Thread: info on memset and recv

> I have to say that vart and Salem are both way, way, way off base when they claim the point is to cover a bug or because the use of recv is "incorrect".

Example

Code:

memset( buff, 0, sizeof buff )
recv( sock, buff, sizeof buff, 0 );

If recv() actually FILLS the buffer, then two things
a) the memset was a complete and utter waste of time,
b) the resulting buffer STILL DOES NOT have a \0, nor does it have room for one either.

In other words, a total loss.

Consider

Code:

// drop the -1 if you're not interested in making a string
n = recv( sock, buff, sizeof buff - 1, 0 );  
if ( n > 0 ) {
  buff[n] = '\0';  // if you really want a \0 string
  // do stuff with 'n' bytes
}

Done this way, the need for memset hokus-pokus vanishes, the buffer is correctly \0 terminated in a single instruction (or two, but certainly much more efficiently than memset), if that is what you want to do.
In any event, the real size of the received data is available to make sure you can do the right thing.


> My preference would be to add or at least check for the null terminator after the recv, which seems more optimal.
Who said that you were going to get a \0 from recv()
Who said that you were going to receive it in a timely manner, even if it was sent?

It's quite simple. Use the return result of the function properly, and you're not going to go wrong.

Originally Posted by Salem

Use the return result of the function properly, and you're not going to go wrong.

Sure, and that's the byte where I would place the zero.

However, I still can't say that it's wrong to use memset there. You just made up a ridiculous example:

Code:

memset( buff, 0, sizeof buff )
recv( sock, buff, sizeof buff, 0 );

The error here IS NOT MEMSET, it's that the recv parameter should be "sizeof buff" minus 1.

Then you reinterate two points that I made explicitly, as if I had not accounted for them, which I did -- explicitly:

Originally Posted by Salem

Who said that you were going to get a \0 from recv()
Who said that you were going to receive it in a timely manner, even if it was sent?

Originally Posted by mk27

sometimes with networking you cannot be held responsible for the string you are receiving, so you may want to make sure it is null terminated if you need it to be. Also, you are not guaranteed to "recv" the entire string, which means if you "properly" presume it will be there, it may not.

With your level of experience, etc, I don't think you have any excuses for failing to read properly, so either do so or stop overtly trying to confuse the OP with your tish.

Originally Posted by MK27

The error here IS NOT MEMSET, it's that the recv parameter should be "sizeof buff" minus 1.

It's not an error to do this:

Code:

#define THISROCKS { \
    size_t thisrocks = 1; \
    while( thisrocks++ ); \
    }

...
THISROCKS
// drop the -1 if you're not interested in making a string
n = recv( sock, buff, sizeof buff - 1, 0 );  
THISROCKS
if ( n > 0 ) {
THISROCKS
  buff[n] = '\0';  // if you really want a \0 string
  // do stuff with 'n' bytes
}

But it doesn't make it good thing to do either.


Quzah.