OpenSSL.fixed_length_secure_compare

static VALUE
ossl_crypto_fixed_length_secure_compare(VALUE dummy, VALUE str1, VALUE str2)
{
    const unsigned char *p1 = (const unsigned char *)StringValuePtr(str1);
    const unsigned char *p2 = (const unsigned char *)StringValuePtr(str2);
    long len1 = RSTRING_LEN(str1);
    long len2 = RSTRING_LEN(str2);

    if (len1 != len2) {
        ossl_raise(rb_eArgError, "inputs must be of equal length");
    }

    switch (CRYPTO_memcmp(p1, p2, len1)) {
        case 0: return Qtrue;
        default: return Qfalse;
    }
}