Support streaming of compressed assets > 1 megabyte

Compressed assets larger than one megabyte are now decompressed on demand
rather than being decompressed in their entirety and held in memory.  Reading
the data in order is relatively efficient, as is seeking forward in the stream.
Seeking backwards is supported, but requires reprocessing the compressed data
from the beginning, so is very inefficient.

In addition, the size limit on compressed assets has been eliminated.

Change-Id: I6e68247957e6c53e7e8ba70d12764695f1723bad

2 files changed, 84 insertions, 9 deletions

diff --git a/include/utils/Asset.h b/include/utils/Asset.h
index 5908bcc..2a09095 100644
--- a/include/utils/Asset.h
+++ b/include/utils/Asset.h
@@ -61,15 +61,6 @@ public:
         ACCESS_BUFFER,
     } AccessMode;
 
-    enum {
-        /* data larger than this does not get uncompressed into a buffer */
-#ifdef HAVE_ANDROID_OS
-        UNCOMPRESS_DATA_MAX = 1 * 1024 * 1024
-#else
-        UNCOMPRESS_DATA_MAX = 2 * 1024 * 1024
-#endif
-    };
-
     /*
      * Read data from the current offset.  Returns the actual number of
      * bytes read, 0 on EOF, or -1 on error.
@@ -317,6 +308,8 @@ private:
     FileMap*    mMap;           // for memory-mapped input
     int         mFd;            // for file input
 
+    class StreamingZipInflater* mZipInflater;  // for streaming large compressed assets
+
     unsigned char*  mBuf;       // for getBuffer()
 };
 
diff --git a/include/utils/StreamingZipInflater.h b/include/utils/StreamingZipInflater.h
new file mode 100644
index 0000000..16867d8
--- /dev/null
+++ b/include/utils/StreamingZipInflater.h
@@ -0,0 +1,82 @@
+/*
+ * Copyright (C) 2010 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef __LIBS_STREAMINGZIPINFLATER_H
+#define __LIBS_STREAMINGZIPINFLATER_H
+
+#include <unistd.h>
+#include <inttypes.h>
+#include <zlib.h>
+
+namespace android {
+
+class StreamingZipInflater {
+public:
+    static const size_t INPUT_CHUNK_SIZE = 64 * 1024;
+    static const size_t OUTPUT_CHUNK_SIZE = 64 * 1024;
+
+    // Flavor that pages in the compressed data from a fd
+    StreamingZipInflater(int fd, off_t compDataStart, size_t uncompSize, size_t compSize);
+
+    // Flavor that gets the compressed data from an in-memory buffer
+    StreamingZipInflater(class FileMap* dataMap, size_t uncompSize);
+
+    ~StreamingZipInflater();
+
+    // read 'count' bytes of uncompressed data from the current position.  outBuf may
+    // be NULL, in which case the data is consumed and discarded.
+    ssize_t read(void* outBuf, size_t count);
+
+    // seeking backwards requires uncompressing fom the beginning, so is very
+    // expensive.  seeking forwards only requires uncompressing from the current
+    // position to the destination.
+    off_t seekAbsolute(off_t absoluteInputPosition);
+
+private:
+    void initInflateState();
+    int readNextChunk();
+
+    // where to find the uncompressed data
+    int mFd;
+    off_t mInFileStart;         // where the compressed data lives in the file
+    class FileMap* mDataMap;
+
+    z_stream mInflateState;
+    bool mStreamNeedsInit;
+
+    // output invariants for this asset
+    uint8_t* mOutBuf;           // output buf for decompressed bytes
+    size_t mOutBufSize;         // allocated size of mOutBuf
+    size_t mOutTotalSize;       // total uncompressed size of the blob
+
+    // current output state bookkeeping
+    off_t mOutCurPosition;      // current position in total offset
+    size_t mOutLastDecoded;     // last decoded byte + 1 in mOutbuf
+    size_t mOutDeliverable;     // next undelivered byte of decoded output in mOutBuf
+
+    // input invariants
+    uint8_t* mInBuf;
+    size_t mInBufSize;          // allocated size of mInBuf;
+    size_t mInTotalSize;        // total size of compressed data for this blob
+
+    // input state bookkeeping
+    size_t mInNextChunkOffset;  // offset from start of blob at which the next input chunk lies
+    // the z_stream contains state about input block consumption
+};
+
+}
+
+#endif