基于Context进行Digest摘要操作

struct wcrypto_digest_op_data op_data;

memset((void *)&op_data, 0, sizeof(op_data));
op_data.in = test_alloc_buf(pool, buf_len); 
memcpy(op_data.in, buf_in, buf_len);
    op_data.in_bytes = buf_len;
    op_data.out = test_alloc_buf(pool, buf_len );
    op_data.out_bytes = buf_len;
    op_data.iv = test_alloc_buf(pool, iv_len);
    memcpy(op_data.iv, iv, iv_len);
    op_data.iv_bytes = iv_len;

wcrypto_do_digest(ctx, &op_data, NULL);
memcpy(digest_out, op_data.out, md_len);