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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"
+#include "mozilla/ResultVariant.h"
+#include "mozilla/Span.h"
+#include "mozilla/UniquePtr.h"
+
+struct LZ4F_cctx_s; // compression context
+struct LZ4F_dctx_s; // decompression context
+
+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 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
+ */
+ [[nodiscard]] static MFBT_API bool decompress(const char* aSource,
+ size_t aInputSize, char* aDest,
+ size_t aMaxOutputSize,
+ 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. It also ignores
+ * unconsumed input upon reaching aMaxOutputSize and can therefore be used
+ * for partial decompression.
+ *
+ * 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
+ */
+ [[nodiscard]] static MFBT_API bool decompressPartial(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;
+ }
+};
+
+/**
+ * Context for LZ4 Frame-based streaming compression. Use this if you
+ * want to incrementally compress something or if you want to compress
+ * something such that another application can read it.
+ */
+class LZ4FrameCompressionContext final {
+ public:
+ MFBT_API LZ4FrameCompressionContext(int aCompressionLevel, size_t aMaxSrcSize,
+ bool aChecksum, bool aStableSrc = false);
+
+ MFBT_API ~LZ4FrameCompressionContext();
+
+ size_t GetRequiredWriteBufferLength() { return mWriteBufLen; }
+
+ /**
+ * Begin streaming frame-based compression.
+ *
+ * @return a Result with a Span containing the frame header, or an lz4 error
+ * code (size_t).
+ */
+ MFBT_API Result<Span<const char>, size_t> BeginCompressing(
+ Span<char> aWriteBuffer);
+
+ /**
+ * Continue streaming frame-based compression with the provided input.
+ *
+ * @param aInput input buffer to be compressed.
+ * @return a Result with a Span containing compressed output, or an lz4 error
+ * code (size_t).
+ */
+ MFBT_API Result<Span<const char>, size_t> ContinueCompressing(
+ Span<const char> aInput);
+
+ /**
+ * Finalize streaming frame-based compression with the provided input.
+ *
+ * @return a Result with a Span containing compressed output and the frame
+ * footer, or an lz4 error code (size_t).
+ */
+ MFBT_API Result<Span<const char>, size_t> EndCompressing();
+
+ private:
+ LZ4F_cctx_s* mContext;
+ int mCompressionLevel;
+ bool mGenerateChecksum;
+ bool mStableSrc;
+ size_t mMaxSrcSize;
+ size_t mWriteBufLen;
+ Span<char> mWriteBuffer;
+};
+
+struct LZ4FrameDecompressionResult {
+ size_t mSizeRead;
+ size_t mSizeWritten;
+ bool mFinished;
+};
+
+/**
+ * Context for LZ4 Frame-based streaming decompression. Use this if you
+ * want to decompress something compressed by LZ4FrameCompressionContext
+ * or by another application.
+ */
+class LZ4FrameDecompressionContext final {
+ public:
+ explicit MFBT_API LZ4FrameDecompressionContext(bool aStableDest = false);
+ MFBT_API ~LZ4FrameDecompressionContext();
+
+ /**
+ * Decompress a buffer/part of a buffer compressed with
+ * LZ4FrameCompressionContext or another application.
+ *
+ * @param aOutput output buffer to be write results into.
+ * @param aInput input buffer to be decompressed.
+ * @return a Result with information on bytes read/written and whether we
+ * completely decompressed the input into the output, or an lz4 error code
+ * (size_t).
+ */
+ MFBT_API Result<LZ4FrameDecompressionResult, size_t> Decompress(
+ Span<char> aOutput, Span<const char> aInput);
+
+ private:
+ LZ4F_dctx_s* mContext;
+ bool mStableDest;
+};
+
+} /* namespace Compression */
+} /* namespace mozilla */
+
+#endif /* mozilla_Compression_h_ */
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