MityDSP::tcDspStorageCache Class Reference

Instances of this class provide a simple cache between an application or filesystem (or other) driver. More...

#include <core/DspStorageCache.h>

Inheritance diagram for MityDSP::tcDspStorageCache:

Classes
struct	buf_list
	cache-list header structure More...
Public Member Functions
	tcDspStorageCache (tcDspStorageBase *apDevice, unsigned int anNumSectors)
	This constructor is used to create a read/write cache of the specified number of sectors for a tcDspStorageBase-derived class instance.
	~tcDspStorageCache ()
	Default destructor.
virtual void	reset (void)
	This routine resets all cache entries, without flushing any dirty entries.
virtual int	write (void apAddr, void apData, int anBytes)
	This routine writes an arbitrary amount of data to an MMC device at a specified offset from the start of the device.
virtual int	write (unsigned int anSector, unsigned int anOffset, void *apData, int anBytes)
	Sector-based version of the write method.
virtual int	read (void apStartAddr, void apBuffer, int anBytes)
	This routine reads an arbitrary amount of data from an MMC device from the specified offset position.
virtual int	read (unsigned int anSector, unsigned int anOffset, void *apBuffer, int anBytes)
	Sector-based version of the read method.
Protected Types
typedef struct MityDSP::tcDspStorageCache::buf_list	tsBufferList
	cache-list header structure
Protected Member Functions
void	resetDeviceInfo (void)
	This routine reads sector map information from the underlying device and creates copies of the map and the required cache buffers to match.
tsBufferList *	getCacheSector (unsigned int anSector, unsigned int anExpectedSize, bool abLoad)
	This method checks the current cache for the sector in question.
tsBufferList *	flushCacheSector (tsBufferList *anEntry)
	This method checks the specified cache entry to see if it's "dirty".
Protected Attributes
LCK_Handle	mhMutex
	Lock to serialize access.
BUF_Handle	mhSectorPool
	Pool of sector buffers.
BUF_Handle	mhSectorListPool
	Pool of cache list entries.
tcDspStorageBase *	mpDevice
	Access to the storage device to cache.
unsigned int	mnCacheSectors
	Maximum sectors in cache.
unsigned int	mnMaxSectorSize
	Largest sector size (bytes).
tsBufferList *	mpCacheHead
	Head of cache linked list.
bool	mbAnyDirty
	Set whenever any cache entries need to be flushed.

Detailed Description

Instances of this class provide a simple cache between an application or filesystem (or other) driver.

See also:: tcDspStorageCache Page

Member Typedef Documentation

typedef struct MityDSP::tcDspStorageCache::buf_list MityDSP::tcDspStorageCache::tsBufferList [protected]

cache-list header structure

Constructor & Destructor Documentation

tcDspStorageCache::tcDspStorageCache	(	tcDspStorageBase *	apDevice,
		unsigned int	anNumSectors
	)

This constructor is used to create a read/write cache of the specified number of sectors for a tcDspStorageBase-derived class instance.

Parameters:

`[in]`	apDevice	Pointer to the underlying tcDspStorageBase device.
`[in]`	anNumSectors	Maximum number of sectors to cache.

Returns:: None.

See also:: DspStorageCache.h

tcDspStorageCache::~tcDspStorageCache ( )

Default destructor.

Returns:: None.

See also:: DspStorageCache.h

Member Function Documentation

void tcDspStorageCache::reset ( void ) [virtual]

This routine resets all cache entries, without flushing any dirty entries.

This is necessary when a removable device is removed, and subsequently reinserted (with unknown changes made in the mean time).

Writing out dirty cache entries in this case would be bad... a flush should have been done prior to removal by the application.

Returns:: None.

See also:: DspStorageCache.h

int tcDspStorageCache::write	(	void *	apAddr,
		void *	apData,
		int	anBytes
	)			`[virtual]`

This routine writes an arbitrary amount of data to an MMC device at a specified offset from the start of the device.

The routine handles preservation of data when only a partial sector is written. The data does not have to be sector aligned, although writing aligned, full sectors is most efficient.

Parameters:

`[in]`	apAddr	Pointer to the offset position on the MMC device.
`[in]`	apData	A buffer containing the data to be written.
`[in]`	anBytes	Size of the data to be written in bytes.

Returns:: The number of bytes successfully written.

See also:: DspStorageCache.h

Implements MityDSP::tcDspStorageBase.

int tcDspStorageCache::write	(	unsigned int	anSector,
		unsigned int	anOffset,
		void *	apData,
		int	anBytes
	)			`[virtual]`

Sector-based version of the write method.

Note:: A request to write sector 0xFFFFFFFF is taken to be a request to flush all dirty cache entries.

Parameters:

`[in]`	anSector	The sector to write to.
`[in]`	anOffset	The offset from the start of the sector.
`[in]`	apData	A buffer containing the data to be written.
`[in]`	anBytes	Size of the data to be written in bytes.

Returns:: The number of bytes successfully written.

See also:: DspStorageCache.h

Implements MityDSP::tcDspStorageBase.

int tcDspStorageCache::read	(	void *	apStartAddr,
		void *	apBuffer,
		int	anBytes
	)			`[virtual]`

This routine reads an arbitrary amount of data from an MMC device from the specified offset position.

Results of the read are stored in apBuffer.

Parameters:

`[in]`	apStartAddr	Pointer to the data offset on the MMC device.
`[out]`	apBuffer	A buffer to hold the data that is read.
`[in]`	anBytes	Size of the data to be read in bytes.

Returns:: The number of bytes successfully read.

See also:: DspStorageCache.h

Implements MityDSP::tcDspStorageBase.

int tcDspStorageCache::read	(	unsigned int	anSector,
		unsigned int	anOffset,
		void *	apBuffer,
		int	anBytes
	)			`[virtual]`

Sector-based version of the read method.

Parameters:

`[in]`	anSector	The sector to copy from.
`[in]`	anOffset	The offset from the start of the sector.
`[out]`	apBuffer	A buffer to hold the data that is read.
`[in]`	anBytes	Size of the data to be read in bytes.

Returns:: The number of bytes successfully read.

See also:: DspStorageCache.h

Implements MityDSP::tcDspStorageBase.

void tcDspStorageCache::resetDeviceInfo ( void ) [protected]

This routine reads sector map information from the underlying device and creates copies of the map and the required cache buffers to match.

Any outstanding cache buffer should be freed prior to this call.

Returns:: None

See also:: DspStorageCache.h

tcDspStorageCache::tsBufferList * tcDspStorageCache::getCacheSector	(	unsigned int	anSector,
		unsigned int	anExpectedSize,
		bool	abLoad
	)			`[protected]`

This method checks the current cache for the sector in question.

If not found, the sector is loaded (flushing the oldest entry, if necessary). A pointer to the cache entry is returned.

In either case, the sector is moved to the front of the cache list.

Parameters:

`[in]`	anSector	The sector to load or retrieve from cache
`[in]`	anExpectedSize	The expected sector size
`[in]`	abLoad	If false, the entire sector is about to be written, so don't load it from the underlying device.