EVP_DecodeFinal
if (EVP_DecodeFinal(ctx->base64, NULL, &num) < 0)
|| EVP_DecodeFinal(ctx, (unsigned char *)&(buf_mem->data[len]),
EVP_DecodeFinal(ctx, a + outl, &outl2);
int EVP_DecodeFinal(EVP_ENCODE_CTX *ctx, unsigned char *out, int *outl);
if (EVP_DecodeFinal(decode_ctx, decode_out + output_len, &chunk_len) != 1) {