1 /**************************************************************************
3 * Copyright 2011 Zack Rusin
6 * Permission is hereby granted, free of charge, to any person obtaining a copy
7 * of this software and associated documentation files (the "Software"), to deal
8 * in the Software without restriction, including without limitation the rights
9 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
10 * copies of the Software, and to permit persons to whom the Software is
11 * furnished to do so, subject to the following conditions:
13 * The above copyright notice and this permission notice shall be included in
14 * all copies or substantial portions of the Software.
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
19 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
21 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
24 **************************************************************************/
27 #include "trace_snappyfile.hpp"
34 using namespace Trace;
40 * Snappy at its core is just a compressoin algorithm so we're
41 * creating a new file format which uses snappy compression
42 * to hold the trace data.
44 * The file is composed of a number of chunks, they are:
46 * uint32 - specifying the length of the compressed data
49 * File can contain any number of such chunks.
50 * The default size of an uncompressed chunk is specified in
54 * Currently the default size for a a to-be-compressed data is
55 * 1mb, meaning that the compressed data will be <= 1mb.
56 * The reason it's 1mb is because it seems
57 * to offer a pretty good compression/disk io speed ratio
58 * but that might change.
62 SnappyFile::SnappyFile(const std::string &filename,
69 m_compressedCache = new char[SNAPPY_CHUNK_SIZE];
72 SnappyFile::~SnappyFile()
74 delete [] m_compressedCache;
77 bool SnappyFile::rawOpen(const std::string &filename, File::Mode mode)
79 std::ios_base::openmode fmode = std::fstream::binary;
80 if (mode == File::Write) {
81 fmode |= (std::fstream::out | std::fstream::trunc);
82 createCache(SNAPPY_CHUNK_SIZE);
83 } else if (mode == File::Read) {
84 fmode |= std::fstream::in;
87 m_stream.open(filename.c_str(), fmode);
89 //read in the initial buffer if we're reading
90 if (m_stream.is_open() && mode == File::Read) {
91 // read the snappy file identifier
92 unsigned char byte1, byte2;
95 assert(byte1 == SNAPPY_BYTE1 && byte2 == SNAPPY_BYTE2);
98 } else if (m_stream.is_open() && mode == File::Write) {
99 // write the snappy file identifier
100 m_stream << SNAPPY_BYTE1;
101 m_stream << SNAPPY_BYTE2;
103 return m_stream.is_open();
106 bool SnappyFile::rawWrite(const void *buffer, int length)
108 if (freeCacheSize() > length) {
109 memcpy(m_cachePtr, buffer, length);
110 m_cachePtr += length;
111 } else if (freeCacheSize() == length) {
112 memcpy(m_cachePtr, buffer, length);
113 m_cachePtr += length;
116 int sizeToWrite = length;
118 while (sizeToWrite >= freeCacheSize()) {
119 int endSize = freeCacheSize();
120 int offset = length - sizeToWrite;
121 memcpy(m_cachePtr, (char*)buffer + offset, endSize);
122 sizeToWrite -= endSize;
123 m_cachePtr += endSize;
127 int offset = length - sizeToWrite;
128 memcpy(m_cachePtr, (char*)buffer + offset, sizeToWrite);
129 m_cachePtr += sizeToWrite;
136 bool SnappyFile::rawRead(void *buffer, int length)
142 if (freeCacheSize() >= length) {
143 memcpy(buffer, m_cachePtr, length);
144 m_cachePtr += length;
146 int sizeToRead = length;
149 int chunkSize = std::min(freeCacheSize(), sizeToRead);
150 offset = length - sizeToRead;
151 memcpy((char*)buffer + offset, m_cachePtr, chunkSize);
152 m_cachePtr += chunkSize;
153 sizeToRead -= chunkSize;
164 int SnappyFile::rawGetc()
172 void SnappyFile::rawClose()
181 void SnappyFile::rawFlush()
187 void SnappyFile::flushCache()
189 if (m_mode == File::Write) {
190 size_t compressedLength;
192 ::snappy::RawCompress(m_cache, SNAPPY_CHUNK_SIZE - freeCacheSize(),
193 m_compressedCache, &compressedLength);
195 writeCompressedLength(compressedLength);
196 m_stream.write(m_compressedCache, compressedLength);
197 m_cachePtr = m_cache;
198 } else if (m_mode == File::Read) {
201 //assert(m_cachePtr == m_cache + m_cacheSize);
202 size_t compressedLength;
203 compressedLength = readCompressedLength();
204 m_stream.read((char*)m_compressedCache, compressedLength);
206 * The reason we peek here is because the last read will
207 * read all the way until the last character, but that will not
208 * trigger m_stream.eof() to be set, so by calling peek
209 * we assure that if we in fact have read the entire stream
210 * then the m_stream.eof() is always set.
213 ::snappy::GetUncompressedLength(m_compressedCache, compressedLength,
217 createCache(m_cacheSize);
218 ::snappy::RawUncompress(m_compressedCache, compressedLength,
223 void SnappyFile::createCache(size_t size)
225 m_cache = new char[size];
226 m_cachePtr = m_cache;
230 void SnappyFile::writeCompressedLength(uint32_t value)
232 m_stream.write((const char*)&value, sizeof value);
235 uint32_t SnappyFile::readCompressedLength()
238 m_stream.read((char*)&len, sizeof len);