1 files changed, 154 insertions, 0 deletions
diff --git a/mozglue/linker/SeekableZStream.h b/mozglue/linker/SeekableZStream.h
new file mode 100644
index 000000000..3505c681e
--- /dev/null
+++ b/mozglue/linker/SeekableZStream.h
@@ -0,0 +1,154 @@
+/* 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/. */
+
+#ifndef SeekableZStream_h
+#define SeekableZStream_h
+
+#include "Zip.h"
+
+/**
+ * Seekable compressed stream are created by splitting the original
+ * decompressed data in small chunks and compress these chunks
+ * individually.
+ *
+ * The seekable compressed file format consists in a header defined below,
+ * followed by a table of 32-bits words containing the offsets for each
+ * individual compressed chunk, then followed by the compressed chunks.
+ */
+
+#pragma pack(1)
+struct SeekableZStreamHeader: public Zip::SignedEntity<SeekableZStreamHeader>
+{
+  SeekableZStreamHeader()
+  : Zip::SignedEntity<SeekableZStreamHeader>(magic)
+  , totalSize(0), chunkSize(0), dictSize(0), nChunks(0), lastChunkSize(0)
+  , windowBits(0), filter(0) { }
+
+  /* Reuse Zip::SignedEntity to handle the magic number used in the Seekable
+   * ZStream file format. The magic number is "SeZz". */
+  static const uint32_t magic = 0x7a5a6553;
+
+  /* Total size of the stream, including the 4 magic bytes. */
+  le_uint32 totalSize;
+
+  /* Chunk size */
+  le_uint16 chunkSize;
+
+  /* Size of the dictionary */
+  le_uint16 dictSize;
+
+  /* Number of chunks */
+  le_uint32 nChunks;
+
+  /* Size of last chunk (> 0, <= Chunk size) */
+  le_uint16 lastChunkSize;
+
+  /* windowBits value used when deflating */
+  signed char windowBits;
+
+  /* Filter Id */
+  unsigned char filter;
+};
+#pragma pack()
+
+static_assert(sizeof(SeekableZStreamHeader) == 5 * 4,
+              "SeekableZStreamHeader should be 5 32-bits words");
+
+/**
+ * Helper class used to decompress Seekable ZStreams.
+ */
+class SeekableZStream {
+public:
+  /* Initialize from the given buffer. Returns whether initialization
+   * succeeded (true) or failed (false). */
+  bool Init(const void *buf, size_t length);
+
+  /* Decompresses starting from the given chunk. The decompressed data is
+   * stored at the given location. The given length, in bytes, indicates
+   * how much data to decompress. If length is 0, then exactly one chunk
+   * is decompressed.
+   * Returns whether decompression succeeded (true) or failed (false). */
+  bool Decompress(void *where, size_t chunk, size_t length = 0);
+
+  /* Decompresses the given chunk at the given address. If a length is given,
+   * only decompresses that amount of data instead of the entire chunk.
+   * Returns whether decompression succeeded (true) or failed (false). */
+  bool DecompressChunk(void *where, size_t chunk, size_t length = 0);
+ 
+  /* Returns the uncompressed size of the complete zstream */
+  size_t GetUncompressedSize() const
+  {
+    return (offsetTable.numElements() - 1) * chunkSize + lastChunkSize;
+  }
+
+  /* Returns the chunk size of the given chunk */
+  size_t GetChunkSize(size_t chunk = 0) const {
+    return (chunk == offsetTable.numElements() - 1) ? lastChunkSize : chunkSize;
+  }
+
+  /* Returns the number of chunks */
+  size_t GetChunksNum() const {
+    return offsetTable.numElements();
+  }
+
+  /**
+   * Filters used to improve compression rate.
+   */
+  enum FilterDirection {
+    FILTER,
+    UNFILTER
+  };
+  typedef void (*ZStreamFilter)(off_t, FilterDirection,
+                                  unsigned char *, size_t);
+
+  enum FilterId {
+    NONE,
+    BCJ_THUMB,
+    BCJ_ARM,
+    BCJ_X86,
+    FILTER_MAX
+  };
+  static ZStreamFilter GetFilter(FilterId id);
+
+  static ZStreamFilter GetFilter(uint16_t id) {
+    return GetFilter(static_cast<FilterId>(id));
+  }
+
+private:
+  /* RAW Seekable SZtream buffer */
+  const unsigned char *buffer;
+
+  /* Total size of the stream, including the 4 magic bytes. */
+  uint32_t totalSize;
+
+  /* Chunk size */
+  uint32_t chunkSize;
+
+  /* Size of last chunk (> 0, <= Chunk size) */
+  uint32_t lastChunkSize;
+
+  /* windowBits value used when deflating */
+  int windowBits;
+
+  /* Offsets table */
+  Array<le_uint32> offsetTable;
+
+  /* Filter */
+  ZStreamFilter filter;
+
+  /* Deflate dictionary */
+  Array<unsigned char> dictionary;
+
+  /* Special allocator for inflate to use the same buffers for every chunk */
+  zxx_stream::StaticAllocator allocator;
+};
+
+inline void
+operator++(SeekableZStream::FilterId &other)
+{
+  const int orig = static_cast<int>(other);
+  other = static_cast<SeekableZStream::FilterId>(orig + 1);
+}
+
+#endif /* SeekableZStream_h */