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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* Various simple compression/decompression functions. */
+
+#ifndef mozilla_Compression_h_
+#define mozilla_Compression_h_
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Types.h"
+
+namespace mozilla {
+namespace Compression {
+
+/**
+ * LZ4 is a very fast byte-wise compression algorithm.
+ *
+ * Compared to Google's Snappy it is faster to compress and decompress and
+ * generally produces output of about the same size.
+ *
+ * Compared to zlib it compresses at about 10x the speed, decompresses at about
+ * 4x the speed and produces output of about 1.5x the size.
+ */
+
+class LZ4
+{
+public:
+ /**
+ * Compresses |aInputSize| bytes from |aSource| into |aDest|. Destination
+ * buffer must be already allocated, and must be sized to handle worst cases
+ * situations (input data not compressible). Worst case size evaluation is
+ * provided by function maxCompressedSize()
+ *
+ * @param aInputSize is the input size. Max supported value is ~1.9GB
+ * @return the number of bytes written in buffer |aDest|
+ */
+ static MFBT_API size_t
+ compress(const char* aSource, size_t aInputSize, char* aDest);
+
+ /**
+ * Compress |aInputSize| bytes from |aSource| into an output buffer
+ * |aDest| of maximum size |aMaxOutputSize|. If it cannot achieve it,
+ * compression will stop, and result of the function will be zero,
+ * |aDest| will still be written to, but since the number of input
+ * bytes consumed is not returned the result is not usable.
+ *
+ * This function never writes outside of provided output buffer.
+ *
+ * @param aInputSize is the input size. Max supported value is ~1.9GB
+ * @param aMaxOutputSize is the size of the destination buffer (which must
+ * be already allocated)
+ * @return the number of bytes written in buffer |aDest| or 0 if the
+ * compression fails
+ */
+ static MFBT_API size_t
+ compressLimitedOutput(const char* aSource, size_t aInputSize, char* aDest,
+ size_t aMaxOutputSize);
+
+ /**
+ * If the source stream is malformed, the function will stop decoding
+ * and return false.
+ *
+ * This function never writes outside of provided buffers, and never
+ * modifies input buffer.
+ *
+ * Note: destination buffer must be already allocated, and its size must be a
+ * minimum of |aOutputSize| bytes.
+ *
+ * @param aOutputSize is the output size, therefore the original size
+ * @return true on success, false on failure
+ */
+ static MFBT_API MOZ_MUST_USE bool
+ decompress(const char* aSource, char* aDest, size_t aOutputSize);
+
+ /**
+ * If the source stream is malformed, the function will stop decoding
+ * and return false.
+ *
+ * This function never writes beyond aDest + aMaxOutputSize, and is
+ * therefore protected against malicious data packets.
+ *
+ * Note: Destination buffer must be already allocated. This version is
+ * slightly slower than the decompress without the aMaxOutputSize.
+ *
+ * @param aInputSize is the length of the input compressed data
+ * @param aMaxOutputSize is the size of the destination buffer (which must be
+ * already allocated)
+ * @param aOutputSize the actual number of bytes decoded in the destination
+ * buffer (necessarily <= aMaxOutputSize)
+ * @return true on success, false on failure
+ */
+ static MFBT_API MOZ_MUST_USE bool
+ decompress(const char* aSource, size_t aInputSize, char* aDest,
+ size_t aMaxOutputSize, size_t* aOutputSize);
+
+ /*
+ * Provides the maximum size that LZ4 may output in a "worst case"
+ * scenario (input data not compressible) primarily useful for memory
+ * allocation of output buffer.
+ * note : this function is limited by "int" range (2^31-1)
+ *
+ * @param aInputSize is the input size. Max supported value is ~1.9GB
+ * @return maximum output size in a "worst case" scenario
+ */
+ static inline size_t maxCompressedSize(size_t aInputSize)
+ {
+ size_t max = (aInputSize + (aInputSize / 255) + 16);
+ MOZ_ASSERT(max > aInputSize);
+ return max;
+ }
+};
+
+} /* namespace Compression */
+} /* namespace mozilla */
+
+#endif /* mozilla_Compression_h_ */