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