[addit]

Hello all, I've stumbled across a slight problem while trying to port some java code to c++. The following java code is:

Code:

...
DataInputStream dis = null;
try {
dis = new DataInputStream (new BufferedInputStream(new FileInputStream("fileblah"))); // create the stream
}
...
try {
int number = dis.readInt();
}
....

Now all the above is doing is reading an interger from the file right? In other words four bytes from a file. So this is the my code in C++: (i'm using stdio, yes yes yes i know, i know?!)

Code:

...
int number;
fread ((char *) &number,4,1,file);
...

However the java code returns: 435
Where as my c++ code returns: -1291780096

Whats going on? I'm still quite a new at all this. Can anyone try and help me port that java code to c++ so it returns the same number! (you don't have to use the standard library).

Thanking you in anticipation,
Adam

[Sokolov]

Hi Adam,

Your code looks fie, nothing wrong. Maybe you need to check if you opened the file correctly. Also check the return value of the read function.

Here a simple C and C++ exaple of writing and reading a number from file (binary):

Code:

#include <stdio.h>
#include <stdlib.h>


int main(void)
{
   FILE *fp;
   int number = 9;
   char *filename = "c:\\test.bin";

   if((fp = fopen(filename, "wb")) == NULL)
   {
      perror(filename);
      return EXIT_FAILURE;
   }

   fwrite(&number, sizeof number, 1, fp);
   fclose(fp);

   if((fp = fopen(filename, "rb")) == NULL)
   {
      perror(filename);
      return EXIT_FAILURE;
   }

   fread(&number, sizeof number, 1, fp);
   printf("number = %d\n", number);
   fclose(fp);
   return EXIT_SUCCESS;
}

Code:

#include <iostream>
#include <fstream>

using namespace std;

int main(void)
{
   char *filename = "c:\\test.bin";
   int number = 9;
	
   ofstream out(filename, ios::out|ios::binary);

   if(!out.is_open()) 
   {
      cerr << "Error opening output file" << endl;
      return EXIT_FAILURE;
   }
   out.write((char *)&number, sizeof number);
   out.close();

   std::ifstream in(filename, ios::in|ios::binary);
	
   if(!in.is_open()) 
   {
      cerr << "Error opening input file" << endl;
      return EXIT_FAILURE;
   }
   in.read((char *)&number, sizeof number);
   cout << "number = "<< number << endl;
   in.close();

   return EXIT_SUCCESS;
}

[addit]

Thank you for the reply... However I fixed my problem by myself. It was either c++ or java reading the bytes in a fishy order... reverse I think! Well thank you anyway.

It's nice to know theres always someone there trying to help ya out!

Adam

EDITED: Oh yeh before I forget I got another problem! Do you know the equivilant of the java triple right shift operator ie. >>>?

[Sokolov]

variable >>= 3 (or variable = variable >> 3)