cases; fuzz, test & bench
This commit is contained in:
parent
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commit
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@ -16,78 +16,129 @@
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package bitutil
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package bitutil
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/*
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import "errors"
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The compression algorithm implemented by CompressBytes and DecompressBytes is
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optimized for "sparse" input data which contains a lot of zero bytes. Decompression
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requires knowledge of the decompressed data length. Compression works as follows:
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if data only contains zeroes,
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var (
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CompressBytes(data) == nil
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// ErrMissingData is returned from decompression if the byte referenced by
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otherwise if len(data) <= 1,
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// the bitset header overflows the input data.
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CompressBytes(data) == data
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ErrMissingData = errors.New("missing bytes on input")
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otherwise:
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CompressBytes(data) == append(CompressBytes(nonZeroBits(data)), nonZeroBytes(data)...)
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where
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nonZeroBits(data) is a bit vector with len(data) bits (MSB first):
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nonZeroBits(data)[i/8] && (1 << (7-i%8)) != 0 if data[i] != 0
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len(nonZeroBits(data)) == (len(data)+7)/8
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nonZeroBytes(data) contains the non-zero bytes of data in the same order
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*/
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// CompressBytes compresses the input byte slice
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// ErrUnreferencedData is returned from decompression if not all bytes were used
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// up from the input data after decompressing it.
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ErrUnreferencedData = errors.New("extra bytes on input")
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// ErrExceededTarget is returned from decompression if the bitset header has
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// more bits defined than the number of target buffer space available.
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ErrExceededTarget = errors.New("target data size exceeded")
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// ErrZeroContent is returned from decompression if a data byte referenced in
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// the bitset header is actually a zero byte.
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ErrZeroContent = errors.New("zero byte in input content")
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)
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// The compression algorithm implemented by CompressBytes and DecompressBytes is
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// optimized for sparse input data which contains a lot of zero bytes. Decompression
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// requires knowledge of the decompressed data length.
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//
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// Compression works as follows:
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//
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// if data only contains zeroes,
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// CompressBytes(data) == nil
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// otherwise if len(data) <= 1,
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// CompressBytes(data) == data
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// otherwise:
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// CompressBytes(data) == append(CompressBytes(nonZeroBitset(data)), nonZeroBytes(data)...)
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// where
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// nonZeroBitset(data) is a bit vector with len(data) bits (MSB first):
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// nonZeroBitset(data)[i/8] && (1 << (7-i%8)) != 0 if data[i] != 0
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// len(nonZeroBitset(data)) == (len(data)+7)/8
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// nonZeroBytes(data) contains the non-zero bytes of data in the same order
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// CompressBytes compresses the input byte slice according to the sparse bitset
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// representation algorithm.
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func CompressBytes(data []byte) []byte {
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func CompressBytes(data []byte) []byte {
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// Empty slices get compressed to nil
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if len(data) == 0 {
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if len(data) == 0 {
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return nil
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return nil
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}
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}
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// One byte slices compress to nil or retain the single byte
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if len(data) == 1 {
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if len(data) == 1 {
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if data[0] == 0 {
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if data[0] == 0 {
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return nil
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return nil
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} else {
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}
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return data
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return data
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}
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}
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}
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// Calculate the bitset of set bytes, and gather the non-zero bytes
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nonZeroBitset := make([]byte, (len(data)+7)/8)
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bitsLen := (len(data) + 7) / 8
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nonZeroBits := make([]byte, bitsLen)
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nonZeroBytes := make([]byte, 0, len(data))
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nonZeroBytes := make([]byte, 0, len(data))
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for i, b := range data {
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for i, b := range data {
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if b != 0 {
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if b != 0 {
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nonZeroBytes = append(nonZeroBytes, b)
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nonZeroBytes = append(nonZeroBytes, b)
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nonZeroBits[i/8] |= 1 << byte(7-i%8)
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nonZeroBitset[i/8] |= 1 << byte(7-i%8)
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}
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}
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}
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}
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if len(nonZeroBytes) == 0 {
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if len(nonZeroBytes) == 0 {
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return nil
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return nil
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}
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}
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return append(CompressBytes(nonZeroBits), nonZeroBytes...)
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return append(CompressBytes(nonZeroBitset), nonZeroBytes...)
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}
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}
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// DecompressBytes decompresses data with a known target size.
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// DecompressBytes decompresses data with a known target size. In addition to the
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// In addition to the decompressed output, the function returns the length of
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// decompressed output, the function returns the length of compressed input data
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// compressed input data corresponding to the output. The input slice may be longer.
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// corresponding to the output as the input slice may be longer.
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// If the input slice is too short, (nil, -1) is returned.
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func DecompressBytes(data []byte, target int) ([]byte, error) {
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func DecompressBytes(data []byte, targetLen int) ([]byte, int) {
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out, size, err := decompressBytes(data, target)
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decomp := make([]byte, targetLen)
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if err != nil {
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return nil, err
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}
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if size != len(data) {
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return nil, ErrUnreferencedData
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}
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return out, nil
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}
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// decompressBytes decompresses data with a known target size. In addition to the
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// decompressed output, the function returns the length of compressed input data
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// corresponding to the output as the input slice may be longer.
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func decompressBytes(data []byte, target int) ([]byte, int, error) {
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// Sanity check 0 targets to avoid infinite recursion
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if target == 0 {
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return nil, 0, nil
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}
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// Handle the zero and single byte corner cases
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decomp := make([]byte, target)
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if len(data) == 0 {
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if len(data) == 0 {
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return decomp, 0
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return decomp, 0, nil
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}
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}
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if targetLen == 1 {
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if target == 1 {
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return data[0:1], 1
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decomp[0] = data[0] // copy to avoid referencing the input slice
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if data[0] != 0 {
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return decomp, 1, nil
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}
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}
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return decomp, 0, nil
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bitsLen := (targetLen + 7) / 8
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nonZeroBits, ptr := DecompressBytes(data, bitsLen)
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if ptr < 0 {
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return nil, -1
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}
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}
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for i, _ := range decomp {
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// Decompress the bitset of set bytes and distribute the non zero bytes
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if nonZeroBits[i/8]&(1<<byte(7-i%8)) != 0 {
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nonZeroBitset, ptr, err := decompressBytes(data, (target+7)/8)
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if ptr == len(data) {
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if err != nil {
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return nil, -1
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return nil, ptr, err
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}
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for i := 0; i < 8*len(nonZeroBitset); i++ {
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if nonZeroBitset[i/8]&(1<<byte(7-i%8)) != 0 {
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// Make sure we have enough data to push into the correct slot
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if ptr >= len(data) {
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return nil, 0, ErrMissingData
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}
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if i >= len(decomp) {
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return nil, 0, ErrExceededTarget
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}
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// Make sure the data is valid and push into the slot
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if data[ptr] == 0 {
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return nil, 0, ErrZeroContent
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}
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}
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decomp[i] = data[ptr]
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decomp[i] = data[ptr]
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ptr++
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ptr++
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}
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}
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}
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}
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return decomp, ptr
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return decomp, ptr, nil
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}
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}
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56
common/bitutil/compress_fuzz.go
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56
common/bitutil/compress_fuzz.go
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@ -0,0 +1,56 @@
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// Copyright 2017 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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// +build gofuzz
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package bitutil
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import "bytes"
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// Fuzz implements a go-fuzz fuzzer method to test various compression method
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// invocations.
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func Fuzz(data []byte) int {
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if len(data) == 0 {
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return -1
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}
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if data[0]%2 == 0 {
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return fuzzCompress(data[1:])
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}
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return fuzzDecompress(data[1:])
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}
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// fuzzCompress implements a go-fuzz fuzzer method to test the bit compression and
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// decompression algorithm.
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func fuzzCompress(data []byte) int {
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proc, _ := DecompressBytes(CompressBytes(data), len(data))
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if !bytes.Equal(data, proc) {
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panic("content mismatch")
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}
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return 0
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}
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// fuzzDecompress implements a go-fuzz fuzzer method to test the bit decompression
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// and recompression algorithm.
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func fuzzDecompress(data []byte) int {
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blob, err := DecompressBytes(data, 1024)
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if err != nil {
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return 0
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}
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if comp := CompressBytes(blob); !bytes.Equal(comp, data) {
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panic("content mismatch")
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}
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return 0
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}
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152
common/bitutil/compress_test.go
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152
common/bitutil/compress_test.go
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@ -0,0 +1,152 @@
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// Copyright 2017 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package bitutil
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import (
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"bytes"
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"math/rand"
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"testing"
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"github.com/ethereum/go-ethereum/common/hexutil"
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)
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// Tests that data compression and decompression works correctly.
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func TestCompressCycle(t *testing.T) {
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tests := []string{
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// Tests generated by go-fuzz to maximize code coverage
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"0x000000000000000000",
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"0xef0400",
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"0xdf7070533534333636313639343638373532313536346c1bc33339343837313070706336343035336336346c65fefb3930393233383838ac2f65fefb",
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"0x7b64000000",
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"0x000034000000000000",
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"0x0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000f0000000000000000000",
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"0x4912385c0e7b64000000",
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"0x000034000000000000000000000000000000",
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"0x00",
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"0x000003e834ff7f0000",
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"0x0000",
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"0x0000000000000000000000000000000000000000000000000000000000ff00",
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"0x895f0c6a020f850c6a020f85f88df88d",
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"0xdf7070533534333636313639343638373432313536346c1bc3315aac2f65fefb",
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"0x0000000000",
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"0xdf70706336346c65fefb",
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"0x00006d643634000000",
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"0xdf7070533534333636313639343638373532313536346c1bc333393438373130707063363430353639343638373532313536346c1bc333393438336336346c65fe",
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}
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for i, tt := range tests {
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data := hexutil.MustDecode(tt)
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proc, err := DecompressBytes(CompressBytes(data), len(data))
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if err != nil {
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t.Errorf("test %d: failed to decompress compressed data: %v", i, err)
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continue
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}
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if !bytes.Equal(data, proc) {
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t.Errorf("test %d: compress/decompress mismatch: have %x, want %x", i, proc, data)
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}
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}
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}
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// Tests that data decompression works
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func TestDecompress(t *testing.T) {
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tests := []struct {
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size int
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input string
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fail error
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}{
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{size: 0, input: "0x"},
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// Crashers generated by go-fuzz
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{size: 0, input: "0x0020", fail: ErrUnreferencedData},
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{size: 0, input: "0x30", fail: ErrUnreferencedData},
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{size: 1, input: "0x00", fail: ErrUnreferencedData},
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{size: 2, input: "0x07", fail: ErrMissingData},
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{size: 1024, input: "0x8000", fail: ErrZeroContent},
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// Tests generated by go-fuzz to maximize code coverage
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{size: 29490, input: "0x343137343733323134333839373334323073333930783e3078333930783e70706336346c65303e", fail: ErrMissingData},
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{size: 59395, input: "0x00", fail: ErrUnreferencedData},
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{size: 52574, input: "0x70706336346c65c0de", fail: ErrExceededTarget},
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{size: 42264, input: "0x07", fail: ErrMissingData},
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{size: 52, input: "0xa5045bad48f4", fail: ErrExceededTarget},
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{size: 52574, input: "0xc0de", fail: ErrMissingData},
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{size: 52574, input: "0x"},
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{size: 29490, input: "0x34313734373332313433383937333432307333393078073034333839373334323073333930783e3078333937333432307333393078073061333930783e70706336346c65303e", fail: ErrMissingData},
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{size: 29491, input: "0x3973333930783e30783e", fail: ErrMissingData},
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{size: 1024, input: "0x808080608080"},
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{size: 1024, input: "0x808470705e3632383337363033313434303137393130306c6580ef46806380635a80"},
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{size: 1024, input: "0x8080808070"},
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{size: 1024, input: "0x808070705e36346c6580ef46806380635a80"},
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{size: 1024, input: "0x80808046802680"},
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{size: 1024, input: "0x4040404035"},
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{size: 1024, input: "0x4040bf3ba2b3f684402d353234373438373934409fe5b1e7ada94ebfd7d0505e27be4035"},
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{size: 1024, input: "0x404040bf3ba2b3f6844035"},
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{size: 1024, input: "0x40402d35323437343837393440bfd7d0505e27be4035"},
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}
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for i, tt := range tests {
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data := hexutil.MustDecode(tt.input)
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orig, err := DecompressBytes(data, tt.size)
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if err != tt.fail {
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t.Errorf("test %d: failure mismatch: have %v, want %v", i, err, tt.fail)
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}
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if err != nil {
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continue
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}
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if comp := CompressBytes(orig); !bytes.Equal(comp, data) {
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t.Errorf("test %d: decompress/compress mismatch: have %x, want %x", i, comp, data)
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}
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}
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}
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// Crude benchmark for compressing random slices of bytes.
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func BenchmarkCompress1KBVerySparse(b *testing.B) { benchmarkCompress(b, 1024, 0.0001) }
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func BenchmarkCompress2KBVerySparse(b *testing.B) { benchmarkCompress(b, 2048, 0.0001) }
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func BenchmarkCompress4KBVerySparse(b *testing.B) { benchmarkCompress(b, 4096, 0.0001) }
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func BenchmarkCompress1KBSparse(b *testing.B) { benchmarkCompress(b, 1024, 0.001) }
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func BenchmarkCompress2KBSparse(b *testing.B) { benchmarkCompress(b, 2048, 0.001) }
|
||||||
|
func BenchmarkCompress4KBSparse(b *testing.B) { benchmarkCompress(b, 4096, 0.001) }
|
||||||
|
|
||||||
|
func BenchmarkCompress1KBDense(b *testing.B) { benchmarkCompress(b, 1024, 0.1) }
|
||||||
|
func BenchmarkCompress2KBDense(b *testing.B) { benchmarkCompress(b, 2048, 0.1) }
|
||||||
|
func BenchmarkCompress4KBDense(b *testing.B) { benchmarkCompress(b, 4096, 0.1) }
|
||||||
|
|
||||||
|
func BenchmarkCompress1KBSaturated(b *testing.B) { benchmarkCompress(b, 1024, 0.5) }
|
||||||
|
func BenchmarkCompress2KBSaturated(b *testing.B) { benchmarkCompress(b, 2048, 0.5) }
|
||||||
|
func BenchmarkCompress4KBSaturated(b *testing.B) { benchmarkCompress(b, 4096, 0.5) }
|
||||||
|
|
||||||
|
func benchmarkCompress(b *testing.B, bytes int, fill float64) {
|
||||||
|
// Generate a random slice of bytes to compress
|
||||||
|
random := rand.NewSource(0) // reproducible and comparable
|
||||||
|
|
||||||
|
data := make([]byte, bytes)
|
||||||
|
bits := int(float64(bytes) * 8 * fill)
|
||||||
|
|
||||||
|
for i := 0; i < bits; i++ {
|
||||||
|
idx := random.Int63() % int64(len(data))
|
||||||
|
bit := uint(random.Int63() % 8)
|
||||||
|
data[idx] |= 1 << bit
|
||||||
|
}
|
||||||
|
// Reset the benchmark and measure compression/decompression
|
||||||
|
b.ResetTimer()
|
||||||
|
b.ReportAllocs()
|
||||||
|
for i := 0; i < b.N; i++ {
|
||||||
|
DecompressBytes(CompressBytes(data), len(data))
|
||||||
|
}
|
||||||
|
}
|
Loading…
Reference in New Issue
Block a user