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authorMatt A. Tobin <mattatobin@localhost.localdomain>2018-02-02 04:16:08 -0500
committerMatt A. Tobin <mattatobin@localhost.localdomain>2018-02-02 04:16:08 -0500
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parent49ee0794b5d912db1f95dce6eb52d781dc210db5 (diff)
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Add m-esr52 at 52.6.0
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+/* 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 */