size_t strcspn_P(const char *__s, const char *__reject) __ATTR_PURE__
The strcspn_P() function calculates the length of the initial segment of s which consists entirely of characters not in reject. This function is similar to strcspn() except that reject is a pointer to a string in program space.
The strcspn_P() function returns the number of characters in the initial segment of s which are not in the string reject. The terminating zero is not considered as a part of string.