ASN1_TIME_print功能，而BIO？ [英] ASN1_TIME_print functionality without BIO?

问题描述

在本问题中所述： Openssl的C ++获取到期日，有可能写一个ASN1时间到BIO缓冲区，然后读回到自定义缓冲 BUF ：

As described in this question: Openssl C++ get expiry date, there is the possibility to write an ASN1 time into a BIO buffer and then read it back into a custom buffer buf:

BIO *bio;
int write = 0;
bio = BIO_new(BIO_s_mem());
if (bio) {
  if (ASN1_TIME_print(bio, tm))
    write = BIO_read(bio, buf, len-1);
  BIO_free(bio);
}
buf[write]='\0';
return write;

这怎么可能不使用BIO都可以实现吗？在 ASN1_TIME_print 作用是当 OPENSSL_NO_BIO 不是只定义了present。有没有直接写入时间到一个给定的缓冲区的方式？

How could this be achieved without using BIO at all? The ASN1_TIME_print function is only present when OPENSSL_NO_BIO is not defined. Is there a way to write the time directly into a given buffer?

推荐答案

我想这应该是可能的，至少在直接写入时间为一个给定的缓冲区而言 - 但你仍然需要使用BIOS

I think this should be possible, at least in terms of writing the time directly into a given buffer -- but you'll still need to use BIOs.

在理想情况下， BIO_new_mem_buf 将适合，因为它使用的是定的缓冲区作为源创建一个内存BIO。不幸的是，该函数把给定的缓冲区的只读的，这不是我们想要的。但是，我们可以创建自己的函数（我们称之为 BIO_new_mem_buf2 ）的基础上， BIO_new_mem_buf 的来源$ C ​​$ C ：

Ideally, BIO_new_mem_buf would suit, given that it creates an in-memory BIO using a given buffer as the source. Unfortunately, that function treats the given buffer as read-only, which is not what we want. However, we can create our own function (let's call it BIO_new_mem_buf2), based on the BIO_new_mem_buf source code:

BIO *BIO_new_mem_buf2(void *buf, int len)
{
    BIO *ret;
    BUF_MEM *b;
    size_t sz;

    if (!buf) {
        BIOerr(BIO_F_BIO_NEW_MEM_BUF, BIO_R_NULL_PARAMETER);
        return NULL;
    }
    sz = (size_t)len;
    if (!(ret = BIO_new(BIO_s_mem())))
        return NULL;
    b = (BUF_MEM *)ret->ptr;
    b->data = buf;
    b->length = sz;
    b->max = sz;
    return ret;
}

这就像 BIO_new_mem_buf ，除了的是 A）的的 LEN 参数的必须表示给定的缓冲区的大小，和 b）的的BIO是的不的标记为只读。

This is just like BIO_new_mem_buf, except that a) the len argument must indicate the size of the given buffer, and b) the BIO is not marked "readonly".

通过上面的，你现在应该能够调用：

With the above, you should now be able to call:

ASN1_TIME_print(bio, tm)

和有时间出现在你给出的缓冲区。

and have the time appear in your given buffer.

的注意的，我没有测试过上述code，所以因人而异。希望这有助于！

Note that I have not tested the above code, so YMMV. Hope this helps!

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