StreamingZipInflater.h revision 16c4d154dca43c662571129af31b27433b919a32 
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
24#include <utils/Compat.h>
25
26namespace android {
27
28class StreamingZipInflater {
29public:
30    static const size_t INPUT_CHUNK_SIZE = 64 * 1024;
31    static const size_t OUTPUT_CHUNK_SIZE = 64 * 1024;
32
33    // Flavor that pages in the compressed data from a fd
34    StreamingZipInflater(int fd, off64_t compDataStart, size_t uncompSize, size_t compSize);
35
36    // Flavor that gets the compressed data from an in-memory buffer
37    StreamingZipInflater(class FileMap* dataMap, size_t uncompSize);
38
39    ~StreamingZipInflater();
40
41    // read 'count' bytes of uncompressed data from the current position.  outBuf may
42    // be NULL, in which case the data is consumed and discarded.
43    ssize_t read(void* outBuf, size_t count);
44
45    // seeking backwards requires uncompressing fom the beginning, so is very
46    // expensive.  seeking forwards only requires uncompressing from the current
47    // position to the destination.
48    off64_t seekAbsolute(off64_t absoluteInputPosition);
49
50private:
51    void initInflateState();
52    int readNextChunk();
53
54    // where to find the uncompressed data
55    int mFd;
56    off64_t mInFileStart;         // where the compressed data lives in the file
57    class FileMap* mDataMap;
58
59    z_stream mInflateState;
60    bool mStreamNeedsInit;
61
62    // output invariants for this asset
63    uint8_t* mOutBuf;           // output buf for decompressed bytes
64    size_t mOutBufSize;         // allocated size of mOutBuf
65    size_t mOutTotalSize;       // total uncompressed size of the blob
66
67    // current output state bookkeeping
68    off64_t mOutCurPosition;      // current position in total offset
69    size_t mOutLastDecoded;     // last decoded byte + 1 in mOutbuf
70    size_t mOutDeliverable;     // next undelivered byte of decoded output in mOutBuf
71
72    // input invariants
73    uint8_t* mInBuf;
74    size_t mInBufSize;          // allocated size of mInBuf;
75    size_t mInTotalSize;        // total size of compressed data for this blob
76
77    // input state bookkeeping
78    size_t mInNextChunkOffset;  // offset from start of blob at which the next input chunk lies
79    // the z_stream contains state about input block consumption
80};
81
82}
83
84#endif
85