include/utils/Asset.h - platform/frameworks/base - Gitiles

 /*
  * 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;

     /*
      * 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

     class StreamingZipInflater* mZipInflater;  // for streaming large compressed assets

     unsigned char*  mBuf;       // for getBuffer()
 };

 // need: shared mmap version?

 }; // namespace android

 #endif // __LIBS_ASSET_H
	/*
	* 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;

	/*
	* 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

	class StreamingZipInflater* mZipInflater; // for streaming large compressed assets

	unsigned char* mBuf; // for getBuffer()
	};

	// need: shared mmap version?

	}; // namespace android

	#endif // __LIBS_ASSET_H