string to int

This is a discussion on string to int within the C++ Programming forums, part of the General Programming Boards category; OK last question: Code: unsigned int j = 0; do { if (recv(h,&buf[j],1,0)==SOCKET_ERROR) { addlog("retlinehttp(): recv() Failed! %d", WSAGetLastError()); return ...

  1. #1
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    Feb 2006
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    71

    string to int

    OK last question:

    Code:
       		unsigned int j = 0;
    		do { 
    			if (recv(h,&buf[j],1,0)==SOCKET_ERROR) {
    				addlog("retlinehttp(): recv() Failed! %d", WSAGetLastError());
    				return -2;
    			}
    			if (data = strstr(buf, "\r\n\r\n")) {
    				data2 = strstr(buf, "Content-Length:");
    				data2+=15;
    				break;
    			}
    			//fwrite (&buf[j] , 1 , 1 , file);
    			j++;
    		} while (j < sizeof(buf));
    		buf[j-1]='\0';
    		
    		int size = atoi(data2);
    
    		char* buffer;
    		buffer = new char[size];
    
       		unsigned int k = 0;
    		do { 
    			if (recv(h,&buffer[k],1,0)==SOCKET_ERROR) {
    				addlog("retlinehttp(): recv() Failed! %d", WSAGetLastError());
    				return -2;
    			}
    			fwrite (&buffer[k] , 1 , 1 , file);
    			k++;
    		} while (k < sizeof(buffer));
    At this point somthing went wrong buffer = new char[size];
    Lets say I download a file then I get back the information Content-Length: 24576 this value I have as a char and the pointer data2 points to it. Then I convert the char into int. Now the value is in size. But when I try to create a new buffer, the buffer is not big as size, but has a sizeof 4?
    Whats wrong?

  2. #2
    Registered User hk_mp5kpdw's Avatar
    Join Date
    Jan 2002
    Location
    Northern Virginia/Washington DC Metropolitan Area
    Posts
    3,788
    sizeof returns the size in bytes of the buffer variable (not the value of the contents of said variable) which is 4 because buffer is a 4-byte pointer variable. What you probably want is to use the value in the variable size again in your loop instead:

    Code:
    int size = atoi(data2);
    
    char* buffer;
    buffer = new char[size];
    
    unsigned int k = 0;
    do { 
        if (recv(h,&buffer[k],1,0)==SOCKET_ERROR) {
            addlog("retlinehttp(): recv() Failed! %d", WSAGetLastError());
            return -2;
        }
        fwrite (&buffer[k] , 1 , 1 , file);
        k++;
    } while (k < size);
    "Owners of dogs will have noticed that, if you provide them with food and water and shelter and affection, they will think you are god. Whereas owners of cats are compelled to realize that, if you provide them with food and water and shelter and affection, they draw the conclusion that they are gods."
    -Christopher Hitchens

  3. #3
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    Join Date
    Feb 2006
    Posts
    71
    Quote Originally Posted by hk_mp5kpdw
    sizeof returns the size in bytes of the buffer variable (not the value of the contents of said variable) which is 4 because buffer is a 4-byte pointer variable. What you probably want is to use the value in the variable size again in your loop instead:

    Code:
    int size = atoi(data2);
    
    char* buffer;
    buffer = new char[size];
    
    unsigned int k = 0;
    do { 
        if (recv(h,&buffer[k],1,0)==SOCKET_ERROR) {
            addlog("retlinehttp(): recv() Failed! %d", WSAGetLastError());
            return -2;
        }
        fwrite (&buffer[k] , 1 , 1 , file);
        k++;
    } while (k < size);

    WUHU works perfect
    But I don't understand why this works

    } while (j < sizeof(buf));

    same as the

    } while (k < sizeof(buffer));

  4. #4
    Registered User
    Join Date
    Jan 2005
    Posts
    847
    Because a char array is different from a pointer.

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