Don Newton | 379ae25 | 2019-04-01 12:17:06 -0400 | [diff] [blame^] | 1 | // Copyright (C) MongoDB, Inc. 2017-present. |
| 2 | // |
| 3 | // Licensed under the Apache License, Version 2.0 (the "License"); you may |
| 4 | // not use this file except in compliance with the License. You may obtain |
| 5 | // a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 |
| 6 | |
| 7 | package compressor |
| 8 | |
| 9 | import ( |
| 10 | "bytes" |
| 11 | "compress/zlib" |
| 12 | |
| 13 | "io" |
| 14 | |
| 15 | "github.com/golang/snappy" |
| 16 | "github.com/mongodb/mongo-go-driver/x/network/wiremessage" |
| 17 | ) |
| 18 | |
| 19 | // Compressor is the interface implemented by types that can compress and decompress wire messages. This is used |
| 20 | // when sending and receiving messages to and from the server. |
| 21 | type Compressor interface { |
| 22 | CompressBytes(src, dest []byte) ([]byte, error) |
| 23 | UncompressBytes(src, dest []byte) ([]byte, error) |
| 24 | CompressorID() wiremessage.CompressorID |
| 25 | Name() string |
| 26 | } |
| 27 | |
| 28 | type writer struct { |
| 29 | buf []byte |
| 30 | } |
| 31 | |
| 32 | // Write appends bytes to the writer |
| 33 | func (w *writer) Write(p []byte) (n int, err error) { |
| 34 | index := len(w.buf) |
| 35 | if len(p) > cap(w.buf)-index { |
| 36 | buf := make([]byte, 2*cap(w.buf)+len(p)) |
| 37 | copy(buf, w.buf) |
| 38 | w.buf = buf |
| 39 | } |
| 40 | |
| 41 | w.buf = w.buf[:index+len(p)] |
| 42 | copy(w.buf[index:], p) |
| 43 | return len(p), nil |
| 44 | } |
| 45 | |
| 46 | // SnappyCompressor uses the snappy method to compress data |
| 47 | type SnappyCompressor struct { |
| 48 | } |
| 49 | |
| 50 | // ZlibCompressor uses the zlib method to compress data |
| 51 | type ZlibCompressor struct { |
| 52 | level int |
| 53 | zlibWriter *zlib.Writer |
| 54 | } |
| 55 | |
| 56 | // CompressBytes uses snappy to compress a slice of bytes. |
| 57 | func (s *SnappyCompressor) CompressBytes(src, dest []byte) ([]byte, error) { |
| 58 | dest = dest[:0] |
| 59 | dest = snappy.Encode(dest, src) |
| 60 | return dest, nil |
| 61 | } |
| 62 | |
| 63 | // UncompressBytes uses snappy to uncompress a slice of bytes. |
| 64 | func (s *SnappyCompressor) UncompressBytes(src, dest []byte) ([]byte, error) { |
| 65 | var err error |
| 66 | dest, err = snappy.Decode(dest, src) |
| 67 | if err != nil { |
| 68 | return dest, err |
| 69 | } |
| 70 | |
| 71 | return dest, nil |
| 72 | } |
| 73 | |
| 74 | // CompressorID returns the ID for the snappy compressor. |
| 75 | func (s *SnappyCompressor) CompressorID() wiremessage.CompressorID { |
| 76 | return wiremessage.CompressorSnappy |
| 77 | } |
| 78 | |
| 79 | // Name returns the string name for the snappy compressor. |
| 80 | func (s *SnappyCompressor) Name() string { |
| 81 | return "snappy" |
| 82 | } |
| 83 | |
| 84 | // CompressBytes uses zlib to compress a slice of bytes. |
| 85 | func (z *ZlibCompressor) CompressBytes(src, dest []byte) ([]byte, error) { |
| 86 | dest = dest[:0] |
| 87 | z.zlibWriter.Reset(&writer{ |
| 88 | buf: dest, |
| 89 | }) |
| 90 | |
| 91 | _, err := z.zlibWriter.Write(src) |
| 92 | if err != nil { |
| 93 | _ = z.zlibWriter.Close() |
| 94 | return dest, err |
| 95 | } |
| 96 | |
| 97 | err = z.zlibWriter.Close() |
| 98 | if err != nil { |
| 99 | return dest, err |
| 100 | } |
| 101 | return dest, nil |
| 102 | } |
| 103 | |
| 104 | // UncompressBytes uses zlib to uncompress a slice of bytes. It assumes dest is empty and is the exact size that it |
| 105 | // needs to be. |
| 106 | func (z *ZlibCompressor) UncompressBytes(src, dest []byte) ([]byte, error) { |
| 107 | reader := bytes.NewReader(src) |
| 108 | zlibReader, err := zlib.NewReader(reader) |
| 109 | |
| 110 | if err != nil { |
| 111 | return dest, err |
| 112 | } |
| 113 | defer func() { |
| 114 | _ = zlibReader.Close() |
| 115 | }() |
| 116 | |
| 117 | _, err = io.ReadFull(zlibReader, dest) |
| 118 | if err != nil { |
| 119 | return dest, err |
| 120 | } |
| 121 | |
| 122 | return dest, nil |
| 123 | } |
| 124 | |
| 125 | // CompressorID returns the ID for the zlib compressor. |
| 126 | func (z *ZlibCompressor) CompressorID() wiremessage.CompressorID { |
| 127 | return wiremessage.CompressorZLib |
| 128 | } |
| 129 | |
| 130 | // Name returns the name for the zlib compressor. |
| 131 | func (z *ZlibCompressor) Name() string { |
| 132 | return "zlib" |
| 133 | } |
| 134 | |
| 135 | // CreateSnappy creates a snappy compressor |
| 136 | func CreateSnappy() Compressor { |
| 137 | return &SnappyCompressor{} |
| 138 | } |
| 139 | |
| 140 | // CreateZlib creates a zlib compressor |
| 141 | func CreateZlib(level int) (Compressor, error) { |
| 142 | if level < 0 { |
| 143 | level = wiremessage.DefaultZlibLevel |
| 144 | } |
| 145 | |
| 146 | var compressBuf bytes.Buffer |
| 147 | zlibWriter, err := zlib.NewWriterLevel(&compressBuf, level) |
| 148 | |
| 149 | if err != nil { |
| 150 | return &ZlibCompressor{}, err |
| 151 | } |
| 152 | |
| 153 | return &ZlibCompressor{ |
| 154 | level: level, |
| 155 | zlibWriter: zlibWriter, |
| 156 | }, nil |
| 157 | } |