How to get pointer to buffer to read the contents and check the remaining data

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Hi All,

I am doing an application in c++ in which i need to use pointer to read the contents of the buffer. I used the following code to declare pointer to the buffer.

unsigned char *ptrToBuf = gchOBDReplyBuf;

The buffer has the data from a text file in it. My question is how can i read the contents of this buffer using pointers? Also each time i need to check the buffer remaining contents as I need to exit when the buffer data have been fully read.Please help as I am not familiar with the contents of pointers..

Thanks in Advance

Posted 11-Nov-13 18:33pm

Lekshmi KR

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Suk@nta · Answer 1 · 2013-11-11T19:35:00

try this...and let me know.

C#

if (gchOBDReplyBuf) {
    // get length of file:
    gchOBDReplyBuf.seekg (0, gchOBDReplyBuf.end);
    int length = gchOBDReplyBuf.tellg();
    gchOBDReplyBuf.seekg (0, gchOBDReplyBuf.beg);

    char * buffer = new char [length];

    std::cout &amp;lt;&amp;lt; &amp;quot;Reading &amp;quot; &amp;lt;&amp;lt; length &amp;lt;&amp;lt; &amp;quot; characters... &amp;quot;;
    // read data as a block:
    gchOBDReplyBuf.read (buffer,length);

    if (gchOBDReplyBuf)
      std::cout <<"all characters read successfully";
    else
      std::cout<< "error: only << gchOBDReplyBuf.gcount()<< could be read;
    gchOBDReplyBuf.close();

    // ...buffer contains the entire file...

    delete[] buffer;
  }
  return 0;
}

if u getting any error please revert back....

agent_suwastica · Answer 2 · 2013-11-11T22:16:00

Solution 2

Try this..

C++

#include <iostream.h>
main() {
	unsigned char gchOBDReplyBuf[]= "abcdefghijklmnopqrstuvwxyz";
	unsigned char *ptrToBuf = gchOBDReplyBuf;
	for ( int index = 0; index < 26; index++ ) {
		cout << char(*ptrToBuf+index);
	}
	cout << endl;
}

Posted 11-Nov-13 22:16pm

agent_suwastica

Updated 11-Nov-13 22:18pm

v2

Comments

Lekshmi KR 13-Nov-13 1:50am

Ok Its working. But now i have to pass this pointer (ptrToBuf) to another buffer(gchOBDResponseBuf) in another class which is c++ class.I did it in following way and caused error:

CMainFrame *myframe;
myframe=(CMainFrame *)AfxGetApp()->m_pMainWnd;
CECUSimulatorView *myview;
myview=(CECUSimulatorView *)myframe->GetActiveView();

gchOBDResponseBuf = myview->ptrToBuf;

I am getting compilation error as:

: error C2440: '=' : cannot convert from 'unsigned char *' to 'unsigned char [4100]'

why is it sooo?? Please Help

agent_suwastica 13-Nov-13 2:21am

Try to use:

*gchOBDResponseBuf = *myview->ptrToBuf;

if you are getting an error please post more codes.

Lekshmi KR 13-Nov-13 4:18am

I tried the above code and the error have gone. but the buffer gchOBDResponseBuf is not having the content of buffer pointed by ptrToBuf. Why is it so?

agent_suwastica 13-Nov-13 4:37am

How did you know that the buffer gchOBDResponseBuf is having an unexpected content?
If the pointer ptrToBuf is having the expected content then the buffer gchOBDResponseBuf must be correct.

Lekshmi KR 13-Nov-13 4:38am

While debugging i found it out the content in the buffer is not same as that of ptrToBuf