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 
26 namespace android {
27 
28 class StreamingZipInflater {
29 public:
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 
50 private:
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