include/android/asset_manager.h

/*
 * Copyright (C) 2010 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.
 */

/**
 * @addtogroup Asset
 * @{
 */

/**
 * @file asset_manager.h
 */

#ifndef ANDROID_ASSET_MANAGER_H
#define ANDROID_ASSET_MANAGER_H

#ifdef __cplusplus
extern "C" {
#endif

struct AAssetManager;
/**
 * {@link AAssetManager} provides access to an application's raw assets by
 * creating {@link AAsset} objects.
 *
 * AAssetManager is a wrapper to the low-level native implementation
 * of the java {@link AAssetManager}, a pointer can be obtained using
 * AAssetManager_fromJava().
 *
 * The asset hierarchy may be examined like a filesystem, using
 * {@link AAssetDir} objects to peruse a single directory.
 *
 * A native {@link AAssetManager} pointer may be shared across multiple threads.
 */
typedef struct AAssetManager AAssetManager;

struct AAssetDir;
/**
 * {@link AAssetDir} provides access to a chunk of the asset hierarchy as if
 * it were a single directory. The contents are populated by the
 * {@link AAssetManager}.
 *
 * The list of files will be sorted in ascending order by ASCII value.
 */
typedef struct AAssetDir AAssetDir;

struct AAsset;
/**
 * {@link AAsset} provides access to a read-only asset.
 *
 * {@link AAsset} objects are NOT thread-safe, and should not be shared across
 * threads.
 */
typedef struct AAsset AAsset;

/** Available access modes for opening assets with {@link AAssetManager_open} */
enum {
    /** No specific information about how data will be accessed. **/
    AASSET_MODE_UNKNOWN      = 0,
    /** Read chunks, and seek forward and backward. */
    AASSET_MODE_RANDOM       = 1,
    /** Read sequentially, with an occasional forward seek. */
    AASSET_MODE_STREAMING    = 2,
    /** Caller plans to ask for a read-only buffer with all data. */
    AASSET_MODE_BUFFER       = 3
};


/**
 * Open the named directory within the asset hierarchy.  The directory can then
 * be inspected with the AAssetDir functions.  To open the top-level directory,
 * pass in "" as the dirName.
 *
 * The object returned here should be freed by calling AAssetDir_close().
 */
AAssetDir* AAssetManager_openDir(AAssetManager* mgr, const char* dirName);

/**
 * Open an asset.
 *
 * The object returned here should be freed by calling AAsset_close().
 */
AAsset* AAssetManager_open(AAssetManager* mgr, const char* filename, int mode);

/**
 * Iterate over the files in an asset directory.  A NULL string is returned
 * when all the file names have been returned.
 *
 * The returned file name is suitable for passing to AAssetManager_open().
 *
 * The string returned here is owned by the AssetDir implementation and is not
 * guaranteed to remain valid if any other calls are made on this AAssetDir
 * instance.
 */
const char* AAssetDir_getNextFileName(AAssetDir* assetDir);

/**
 * Reset the iteration state of AAssetDir_getNextFileName() to the beginning.
 */
void AAssetDir_rewind(AAssetDir* assetDir);

/**
 * Close an opened AAssetDir, freeing any related resources.
 */
void AAssetDir_close(AAssetDir* assetDir);

/**
 * Attempt to read 'count' bytes of data from the current offset.
 *
 * Returns the number of bytes read, zero on EOF, or < 0 on error.
 */
int AAsset_read(AAsset* asset, void* buf, size_t count);

/**
 * Seek to the specified offset within the asset data.  'whence' uses the
 * same constants as lseek()/fseek().
 *
 * Returns the new position on success, or (off_t) -1 on error.
 */
off_t AAsset_seek(AAsset* asset, off_t offset, int whence);

/**
 * Seek to the specified offset within the asset data.  'whence' uses the
 * same constants as lseek()/fseek().
 *
 * Uses 64-bit data type for large files as opposed to the 32-bit type used
 * by AAsset_seek.
 *
 * Returns the new position on success, or (off64_t) -1 on error.
 */
off64_t AAsset_seek64(AAsset* asset, off64_t offset, int whence);

/**
 * Close the asset, freeing all associated resources.
 */
void AAsset_close(AAsset* asset);

/**
 * Get a pointer to a buffer holding the entire contents of the assset.
 *
 * Returns NULL on failure.
 */
const void* AAsset_getBuffer(AAsset* asset);

/**
 * Report the total size of the asset data.
 */
off_t AAsset_getLength(AAsset* asset);

/**
 * Report the total size of the asset data. Reports the size using a 64-bit
 * number insted of 32-bit as AAsset_getLength.
 */
off64_t AAsset_getLength64(AAsset* asset);

/**
 * Report the total amount of asset data that can be read from the current position.
 */
off_t AAsset_getRemainingLength(AAsset* asset);

/**
 * Report the total amount of asset data that can be read from the current position.
 *
 * Uses a 64-bit number instead of a 32-bit number as AAsset_getRemainingLength does.
 */
off64_t AAsset_getRemainingLength64(AAsset* asset);

/**
 * Open a new file descriptor that can be used to read the asset data. If the
 * start or length cannot be represented by a 32-bit number, it will be
 * truncated. If the file is large, use AAsset_openFileDescriptor64 instead.
 *
 * Returns < 0 if direct fd access is not possible (for example, if the asset is
 * compressed).
 */
int AAsset_openFileDescriptor(AAsset* asset, off_t* outStart, off_t* outLength);

/**
 * Open a new file descriptor that can be used to read the asset data.
 *
 * Uses a 64-bit number for the offset and length instead of 32-bit instead of
 * as AAsset_openFileDescriptor does.
 *
 * Returns < 0 if direct fd access is not possible (for example, if the asset is
 * compressed).
 */
int AAsset_openFileDescriptor64(AAsset* asset, off64_t* outStart, off64_t* outLength);

/**
 * Returns whether this asset's internal buffer is allocated in ordinary RAM (i.e. not
 * mmapped).
 */
int AAsset_isAllocated(AAsset* asset);



#ifdef __cplusplus
};
#endif

#endif      // ANDROID_ASSET_MANAGER_H

/** @} */