int memcmp_P(const void *, const void *, size_t) __ATTR_PURE__
The memcmp_P() function compares the first len bytes of the memory areas s1 and flash s2. The comparision is performed using unsigned char operations.
The memcmp_P() function returns an integer less than, equal to, or greater than zero if the first len bytes of s1 is found, respectively, to be less than, to match, or be greater than the first len bytes of s2.