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// Copyright 2005 and onwards Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// 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 UTIL_SNAPPY_SNAPPY_H__
#define UTIL_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);
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);
// ------------------------------------------------------------------------
// 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);
// 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);
// *** DO NOT CHANGE THE VALUE OF kBlockSize ***
//
// New Compression code chops up the input into blocks of at most
// the following size. This ensures that back-references in the
// output never cross kBlockSize block boundaries. This can be
// helpful in implementing blocked decompression. However the
// decompression code should not rely on this guarantee since older
// compression code may not obey it.
static const int kBlockLog = 15;
static const int kBlockSize = 1 << kBlockLog;
static const int kMaxHashTableBits = 14;
static const int kMaxHashTableSize = 1 << kMaxHashTableBits;
} // end namespace snappy
#endif // UTIL_SNAPPY_SNAPPY_H__
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