const void * memchr_P(const void *, int __val, size_t __len)
The memchr_P() function scans the first len bytes of the flash memory area pointed to by s for the character val. The first byte to match val (interpreted as an unsigned character) stops the operation.
The memchr_P() function returns a pointer to the matching byte or NULL if the character does not occur in the given memory area.