Inside Macintosh: QuickTime

Application-Defined Functions

This section describes four callback functions that you may provide to compressor components and an application-defined function that specifies alignment behavior.

The Image Compression Manager defines four callback functions that applications may provide to compressors or decompressors. These callbacks are data-loading functions, data-unloading functions, completion functions, and progress functions.

Data-loading functions and data-unloading functions support spooling of compressed data.
Completion functions allow compressors and decompressors to report that asynchronous operations have completed.
Progress functions provide a mechanism for compressors and decompressors to report their progress toward completing an operation.

This section describes the interfaces presented when compressors invoke your callback functions. These application-defined functions may be called by compressor components during a compression or decompression operation.

You identify a callback function to an Image Compression Manager function by specifying a pointer to a callback function structure. These structures contain two fields: a pointer to the callback function and a reference constant value. There is one callback function structure for each type of callback function. See the individual function descriptions in the sections that follow for descriptions of the structures.

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