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
47 * compressed data, in little endian
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 size_t maxCompressedLength =
70 snappy::MaxCompressedLength(SNAPPY_CHUNK_SIZE);
71 m_compressedCache = new char[maxCompressedLength];
74 SnappyFile::~SnappyFile()
76 delete [] m_compressedCache;
80 bool SnappyFile::rawOpen(const std::string &filename, File::Mode mode)
82 std::ios_base::openmode fmode = std::fstream::binary;
83 if (mode == File::Write) {
84 fmode |= (std::fstream::out | std::fstream::trunc);
85 createCache(SNAPPY_CHUNK_SIZE);
86 } else if (mode == File::Read) {
87 fmode |= std::fstream::in;
90 m_stream.open(filename.c_str(), fmode);
92 //read in the initial buffer if we're reading
93 if (m_stream.is_open() && mode == File::Read) {
94 // read the snappy file identifier
95 unsigned char byte1, byte2;
98 assert(byte1 == SNAPPY_BYTE1 && byte2 == SNAPPY_BYTE2);
101 } else if (m_stream.is_open() && mode == File::Write) {
102 // write the snappy file identifier
103 m_stream << SNAPPY_BYTE1;
104 m_stream << SNAPPY_BYTE2;
106 return m_stream.is_open();
109 bool SnappyFile::rawWrite(const void *buffer, size_t length)
111 if (freeCacheSize() > length) {
112 memcpy(m_cachePtr, buffer, length);
113 m_cachePtr += length;
114 } else if (freeCacheSize() == length) {
115 memcpy(m_cachePtr, buffer, length);
116 m_cachePtr += length;
119 int sizeToWrite = length;
121 while (sizeToWrite >= freeCacheSize()) {
122 int endSize = freeCacheSize();
123 int offset = length - sizeToWrite;
124 memcpy(m_cachePtr, (const char*)buffer + offset, endSize);
125 sizeToWrite -= endSize;
126 m_cachePtr += endSize;
130 int offset = length - sizeToWrite;
131 memcpy(m_cachePtr, (const char*)buffer + offset, sizeToWrite);
132 m_cachePtr += sizeToWrite;
139 bool SnappyFile::rawRead(void *buffer, size_t length)
145 if (freeCacheSize() >= length) {
146 memcpy(buffer, m_cachePtr, length);
147 m_cachePtr += length;
149 size_t sizeToRead = length;
152 size_t chunkSize = std::min(freeCacheSize(), sizeToRead);
153 offset = length - sizeToRead;
154 memcpy((char*)buffer + offset, m_cachePtr, chunkSize);
155 m_cachePtr += chunkSize;
156 sizeToRead -= chunkSize;
157 if (sizeToRead > 0) {
169 int SnappyFile::rawGetc()
177 void SnappyFile::rawClose()
179 if (m_mode == File::Write) {
188 void SnappyFile::rawFlush()
190 assert(m_mode == File::Write);
195 void SnappyFile::flushWriteCache()
197 size_t inputLength = usedCacheSize();
200 size_t compressedLength;
202 ::snappy::RawCompress(m_cache, inputLength,
203 m_compressedCache, &compressedLength);
205 writeCompressedLength(compressedLength);
206 m_stream.write(m_compressedCache, compressedLength);
207 m_cachePtr = m_cache;
209 assert(m_cachePtr == m_cache);
212 void SnappyFile::flushReadCache()
214 //assert(m_cachePtr == m_cache + m_cacheSize);
215 size_t compressedLength;
216 compressedLength = readCompressedLength();
218 if (compressedLength) {
219 m_stream.read((char*)m_compressedCache, compressedLength);
220 ::snappy::GetUncompressedLength(m_compressedCache, compressedLength,
222 createCache(m_cacheSize);
223 ::snappy::RawUncompress(m_compressedCache, compressedLength,
230 void SnappyFile::createCache(size_t size)
232 // TODO: only re-allocate if the current buffer is not big enough
239 m_cache = new char[size];
244 m_cachePtr = m_cache;
248 void SnappyFile::writeCompressedLength(size_t length)
250 unsigned char buf[4];
251 buf[0] = length & 0xff; length >>= 8;
252 buf[1] = length & 0xff; length >>= 8;
253 buf[2] = length & 0xff; length >>= 8;
254 buf[3] = length & 0xff; length >>= 8;
256 m_stream.write((const char *)buf, sizeof buf);
259 size_t SnappyFile::readCompressedLength()
261 unsigned char buf[4];
263 m_stream.read((char *)buf, sizeof buf);
264 if (m_stream.fail()) {
267 length = (size_t)buf[0];
268 length |= ((size_t)buf[1] << 8);
269 length |= ((size_t)buf[2] << 16);
270 length |= ((size_t)buf[3] << 24);