PCRE2 - Perl-compatible regular expressions (revised API) .rs #include <pcre2.h>

 int pcre2_set_callout(pcre2_match_context *mcontext,  " int (*callout_function)(pcre2_callout_block *),"  " void *callout_data);" 

. .rs This function sets the callout fields in a match context (the first argument). The second argument specifies a callout function, and the third argument is an opaque data item that is passed to it. The result of this function is always zero.

There is a complete description of the PCRE2 native API in the HREF
pcre2api
page and a description of the POSIX API in the HREF
pcre2posix
page.