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public/tier1/snappy.h

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+// 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 UTIL_SNAPPY_SNAPPY_H__
+#define UTIL_SNAPPY_SNAPPY_H__
+
+// fletcherd@valvesoftware.com: Added this kludge.  We really need to stop #defining this in our code.
+#undef min
+#undef max
+
+#include <stddef.h>
+#ifdef _WIN32
+#pragma warning(disable:4530) // warning C4530: C++ exception handler used, but unwind semantics are not enabled. Specify /EHsc
+#endif //_WIN32
+#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, std::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,
+                  std::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);
+
+  // 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);
+
+  // 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  // UTIL_SNAPPY_SNAPPY_H__