Send a byte or whole text

Ducky · 08-08-2009, 09:57 AM

Is there any preference when sending data as to send it byte by byte or sending
a whole buffer (the whole file) at once?

Is the latter faster than the former for example?

**Salem** · 08-08-2009, 10:35 AM

You can pass as many bytes as you like to send(), but you'd better pay attention to the return result.

If it's less than the amount you asked to be sent, then you need to call send() again, from the point where the previous attempt left off.

A bit like this.

Code:

size_t num_to_send;
char *buff;
while ( num_to_send ) {
  int num_sent = send( sock, buff, num_to_send, 0 );
  if ( num_sent > 0 ) {
    num_to_send -= num_sent;
    buff += num_sent;
  }
}

Cactus_Hugger · 08-08-2009, 12:08 PM

In addition to what Salem said: send as much as you have available to send, but obviously try to keep the size of what you must send small (if you have control over the protocol/its contents) - ie, a PNG or a GIF is better than a BMP.
recv as much as you can recv.

Ducky · 08-09-2009, 04:43 AM

Thank you Salem and Cactus_Hugger!

I see you use a char *buff; in your code.

Does it matter as to which one of the 3 we use?

Code:

char *buffer;
char  buffer[256];
char *buffer = new char[256];

**Salem** · 08-09-2009, 04:47 AM

So long as it's allocated, no.

Ducky · 08-22-2009, 02:46 AM

May i ask whats the point of this line in your code Salem?

Code:

buff += num_sent;

I suppose its for decreasing the length of buff.

But if i do a test like this, i get completely random values for buf:

Code:

#include <iostream>

using namespace std;

int  main()
{
   int i = 0;
   char * buf = new char[i];
   while(i<15)
   {
        buf  += i;
        i++;
        cout << strlen(buf) <<"\n";
   }

   delete [] buf;

   return  0;
}

**Salem** · 08-22-2009, 06:07 AM

> buff += num_sent;
If you've got a buffer of 100 bytes, and send 10, that means you've got 90 left (that's what the -= is for).
It also means that you need to try the next send from 10 bytes into the buffer (that's what the += is for).

Ducky · 08-22-2009, 07:04 AM

Ah, ok thanks!

08-08-2009, 09:57 AM	#1
Ducky Registered User Join Date: Dec 2007 Location: France Posts: 396	Send a byte or whole text Is there any preference when sending data as to send it byte by byte or sending a whole buffer (the whole file) at once? Is the latter faster than the former for example? __________________ Using Code::Blocks,MingW with Windows.
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08-08-2009, 10:35 AM	#2
Salem and the hat of vanishing Join Date: Aug 2001 Location: The edge of the known universe Posts: 21,214	You can pass as many bytes as you like to send(), but you'd better pay attention to the return result. If it's less than the amount you asked to be sent, then you need to call send() again, from the point where the previous attempt left off. A bit like this. Code: size_t num_to_send; char *buff; while ( num_to_send ) { int num_sent = send( sock, buff, num_to_send, 0 ); if ( num_sent > 0 ) { num_to_send -= num_sent; buff += num_sent; } } __________________ If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut. Up to 8Mb PlusNet broadband from only £5.99 a month!
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08-08-2009, 12:08 PM	#3
Cactus_Hugger int x = ((int ) NULL); Join Date: Jul 2003 Location: Banks of the River Styx Posts: 891	In addition to what Salem said: send as much as you have available to send, but obviously try to keep the size of what you must send small (if you have control over the protocol/its contents) - ie, a PNG or a GIF is better than a BMP. recv as much as you can recv. __________________ long time; /* know C? */ Unprecedented performance: Nothing ever ran this slow before. Any sufficiently advanced bug is indistinguishable from a feature. Real Programmers confuse Halloween and Christmas, because dec 25 == oct 31. The best way to accelerate an IBM is at 9.8 m/s/s. recursion (re - cur' - zhun) n. 1. (see recursion)
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08-09-2009, 04:43 AM	#4
Ducky Registered User Join Date: Dec 2007 Location: France Posts: 396	Thank you Salem and Cactus_Hugger! I see you use a char buff; in your code. Does it matter as to which one of the 3 we use? Code: char buffer; char buffer[256]; char buffer = new char[256]; __________________ Using Code::Blocks,MingW with Windows. Last edited by Ducky; 08-09-2009 at 05:31 AM.*
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08-09-2009, 04:47 AM	#5
Salem and the hat of vanishing Join Date: Aug 2001 Location: The edge of the known universe Posts: 21,214	So long as it's allocated, no. __________________ If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut. Up to 8Mb PlusNet broadband from only £5.99 a month!
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08-22-2009, 02:46 AM	#6
Ducky Registered User Join Date: Dec 2007 Location: France Posts: 396	May i ask whats the point of this line in your code Salem? Code: buff += num_sent; I suppose its for decreasing the length of buff. But if i do a test like this, i get completely random values for buf: Code: #include <iostream> using namespace std; int main() { int i = 0; char * buf = new char[i]; while(i<15) { buf += i; i++; cout << strlen(buf) <<"\n"; } delete [] buf; return 0; } __________________ Using Code::Blocks,MingW with Windows.
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08-22-2009, 06:07 AM	#7
Salem and the hat of vanishing Join Date: Aug 2001 Location: The edge of the known universe Posts: 21,214	> buff += num_sent; If you've got a buffer of 100 bytes, and send 10, that means you've got 90 left (that's what the -= is for). It also means that you need to try the next send from 10 bytes into the buffer (that's what the += is for). __________________ If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut. Up to 8Mb PlusNet broadband from only £5.99 a month!
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08-22-2009, 07:04 AM	#8
Ducky Registered User Join Date: Dec 2007 Location: France Posts: 396	Ah, ok thanks! __________________ Using Code::Blocks,MingW with Windows.
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