/* * Copyright (C) 2006 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ // // Class providing access to a read-only asset. Asset objects are NOT // thread-safe, and should not be shared across threads. // #ifndef __LIBS_ASSET_H #define __LIBS_ASSET_H #include <stdio.h> #include <sys/types.h> #include "FileMap.h" #include "String8.h" #include "Errors.h" namespace android { /* * Instances of this class provide read-only operations on a byte stream. * * Access may be optimized for streaming, random, or whole buffer modes. All * operations are supported regardless of how the file was opened, but some * things will be less efficient. [pass that in??] * * "Asset" is the base class for all types of assets. The classes below * provide most of the implementation. The AssetManager uses one of the * static "create" functions defined here to create a new instance. */ class Asset { public: virtual ~Asset(void); static int32_t getGlobalCount(); static String8 getAssetAllocations(); /* used when opening an asset */ typedef enum AccessMode { ACCESS_UNKNOWN = 0, /* read chunks, and seek forward and backward */ ACCESS_RANDOM, /* read sequentially, with an occasional forward seek */ ACCESS_STREAMING, /* caller plans to ask for a read-only buffer with all data */ ACCESS_BUFFER, } AccessMode; enum { /* data larger than this does not get uncompressed into a buffer */ #ifdef HAVE_ANDROID_OS UNCOMPRESS_DATA_MAX = 1 * 1024 * 1024 #else UNCOMPRESS_DATA_MAX = 2 * 1024 * 1024 #endif }; /* * Read data from the current offset. Returns the actual number of * bytes read, 0 on EOF, or -1 on error. */ virtual ssize_t read(void* buf, size_t count) = 0; /* * Seek to the specified offset. "whence" uses the same values as * lseek/fseek. Returns the new position on success, or (off_t) -1 * on failure. */ virtual off_t seek(off_t offset, int whence) = 0; /* * Close the asset, freeing all associated resources. */ virtual void close(void) = 0; /* * Get a pointer to a buffer with the entire contents of the file. */ virtual const void* getBuffer(bool wordAligned) = 0; /* * Get the total amount of data that can be read. */ virtual off_t getLength(void) const = 0; /* * Get the total amount of data that can be read from the current position. */ virtual off_t getRemainingLength(void) const = 0; /* * Open a new file descriptor that can be used to read this asset. * Returns -1 if you can not use the file descriptor (for example if the * asset is compressed). */ virtual int openFileDescriptor(off_t* outStart, off_t* outLength) const = 0; /* * Return whether this asset's buffer is allocated in RAM (not mmapped). * Note: not virtual so it is safe to call even when being destroyed. */ virtual bool isAllocated(void) const { return false; } /* * Get a string identifying the asset's source. This might be a full * path, it might be a colon-separated list of identifiers. * * This is NOT intended to be used for anything except debug output. * DO NOT try to parse this or use it to open a file. */ const char* getAssetSource(void) const { return mAssetSource.string(); } protected: Asset(void); // constructor; only invoked indirectly /* handle common seek() housekeeping */ off_t handleSeek(off_t offset, int whence, off_t curPosn, off_t maxPosn); /* set the asset source string */ void setAssetSource(const String8& path) { mAssetSource = path; } AccessMode getAccessMode(void) const { return mAccessMode; } private: /* these operations are not implemented */ Asset(const Asset& src); Asset& operator=(const Asset& src); /* AssetManager needs access to our "create" functions */ friend class AssetManager; /* * Create the asset from a named file on disk. */ static Asset* createFromFile(const char* fileName, AccessMode mode); /* * Create the asset from a named, compressed file on disk (e.g. ".gz"). */ static Asset* createFromCompressedFile(const char* fileName, AccessMode mode); #if 0 /* * Create the asset from a segment of an open file. This will fail * if "offset" and "length" don't fit within the bounds of the file. * * The asset takes ownership of the file descriptor. */ static Asset* createFromFileSegment(int fd, off_t offset, size_t length, AccessMode mode); /* * Create from compressed data. "fd" should be seeked to the start of * the compressed data. This could be inside a gzip file or part of a * Zip archive. * * The asset takes ownership of the file descriptor. * * This may not verify the validity of the compressed data until first * use. */ static Asset* createFromCompressedData(int fd, off_t offset, int compressionMethod, size_t compressedLength, size_t uncompressedLength, AccessMode mode); #endif /* * Create the asset from a memory-mapped file segment. * * The asset takes ownership of the FileMap. */ static Asset* createFromUncompressedMap(FileMap* dataMap, AccessMode mode); /* * Create the asset from a memory-mapped file segment with compressed * data. "method" is a Zip archive compression method constant. * * The asset takes ownership of the FileMap. */ static Asset* createFromCompressedMap(FileMap* dataMap, int method, size_t uncompressedLen, AccessMode mode); /* * Create from a reference-counted chunk of shared memory. */ // TODO AccessMode mAccessMode; // how the asset was opened String8 mAssetSource; // debug string Asset* mNext; // linked list. Asset* mPrev; }; /* * =========================================================================== * * Innards follow. Do not use these classes directly. */ /* * An asset based on an uncompressed file on disk. It may encompass the * entire file or just a piece of it. Access is through fread/fseek. */ class _FileAsset : public Asset { public: _FileAsset(void); virtual ~_FileAsset(void); /* * Use a piece of an already-open file. * * On success, the object takes ownership of "fd". */ status_t openChunk(const char* fileName, int fd, off_t offset, size_t length); /* * Use a memory-mapped region. * * On success, the object takes ownership of "dataMap". */ status_t openChunk(FileMap* dataMap); /* * Standard Asset interfaces. */ virtual ssize_t read(void* buf, size_t count); virtual off_t seek(off_t offset, int whence); virtual void close(void); virtual const void* getBuffer(bool wordAligned); virtual off_t getLength(void) const { return mLength; } virtual off_t getRemainingLength(void) const { return mLength-mOffset; } virtual int openFileDescriptor(off_t* outStart, off_t* outLength) const; virtual bool isAllocated(void) const { return mBuf != NULL; } private: off_t mStart; // absolute file offset of start of chunk off_t mLength; // length of the chunk off_t mOffset; // current local offset, 0 == mStart FILE* mFp; // for read/seek char* mFileName; // for opening /* * To support getBuffer() we either need to read the entire thing into * a buffer or memory-map it. For small files it's probably best to * just read them in. */ enum { kReadVsMapThreshold = 4096 }; FileMap* mMap; // for memory map unsigned char* mBuf; // for read const void* ensureAlignment(FileMap* map); }; /* * An asset based on compressed data in a file. */ class _CompressedAsset : public Asset { public: _CompressedAsset(void); virtual ~_CompressedAsset(void); /* * Use a piece of an already-open file. * * On success, the object takes ownership of "fd". */ status_t openChunk(int fd, off_t offset, int compressionMethod, size_t uncompressedLen, size_t compressedLen); /* * Use a memory-mapped region. * * On success, the object takes ownership of "fd". */ status_t openChunk(FileMap* dataMap, int compressionMethod, size_t uncompressedLen); /* * Standard Asset interfaces. */ virtual ssize_t read(void* buf, size_t count); virtual off_t seek(off_t offset, int whence); virtual void close(void); virtual const void* getBuffer(bool wordAligned); virtual off_t getLength(void) const { return mUncompressedLen; } virtual off_t getRemainingLength(void) const { return mUncompressedLen-mOffset; } virtual int openFileDescriptor(off_t* outStart, off_t* outLength) const { return -1; } virtual bool isAllocated(void) const { return mBuf != NULL; } private: off_t mStart; // offset to start of compressed data off_t mCompressedLen; // length of the compressed data off_t mUncompressedLen; // length of the uncompressed data off_t mOffset; // current offset, 0 == start of uncomp data FileMap* mMap; // for memory-mapped input int mFd; // for file input unsigned char* mBuf; // for getBuffer() }; // need: shared mmap version? }; // namespace android #endif // __LIBS_ASSET_H