Get the start index of a match.
int strpattern_match_start_index(const strpattern_match *match, int *err)
The match whose start index is returned.
STRPATTERN_EOK if there is no error.
This function returns the start index of a match. The start index represents the offset, from the beginning of the string which was analyzed, to the first character of the match. The offset is counted in terms of characters in the analyzed string using Unicode code points. Characters are not reinterpreted in any way. For example, each code point is counted as a character even if it represents a character decoration associated with the preceding character.
The start index of the match (-1 on error).