| // Licensed to the Apache Software Foundation (ASF) under one |
| // or more contributor license agreements. See the NOTICE file |
| // distributed with this work for additional information |
| // regarding copyright ownership. The ASF licenses this file |
| // to you 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. |
| |
| package compression |
| |
| import ( |
| "github.com/pierrec/lz4" |
| ) |
| |
| type lz4Provider struct{} |
| |
| // NewLz4Provider return a interface of Provider. |
| func NewLz4Provider() Provider { |
| return &lz4Provider{} |
| } |
| |
| func (lz4Provider) CanCompress() bool { |
| return true |
| } |
| |
| func (lz4Provider) Compress(data []byte) []byte { |
| const tableSize = 1 << 16 |
| hashTable := make([]int, tableSize) |
| |
| maxSize := lz4.CompressBlockBound(len(data)) |
| compressed := make([]byte, maxSize) |
| size, err := lz4.CompressBlock(data, compressed, hashTable) |
| if err != nil { |
| panic("Failed to compress") |
| } |
| |
| if size == 0 { |
| // The data block was not compressed. Just repeat it with |
| // the block header flag to signal it's not compressed |
| headerSize := writeSize(len(data), compressed) |
| copy(compressed[headerSize:], data) |
| return compressed[:len(data)+headerSize] |
| } |
| return compressed[:size] |
| } |
| |
| // Write the encoded size for the uncompressed payload |
| func writeSize(size int, dst []byte) int { |
| if size < 0xF { |
| dst[0] |= byte(size << 4) |
| return 1 |
| } |
| dst[0] |= 0xF0 |
| l := size - 0xF |
| i := 1 |
| for ; l >= 0xFF; l -= 0xFF { |
| dst[i] = 0xFF |
| i++ |
| } |
| dst[i] = byte(l) |
| return i + 1 |
| } |
| |
| func (lz4Provider) Decompress(compressedData []byte, originalSize int) ([]byte, error) { |
| uncompressed := make([]byte, originalSize) |
| _, err := lz4.UncompressBlock(compressedData, uncompressed) |
| return uncompressed, err |
| } |