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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 | // Copyright 2005 and onwards Google Inc.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// A light-weight compression algorithm. It is designed for speed of
// compression and decompression, rather than for the utmost in space
// savings.
//
// For getting better compression ratios when you are compressing data
// with long repeated sequences or compressing data that is similar to
// other data, while still compressing fast, you might look at first
// using BMDiff and then compressing the output of BMDiff with
// Snappy.
#ifndef THIRD_PARTY_SNAPPY_SNAPPY_H__
#define THIRD_PARTY_SNAPPY_SNAPPY_H__
#include <stddef.h>
#include <string>
#include "snappy-stubs-public.h"
namespace snappy {
class Source;
class Sink;
// ------------------------------------------------------------------------
// Generic compression/decompression routines.
// ------------------------------------------------------------------------
// Compress the bytes read from "*source" and append to "*sink". Return the
// number of bytes written.
size_t Compress(Source* source, Sink* sink);
// Find the uncompressed length of the given stream, as given by the header.
// Note that the true length could deviate from this; the stream could e.g.
// be truncated.
//
// Also note that this leaves "*source" in a state that is unsuitable for
// further operations, such as RawUncompress(). You will need to rewind
// or recreate the source yourself before attempting any further calls.
bool GetUncompressedLength(Source* source, uint32* result);
// ------------------------------------------------------------------------
// Higher-level string based routines (should be sufficient for most users)
// ------------------------------------------------------------------------
// Sets "*output" to the compressed version of "input[0,input_length-1]".
// Original contents of *output are lost.
//
// REQUIRES: "input[]" is not an alias of "*output".
size_t Compress(const char* input, size_t input_length, string* output);
// Decompresses "compressed[0,compressed_length-1]" to "*uncompressed".
// Original contents of "*uncompressed" are lost.
//
// REQUIRES: "compressed[]" is not an alias of "*uncompressed".
//
// returns false if the message is corrupted and could not be decompressed
bool Uncompress(const char* compressed, size_t compressed_length,
string* uncompressed);
// Decompresses "compressed" to "*uncompressed".
//
// returns false if the message is corrupted and could not be decompressed
bool Uncompress(Source* compressed, Sink* uncompressed);
// This routine uncompresses as much of the "compressed" as possible
// into sink. It returns the number of valid bytes added to sink
// (extra invalid bytes may have been added due to errors; the caller
// should ignore those). The emitted data typically has length
// GetUncompressedLength(), but may be shorter if an error is
// encountered.
size_t UncompressAsMuchAsPossible(Source* compressed, Sink* uncompressed);
// ------------------------------------------------------------------------
// Lower-level character array based routines. May be useful for
// efficiency reasons in certain circumstances.
// ------------------------------------------------------------------------
// REQUIRES: "compressed" must point to an area of memory that is at
// least "MaxCompressedLength(input_length)" bytes in length.
//
// Takes the data stored in "input[0..input_length]" and stores
// it in the array pointed to by "compressed".
//
// "*compressed_length" is set to the length of the compressed output.
//
// Example:
// char* output = new char[snappy::MaxCompressedLength(input_length)];
// size_t output_length;
// RawCompress(input, input_length, output, &output_length);
// ... Process(output, output_length) ...
// delete [] output;
void RawCompress(const char* input,
size_t input_length,
char* compressed,
size_t* compressed_length);
// Given data in "compressed[0..compressed_length-1]" generated by
// calling the Snappy::Compress routine, this routine
// stores the uncompressed data to
// uncompressed[0..GetUncompressedLength(compressed)-1]
// returns false if the message is corrupted and could not be decrypted
bool RawUncompress(const char* compressed, size_t compressed_length,
char* uncompressed);
// Given data from the byte source 'compressed' generated by calling
// the Snappy::Compress routine, this routine stores the uncompressed
// data to
// uncompressed[0..GetUncompressedLength(compressed,compressed_length)-1]
// returns false if the message is corrupted and could not be decrypted
bool RawUncompress(Source* compressed, char* uncompressed);
// Given data in "compressed[0..compressed_length-1]" generated by
// calling the Snappy::Compress routine, this routine
// stores the uncompressed data to the iovec "iov". The number of physical
// buffers in "iov" is given by iov_cnt and their cumulative size
// must be at least GetUncompressedLength(compressed). The individual buffers
// in "iov" must not overlap with each other.
//
// returns false if the message is corrupted and could not be decrypted
bool RawUncompressToIOVec(const char* compressed, size_t compressed_length,
const struct iovec* iov, size_t iov_cnt);
// Given data from the byte source 'compressed' generated by calling
// the Snappy::Compress routine, this routine stores the uncompressed
// data to the iovec "iov". The number of physical
// buffers in "iov" is given by iov_cnt and their cumulative size
// must be at least GetUncompressedLength(compressed). The individual buffers
// in "iov" must not overlap with each other.
//
// returns false if the message is corrupted and could not be decrypted
bool RawUncompressToIOVec(Source* compressed, const struct iovec* iov,
size_t iov_cnt);
// Returns the maximal size of the compressed representation of
// input data that is "source_bytes" bytes in length;
size_t MaxCompressedLength(size_t source_bytes);
// REQUIRES: "compressed[]" was produced by RawCompress() or Compress()
// Returns true and stores the length of the uncompressed data in
// *result normally. Returns false on parsing error.
// This operation takes O(1) time.
bool GetUncompressedLength(const char* compressed, size_t compressed_length,
size_t* result);
// Returns true iff the contents of "compressed[]" can be uncompressed
// successfully. Does not return the uncompressed data. Takes
// time proportional to compressed_length, but is usually at least
// a factor of four faster than actual decompression.
bool IsValidCompressedBuffer(const char* compressed,
size_t compressed_length);
// Returns true iff the contents of "compressed" can be uncompressed
// successfully. Does not return the uncompressed data. Takes
// time proportional to *compressed length, but is usually at least
// a factor of four faster than actual decompression.
// On success, consumes all of *compressed. On failure, consumes an
// unspecified prefix of *compressed.
bool IsValidCompressed(Source* compressed);
// The size of a compression block. Note that many parts of the compression
// code assumes that kBlockSize <= 65536; in particular, the hash table
// can only store 16-bit offsets, and EmitCopy() also assumes the offset
// is 65535 bytes or less. Note also that if you change this, it will
// affect the framing format (see framing_format.txt).
//
// Note that there might be older data around that is compressed with larger
// block sizes, so the decompression code should not rely on the
// non-existence of long backreferences.
static const int kBlockLog = 16;
static const size_t kBlockSize = 1 << kBlockLog;
static const int kMaxHashTableBits = 14;
static const size_t kMaxHashTableSize = 1 << kMaxHashTableBits;
} // end namespace snappy
#endif // THIRD_PARTY_SNAPPY_SNAPPY_H__
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