tetrees/Plugins/Wwise/ThirdParty/include/AK/SoundEngine/Common/AkStreamMgrModule.h

/*******************************************************************************
The content of this file includes portions of the AUDIOKINETIC Wwise Technology
released in source code form as part of the SDK installer package.

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Licensees holding valid commercial licenses to the AUDIOKINETIC Wwise Technology
may use this file in accordance with the end user license agreement provided 
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  Copyright (c) 2023 Audiokinetic Inc.
*******************************************************************************/

/// \file 
/// Audiokinetic's implementation-specific definitions and factory of 
/// overridable Stream Manager module.
/// Contains the default Stream Manager's implementation-specific interfaces that altogether constitute
/// the Low-Level I/O submodule. This submodule needs to be implemented by the game. All I/O requests 
/// generated by the Stream Manager end up to one of the I/O hooks defined herein.
/// Read \ref streamingmanager_lowlevel to learn more about the Low-Level I/O.

#ifndef _AK_STREAM_MGR_MODULE_H_
#define _AK_STREAM_MGR_MODULE_H_

#include <AK/SoundEngine/Common/IAkStreamMgr.h>
#include <AK/Tools/Common/AkPlatformFuncs.h>

class CAkFilePackage;

/// \name Audiokinetic Stream Manager's implementation-specific definitions.
//@{
/// Stream Manager initialization settings.
/// \sa 
/// - AK::IAkStreamMgr
/// - AK::StreamMgr::Create()
/// - \ref streamingmanager_settings

struct AkStreamMgrSettings
{
};

/// High-level IO devices initialization settings.
/// \sa 
/// - AK::IAkStreamMgr
/// - AK::StreamMgr::CreateDevice()
/// - \ref streamingmanager_settings
struct AkDeviceSettings
{
	void *				pIOMemory;					///< Pointer for I/O memory allocated by user.
													///< Pass NULL if you want memory to be allocated via AK::MemoryMgr::Malign().
													///< If specified, uIOMemorySize, uIOMemoryAlignment and ePoolAttributes are ignored.
	AkUInt32			uIOMemorySize;				///< Size of memory for I/O (for automatic streams). It is passed directly to AK::MemoryMgr::Malign(), after having been rounded down to a multiple of uGranularity.
	AkUInt32			uIOMemoryAlignment;			///< I/O memory alignment. It is passed directly to AK::MemoryMgr::Malign().
	AkUInt32			ePoolAttributes;			///< Attributes for I/O memory. Here, specify the allocation type (AkMemType_Device, and so on). It is passed directly to AK::MemoryMgr::Malign().
	AkUInt32			uGranularity;				///< I/O requests granularity (typical bytes/request).
	AkUInt32			uSchedulerTypeFlags;		///< Scheduler type flags.
    AkThreadProperties	threadProperties;			///< Scheduler thread properties.
	AkReal32			fTargetAutoStmBufferLength;	///< Targetted automatic stream buffer length (ms). When a stream reaches that buffering, it stops being scheduled for I/O except if the scheduler is idle.
	AkUInt32			uMaxConcurrentIO;			///< Maximum number of transfers that can be sent simultaneously to the Low-Level I/O.
	bool				bUseStreamCache;			///< If true, the device attempts to reuse I/O buffers that have already been streamed from disk. This is particularly useful when streaming small looping sounds. However, there is a small increase in CPU usage when allocating memory, and a slightly larger memory footprint in the StreamManager pool. 													
	AkUInt32			uMaxCachePinnedBytes;		///< Maximum number of bytes that can be "pinned" using AK::SoundEngine::PinEventInStreamCache() or AK::IAkStreamMgr::PinFileInCache()
};

/// \name Scheduler type flags.

/// Requests to Low-Level IO are synchronous. The streaming device expects a blocking I/O hook at creation time (IAkIOHookBlocking interface, see CreateDevice()). 
/// Functions of this interface should return only when the transfer is complete.
#define AK_SCHEDULER_BLOCKING          (0x01)
/// Requests to Low-Level IO are asynchronous, but posted one after the other, starting with streams that need data the most. 
/// The streaming device expects a deferred I/O hook at creation time (IAkIOHookDeferredBatch interface, see CreateDevice()). 
/// Up to AkDeviceSettings::uMaxConcurrentIO requests can be sent to the Low-Level I/O at the same time.
#define AK_SCHEDULER_DEFERRED_LINED_UP (0x02)

/// File descriptor. File identification for the low-level I/O.
/// \sa
/// - AK::StreamMgr::IAkLowLevelIOHook
struct AkFileDesc
{
    AkInt64				iFileSize;			///< File size in bytes
    AkUInt64			uSector;			///< Start sector (the sector size is specified by the low-level I/O)
											///< \sa
											///< - AK::StreamMgr::IAkFileLocationResolver::Open()
											///< - AK::StreamMgr::IAkLowLevelIOHook::GetBlockSize()
    AkUInt32			uCustomParamSize;	///< Size of the custom parameter
    void *				pCustomParam;		///< Custom parameter
    AkFileHandle		hFile;              ///< File handle/identifier
    AkDeviceID			deviceID;			///< Device ID, obtained from CreateDevice() \sa AK::IAkStreamMgr::CreateDevice()
	CAkFilePackage*		pPackage;			///< If this file is in a File Package, this will be the 
};

/// Structure for synchronous transfers handshaking with the Low-Level I/O. Used with blocking I/O hooks.
/// \sa AK::StreamMgr::IAkIOHookBlocking
struct AkIOTransferInfo
{
	AkUInt64		uFilePosition;		///< File offset where transfer should begin.
    AkUInt32		uBufferSize;		///< Size of the buffer in which the I/O hook can write to.
	AkUInt32		uRequestedSize;		///< Exact number of requested bytes for this transfer. Always equal to or smaller than uBufferSize.
};

struct AkAsyncIOTransferInfo;

/// Callback function prototype definition used for asynchronous I/O transfers between the Stream Manager
/// and the Low-Level IO. Used with deferred I/O hooks.
/// Notes:
/// - If you pass in_eResult of AK_Fail, all streams awaiting for this transfer are marked as invalid and will stop. An "IO error" notification is posted to the capture log.
/// - If the transfer was cancelled by the Stream Manager while it was in the Low-Level IO, you must return AK_Success, whether
/// you performed the operation or not. The Stream Manager knows that it was cancelled, so it will not try to use it after you call it back.
/// \sa 
/// - AkAsyncIOTransferInfo
/// - AK::StreamMgr::IAkIOHookDeferredBatch
AK_CALLBACK( void, AkIOCallback )( 
	AkAsyncIOTransferInfo * in_pTransferInfo,	///< Pointer to the AkAsyncIOTransferInfo structure that was passed to corresponding Read() or Write() call.
	AKRESULT		in_eResult					///< Result of transfer: AK_Success or AK_Fail (streams waiting for this transfer become invalid).
	);

/// Callback function prototype definition used for asynchronous I/O transfers between the Stream Manager
/// and the Low-Level IO. Used with batch deferred I/O hooks.
/// Notes:
/// - in_peResult and in_ppTransferInfo must both contain in_uNumTransfers number of elements
/// - For each in_peResult with a value of AK_Fail, all streams awaiting for the corresponding transfer are marked as invalid and will stop. An "IO error" notification is posted to the capture log.
/// - If a given transfer was cancelled by the Stream Manager while it was in the Low-Level IO, you must return AK_Success for that result, whether
/// you performed the operation or not. The Stream Manager knows that it was cancelled, so it will not try to use it after you call it back.
/// - Note that one call to BatchRead, BatchWrite or BatchCancel does not have to result in one execution of the callback. The only requirement is that
/// each element of in_ppTransferInfo passed in only has the IOCallback fired on it one time.
/// \sa 
/// - AkAsyncIOTransferInfo
/// - AK::StreamMgr::IAkIOHookDeferredBatch
AK_CALLBACK(void, AkBatchIOCallback)(
	AkUInt32				in_uNumTransfers,	///< Number of transfers to process
	AkAsyncIOTransferInfo** in_ppTransferInfo,	///< List of pointers to AkAsyncIOTransferInfo structures that were previously passed in to BatchRead() or BatchWrite()
	AKRESULT*				in_peResult			///< Array of results of each transfer: AK_Success or AK_Fail (streams waiting for this transfer become invalid).
	);

/// Structure for asynchronous transfers handshaking with the Low-Level I/O. Extends AkIOTransferInfo.
/// \sa 
/// - AK::StreamMgr::IAkIOHookDeferredBatch
/// - AkIOTransferInfo
/// - AkAIOCallback
struct AkAsyncIOTransferInfo : public AkIOTransferInfo
{
	void *			pBuffer;			///< Buffer for data transfer.
	AkIOCallback	pCallback;			///< Callback function used to notify the high-level device when the transfer is complete.
	void *			pCookie;			///< Reserved. The I/O device uses this cookie to retrieve the owner of the transfer.
	void *			pUserData;			///< Custom user data.
};

/// Low-Level I/O requests heuristics.
/// Used for asynchronous read requests. 
/// \sa 
/// - AK::StreamMgr::IAkIOHookBlocking::Read()
/// - AK::StreamMgr::IAkIOHookBlocking::Write()
/// - AK::StreamMgr::IAkIOHookDeferredBatch::Read()
/// - AK::StreamMgr::IAkIOHookDeferredBatch::Write()
struct AkIoHeuristics
{
	AkReal32		fDeadline;			///< Operation deadline (ms). 
	AkPriority		priority;			///< Operation priority (at the time it was scheduled and sent to the Low-Level I/O). Range is [AK_MIN_PRIORITY,AK_MAX_PRIORITY], inclusively.
};



//@}

namespace AK
{
	/// Audiokinetic Stream Manager's implementation-specific interfaces of the Low-Level IO submodule.
	namespace StreamMgr
	{
		/// Base interface for Low-Level I/O hooks. Defines common methods across both types of hooks.
		class IAkLowLevelIOHook
		{
		protected:
			/// Virtual destructor on interface to avoid warnings.
			virtual ~IAkLowLevelIOHook(){}

		public:
			/// Cleans up a file.
			/// \return AK_Success if the file was properly cleaned-up.
			virtual AKRESULT Close(
				AkFileDesc &			in_fileDesc			///< File descriptor.
				) = 0;

			/// Returns the block size for the file or its storage device. 
			/// The block size is a constraint for clients
			/// of the Stream Manager: All reads, writes and position changes need to be a multiple of
			/// that size.
			/// \return 
			/// The block size for a specific file or storage device.
			/// \remarks 
			/// - Some files might be opened with flags that require I/O transfers to be a multiple 
			/// of this size. The stream manager will query this function to resolve calls 
			/// to IAk(Auto)Stream::GetBlockSize( ).
			/// - Also, AkFileDesc::uSector specifies a number of sectors in multiples of this value.
			/// - Files/IO devices that do not require byte alignment should return 1.
			///	- Whether file opening was deferred or not, GetBlockSize() is always called right 
			/// after the first call to Open(), in the client's thread, and is never called again.
			/// \warning 
			/// Returning 0 is not allowed and will likely make the Stream Manager crash.
			/// \sa 
			///	- AK::StreamMgr::IAkFileLocationResolver::Open()
			/// - AK::StreamMgr::IAkIOHookBlocking::Read()
			/// - AK::StreamMgr::IAkIOHookBlocking::Write()
			/// - AK::StreamMgr::IAkIOHookDeferredBatch::Read()
			/// - AK::StreamMgr::IAkIOHookDeferredBatch::Write()
			virtual AkUInt32 GetBlockSize(
				AkFileDesc &			in_fileDesc			///< File descriptor.
				) = 0;

			/// Returns a description for the streaming device above this low-level hook.
			/// \remarks For profiling purposes only. The Release configuration of the 
			/// Stream Manager never calls it.
			virtual void GetDeviceDesc(
				AkDeviceDesc &			out_deviceDesc      ///< Device description.
				) = 0;

			/// Returns custom profiling data for the streaming device above this low-level hook.
			/// As opposed to GetDeviceDesc(), this is called at every monitoring frame.
			/// You may implement this function in order to display any value you find useful 
			/// in the "Streaming Devices" tab of the Wwise profiler ("Custom Param" column).
			/// \remarks For profiling purposes only. The Release configuration of the 
			/// Stream Manager never calls it.
			/// \return A 32-bit unsigned value to display in the Wwise profiler.
			virtual AkUInt32 GetDeviceData() = 0;
		};

		/// Interface for blocking low-level I/O transfers. Used by streaming devices created with the
		/// AK_SCHEDULER_BLOCKING flag.
		/// This is the simplest I/O hook. Calls to Read()/Write() must block until they are completed.
		/// The streaming device's I/O thread sends one transfer at a time.
		class IAkIOHookBlocking : public IAkLowLevelIOHook
		{
		protected:
			/// Virtual destructor on interface to avoid warnings.
			virtual ~IAkIOHookBlocking(){}

		public:

			/// Reads data from a file (synchronous). 
			/// Read data from the file described by in_fileDesc, in address out_pBuffer and with size and position 
			/// passed within io_transferInfo. When transfer is complete, return with the proper return code.
			/// \remarks 
			/// File position passed in io_transferInfo takes the offset of this file relative 
			/// to AkFileDesc::hFile (described with AkFileDesc::uSector). It is computed by the high-level 
			/// device as "in_fileDesc.uSector * Block_Size + Stream_Position", where Block_Size is obtained 
			/// via AK::StreamMgr::IAkLowLevelIOHook::GetBlockSize(). 
			/// \return 
			///     - AK_Success:	transfer was successful and out_pBuffer is filled with data.
			///     - AK_Fail:		an error occured.
			virtual AKRESULT Read(
				AkFileDesc &			in_fileDesc,        ///< File descriptor.
				const AkIoHeuristics &	in_heuristics,		///< Heuristics for this data transfer.
				void *					out_pBuffer,        ///< Buffer to be filled with data.
				AkIOTransferInfo &		in_transferInfo		///< Synchronous data transfer info. 
				) = 0;

			/// Writes data to a file (synchronous). 
			/// Write data to the file described by in_fileDesc, from address in_pData and with size and position 
			/// passed within io_transferInfo. When transfer is complete, return with the proper return code.
			/// \remarks File position passed in io_transferInfo takes the offset of this file relative 
			/// to AkFileDesc::hFile (described with AkFileDesc::uSector). It is computed by the high-level 
			/// device as "in_fileDesc.uSector * Block_Size + Stream_Position", where Block_Size is obtained 
			/// via AK::StreamMgr::IAkLowLevelIOHook::GetBlockSize(). 
			/// \return 
			///     - AK_Success:   transfer was successful.
			///     - AK_Fail:      an error occured.
			virtual AKRESULT Write(
				AkFileDesc &			in_fileDesc,        ///< File descriptor.
				const AkIoHeuristics &	in_heuristics,		///< Heuristics for this data transfer.
				void *					in_pData,           ///< Data to be written.
				AkIOTransferInfo &		io_transferInfo		///< Synchronous data transfer info. 
				) = 0;
		};

		/// Interface for batched deferred low-level I/O transfers. Used by streaming devices created
		/// with the AK_SCHEDULER_DEFERRED_LINED_UP flag.
		/// This I/O transfer handshaking method is preferred when you want to hook I/O to your own
		/// I/O streaming technology, and you want to submit multiple I/O requests in one call, so as
		/// to allow for better opportunities for CPU and I/O performance.
		/// You may queue them into your own system, and even use the heuristics passed down to this
		/// level for your convenience. Note that the requests are always sent in the order that the
		/// Stream Manager considers to be the most appropriate. You may receive less than
		/// AkDeviceSettings::uMaxConcurrentIO at any given time. The number of concurrent transfers
		/// depends on the number of streams running in the high-level streaming device, and on its
		/// target buffering length and granularity. Your advantage at this level is to be aware of
		/// file placement, so you may try to re-order requests in order to minimize seeking on disk. 
		/// Calls to BatchRead()/BatchWrite() should return as soon as possible. You need to call 
		/// AkAsyncIOTransferInfo::pCallback for an individual item, or AkBatchIOCallback for a collection
		/// of items as soon as a transfer is completed.
		/// Cancel() is provided in order to inform you that the streaming device will flush this transfer
		/// upon completion. You may implement it or not. In all cases, you must call the callback.
		class IAkIOHookDeferredBatch : public IAkLowLevelIOHook
		{
		protected:
			/// Virtual destructor on interface to avoid warnings.
			virtual ~IAkIOHookDeferredBatch() {}

		public:
			struct BatchIoTransferItem
			{
				AkFileDesc* pFileDesc;
				AkIoHeuristics ioHeuristics;
				AkAsyncIOTransferInfo* pTransferInfo;
			};

			/// Reads multiple data from multiple files (asynchronous).
			/// \remarks 
			/// - Queue up multiple read requests at once, using the provided array of in_pTransferItems. There will
			/// be in_uNumTransfers number of items in the array.
			/// - io_pDispatchResults will contain an in_uNumTransfers number of items in the array. Each item in
			/// io_pDispatchResults should be set to AK_Success if the corresponding Read was successfully dispatched,
			/// and set to AK_Failure otherwise. As well, the return value should be a cumulative result of the
			/// dispatches, where AK_Success indicates all requests were dispatched successfully, and
			/// io_pDispatchResults will not be investigated, whereas AK_Fail indicates at least one failure.
			/// - When a given Read, or some set of reads has completed - whether it was successful, cancelled,
			/// or failed - call in_pBatchIoCallback for the corresponding transfer. Pass in the list of
			/// AkAsyncIOTransferInfo objects to receive the callback, as well as a list of results for each transfer,
			/// e.g. AK_Success or some other AKRESULT. Do not call in_pBatchIoCallback for transfers that were not
			/// dispatched (as indicated by the corresponding value in io_pDispatchResults).
			/// - The pointer to each BatchIoTransferItem::pTransferInfo will be valid until the high-level
			/// device is notified through the callback. The array of in_pTransferItems will not be valid, though.
			/// - File position passed in each BatchIoTransferItem::pTransferInfo takes the offset of this file relative 
			/// to AkFileDesc::hFile (described with AkFileDesc::uSector). It is computed by the high-level 
			/// device as "pFileDesc->uSector * Block_Size + Stream_Position", where Block_Size is obtained 
			/// via AK::StreamMgr::IAkLowLevelIOHook::GetBlockSize(). 
			///
			/// \return 
			///     - AK_Success:    All I/O requests were successfully dispatched.
			///                      in_pBatchIoCallback must be called for each read that completes.
			///     - AK_Fail:       At least one failure occurred when dispatching reads.
			///                      The values of io_pDispatchResults should indicate which operation failed to be dispatched.
			virtual AKRESULT BatchRead(
				AkUInt32						in_uNumTransfers,		///< Number of transfers to process
				BatchIoTransferItem*			in_pTransferItems,		///< List of transfer items to process
				AkBatchIOCallback				in_pBatchIoCallback,	///< Callback to execute to handle completion of multiple items simultaneously
				AKRESULT*						io_pDispatchResults		///< Output result codes to indicate if a transfer was successfully dispatched
			) = 0;

			/// Write multiple data to multiple files (asynchronous).
			/// \remarks 
			/// - Queue up multiple write requests at once, using the provided array of in_pTransferItems. There will
			/// be in_uNumTransfers number of items in the array.
			/// - io_pDispatchResults will contain an in_uNumTransfers number of items in the array. Each item in
			/// io_pDispatchResults should be set to AK_Success if the corresponding write was successfully dispatched,
			/// and set to AK_Failure otherwise. As well, the return value should be a cumulative result of the
			/// dispatches, where AK_Success indicates all requests were dispatched successfully, and
			/// io_pDispatchResults will not be investigated, whereas AK_Fail indicates at least one failure.
			/// - When a given write, or some set of writes has completed - whether it was successful, cancelled,
			/// or failed - call in_pBatchIoCallback for the corresponding transfer. Pass in the list of
			/// AkAsyncIOTransferInfo objects to receive the callback, as well as a list of results for each transfer,
			/// e.g. AK_Success or some other AKRESULT. Do not call in_pBatchIoCallback for transfers that were not
			/// dispatched (as indicated by the corresponding value in io_pDispatchResults).
			/// - The pointer to each BatchIoTransferItem::pTransferInfo will be valid until the high-level
			/// device is notified through the callback. The array of in_pTransferItems will not be valid, though.
			/// - File position passed in each BatchIoTransferItem::pTransferInfo takes the offset of this file relative 
			/// to AkFileDesc::hFile (described with AkFileDesc::uSector). It is computed by the high-level 
			/// device as "pFileDesc->uSector * Block_Size + Stream_Position", where Block_Size is obtained 
			/// via AK::StreamMgr::IAkLowLevelIOHook::GetBlockSize(). 
			///
			/// \return 
			///     - AK_Success:    All I/O requests were successfully dispatched.
			///                      in_pBatchIoCallback must be called for each write that completes.
			///     - AK_Fail:       At least one failure occurred when dispatching writes.
			///                      The values of io_pDispatchResults should indicate which operation failed to be dispatched.
			virtual AKRESULT BatchWrite(
				AkUInt32						in_uNumTransfers,		///< Number of transfers to process
				BatchIoTransferItem*			in_pTransferItems,		///< List of transfer items to process
				AkBatchIOCallback				in_pBatchIoCallback,	///< Callback to execute to handle completion of multiple items simultaneously
				AKRESULT*						io_pDispatchResults		///< Output result codes to indicate if a transfer was successfully dispatched
			) = 0;

			/// Notifies that a transfer request is cancelled. It will be flushed by the streaming device when completed.
			/// Cancellation is normal and happens regularly; for example, whenever a sound stops before the end
			/// or stops looping. It happens even more frequently when buffering (AkDeviceSettings::fTargetAutoStmBufferLength 
			/// and AkDeviceSettings::uGranularity) is large and when you low-level IO hook accepts many concurrent requests
			/// at the same time.
			/// \remarks
			/// - Cancel() simply informs the Low-Level I/O that a specific transfer will be flushed upon reception. 
			///	The Low-Level I/O may use this information to stop this transfer right away, or not (it is internally tagged
			///	by the high-level device as cancelled). Nevertheless, the callback function MUST be called for cancelled 
			///	transfers to be resolved.
			/// - When calling the callback function of a cancelled transfer, pass it *AK_Success*. Passing AK_Fail 
			/// to AkAsyncIOTransfer::pCallback has the effect of killing the stream once and for all. This is not
			/// what you want.
			/// - If io_bCancelAllTransfersForThisFile is set, you may cancel all transfers for this file at once.
			///	Leave io_bCancelAllTransfersForThisFile to true if you don't want to be called again. For example, if
			/// you don't do anything special in Cancel(), leave it to true. This will reduce the amount of useless calls.
			/// If you set it to false, Cancel() will be called again for each remaining pending transfer that need to be cancelled. 
			/// - If io_bCancelAllTransfersForThisFile is not set, Cancel() is only called for a subset of pending 
			///	transfers for this file. You must not set it to true, as Cancel() needs to be called explicitly for each transfer that should be cancelled.
			/// \warning
			/// - The calling thread holds the stream's lock. You may call the callback function directly from here
			/// (if you can guarantee that the I/O buffer will not be accessed in the meantime), but you must not wait here 
			/// for another thread to call the callback function.
			/// - Likewise, if you resolve transfers with your own thread and use a lock to protect your transfers queue, 
			/// be careful not to run into a deadlock. Cancel() can be executed by any thread. Thus, if you need to lock your queue 
			/// in Cancel(), you must never hold this lock when calling back transfers, either from within Cancel() or from your 
			/// worker thread's routine. Lock your list, dequeue the transfer if you can, unlock, and call pCallback if and only if 
			/// the transfer was found and dequeued. On the other hand, if you choose not to do anything in Cancel(), the lock only protects 
			/// your list between Read()/Write() and your worker thread's routine, and since the device I/O thread does not hold the 
			/// stream's lock while calling Read()/Write(), your worker thread may therefore hold it while calling back transfers.
			/// - A race condition exists when cancelling all transfers (io_bCancelAllTransfersForThisFile is true) directly from within this hook. 
			/// If you handle the io_bCancelAllTransfersForThisFile == true case, you need to defer calling the completion callback to later 
			/// (from your usual I/O completion thread, for example). This will be fixed in a future version of Wwise.
			virtual void BatchCancel(
				AkUInt32						in_uNumTransfers,						///< Number of transfers to process
				BatchIoTransferItem*			in_pTransferItems,						///< List of transfer items to process
				bool**							io_ppbCancelAllTransfersForThisFile		///< Flag for each transfer indicating whether all transfers should be cancelled for this file (see notes in function description).
			) = 0;
		};


		/// Interface for deferred low-level I/O transfers. Used by streaming devices created with the
		/// AK_SCHEDULER_DEFERRED_LINED_UP flag.
		/// This is an "adapter" interface to forward calls to IAkIOHookDeferredBatch, to maintain
		/// compatibility with existing implementations, as well as provide a simpler interface for new
		/// implementations.
		/// This I/O transfer handshaking method is preferred when you want to hook I/O to your own
		/// I/O streaming technology. You will receive up to AkDeviceSettings::uMaxConcurrentIO requests
		/// at the same time. You may queue them into your own system, and even use the heuristics passed
		/// down to this level for your convenience. 
		/// Note that the requests are always sent in the order that the Stream Manager considers to be
		/// the most appropriate. You may receive less than AkDeviceSettings::uMaxConcurrentIO at any
		/// given time. The number of concurrent transfers depends on the number of streams running in 
		/// the high-level streaming device, and on its target buffering length and granularity.
		/// Your advantage at this level is to be aware of file placement, so you may try to re-order 
		/// requests in order to minimize seeking on disk. 
		/// Calls to Read()/Write() should return as soon as possible. You need to call 
		/// AkAsyncIOTransferInfo::pCallback as soon as a transfer is completed.
		/// Cancel() is provided in order to inform you that the streaming device will flush this transfer
		/// upon completion. You may implement it or not. In all cases, you must call the callback.
		class IAkIOHookDeferred : public IAkIOHookDeferredBatch
		{
		protected:
			/// Virtual destructor on interface to avoid warnings.
			virtual ~IAkIOHookDeferred(){}

		public:
			/// Reads data from a file (asynchronous).
			/// \remarks 
			/// - Queue up your read request with address, size and file position specified in io_transferInfo.
			/// - When transfer is complete (whether it was successful, cancelled or failed), call 
			/// AkAsyncIOTransferInfo::pCallback. However, if you return AK_Fail() from Read(), do not call
			/// AkAsyncIOTransferInfo::pCallback.
			/// - AkAsyncIOTransferInfo::pCookie must be passed to the callback function as-is. It must not
			/// be changed by the Low-Level I/O.
			/// - The reference to io_transferInfo will be valid until the high-level device is notified 
			/// through the callback.
			/// - File position passed in io_transferInfo takes the offset of this file relative 
			/// to AkFileDesc::hFile (described with AkFileDesc::uSector). It is computed by the high-level 
			/// device as "in_fileDesc.uSector * Block_Size + Stream_Position", where Block_Size is obtained 
			/// via AK::StreamMgr::IAkLowLevelIOHook::GetBlockSize(). 
			/// \return 
			///     - AK_Success:   An I/O request was successfully dispatched and is pending: 
			///                     AkAsyncIOTransferInfo::pCallback must be called when it completes.
			///     - AK_Fail:      An error occurred, no I/O request was dispatched
			virtual AKRESULT Read(
				AkFileDesc &			in_fileDesc,        ///< File descriptor.
				const AkIoHeuristics &	in_heuristics,		///< Heuristics for this data transfer.
				AkAsyncIOTransferInfo & io_transferInfo		///< Asynchronous data transfer info.
				) = 0;

			/// Writes data to a file (asynchronous).
			/// \remarks 
			/// - Queue up your write request with address, size and file position specified in io_transferInfo.
			/// - When transfer is complete (whether it was successful, cancelled or failed), call 
			/// AkAsyncIOTransferInfo::pCallback. However, if you return AK_Fail() from Write(), do not call
			/// AkAsyncIOTransferInfo::pCallback.
			/// - AkAsyncIOTransferInfo::pCookie must be passed to the callback function as-is. It must not
			/// be changed by the Low-Level I/O.
			/// - The reference to io_transferInfo will be valid until the high-level device is notified 
			/// through the callback.
			/// - File position passed in io_transferInfo takes the offset of this file relative 
			/// to AkFileDesc::hFile (described with AkFileDesc::uSector). It is computed by the high-level 
			/// device as "in_fileDesc.uSector * Block_Size + Stream_Position", where Block_Size is obtained 
			/// via AK::StreamMgr::IAkLowLevelIOHook::GetBlockSize(). 
			/// \return 
			///     - AK_Success:	 An I/O request was successfully processed and is pending: 
			///							AkAsyncIOTransferInfo::pCallback must be called when it completes.
			///     - AK_Fail:        an error occured.
			virtual AKRESULT Write(
				AkFileDesc &			in_fileDesc,        ///< File descriptor.
				const AkIoHeuristics &	in_heuristics,		///< Heuristics for this data transfer.
				AkAsyncIOTransferInfo & io_transferInfo		///< Platform-specific asynchronous IO operation info.
				) = 0;

			/// Notifies that a transfer request is cancelled. It will be flushed by the streaming device when completed.
			/// Cancellation is normal and happens regularly; for example, whenever a sound stops before the end
			/// or stops looping. It happens even more frequently when buffering (AkDeviceSettings::fTargetAutoStmBufferLength 
			/// and AkDeviceSettings::uGranularity) is large and when you low-level IO hook accepts many concurrent requests
			/// at the same time.
			/// \remarks
			/// - Cancel() simply informs the Low-Level I/O that a specific transfer will be flushed upon reception. 
			///	The Low-Level I/O may use this information to stop this transfer right away, or not (it is internally tagged
			///	by the high-level device as cancelled). Nevertheless, the callback function MUST be called for cancelled 
			///	transfers to be resolved.
			/// - When calling the callback function of a cancelled transfer, pass it *AK_Success*. Passing AK_Fail 
			/// to AkAsyncIOTransfer::pCallback has the effect of killing the stream once and for all. This is not
			/// what you want.
			/// - If io_bCancelAllTransfersForThisFile is set, you may cancel all transfers for this file at once.
			///	Leave io_bCancelAllTransfersForThisFile to true if you don't want to be called again. For example, if
			/// you don't do anything special in Cancel(), leave it to true. This will reduce the amount of useless calls.
			/// If you set it to false, Cancel() will be called again for each remaining pending transfer that need to be cancelled. 
			/// - If io_bCancelAllTransfersForThisFile is not set, Cancel() is only called for a subset of pending 
			///	transfers for this file. You must not set it to true, as Cancel() needs to be called explicitly for each transfer that should be cancelled.
			/// \warning
			/// - The calling thread holds the stream's lock. You may call the callback function directly from here
			/// (if you can guarantee that the I/O buffer will not be accessed in the meantime), but you must not wait here 
			/// for another thread to call the callback function.
			/// - Likewise, if you resolve transfers with your own thread and use a lock to protect your transfers queue, 
			/// be careful not to run into a deadlock. Cancel() can be executed by any thread. Thus, if you need to lock your queue 
			/// in Cancel(), you must never hold this lock when calling back transfers, either from within Cancel() or from your 
			/// worker thread's routine. Lock your list, dequeue the transfer if you can, unlock, and call pCallback if and only if 
			/// the transfer was found and dequeued. On the other hand, if you choose not to do anything in Cancel(), the lock only protects 
			/// your list between Read()/Write() and your worker thread's routine, and since the device I/O thread does not hold the 
			/// stream's lock while calling Read()/Write(), your worker thread may therefore hold it while calling back transfers.
			/// - A race condition exists when cancelling all transfers (io_bCancelAllTransfersForThisFile is true) directly from within this hook. 
			/// If you handle the io_bCancelAllTransfersForThisFile == true case, you need to defer calling the completion callback to later 
			/// (from your usual I/O completion thread, for example). This will be fixed in a future version of Wwise.
			virtual void Cancel(
				AkFileDesc &		in_fileDesc,			///< File descriptor.
				AkAsyncIOTransferInfo & io_transferInfo,	///< Transfer info to cancel.
				bool & io_bCancelAllTransfersForThisFile	///< Flag indicating whether all transfers should be cancelled for this file (see notes in function description).
				) = 0;

			/// The following functions each provide "stub" implementations of IAkHookDeferredIOBatch operations, so as to forward calls to 
			/// the existing single-transfer variants. The soundengine never calls IAkHookDeferred::Read et al, internally, and only
			/// ever calls IAkIOHookDeferredBatch::BatchRead et al. 
			virtual AKRESULT BatchRead(
				AkUInt32				in_uNumTransfers,		///< Number of transfers to process
				BatchIoTransferItem*	in_pTransferItems,		///< List of transfer items to process
				AkBatchIOCallback		/*in_pBatchIoCallback*/,///< Callback to execute to handle completion of multiple items simultaneously
				AKRESULT*				io_pDispatchResults		///< Output result codes to indicate if a transfer was successfully dispatched
			)
			{
				AKRESULT cumulativeResult = AK_Success;
				for (AkUInt32 i = 0; i < in_uNumTransfers; ++i)
				{
					BatchIoTransferItem ioTransferItem = in_pTransferItems[i];
					AKRESULT result = Read(*(ioTransferItem.pFileDesc), ioTransferItem.ioHeuristics, *(ioTransferItem.pTransferInfo));
					io_pDispatchResults[i] = result;
					cumulativeResult = result == AK_Success ? cumulativeResult : AK_Fail;
				}
				return cumulativeResult;
			}

			virtual AKRESULT BatchWrite(
				AkUInt32				in_uNumTransfers,		///< Number of transfers to process
				BatchIoTransferItem*	in_pTransferItems,		///< List of transfer items to process
				AkBatchIOCallback		/*in_pBatchIoCallback*/,///< Callback to execute to handle completion of multiple items simultaneously
				AKRESULT*				io_pDispatchResults		///< Output result codes to indicate if a transfer was successfully dispatched
			)
			{
				AKRESULT cumulativeResult = AK_Success;
				for (AkUInt32 i = 0; i < in_uNumTransfers; ++i)
				{
					BatchIoTransferItem ioTransferItem = in_pTransferItems[i];
					AKRESULT result = Write(*(ioTransferItem.pFileDesc), ioTransferItem.ioHeuristics, *(ioTransferItem.pTransferInfo));
					io_pDispatchResults[i] = result;
					cumulativeResult = result == AK_Success ? cumulativeResult : AK_Fail;
				}
				return cumulativeResult;
			}
			virtual void BatchCancel(
				AkUInt32				in_uNumTransfers,		///< Number of transfers to process
				BatchIoTransferItem*	in_pTransferItems,		///< List of transfer items to process
				bool** io_ppbCancelAllTransfersForThisFile		///< Flag for each transfer indicating whether all transfers should be cancelled for this file (see notes in function description).
			)
			{
				for (AkUInt32 i = 0; i < in_uNumTransfers; ++i)
				{
					BatchIoTransferItem ioTransferItem = in_pTransferItems[i];
					Cancel(*(ioTransferItem.pFileDesc), *(ioTransferItem.pTransferInfo), *(io_ppbCancelAllTransfersForThisFile[i]));
				}
			}

		};

		/// File location resolver interface. There is one and only one File Location Resolver that is
		/// registered to the Stream Manager (using AK::StreamMgr::SetFileLocationResolver()). Its purpose
		/// is to map a file name or ID to 
		/// 1) a streaming device / I/O hook;
		/// 2) a valid file descriptor (AkFileDesc) usable by the I/O hook.
		/// When your Low-Level I/O submodule uses a single device, you should create a standalone I/O
		/// hook which implements one of the I/O hooks defined above (blocking or deferred), as well 
		/// as the File Location Resolver. You then register this object to the Stream Manager as the 
		/// File Location Resolver.
		/// If you wish to create multiple devices, then you should have a separate object that implements
		/// AK::StreamMgr::IAkFileLocationResolver and registers to the Stream Manager as such. This object
		/// will be used to dispatch the file open request to the appropriate device. The strategy you will 
		/// use to select the correct device is up to you to implement. You may also implement a set of
		/// hooks that delegate opening to the next device when they can't find the file requested 
		/// (like a chain of responsiblity pattern), although this will likely be less efficient.
		class IAkFileLocationResolver
		{
		protected:
			/// Virtual destructor on interface to avoid warnings.
			virtual ~IAkFileLocationResolver(){}

		public:

			/// Returns a file descriptor for a given file name (string).
			/// Performs the operations needed to make the file descriptor usable by
			/// the other methods of the interface (for e.g. ask the OS for a valid file handle).
			/// \return 
			///     - AK_Success:       A valid file descriptor is returned
			///     - AK_FileNotFound:  File was not found.
			///     - AK_Fail:          File could not be open for any other reason.
			/// \return 
			///		- A file descriptor, that contains 
			///         - an unique identifier to be used with functions of the low-level IO 
			///           interface.
			///         - the total stream size in bytes.
			///         - the offset from the beginning of the file (in blocks).
			///         - a device ID, that was obtained through AK::StreamMgr::CreateDevice().
			///		- The updated io_bSyncOpen flag depending on the File Resolver's deferred opening policy.
			/// \remarks
			///		- The file descriptor is unique for each stream, and its address remains the same 
			///		throughout its lifetime. In other words, the value of &in_fileDesc inside Read() or
			///		Close() is the same as &out_fileDesc in Open().
			///		- Open() is always called first in the client thread.
			///		- If io_bSyncOpen is true, file opening must be executed now. If it is false,
			///		the File Location Resolver may choose whether it wants open it now, or later
			///		from the streaming device's thread. If it wishes to open it now, then it must
			///		set io_bSyncOpen to true. Otherwise, it needs to do the following: leave 
			///		io_bSyncOpen to false, clear out_fileDesc::iFileSize and out_fileDesc::uSector, 
			///		and set out_fileDesc::deviceID to the streaming device's ID that will handle 
			///		this file. By returning io_bSyncOpen as false, the Stream Manager will interpret
			///		this as a request for deferred file opening, and this function will called again
			///		from the streaming device's thread (this time, with this io_bSyncOpen set to true).
			///		- All members of out_fileDesc will be cleared upon first call to Open().
			/// \warning
			///		- It is illegal to return io_bSyncOpen as false if Open() was called with io_bSyncOpen
			///		set to true.
			///		- Deferred file opening requires allocations in the Stream Manager's small object pool.
			///		The File Location Resolver should always choose to open files synchronously if it is 
			///		fast to do so.
			///		- Whether opening is deferred or not, GetBlockSize() is always called right after the
			///		first call to Open(), in the client's thread, and is never called again.
			/// \sa 
			///	- GetBlockSize()
			/// - \ref streamingmanager_lowlevel_location
			virtual AKRESULT Open( 
				const AkOSChar*			in_pszFileName,		///< File name.
				AkOpenMode				in_eOpenMode,		///< Open mode.
				AkFileSystemFlags *		in_pFlags,			///< Special flags. Can pass NULL.
				bool &					io_bSyncOpen,		///< If true, the file must be opened synchronously. Otherwise it is left at the File Location Resolver's discretion. Return false if Open needs to be deferred.
				AkFileDesc &			io_fileDesc         ///< Returned file descriptor.
				) = 0;

			/// Returns a file descriptor for a given file ID.
			/// Performs the operations needed to make the file descriptor usable by
			/// the other methods of the interface (for e.g. ask the OS for a valid file handle).
			/// \return 
			///     - AK_Success:       A valid file descriptor is returned
			///     - AK_FileNotFound:  File was not found.
			///     - AK_Fail:          File could not be open for any other reason.
			/// \return 
			///		- A file descriptor, that contains 
			///         - an unique identifier to be used with functions of the low-level IO 
			///           interface.
			///         - the total stream size in bytes.
			///         - the offset from the beginning of the file (in blocks).
			///         - a device ID, that was obtained through AK::StreamMgr::CreateDevice().
			///		- The updated io_bSyncOpen flag depending on the File Resolver's deferred opening policy.
			/// \remarks
			///		- Open() is always called first in the client thread.
			///		- If io_bSyncOpen is true, file opening must be executed now. If it is false,
			///		the File Location Resolver may choose whether it wants open it now, or later
			///		from the streaming device's thread. If it wishes to open it now, then it must
			///		set io_bSyncOpen to true. Otherwise, it needs to do the following: leave 
			///		io_bSyncOpen to false, clear out_fileDesc::iFileSize and out_fileDesc::uSector, 
			///		and set out_fileDesc::deviceID to the streaming device's ID that will handle 
			///		this file. By returning io_bSyncOpen as false, the Stream Manager will interpret
			///		this as a request for deferred file opening, and this function will called again
			///		from the streaming device's thread (this time, with this io_bSyncOpen set to true).
			///		- All members of out_fileDesc will be cleared upon first call to Open().
			/// \warning
			///		- It is illegal to return io_bSyncOpen as false if Open() was called with io_bSyncOpen
			///		set to true.
			///		- Deferred file opening requires allocations in the Stream Manager's small object pool.
			///		The File Location Resolver should always choose to open files synchronously if it is 
			///		fast to do so.
			///		- Whether opening is deferred or not, GetBlockSize() is always called right after the
			///		first call to Open(), in the client's thread, and is never called again.
			///	- GetBlockSize()
			/// - \ref streamingmanager_lowlevel_location
			virtual AKRESULT Open( 
				AkFileID				in_fileID,          ///< File ID.
				AkOpenMode				in_eOpenMode,       ///< Open mode.
				AkFileSystemFlags *		in_pFlags,			///< Special flags. Can pass NULL.
				bool &					io_bSyncOpen,		///< If true, the file must be opened synchronously. Otherwise it is left at the File Location Resolver's discretion. Return false if Open needs to be deferred.
				AkFileDesc &			io_fileDesc         ///< Returned file descriptor.
				) = 0;

			/// <summary>
			/// This function is called to provide information when file related errors occur. The base paths known by this Resolver should be returned in out_searchedPath.
			/// </summary>			
			virtual AKRESULT OutputSearchedPaths(
				const AKRESULT& in_result,				///< Result of the open call
				const AkOSChar* in_pszFileName,			///< File name that was accessed
				AkFileSystemFlags* in_pFlags,			///< Special flags. Can be NULL.
				AkOpenMode in_eOpenMode,				///< File open mode (read, write, ...).
				AkOSChar* out_searchedPath,				///< Pre-allocated string buffer to be filled with all searched paths searched for the file.
				AkInt32 in_pathSize						///< The maximum size of the string
			) {	return AK_NotImplemented; };

			virtual AKRESULT OutputSearchedPaths(
				const AKRESULT& in_result,				///< Result of the open call
				const AkFileID in_fileID,				///< File ID that was accessed
				AkFileSystemFlags* in_pFlags,			///< Special flags. Can be NULL.
				AkOpenMode in_eOpenMode,				///< File open mode (read, write, ...).
				AkOSChar* out_searchedPath,				///< Pre-allocated string buffer to be filled with all searched paths searched for the file.
				AkInt32 in_pathSize		   				///< The maximum size of the string
			) {	return AK_NotImplemented; };
		};

		/// \name Audiokinetic implementation-specific Stream Manager factory.
		//@{
		/// Stream Manager factory.
		/// \remarks 
		/// - In order for the Stream Manager to work properly, you also need to create 
		/// at least one streaming device (and implement its I/O hook), and register the 
		/// File Location Resolver with AK::StreamMgr::SetFileLocationResolver().
		/// - Use AK::StreamMgr::GetDefaultSettings(), then modify the settings you want,
		/// then feed this function with them.
		/// \sa 
		/// - AK::IAkStreamMgr
		/// - AK::StreamMgr::SetFileLocationResolver()
		/// - AK::StreamMgr::GetDefaultSettings()
		AK_EXTERNAPIFUNC( IAkStreamMgr *, Create )( 
			const AkStreamMgrSettings &	in_settings		///< Stream manager initialization settings.
			);

		/// Get the default values for the Stream Manager's settings.
		/// \sa 
		/// - AK::StreamMgr::Create()
		/// - AkStreamMgrSettings
		/// - \ref streamingmanager_settings
		AK_EXTERNAPIFUNC( void, GetDefaultSettings )(
			AkStreamMgrSettings &		out_settings	///< Returned AkStreamMgrSettings structure with default values.
			);

		/// Get the one and only File Location Resolver registered to the Stream Manager.
		/// \sa
		/// - AK::StreamMgr::IAkFileLocationResolver
		/// - AK::StreamMgr::SetFileLocationResolver()
		AK_EXTERNAPIFUNC( IAkFileLocationResolver *, GetFileLocationResolver )();

		/// Register the one and only File Location Resolver to the Stream Manager.
		/// \sa 
		/// - AK::StreamMgr::IAkFileLocationResolver
		AK_EXTERNAPIFUNC( void, SetFileLocationResolver )(
			IAkFileLocationResolver *	in_pFileLocationResolver ///< Interface to your File Location Resolver
			);

		//@}

		/// \name Stream Manager: High-level I/O devices management.
		//@{
		/// Streaming device creation.
		/// Creates a high-level device, with specific settings. 
		/// You need to provide the associated low-level I/O hook, implemented on your side.
		/// \return The device ID. AK_INVALID_DEVICE_ID if there was an error and it could not be created.
		/// \warning 
		/// - This function is not thread-safe.
		/// - Use a blocking hook (IAkIOHookBlocking) with SCHEDULER_BLOCKING devices, and a 
		/// deferred hook (IAkIOHookDeferredBatch) with SCHEDULER_DEFERRED_LINED_UP devices (these flags are
		/// specified in the device settings (AkDeviceSettings). The pointer to IAkLowLevelIOHook is
		/// statically cast internally into one of these hooks. Implementing the wrong (or no) interface
		/// will result into a crash.
		/// \remarks 
		/// - You may use AK::StreamMgr::GetDefaultDeviceSettings() first to get default values for the 
		/// settings, change those you want, then feed the structure to this function.
		/// - The returned device ID should be kept by the Low-Level IO, to assign it to file descriptors 
		/// in AK::StreamMgr::IAkFileLocationResolver::Open().
		/// \sa
		/// - AK::StreamMgr::IAkLowLevelIOHook
		/// - AK::StreamMgr::GetDefaultDeviceSettings()
		/// - \ref streamingmanager_settings
		AK_EXTERNAPIFUNC( AkDeviceID, CreateDevice )(
			const AkDeviceSettings &	in_settings,		///< Device settings.
			IAkLowLevelIOHook *			in_pLowLevelHook	///< Associated low-level I/O hook. Pass either a IAkIOHookBlocking or a IAkIOHookDeferredBatch interface, consistent with the type of the scheduler.
			);
		/// Streaming device destruction.
		/// \return AK_Success if the device was successfully destroyed.
		/// \warning This function is not thread-safe. No stream should exist for that device when it is destroyed.
		AK_EXTERNAPIFUNC( AKRESULT, DestroyDevice )(
			AkDeviceID					in_deviceID         ///< Device ID of the device to destroy.
			);
		
		/// Execute pending I/O operations on all created I/O devices.
		/// This should only be called in single-threaded environments where an I/O device cannot spawn a thread.
		/// \return AK_Success when called from an appropriate environment, AK_NotCompatible otherwise.
		/// \sa 
		/// - AK::StreamMgr::CreateDevice()
		AK_EXTERNAPIFUNC( AKRESULT, PerformIO )();

		/// Get the default values for the streaming device's settings. Recommended usage
		/// is to call this function first, then pass the settings to AK::StreamMgr::CreateDevice().
		/// \sa 
		/// - AK::StreamMgr::CreateDevice()
		/// - AkDeviceSettings
		/// - \ref streamingmanager_settings
		AK_EXTERNAPIFUNC( void, GetDefaultDeviceSettings )(
			AkDeviceSettings &			out_settings		///< Returned AkDeviceSettings structure with default values.
			);
		//@}

		/// \name Language management.
		//@{
		/// Set the current language once and only once, here. The language name is stored in a static buffer 
		/// inside the Stream Manager. In order to resolve localized (language-specific) file location,
		/// AK::StreamMgr::IAkFileLocationResolver implementations query this string. They may use it to 
		/// construct a file path (for e.g. SDK/samples/SoundEngine/Common/AkFileLocationBase.cpp), or to
		/// find a language-specific file within a look-up table (for e.g. SDK/samples/SoundEngine/Common/AkFilePackageLUT.cpp).
		/// Pass a valid null-terminated string, without a trailing slash or backslash. Empty strings are accepted.
		/// You may register for language changes (see RegisterToLanguageChangeNotification()). 
		/// After changing the current language, all observers are notified.
		/// \return AK_Success if successful (if language string has less than AK_MAX_LANGUAGE_NAME_SIZE characters). AK_Fail otherwise.
		/// \warning Not multithread safe.
		/// \sa 
		/// - AK::StreamMgr::GetCurrentLanguage()
		/// - AK::StreamMgr::AddLanguageChangeObserver()
		AK_EXTERNAPIFUNC( AKRESULT, SetCurrentLanguage )(
			const AkOSChar *	in_pszLanguageName			///< Language name.
			);

		/// Get the current language. The language name is stored in a static buffer inside the Stream Manager, 
		/// with AK::StreamMgr::SetCurrentLanguage(). In order to resolve localized (language-specific) file location,
		/// AK::StreamMgr::IAkFileLocationResolver implementations query this string. They may use it to 
		/// construct a file path (for e.g. SDK/samples/SoundEngine/Common/AkFileLocationBase.cpp), or to
		/// find a language-specific file within a look-up table (for e.g. SDK/samples/SoundEngine/Common/AkFilePackageLUT.cpp).
		/// \return Current language.
		/// \sa AK::StreamMgr::SetCurrentLanguage()
		AK_EXTERNAPIFUNC( const AkOSChar *, GetCurrentLanguage )();

		/// Definition of handlers for language change notifications.
		/// Called after SetCurrentLanguage() is called.
		/// \warning Do not call AddLanguageChangeObserver or SetCurrentLanguage from within your handler.
		/// \warning Not multithread safe.
		/// \sa 
		/// - AK::StreamMgr::SetCurrentLanguage()
		/// - AK::StreamMgr::AddLanguageChangeObserver()
		AK_CALLBACK( void, AkLanguageChangeHandler )( 
			const AkOSChar * const in_pLanguageName,///< New language name.
			void * in_pCookie						///< Cookie that was passed to AddLanguageChangeObserver().
			);

		/// Register to language change notifications.
		/// \return AK_Success if successful, AK_Fail otherwise (no memory or no cookie).
		/// \warning Not multithread safe.
		/// \sa 
		/// - AK::StreamMgr::SetCurrentLanguage()
		/// - AK::StreamMgr::RemoveLanguageChangeObserver()
		AK_EXTERNAPIFUNC( AKRESULT, AddLanguageChangeObserver )(
			AkLanguageChangeHandler in_handler,	///< Callback function.
			void * in_pCookie					///< Cookie, passed back to AkLanguageChangeHandler. Must set.
			);

		/// Unregister to language change notifications. Use the cookie you have passed to 
		/// AddLanguageChangeObserver() to identify the observer.
		/// \warning Not multithread safe.
		/// \sa 
		/// - AK::StreamMgr::SetCurrentLanguage()
		/// - AK::StreamMgr::AddLanguageChangeObserver()
		AK_EXTERNAPIFUNC( void, RemoveLanguageChangeObserver )(
			void * in_pCookie					///< Cookie that was passed to AddLanguageChangeObserver().
			);

		/// \name Stream Manager: Cache management.
		//@{
		/// Flush cache of all devices. This function has no effect for devices where
		/// AkDeviceSettings::bUseStreamCache was set to false (no caching).
		/// \sa
		/// - \ref streamingmanager_settings
		AK_EXTERNAPIFUNC( void, FlushAllCaches )();
		
		//@}
	}
}

#endif //_AK_STREAM_MGR_MODULE_H_