1/*
2 * Copyright (C) 2006 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//
18// Class providing access to a read-only asset.  Asset objects are NOT
19// thread-safe, and should not be shared across threads.
20//
21#ifndef __LIBS_ASSET_H
22#define __LIBS_ASSET_H
23
24#include <stdio.h>
25#include <sys/types.h>
26
27#include <memory>
28
29#include <utils/Compat.h>
30#include <utils/Errors.h>
31#include <utils/String8.h>
32
33namespace android {
34
35class FileMap;
36
37/*
38 * Instances of this class provide read-only operations on a byte stream.
39 *
40 * Access may be optimized for streaming, random, or whole buffer modes.  All
41 * operations are supported regardless of how the file was opened, but some
42 * things will be less efficient.  [pass that in??]
43 *
44 * "Asset" is the base class for all types of assets.  The classes below
45 * provide most of the implementation.  The AssetManager uses one of the
46 * static "create" functions defined here to create a new instance.
47 */
48class Asset {
49public:
50    virtual ~Asset(void) = default;
51
52    static int32_t getGlobalCount();
53    static String8 getAssetAllocations();
54
55    /* used when opening an asset */
56    typedef enum AccessMode {
57        ACCESS_UNKNOWN = 0,
58
59        /* read chunks, and seek forward and backward */
60        ACCESS_RANDOM,
61
62        /* read sequentially, with an occasional forward seek */
63        ACCESS_STREAMING,
64
65        /* caller plans to ask for a read-only buffer with all data */
66        ACCESS_BUFFER,
67    } AccessMode;
68
69    /*
70     * Read data from the current offset.  Returns the actual number of
71     * bytes read, 0 on EOF, or -1 on error.
72     */
73    virtual ssize_t read(void* buf, size_t count) = 0;
74
75    /*
76     * Seek to the specified offset.  "whence" uses the same values as
77     * lseek/fseek.  Returns the new position on success, or (off64_t) -1
78     * on failure.
79     */
80    virtual off64_t seek(off64_t offset, int whence) = 0;
81
82    /*
83     * Close the asset, freeing all associated resources.
84     */
85    virtual void close(void) = 0;
86
87    /*
88     * Get a pointer to a buffer with the entire contents of the file.
89     */
90    virtual const void* getBuffer(bool wordAligned) = 0;
91
92    /*
93     * Get the total amount of data that can be read.
94     */
95    virtual off64_t getLength(void) const = 0;
96
97    /*
98     * Get the total amount of data that can be read from the current position.
99     */
100    virtual off64_t getRemainingLength(void) const = 0;
101
102    /*
103     * Open a new file descriptor that can be used to read this asset.
104     * Returns -1 if you can not use the file descriptor (for example if the
105     * asset is compressed).
106     */
107    virtual int openFileDescriptor(off64_t* outStart, off64_t* outLength) const = 0;
108
109    /*
110     * Return whether this asset's buffer is allocated in RAM (not mmapped).
111     * Note: not virtual so it is safe to call even when being destroyed.
112     */
113    virtual bool isAllocated(void) const { return false; }
114
115    /*
116     * Get a string identifying the asset's source.  This might be a full
117     * path, it might be a colon-separated list of identifiers.
118     *
119     * This is NOT intended to be used for anything except debug output.
120     * DO NOT try to parse this or use it to open a file.
121     */
122    const char* getAssetSource(void) const { return mAssetSource.string(); }
123
124protected:
125    /*
126     * Adds this Asset to the global Asset list for debugging and
127     * accounting.
128     * Concrete subclasses must call this in their constructor.
129     */
130    static void registerAsset(Asset* asset);
131
132    /*
133     * Removes this Asset from the global Asset list.
134     * Concrete subclasses must call this in their destructor.
135     */
136    static void unregisterAsset(Asset* asset);
137
138    Asset(void);        // constructor; only invoked indirectly
139
140    /* handle common seek() housekeeping */
141    off64_t handleSeek(off64_t offset, int whence, off64_t curPosn, off64_t maxPosn);
142
143    /* set the asset source string */
144    void setAssetSource(const String8& path) { mAssetSource = path; }
145
146    AccessMode getAccessMode(void) const { return mAccessMode; }
147
148private:
149    /* these operations are not implemented */
150    Asset(const Asset& src);
151    Asset& operator=(const Asset& src);
152
153    /* AssetManager needs access to our "create" functions */
154    friend class AssetManager;
155    friend class ApkAssets;
156
157    /*
158     * Create the asset from a named file on disk.
159     */
160    static Asset* createFromFile(const char* fileName, AccessMode mode);
161
162    /*
163     * Create the asset from a named, compressed file on disk (e.g. ".gz").
164     */
165    static Asset* createFromCompressedFile(const char* fileName,
166        AccessMode mode);
167
168#if 0
169    /*
170     * Create the asset from a segment of an open file.  This will fail
171     * if "offset" and "length" don't fit within the bounds of the file.
172     *
173     * The asset takes ownership of the file descriptor.
174     */
175    static Asset* createFromFileSegment(int fd, off64_t offset, size_t length,
176        AccessMode mode);
177
178    /*
179     * Create from compressed data.  "fd" should be seeked to the start of
180     * the compressed data.  This could be inside a gzip file or part of a
181     * Zip archive.
182     *
183     * The asset takes ownership of the file descriptor.
184     *
185     * This may not verify the validity of the compressed data until first
186     * use.
187     */
188    static Asset* createFromCompressedData(int fd, off64_t offset,
189        int compressionMethod, size_t compressedLength,
190        size_t uncompressedLength, AccessMode mode);
191#endif
192
193    /*
194     * Create the asset from a memory-mapped file segment.
195     *
196     * The asset takes ownership of the FileMap.
197     */
198    static Asset* createFromUncompressedMap(FileMap* dataMap, AccessMode mode);
199
200    static std::unique_ptr<Asset> createFromUncompressedMap(std::unique_ptr<FileMap> dataMap,
201        AccessMode mode);
202
203    /*
204     * Create the asset from a memory-mapped file segment with compressed
205     * data.
206     *
207     * The asset takes ownership of the FileMap.
208     */
209    static Asset* createFromCompressedMap(FileMap* dataMap,
210        size_t uncompressedLen, AccessMode mode);
211
212    static std::unique_ptr<Asset> createFromCompressedMap(std::unique_ptr<FileMap> dataMap,
213        size_t uncompressedLen, AccessMode mode);
214
215
216    /*
217     * Create from a reference-counted chunk of shared memory.
218     */
219    // TODO
220
221    AccessMode  mAccessMode;        // how the asset was opened
222    String8    mAssetSource;       // debug string
223
224    Asset*		mNext;				// linked list.
225    Asset*		mPrev;
226};
227
228
229/*
230 * ===========================================================================
231 *
232 * Innards follow.  Do not use these classes directly.
233 */
234
235/*
236 * An asset based on an uncompressed file on disk.  It may encompass the
237 * entire file or just a piece of it.  Access is through fread/fseek.
238 */
239class _FileAsset : public Asset {
240public:
241    _FileAsset(void);
242    virtual ~_FileAsset(void);
243
244    /*
245     * Use a piece of an already-open file.
246     *
247     * On success, the object takes ownership of "fd".
248     */
249    status_t openChunk(const char* fileName, int fd, off64_t offset, size_t length);
250
251    /*
252     * Use a memory-mapped region.
253     *
254     * On success, the object takes ownership of "dataMap".
255     */
256    status_t openChunk(FileMap* dataMap);
257
258    /*
259     * Standard Asset interfaces.
260     */
261    virtual ssize_t read(void* buf, size_t count);
262    virtual off64_t seek(off64_t offset, int whence);
263    virtual void close(void);
264    virtual const void* getBuffer(bool wordAligned);
265    virtual off64_t getLength(void) const { return mLength; }
266    virtual off64_t getRemainingLength(void) const { return mLength-mOffset; }
267    virtual int openFileDescriptor(off64_t* outStart, off64_t* outLength) const;
268    virtual bool isAllocated(void) const { return mBuf != NULL; }
269
270private:
271    off64_t     mStart;         // absolute file offset of start of chunk
272    off64_t     mLength;        // length of the chunk
273    off64_t     mOffset;        // current local offset, 0 == mStart
274    FILE*       mFp;            // for read/seek
275    char*       mFileName;      // for opening
276
277    /*
278     * To support getBuffer() we either need to read the entire thing into
279     * a buffer or memory-map it.  For small files it's probably best to
280     * just read them in.
281     */
282    enum { kReadVsMapThreshold = 4096 };
283
284    FileMap*    mMap;           // for memory map
285    unsigned char* mBuf;        // for read
286
287    const void* ensureAlignment(FileMap* map);
288};
289
290
291/*
292 * An asset based on compressed data in a file.
293 */
294class _CompressedAsset : public Asset {
295public:
296    _CompressedAsset(void);
297    virtual ~_CompressedAsset(void);
298
299    /*
300     * Use a piece of an already-open file.
301     *
302     * On success, the object takes ownership of "fd".
303     */
304    status_t openChunk(int fd, off64_t offset, int compressionMethod,
305        size_t uncompressedLen, size_t compressedLen);
306
307    /*
308     * Use a memory-mapped region.
309     *
310     * On success, the object takes ownership of "fd".
311     */
312    status_t openChunk(FileMap* dataMap, size_t uncompressedLen);
313
314    /*
315     * Standard Asset interfaces.
316     */
317    virtual ssize_t read(void* buf, size_t count);
318    virtual off64_t seek(off64_t offset, int whence);
319    virtual void close(void);
320    virtual const void* getBuffer(bool wordAligned);
321    virtual off64_t getLength(void) const { return mUncompressedLen; }
322    virtual off64_t getRemainingLength(void) const { return mUncompressedLen-mOffset; }
323    virtual int openFileDescriptor(off64_t* /* outStart */, off64_t* /* outLength */) const { return -1; }
324    virtual bool isAllocated(void) const { return mBuf != NULL; }
325
326private:
327    off64_t     mStart;         // offset to start of compressed data
328    off64_t     mCompressedLen; // length of the compressed data
329    off64_t     mUncompressedLen; // length of the uncompressed data
330    off64_t     mOffset;        // current offset, 0 == start of uncomp data
331
332    FileMap*    mMap;           // for memory-mapped input
333    int         mFd;            // for file input
334
335    class StreamingZipInflater* mZipInflater;  // for streaming large compressed assets
336
337    unsigned char*  mBuf;       // for getBuffer()
338};
339
340// need: shared mmap version?
341
342}; // namespace android
343
344#endif // __LIBS_ASSET_H
345