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Error reading in file in binary mode

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Join Date: Feb 2005

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winbatch

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Error reading in file in binary mode

Jul 14th, 2005

Guys,

Either there is a bug in the compiler or I'm getting dumber by the day. I want to read an entire file into memory. (Very small file, so no worries about size here). I followed the example here (from www.cplusplus.com)

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
// reading binary file
#include <iostream.h>
#include <fstream.h>
 
const char * filename = "example.txt";
int main ()
{
   char * buffer;
   long size;
   ifstream file (filename, ios::in|ios::binary|ios::ate);
   size = file.tellg();
   file.seekg (0, ios::beg);
   buffer = new char [size];
   file.read (buffer, size);
   file.close();
   cout << "the complete file is in a buffer";
   delete[] buffer;
   return 0;
}
// reading binary file
#include <iostream.h>
#include <fstream.h>

const char * filename = "example.txt";
int main ()
{
   char * buffer;
   long size;
   ifstream file (filename, ios::in|ios::binary|ios::ate);
   size = file.tellg();
   file.seekg (0, ios::beg);
   buffer = new char [size];
   file.read (buffer, size);
   file.close();
   cout << "the complete file is in a buffer";
   delete[] buffer;
   return 0;
}

<< moderator edit: added [code][/code] tags and reformatted >>

However, when I use this code, I always get the first character of the file twice!!! For example, if I have a file which contains:
SAM LOVES TO TEST FILES

I end up with:
SSAM LOVES TO TEST FILES

Is this a known bug or am I not supposed to believe this reputable site? Is there a 'C' way to do this which is better?

Thanks,
Winbatch

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Join Date: Apr 2004

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Dave Sinkula Dave Sinkula is offline

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long time no c

Re: Error reading in file in binary mode

Jul 14th, 2005

I didn't see the issue, but WRT a C version I think it would be something like this.

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
#include <stdio.h>
#include <stdlib.h>
 
int main(void)
{
   static const char filename[] = "file.txt";
   FILE *file = fopen(filename, "rb");
   if ( file )
   {
      char *buffer;
      long size;
      fseek(file, 0, SEEK_END);
      size = ftell(file);
      rewind(file);
      buffer = malloc(size);
      if ( buffer )
      {
         if ( fread(buffer, size, 1, file) == 1 )
         {
            /* puts(buffer); */
         }
      }
      fclose(file);
      free(buffer);
   }
   return 0;
}
#include <stdio.h>
#include <stdlib.h>

int main(void)
{
   static const char filename[] = "file.txt";
   FILE *file = fopen(filename, "rb");
   if ( file )
   {
      char *buffer;
      long size;
      fseek(file, 0, SEEK_END);
      size = ftell(file);
      rewind(file);
      buffer = malloc(size);
      if ( buffer )
      {
         if ( fread(buffer, size, 1, file) == 1 )
         {
            /* puts(buffer); */
         }
      }
      fclose(file);
      free(buffer);
   }
   return 0;
}

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Join Date: Feb 2005

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winbatch

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Re: Error reading in file in binary mode

Jul 14th, 2005

Dave,

When you used the code I posted you didn't have any trouble? Wonder if it's a compiler specific bug - I'm using Sun Workshop 6 on solaris... I tried your code and it works... I put the puts(buffer) back ;)

Winbatch

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Dave Sinkula Dave Sinkula is offline

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long time no c

Re: Error reading in file in binary mode

Jul 14th, 2005

First, I rarely start by looking at the compiler; I'd say about 99% of the time it is the code. Just because I didn't see what you saw doesn't mean there wasn't an issue with it.

I think in part what is missing is what is missing. How do you see what you see? Where is some sort of output statement?

One of the reasons I put the puts line in comments is that it probably isn't what you are doing and it's probably not the correct thing to do. And perhaps that is the issue -- on the output side, not the input side.

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Re: Error reading in file in binary mode

Jul 14th, 2005

This was the code:
// reading binary file
#include <iostream.h>
#include <fstream.h>
const char * filename = "test.txt";
int main ()
{
char * buffer;
long size;
ifstream file (filename, ios::in|ios::binary|ios::ate);
size = file.tellg();
file.seekg (0, ios::beg);
buffer = new char [size];
file.read (buffer, size);
file.close();
cout<<buffer<<endl;
delete[] buffer;
return 0;
}

(Also note that cout<<buffer[0]<<endl; and cout<<buffer[1]<<endl; also produced the same letter.....)

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long time no c

Re: Error reading in file in binary mode

Jul 14th, 2005

Hmm. When I run either C or C++ version in the command shell in SlickEdit (my usual location that helps discover things like the need for fflush(stdout) and such) I get a blank area where the text should be. To me this would tell me that I might be missing something. When I run it in a cmd shell this does not happen. [edit]Ah the CR of the CR-LF was erasing the line for the SlickEdit output window. A fallout of binary mode reading.[/edit]

I am using Windows, so I might suspect my version would have issues with the binary vs text modes. But I wouldn't expect such things on Solaris. Outputting one at a time from 0 to size would have been my suggestion, so I'm a little miffed.

What is the "big picture" of what you are trying to do?

[edit2]This is the code I am using.

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
#include <iostream>
using std::cout;
using std::endl;
using std::ios;
#include <fstream>
using std::ifstream;
 
const char filename[] = "file.txt";
 
int main ()
{
   ifstream file(filename, ios::in | ios::binary | ios::ate);
   long size = file.tellg();
   file.seekg(0, ios::beg);
   char *buffer = new char [size];
   file.read(buffer, size);
   file.close();
   for ( long i = 0; i < size; ++i )
   {
      cout << buffer[i];
   }
   cout << endl;
   delete[] buffer;
   return 0;
}
 
/* file.txt (no newline at end)
SAM LOVES TO TEST FILES
*/
 
/* my output
SAM LOVES TO TEST FILES
*/
#include <iostream>
using std::cout;
using std::endl;
using std::ios;
#include <fstream>
using std::ifstream;

const char filename[] = "file.txt";

int main ()
{
   ifstream file(filename, ios::in | ios::binary | ios::ate);
   long size = file.tellg();
   file.seekg(0, ios::beg);
   char *buffer = new char [size];
   file.read(buffer, size);
   file.close();
   for ( long i = 0; i < size; ++i )
   {
      cout << buffer[i];
   }
   cout << endl;
   delete[] buffer;
   return 0;
}

/* file.txt (no newline at end)
SAM LOVES TO TEST FILES
*/

/* my output
SAM LOVES TO TEST FILES
*/

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Re: Error reading in file in binary mode

Jul 14th, 2005

The big picture is that I am loading an MQ series queue with the text of a file. (It's a command line utility). Since I don't know the size of the message at the start, I am reading it in binary so to that I can set the size of the buffer dynamically. In any case, I was able to get it to work with the C code version, so I'm good to go.

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Re: Error reading in file in binary mode

Jul 14th, 2005

A vector of strings for C++?

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winbatch

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Re: Error reading in file in binary mode

Jul 14th, 2005

I don't need a vector, I have a single string. (The file contains one message, not a bunch of messages)

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Re: Error reading in file in binary mode

#10

Jul 14th, 2005

Another stray thought:

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
#include <iostream>
#include <fstream>
#include <sstream>
 
int main ()
{
   static const char filename[] = "file.txt";
   std::ifstream file(filename);
   std::ostringstream text;
   text << file.rdbuf(); // slurp
   std::cout << text.str() << std::endl;
   return 0;
}
 
/* my output
SAM LOVES TO TEST FILES
*/
#include <iostream>
#include <fstream>
#include <sstream>

int main ()
{
   static const char filename[] = "file.txt";
   std::ifstream file(filename);
   std::ostringstream text;
   text << file.rdbuf(); // slurp
   std::cout << text.str() << std::endl;
   return 0;
}

/* my output
SAM LOVES TO TEST FILES
*/