SHA256_DIGEST_STRING_LENGTH
char* SHA256_Data(const sha2_byte* data, size_t len, char digest[SHA256_DIGEST_STRING_LENGTH]) {
char* SHA256_End __P((SHA256_CTX*, char[SHA256_DIGEST_STRING_LENGTH]));
char* SHA256_Data __P((const u_int8_t*, size_t, char[SHA256_DIGEST_STRING_LENGTH]));
char *SHA256_End(SHA256_CTX *, char[SHA256_DIGEST_STRING_LENGTH]);
char *SHA256_Data(const uint8_t *, size_t, char[SHA256_DIGEST_STRING_LENGTH]);
char output[SHA256_DIGEST_STRING_LENGTH];