github.com/apache/arrow/go/v7@v7.0.1/parquet/compress/brotli.go (about) 1 // Licensed to the Apache Software Foundation (ASF) under one 2 // or more contributor license agreements. See the NOTICE file 3 // distributed with this work for additional information 4 // regarding copyright ownership. The ASF licenses this file 5 // to you under the Apache License, Version 2.0 (the 6 // "License"); you may not use this file except in compliance 7 // with the License. You may obtain a copy of the License at 8 // 9 // http://www.apache.org/licenses/LICENSE-2.0 10 // 11 // Unless required by applicable law or agreed to in writing, software 12 // distributed under the License is distributed on an "AS IS" BASIS, 13 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 // See the License for the specific language governing permissions and 15 // limitations under the License. 16 17 package compress 18 19 import ( 20 "bytes" 21 "io" 22 "io/ioutil" 23 24 "github.com/andybalholm/brotli" 25 "github.com/apache/arrow/go/v7/parquet/internal/debug" 26 ) 27 28 type brotliCodec struct{} 29 30 func (brotliCodec) NewReader(r io.Reader) io.ReadCloser { 31 return ioutil.NopCloser(brotli.NewReader(r)) 32 } 33 34 func (b brotliCodec) EncodeLevel(dst, src []byte, level int) []byte { 35 if level == DefaultCompressionLevel { 36 level = brotli.DefaultCompression 37 } 38 39 maxlen := int(b.CompressBound(int64(len(src)))) 40 if dst == nil || cap(dst) < maxlen { 41 dst = make([]byte, 0, maxlen) 42 } 43 buf := bytes.NewBuffer(dst[:0]) 44 w := brotli.NewWriterLevel(buf, level) 45 _, err := w.Write(src) 46 if err != nil { 47 panic(err) 48 } 49 if err := w.Close(); err != nil { 50 panic(err) 51 } 52 return buf.Bytes() 53 } 54 55 func (b brotliCodec) Encode(dst, src []byte) []byte { 56 return b.EncodeLevel(dst, src, brotli.DefaultCompression) 57 } 58 59 func (brotliCodec) Decode(dst, src []byte) []byte { 60 rdr := brotli.NewReader(bytes.NewReader(src)) 61 if dst != nil { 62 var ( 63 sofar = 0 64 n = -1 65 err error = nil 66 ) 67 for n != 0 && err == nil { 68 n, err = rdr.Read(dst[sofar:]) 69 sofar += n 70 } 71 if err != nil && err != io.EOF { 72 panic(err) 73 } 74 return dst[:sofar] 75 } 76 77 dst, err := ioutil.ReadAll(rdr) 78 if err != nil { 79 panic(err) 80 } 81 82 return dst 83 } 84 85 // taken from brotli/enc/encode.c:1426 86 // BrotliEncoderMaxCompressedSize 87 func (brotliCodec) CompressBound(len int64) int64 { 88 // [window bits / empty metadata] + N * [uncompressed] + [last empty] 89 debug.Assert(len > 0, "brotli compressbound should be > 0") 90 nlarge := len >> 14 91 overhead := 2 + (4 * nlarge) + 3 + 1 92 result := len + overhead 93 if len == 0 { 94 return 2 95 } 96 if result < len { 97 return 0 98 } 99 return len 100 } 101 102 func (brotliCodec) NewWriter(w io.Writer) io.WriteCloser { 103 return brotli.NewWriter(w) 104 } 105 106 func (brotliCodec) NewWriterLevel(w io.Writer, level int) (io.WriteCloser, error) { 107 if level == DefaultCompressionLevel { 108 level = brotli.DefaultCompression 109 } 110 return brotli.NewWriterLevel(w, level), nil 111 } 112 113 func init() { 114 codecs[Codecs.Brotli] = brotliCodec{} 115 }