Add m-esr52 at 52.6.0

1 files changed, 119 insertions, 0 deletions

diff --git a/mfbt/Compression.h b/mfbt/Compression.h
new file mode 100644
index 0000000000..aa50211b36
--- /dev/null
+++ b/mfbt/Compression.h
@@ -0,0 +1,119 @@
+/* -*- 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_ */