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Global Call IP Technology Guide — November 2007 177
Dialogic Corporation
IP-Specific Operations
API Functions for Long Header Values
Because some SIP header fields (particularly those that allow multiple values to be contained in a
single header field in a comma-delimited list) can be arbitrarily long, the Global Call IP library has
been extended to remove the inherent 255 byte data length limitation for parameters that are
contained in a GC_PARM_BLK data structure.
When using the IPSET_SIP_MSGINFO/IPPARM_SIP_HDR parameter, and the new, extended
gc_util_... _ex( ) utility functions (see Section 8.2, “IP-Specific Dialogic
®
Global Call API
Functions”, on page 394, for complete information on these functions), the maximum length of the
parameter value can be configured by the application using
IPCCLIB_START_DATA.max_parm_data_size before the library is started.When an application
has configured an extended maximum parameter length it must not make any attempt to access
parameter block data directly; instead, the new, extended gc_util_..._ex( ) utility functions, which
handle the extended-length data properly, should always be used.
The new, extended gc_util_..._ex( ) utility functions are backwards compatible and can be used
with any GC_PARM_BLOCK regardless of whether it contains parameters that may exceed 255
bytes. For this reason, it is recommended that the extended functions should always be used in
application code that accesses SIP header fields.
Field-Specific Parameters for SIP Header Access
Certain standard SIP header fields can be accessed using header-specific Global Call parameter IDs
instead of the generic IPSET_SIP_MSGINFO / IPPARM_SIP_HDR parameter that is described in
above.
The use of the header-specific parameter IDs has the following limitations:
• This mechanism is being deprecated. The defines will remain in the IP Call Control library for
backward compatibility, but no further development will be done on these parameters and no
issues or problems will be fixed.
• The parameter data associated with header-specific parameter IDs (that is, the header field
contents) is limited to 255 bytes. You must use the generic IPPARM_SIP_HDR parameter ID
rather than a header-specific parameter ID to handle any header field that is longer than 255
bytes.
Supported OPTIONS GCEV_EXTENSION if
E_SIP_OPTIONS_Access is enabled
To
‡
(display string and full
header also returned in
header-specific
parameters)
INFO, NOTIFY, SUBSCRIBE GCEV_EXTENSION
OPTIONS GCEV_EXTENSION if
E_SIP_OPTIONS_Access is enabled
REFER GCEV_REQ_XFER if call transfer is enabled
Table 9. Common Header Fields in Inbound SIP Messages (Continued)
SIP header SIP message Global Call event
† Header field also accessible via field-specific parameter define.
‡ From and To header fields are not retrieved from INVITE messages using SIP message information parameters.