4.9. gc_Extension( )

On DM3 boards, the gc_Extension( ) function is not supported for E-1/T-1.

On Springware boards, the gc_Extension( ) function provides the capability to dynamically configure the behavior of a PDK protocol in a manner that is specific to that protocol. The gc_Extension( ) function is only valid for applications using PDK protocols that support this feature. Check the associated .cdp file or the Global Call Country Dependent Parameters (CDP) Reference for more information regarding the support and configuration of this feature including its usage.

For PDK protocols that support this feature, up to a maximum of three integer values and two strings may be passed to the protocol by configuring the parmp parameter as a pointer to a structure of type PDK_EXT_SIG_BLK:

struct pdk_ext_sig_blk {  
     int  int1Val;  
     int  int2Val;  
     int  int3Val;  
     char *str1Val;  
     char *str2Val;  
} PDK_EXT_SIG_BLK;

The actual meaning and usage of these integers and string values are protocol specific. The PDKRT library only supports this function in asynchronous mode (EV_ASYNC), and therefore the retvalp parameter is ignored.

If the protocol requires unsolicited notification of the application as a result of the completion of a feature triggered by the gc_Extension( ) function, or for any other asynchronous notification for any documented reason, it may send an extension event.

The extension event, GCEV_EXTENSION, is provided to support unsolicited events resulting from PDK protocol-specific features. Refer to the Global Call Country Dependent Parameters (CDP) Reference for the proper handling of any unsolicited extension events as well as the format of the event, that is, identifier mappings and contents of the data buffer.

For this event, the pointer to the extended event data block, exteventdatap, within the METAEVENT structure, points to a structure, EXTENSIONEVTBLK, defined as follows:

typedef struct{  
     unsigned char ext_id;      /* unused for PDK protocols */  
     GC_PARM  gcparm;           /* GC_PARM union to provide technology-specific info */  
     short int parm;  
} EXTENSIONEVTBLK;

The gcparm field of the METAEVENT structure itself points to a structure of type PDK_EXT_SIG_BLK (above) so that three integers and two string values may be returned from the protocol to the application to indicate protocol-specific status information.

The extension block structure, EXTENSIONEVTBLK, referenced in a GCEV_EXTENSION event, has a persistence only until the next call of the gc_GetMetaEvent( ) function. In other words, any information contained or referenced in a GCEV_EXTENSION event must be either processed or cached within the application, or risk being lost upon the next call of the gc_GetMetaEvent( ) function.

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