CGDataProvider Reference

Overview

The CGDataProvider header file declares a data type that supplies Quartz functions with data. Data provider objects abstract the data-access task and eliminate the need for applications to manage data through a raw memory buffer.

For information on how to use CGDataProvider functions, see Quartz 2D Programming Guide Programming Guide.

See also CGDataConsumer Reference.

Functions

CGDataProviderCopyData

Returns a copy of the provider’s data.

CFDataRef CGDataProviderCopyData(
   CGDataProviderRef provider
);

CGDataProviderCreateDirect

Creates a Quartz direct-access data provider.

CGDataProviderRef CGDataProviderCreateDirect (
   void *info,
   off_t size,
   const CGDataProviderDirectCallbacks *callbacks
);

CGDataProviderCreateSequential

Creates a Quartz sequential-access data provider.

CGDataProviderRef CGDataProviderCreateSequential (
   void *info,
   const CGDataProviderSequentialCallbacks *callbacks
);

CGDataProviderCreateWithCFData

Creates a Quartz data provider that reads from a CFData object.

CGDataProviderRef CGDataProviderCreateWithCFData (
   CFDataRef data
);

CGDataProviderCreateWithData

Creates a Quartz direct-access data provider that uses data your program supplies.

CGDataProviderRef CGDataProviderCreateWithData (
   void *info,
   const void *data,
   size_t size,
   CGDataProviderReleaseDataCallback releaseData
);

CGDataProviderCreateWithFilename

Creates a Quartz direct-access data provider that uses a file to supply data.

CGDataProviderRef CGDataProviderCreateWithFilename(
   const char *filename
);

CGDataProviderCreateWithURL

Creates a Quartz direct-access data provider that uses a URL to supply data.

CGDataProviderRef CGDataProviderCreateWithURL (
   CFURLRef url
);

CGDataProviderGetTypeID

Returns the Core Foundation type identifier for Quartz data providers.

CFTypeID CGDataProviderGetTypeID (
   void
);

CGDataProviderRelease

Decrements the retain count of a data provider.

void CGDataProviderRelease (
   CGDataProviderRef provider
);

CGDataProviderRetain

Increments the retain count of a data provider.

CGDataProviderRef CGDataProviderRetain (
   CGDataProviderRef provider
);

Callbacks by Task

Sequential-Access Data Provider Callbacks

• CGDataProviderGetBytesCallback
• CGDataProviderReleaseInfoCallback
• CGDataProviderRewindCallback
• CGDataProviderSkipBytesCallback
• CGDataProviderSkipForwardCallback

Direct-Access Data Provider Callbacks

• CGDataProviderGetBytePointerCallback
• CGDataProviderGetBytesAtOffsetCallback
• CGDataProviderReleaseBytePointerCallback
• CGDataProviderReleaseDataCallback
• CGDataProviderGetBytesAtPositionCallback

Callbacks

CGDataProviderGetBytePointerCallback

A callback function that returns a generic pointer to the provider data.

const void * (*CGDataProviderGetBytePointerCallback) (
   void *info
);
   

If you name your function MyProviderGetBytePointer, you would declare it like this:

void *MyProviderGetBytePointer (
   void *info
);

CGDataProviderGetBytesAtOffsetCallback

A callback function that copies data from the provider into a Quartz buffer.

typedef size_t (*CGDataProviderGetBytesAtOffsetCallback) (
   void *info,
   void *buffer,
   size_t offset,
   size_t count
);
   

If you name your function MyProviderGetBytesWithOffset, you would declare it like this:

size_t MyProviderGetBytesWithOffset (
   void *info,
   void *buffer,
   size_t offset,
   size_t count
);

CGDataProviderGetBytesAtPositionCallback

A callback function that copies data from the provider into a Quartz buffer.

typedef size_t (*CGDataProviderGetBytesAtPositionCallback) (
   void *info,
   void *buffer,
   off_t position,
   size_t count
);

If you name your function MyProviderGetBytesAtPosition, you would declare it like this:

size_t MyProviderGetBytesAtPosition (
   void *info,
   void *buffer,
   off_t position,
   size_t count
);

CGDataProviderGetBytesCallback

A callback function that copies from a provider data stream into a Quartz-supplied buffer.

size_t (*CGDataProviderGetBytesCallback) (
   void *info,
   void *buffer,
   size_t count
);
   

If you name your function MyProviderGetBytes, you would declare it like this:

size_t MyProviderGetBytes (
   void *info,
   void *buffer,
   size_t count
);

CGDataProviderReleaseBytePointerCallback

A callback function that releases the pointer Quartz obtained by calling CGDataProviderGetBytePointerCallback.

typedef void (*CGDataProviderReleaseBytePointerCallback) (
   void *info,
   const void *pointer
);
   

If you name your function MyProviderReleaseBytePointer, you would declare it like this:

void MyProviderReleaseBytePointer (
   void *info,
   const void *pointer
);

CGDataProviderReleaseDataCallback

A callback function that releases data you supply to the function CGDataProviderCreateWithData.

typedef void (*CGDataProviderReleaseDataCallback) (
   void *info,
   const void *data,
   size_t size
);
   

If you name your function MyProviderReleaseData, you would declare it like this:

void MyProviderReleaseData (
   void *info,
   const void *data,
   size_t size
);

CGDataProviderReleaseInfoCallback

A callback function that releases any private data or resources associated with the data provider.

void (*CGDataProviderReleaseInfoCallback) (
   void *info
);
   

If you name your function MyProviderReleaseInfo, you would declare it like this:

void MyProviderReleaseInfo (
   void *info
);

CGDataProviderRewindCallback

A callback function that moves the current position in the data stream back to the beginning.

void (*CGDataProviderRewindCallback) (
   void *info
);
   

If you name your function MyProviderRewind, you would declare it like this:

void MyProviderRewind (
   void *info
);

CGDataProviderSkipBytesCallback

A callback function that advances the current position in the data stream supplied by the provider.

void (*CGDataProviderSkipBytesCallback) (
   void *info,
   size_t count
);
   

If you name your function MyProviderSkipBytes, you would declare it like this:

void MyProviderSkipBytes (
   void *info,
   size_t count
);

CGDataProviderSkipForwardCallback

A callback function that advances the current position in the data stream supplied by the provider.

off_t (*CGDataProviderSkipForwardCallback) (
   void *info,
   off_t count
);

If you name your function MyProviderSkipForwardBytes, you would declare it like this:

off_t MyProviderSkipForwardBytes (
   void *info,
   off_t count
);

Data Types

CGDataProviderRef

Defines an opaque type that supplies Quartz with data.

typedef struct CGDataProvider *CGDataProviderRef;

CGDataProviderCallbacks

Defines a structure containing pointers to client-defined callback functions that manage the sending of data for a sequential-access data provider.

struct CGDataProviderCallbacks {
   CGDataProviderGetBytesCallback getBytes;
   CGDataProviderSkipBytesCallback skipBytes;
   CGDataProviderRewindCallback rewind;
   CGDataProviderReleaseInfoCallback releaseProvider;
};
typedef struct CGDataProviderCallbacks CGDataProviderCallbacks;

Fields

getBytes

A pointer to a function that copies data from the provider. For more information, see CGDataProviderGetBytesCallback.

skipBytes

A pointer to a function that Quartz calls to advance the stream of data supplied by the provider. For more information, see CGDataProviderSkipBytesCallback.

rewind

A pointer to a function Quartz calls to return the provider to the beginning of the data stream. For more information, see CGDataProviderRewindCallback.

releaseProvider

A pointer to a function that handles clean-up for the data provider, or NULL. For more information, see CGDataProviderReleaseInfoCallback.

CGDataProviderDirectAccessCallbacks

Defines pointers to client-defined callback functions that manage the sending of data for a direct-access data provider.

struct CGDataProviderDirectAccessCallbacks {
   CGDataProviderGetBytePointerCallback getBytePointer;
   CGDataProviderReleaseBytePointerCallback releaseBytePointer;
   CGDataProviderGetBytesAtOffsetCallback getBytes;
   CGDataProviderReleaseInfoCallback releaseProvider;
};
typedef struct CGDataProviderDirectAccessCallbacks  CGDataProviderDirectAccessCallbacks;

Fields

getBytePointer

A pointer to a function that returns a pointer to the provider’s data. For more information, see CGDataProviderGetBytePointerCallback.

releaseBytePointer

A pointer to a function that Quartz calls to release a pointer to the provider’s data. For more information, see CGDataProviderReleaseBytePointerCallback.

getBytes

A pointer to a function that copies data from the provider. For more information, see CGDataProviderGetBytesAtOffsetCallback.

releaseProvider

A pointer to a function that handles clean-up for the data provider, or NULL. For more information, see CGDataProviderReleaseInfoCallback.

CGDataProviderDirectCallbacks

Defines pointers to client-defined callback functions that manage the sending of data for a direct-access data provider.

struct CGDataProviderDirectCallbacks {
   unsigned int version;
   CGDataProviderGetBytePointerCallback getBytePointer;
   CGDataProviderReleaseBytePointerCallback releaseBytePointer;
   CGDataProviderGetBytesAtPositionCallback getBytesAtPosition;
   CGDataProviderReleaseInfoCallback releaseInfo;
};
typedef struct CGDataProviderDirectCallbacks  CGDataProviderDirectCallbacks;

Fields

version

The version of this structure. It should be set to 0.

getBytePointer

A pointer to a function that returns a pointer to the provider’s data. For more information, see CGDataProviderGetBytePointerCallback.

releaseBytePointer

A pointer to a function that Quartz calls to release a pointer to the provider’s data. For more information, see CGDataProviderReleaseBytePointerCallback.

getBytesAtPosition

A pointer to a function that copies data from the provider.

releaseInfo

A pointer to a function that handles clean-up for the data provider, or NULL. For more information, see CGDataProviderReleaseInfoCallback.

CGDataProviderSequentialCallbacks

Defines a structure containing pointers to client-defined callback functions that manage the sending of data for a sequential-access data provider.

struct CGDataProviderSequentialCallbacks {
   unsigned int version;
   CGDataProviderGetBytesCallback getBytes;
   CGDataProviderSkipForwardCallback skipForward;
   CGDataProviderRewindCallback rewind;
   CGDataProviderReleaseInfoCallback releaseInfo;
};
typedef struct CGDataProviderSequentialCallbacks CGDataProviderSequentialCallbacks;

Fields

version

The version of this structure. It should be set to 0.

getBytes

A pointer to a function that copies data from the provider. For more information, see CGDataProviderGetBytesCallback.

skipForward

A pointer to a function that Quartz calls to advance the stream of data supplied by the provider.

rewind

A pointer to a function Quartz calls to return the provider to the beginning of the data stream. For more information, see CGDataProviderRewindCallback.

releaseInfo

A pointer to a function that handles clean-up for the data provider, or NULL. For more information, see CGDataProviderReleaseInfoCallback.