#include <pcre2.h>
int pcre2_callout_enumerate(const pcre2_code *code, int (*callback)(pcre2_callout_enumerate_block *, void *), void *callout_data);
This function scans a compiled regular expression and calls the callback() function for each callout within the pattern. The yield of the function is zero for success and non-zero otherwise. The arguments are:
code Points to the compiled pattern
callback The callback function
callout_data User data that is passed to the callback
The callback() function is passed a pointer to a data block containing the following fields (not necessarily in this order):
uint32_t version Block version number
uint32_t callout_number Number for numbered callouts
PCRE2_SIZE pattern_position Offset to next item in pattern
PCRE2_SIZE next_item_length Length of next item in pattern
PCRE2_SIZE callout_string_offset Offset to string within pattern
PCRE2_SIZE callout_string_length Length of callout string
PCRE2_SPTR callout_string Points to callout string or is NULL
The second argument passed to the callback() function is the callout data that was passed to pcre2_callout_enumerate(). The callback() function must return zero for success. Any other value causes the pattern scan to stop, with the value being passed back as the result of pcre2_callout_enumerate().
There is a complete description of the PCRE2 native API in the pcre2api page and a description of the POSIX API in the pcre2posix page.