EVP_EncodeBlock
ctx->buf_len = EVP_EncodeBlock(ctx->buf, ctx->tmp, ctx->tmp_len);
ctx->buf_len = EVP_EncodeBlock(ctx->buf, (unsigned char *)in, n);
ctx->buf_len = EVP_EncodeBlock(ctx->buf,
i = EVP_EncodeBlock((unsigned char *)out, buf, len);
i = EVP_EncodeBlock(sigret, m, m_len);
EVP_EncodeBlock((unsigned char *)b64_str, der_spki, der_len);
int EVP_EncodeBlock(unsigned char *t, const unsigned char *f, int n);