/*
* 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