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#include "FileMap.h"
27#include "String8.h"
28#include "Errors.h"
29
30namespace android {
31
32/*
33 * Instances of this class provide read-only operations on a byte stream.
34 *
35 * Access may be optimized for streaming, random, or whole buffer modes.  All
36 * operations are supported regardless of how the file was opened, but some
37 * things will be less efficient.  [pass that in??]
38 *
39 * "Asset" is the base class for all types of assets.  The classes below
40 * provide most of the implementation.  The AssetManager uses one of the
41 * static "create" functions defined here to create a new instance.
42 */
43class Asset {
44public:
45    virtual ~Asset(void);
46
47    static int32_t getGlobalCount();
48    static String8 getAssetAllocations();
49
50    /* used when opening an asset */
51    typedef enum AccessMode {
52        ACCESS_UNKNOWN = 0,
53
54        /* read chunks, and seek forward and backward */
55        ACCESS_RANDOM,
56
57        /* read sequentially, with an occasional forward seek */
58        ACCESS_STREAMING,
59
60        /* caller plans to ask for a read-only buffer with all data */
61        ACCESS_BUFFER,
62    } AccessMode;
63
64    enum {
65        /* data larger than this does not get uncompressed into a buffer */
66#ifdef HAVE_ANDROID_OS
67        UNCOMPRESS_DATA_MAX = 1 * 1024 * 1024
68#else
69        UNCOMPRESS_DATA_MAX = 2 * 1024 * 1024
70#endif
71    };
72
73    /*
74     * Read data from the current offset.  Returns the actual number of
75     * bytes read, 0 on EOF, or -1 on error.
76     */
77    virtual ssize_t read(void* buf, size_t count) = 0;
78
79    /*
80     * Seek to the specified offset.  "whence" uses the same values as
81     * lseek/fseek.  Returns the new position on success, or (off_t) -1
82     * on failure.
83     */
84    virtual off_t seek(off_t offset, int whence) = 0;
85
86    /*
87     * Close the asset, freeing all associated resources.
88     */
89    virtual void close(void) = 0;
90
91    /*
92     * Get a pointer to a buffer with the entire contents of the file.
93     */
94    virtual const void* getBuffer(bool wordAligned) = 0;
95
96    /*
97     * Get the total amount of data that can be read.
98     */
99    virtual off_t getLength(void) const = 0;
100
101    /*
102     * Get the total amount of data that can be read from the current position.
103     */
104    virtual off_t getRemainingLength(void) const = 0;
105
106    /*
107     * Open a new file descriptor that can be used to read this asset.
108     * Returns -1 if you can not use the file descriptor (for example if the
109     * asset is compressed).
110     */
111    virtual int openFileDescriptor(off_t* outStart, off_t* outLength) const = 0;
112
113    /*
114     * Return whether this asset's buffer is allocated in RAM (not mmapped).
115     * Note: not virtual so it is safe to call even when being destroyed.
116     */
117    virtual bool isAllocated(void) const { return false; }
118
119    /*
120     * Get a string identifying the asset's source.  This might be a full
121     * path, it might be a colon-separated list of identifiers.
122     *
123     * This is NOT intended to be used for anything except debug output.
124     * DO NOT try to parse this or use it to open a file.
125     */
126    const char* getAssetSource(void) const { return mAssetSource.string(); }
127
128protected:
129    Asset(void);        // constructor; only invoked indirectly
130
131    /* handle common seek() housekeeping */
132    off_t handleSeek(off_t offset, int whence, off_t curPosn, off_t maxPosn);
133
134    /* set the asset source string */
135    void setAssetSource(const String8& path) { mAssetSource = path; }
136
137    AccessMode getAccessMode(void) const { return mAccessMode; }
138
139private:
140    /* these operations are not implemented */
141    Asset(const Asset& src);
142    Asset& operator=(const Asset& src);
143
144    /* AssetManager needs access to our "create" functions */
145    friend class AssetManager;
146
147    /*
148     * Create the asset from a named file on disk.
149     */
150    static Asset* createFromFile(const char* fileName, AccessMode mode);
151
152    /*
153     * Create the asset from a named, compressed file on disk (e.g. ".gz").
154     */
155    static Asset* createFromCompressedFile(const char* fileName,
156        AccessMode mode);
157
158#if 0
159    /*
160     * Create the asset from a segment of an open file.  This will fail
161     * if "offset" and "length" don't fit within the bounds of the file.
162     *
163     * The asset takes ownership of the file descriptor.
164     */
165    static Asset* createFromFileSegment(int fd, off_t offset, size_t length,
166        AccessMode mode);
167
168    /*
169     * Create from compressed data.  "fd" should be seeked to the start of
170     * the compressed data.  This could be inside a gzip file or part of a
171     * Zip archive.
172     *
173     * The asset takes ownership of the file descriptor.
174     *
175     * This may not verify the validity of the compressed data until first
176     * use.
177     */
178    static Asset* createFromCompressedData(int fd, off_t offset,
179        int compressionMethod, size_t compressedLength,
180        size_t uncompressedLength, AccessMode mode);
181#endif
182
183    /*
184     * Create the asset from a memory-mapped file segment.
185     *
186     * The asset takes ownership of the FileMap.
187     */
188    static Asset* createFromUncompressedMap(FileMap* dataMap, AccessMode mode);
189
190    /*
191     * Create the asset from a memory-mapped file segment with compressed
192     * data.  "method" is a Zip archive compression method constant.
193     *
194     * The asset takes ownership of the FileMap.
195     */
196    static Asset* createFromCompressedMap(FileMap* dataMap, int method,
197        size_t uncompressedLen, AccessMode mode);
198
199
200    /*
201     * Create from a reference-counted chunk of shared memory.
202     */
203    // TODO
204
205    AccessMode  mAccessMode;        // how the asset was opened
206    String8    mAssetSource;       // debug string
207
208    Asset*		mNext;				// linked list.
209    Asset*		mPrev;
210};
211
212
213/*
214 * ===========================================================================
215 *
216 * Innards follow.  Do not use these classes directly.
217 */
218
219/*
220 * An asset based on an uncompressed file on disk.  It may encompass the
221 * entire file or just a piece of it.  Access is through fread/fseek.
222 */
223class _FileAsset : public Asset {
224public:
225    _FileAsset(void);
226    virtual ~_FileAsset(void);
227
228    /*
229     * Use a piece of an already-open file.
230     *
231     * On success, the object takes ownership of "fd".
232     */
233    status_t openChunk(const char* fileName, int fd, off_t offset, size_t length);
234
235    /*
236     * Use a memory-mapped region.
237     *
238     * On success, the object takes ownership of "dataMap".
239     */
240    status_t openChunk(FileMap* dataMap);
241
242    /*
243     * Standard Asset interfaces.
244     */
245    virtual ssize_t read(void* buf, size_t count);
246    virtual off_t seek(off_t offset, int whence);
247    virtual void close(void);
248    virtual const void* getBuffer(bool wordAligned);
249    virtual off_t getLength(void) const { return mLength; }
250    virtual off_t getRemainingLength(void) const { return mLength-mOffset; }
251    virtual int openFileDescriptor(off_t* outStart, off_t* outLength) const;
252    virtual bool isAllocated(void) const { return mBuf != NULL; }
253
254private:
255    off_t       mStart;         // absolute file offset of start of chunk
256    off_t       mLength;        // length of the chunk
257    off_t       mOffset;        // current local offset, 0 == mStart
258    FILE*       mFp;            // for read/seek
259    char*       mFileName;      // for opening
260
261    /*
262     * To support getBuffer() we either need to read the entire thing into
263     * a buffer or memory-map it.  For small files it's probably best to
264     * just read them in.
265     */
266    enum { kReadVsMapThreshold = 4096 };
267
268    FileMap*    mMap;           // for memory map
269    unsigned char* mBuf;        // for read
270
271    const void* ensureAlignment(FileMap* map);
272};
273
274
275/*
276 * An asset based on compressed data in a file.
277 */
278class _CompressedAsset : public Asset {
279public:
280    _CompressedAsset(void);
281    virtual ~_CompressedAsset(void);
282
283    /*
284     * Use a piece of an already-open file.
285     *
286     * On success, the object takes ownership of "fd".
287     */
288    status_t openChunk(int fd, off_t offset, int compressionMethod,
289        size_t uncompressedLen, size_t compressedLen);
290
291    /*
292     * Use a memory-mapped region.
293     *
294     * On success, the object takes ownership of "fd".
295     */
296    status_t openChunk(FileMap* dataMap, int compressionMethod,
297        size_t uncompressedLen);
298
299    /*
300     * Standard Asset interfaces.
301     */
302    virtual ssize_t read(void* buf, size_t count);
303    virtual off_t seek(off_t offset, int whence);
304    virtual void close(void);
305    virtual const void* getBuffer(bool wordAligned);
306    virtual off_t getLength(void) const { return mUncompressedLen; }
307    virtual off_t getRemainingLength(void) const { return mUncompressedLen-mOffset; }
308    virtual int openFileDescriptor(off_t* outStart, off_t* outLength) const { return -1; }
309    virtual bool isAllocated(void) const { return mBuf != NULL; }
310
311private:
312    off_t       mStart;         // offset to start of compressed data
313    off_t       mCompressedLen; // length of the compressed data
314    off_t       mUncompressedLen; // length of the uncompressed data
315    off_t       mOffset;        // current offset, 0 == start of uncomp data
316
317    FileMap*    mMap;           // for memory-mapped input
318    int         mFd;            // for file input
319
320    unsigned char*  mBuf;       // for getBuffer()
321};
322
323// need: shared mmap version?
324
325}; // namespace android
326
327#endif // __LIBS_ASSET_H
328