EVP_EncodeFinal
EVP_EncodeFinal(&(ctx->base64),
void EVP_EncodeFinal(EVP_ENCODE_CTX *ctx, unsigned char *out, int *outl);
LCRYPTO_ALIAS(EVP_EncodeFinal);
LCRYPTO_USED(EVP_EncodeFinal);
EVP_EncodeFinal(&ctx, buf, &outl);