How to store output of recv()?

Question

In C I had working code but have no idea why it worked, so I started rewriting it so I could actually understand what is going on. So far so good! I rewrote and am 90% sure I understand everything that is going on now; the issue however, is that I have no idea how to store the data chunk received by `recv` (`databff`) into my pre-allocated buffer (`htmlbff`). Consider the following code (note that I stripped this down quite a bit, so it only includes the basics, e.g. no memory reallocation or leak protection, etc...): ``` #define BUFFERSIZE 4096 #define MAXDATASIZE 256 char *htmlbff, databff[MAXDATASIZE]; int c, i = BUFFERSIZE, q = 0; if(!(htmlbff = malloc(i))) { printf("
Error! Memory allocation failed!"); return 0x00; } while((c = recv(sock, databff, MAXDATASIZE, 0)) > 0) { /*memory checks stripped out since they are irrelevent for this post*/ /*store data to the appropriate area in htmlbff*/ q += c; } ``` So (if I am doing this right, and things are going as I think they are) `c`…

Accepted Answer

Use `memcpy`, and offset `htmlbff` by `q`:

```
memcpy(htmlbff + q, databff, c);
```

You can similarly `recv` directly into `htmlbff`:

```
c = recv(sock, htmlbff + q, MAXDATASIZE, 0));
```

But it's fine to keep a separate buffer, and depending upon your full code, it may make things clearer.

Be sure that you add checks against `BUFFERSIZE` so that you don't copy past the bounds of `htmlbff`. You mentioned that you've stripped out `realloc` handling, so maybe you're already handling this.

Your constant names are a bit confusing, when buffering data I would use `BUFFERSIZE` to indicate the size of each chunk, i.e. the size of `databff`.

How to store output of recv()?

Solution

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