// 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__