1/*
2 * Copyright (C) 2010 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef __LIBS_STREAMINGZIPINFLATER_H
18#define __LIBS_STREAMINGZIPINFLATER_H
19
20#include <unistd.h>
21#include <inttypes.h>
22#include <zlib.h>
23
24namespace android {
25
26class StreamingZipInflater {
27public:
28    static const size_t INPUT_CHUNK_SIZE = 64 * 1024;
29    static const size_t OUTPUT_CHUNK_SIZE = 64 * 1024;
30
31    // Flavor that pages in the compressed data from a fd
32    StreamingZipInflater(int fd, off_t compDataStart, size_t uncompSize, size_t compSize);
33
34    // Flavor that gets the compressed data from an in-memory buffer
35    StreamingZipInflater(class FileMap* dataMap, size_t uncompSize);
36
37    ~StreamingZipInflater();
38
39    // read 'count' bytes of uncompressed data from the current position.  outBuf may
40    // be NULL, in which case the data is consumed and discarded.
41    ssize_t read(void* outBuf, size_t count);
42
43    // seeking backwards requires uncompressing fom the beginning, so is very
44    // expensive.  seeking forwards only requires uncompressing from the current
45    // position to the destination.
46    off_t seekAbsolute(off_t absoluteInputPosition);
47
48private:
49    void initInflateState();
50    int readNextChunk();
51
52    // where to find the uncompressed data
53    int mFd;
54    off_t mInFileStart;         // where the compressed data lives in the file
55    class FileMap* mDataMap;
56
57    z_stream mInflateState;
58    bool mStreamNeedsInit;
59
60    // output invariants for this asset
61    uint8_t* mOutBuf;           // output buf for decompressed bytes
62    size_t mOutBufSize;         // allocated size of mOutBuf
63    size_t mOutTotalSize;       // total uncompressed size of the blob
64
65    // current output state bookkeeping
66    off_t mOutCurPosition;      // current position in total offset
67    size_t mOutLastDecoded;     // last decoded byte + 1 in mOutbuf
68    size_t mOutDeliverable;     // next undelivered byte of decoded output in mOutBuf
69
70    // input invariants
71    uint8_t* mInBuf;
72    size_t mInBufSize;          // allocated size of mInBuf;
73    size_t mInTotalSize;        // total size of compressed data for this blob
74
75    // input state bookkeeping
76    size_t mInNextChunkOffset;  // offset from start of blob at which the next input chunk lies
77    // the z_stream contains state about input block consumption
78};
79
80}
81
82#endif
83