1 files changed, 104 insertions, 0 deletions
diff --git a/js/src/vm/Compression.h b/js/src/vm/Compression.h
new file mode 100644
index 000000000..2fb2df5b6
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+++ b/js/src/vm/Compression.h
@@ -0,0 +1,104 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ * 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 vm_Compression_h
+#define vm_Compression_h
+
+#include <zlib.h>
+
+#include "jsalloc.h"
+#include "jstypes.h"
+
+#include "js/Vector.h"
+
+namespace js {
+
+struct CompressedDataHeader
+{
+    uint32_t compressedBytes;
+};
+
+class Compressor
+{
+  public:
+    // After compressing CHUNK_SIZE bytes, we will do a full flush so we can
+    // start decompression at that point.
+    static const size_t CHUNK_SIZE = 64 * 1024;
+
+  private:
+    // Number of bytes we should hand to zlib each compressMore() call.
+    static const size_t MAX_INPUT_SIZE = 2 * 1024;
+
+    z_stream zs;
+    const unsigned char* inp;
+    size_t inplen;
+    size_t outbytes;
+    bool initialized;
+    bool finished;
+
+    // The number of uncompressed bytes written for the current chunk. When this
+    // reaches CHUNK_SIZE, we finish the current chunk and start a new chunk.
+    uint32_t currentChunkSize;
+
+    // At the end of each chunk (and the end of the uncompressed data if it's
+    // not a chunk boundary), we record the offset in the compressed data.
+    js::Vector<uint32_t, 8, SystemAllocPolicy> chunkOffsets;
+
+  public:
+    enum Status {
+        MOREOUTPUT,
+        DONE,
+        CONTINUE,
+        OOM
+    };
+
+    Compressor(const unsigned char* inp, size_t inplen);
+    ~Compressor();
+    bool init();
+    void setOutput(unsigned char* out, size_t outlen);
+    /* Compress some of the input. Return true if it should be called again. */
+    Status compressMore();
+    size_t sizeOfChunkOffsets() const { return chunkOffsets.length() * sizeof(chunkOffsets[0]); }
+
+    // Returns the number of bytes needed to store the data currently written +
+    // the chunk offsets.
+    size_t totalBytesNeeded() const;
+
+    // Append the chunk offsets to |dest|.
+    void finish(char* dest, size_t destBytes);
+
+    static void toChunkOffset(size_t uncompressedOffset, size_t* chunk, size_t* chunkOffset) {
+        *chunk = uncompressedOffset / CHUNK_SIZE;
+        *chunkOffset = uncompressedOffset % CHUNK_SIZE;
+    }
+    static size_t chunkSize(size_t uncompressedBytes, size_t chunk) {
+        MOZ_ASSERT(uncompressedBytes > 0);
+        size_t lastChunk = (uncompressedBytes - 1) / CHUNK_SIZE;
+        MOZ_ASSERT(chunk <= lastChunk);
+        if (chunk < lastChunk || uncompressedBytes % CHUNK_SIZE == 0)
+            return CHUNK_SIZE;
+        return uncompressedBytes % CHUNK_SIZE;
+    }
+};
+
+/*
+ * Decompress a string. The caller must know the length of the output and
+ * allocate |out| to a string of that length.
+ */
+bool DecompressString(const unsigned char* inp, size_t inplen,
+                      unsigned char* out, size_t outlen);
+
+/*
+ * Decompress a single chunk of at most Compressor::CHUNK_SIZE bytes.
+ * |chunk| is the chunk index. The caller must know the length of the output
+ * (the uncompressed chunk) and allocate |out| to a string of that length.
+ */
+bool DecompressStringChunk(const unsigned char* inp, size_t chunk,
+                           unsigned char* out, size_t outlen);
+
+} /* namespace js */
+
+#endif /* vm_Compression_h */