Developer

API Reference

PFNADAPTGET

Brew Release
Brew MP 1.0.2
See Also
- IValueModel_GetValue()
- IValueModel_AdaptGet()
Description
This type definition specifies the prototype for the function pointer used to retrieve specific pieces of data stored in a value model. The value model allows objects to attach themselves to data of some arbitrary size and structure. The data may be as simple and straightforward as a single boolean or integer value -- or it might be very complex, comprised of many fields, structures or could even be dynamic. Quite frequently, it is desirable for a value model to retrieve only a specific portion of a given data structure. For example, a value model that stores directory service information would likely possess fields for name, address and phone number, and perhaps a JPEG image of the person identified by a given record. BREW calls the PFNADAPTGET callback (when present) each time IValueModel_GetValue() is called. The callback then may retrieve a specific portion of the stored data -- perhaps just the phone number or the photo in the example above. The callback provides the code to retrieve the specifically requested information from the data stored in the value model.
Members
  • pvCtx:       A pointer to a private context controlled by the value model.  The callback
                     will use this context information to retrieve specific pieces of information
                     from the data stored in a given value model.  For example, 'pvCtx' could
                     identify a specific field to be retrieved, known only to the value model.
  • pValueIn:    A pointer to the current data stored in the value model.  The value model's
                     PFNADAPTGET function might use the current data as the basis for retrieving the
                     next piece of data.
  • nLen:        The length of the data currently stored in the value model.  The value model's
                     PFNADAPTGET function might use the length of the current data as the basis for
                     retrieving the next piece of data.
  • ppValueOut:  A pointer to the data retrieved by the value model.
  • pnLenOut:    A pointer to the length of the data retrieved by the value model.
    
Definition
    typedef void (*PFNADAPTGET)(void *pvCtx, void *pValueIn, int nLen, void **ppValueOut, int *pnLenOut);
Comment
The PFNADAPTGET callback is issued during calls to IValueModel_GetValue(). Use IValueModel_AdaptGet() to initialize the callback and any private data the callback will need prior to calling IValueModel_GetValue(). When the callback is not present (i.e. NULL) IValueModel_GetValue() will retrieve _all_ the data associated with a given value model.
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