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ios reading problem

Posted on 1999-11-08
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Last Modified: 2010-04-01
I am having a problem reading in plain binary data from a file using ios.

I use the ios.read() funciton and it starts off OK, but about 100 bytes into the data, it sets one of the error flags.  I call ios.good() and it returns a non-zero.

However, when I look at the values for the 4 possible error flags: ios::failbit, ios::badbit, ios::eofbit, and ios::goodbit, they are 0,1,2, and 4, but the ios.rdstate() function returns a 3???  Does anyone know what might be happening here??  

The code was originally written for UNIX and seemed to work fine  there, but now I am porting to PC using MSVC++ compiler and it won't read in all the data.



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Question by:klingej
4 Comments
 
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Expert Comment

by:curri
ID: 2192088
I don't really know, but it may be that the state returned is the (bitwise) ORing of the flags; and you know the error NOT by comparing but by (bitwise) ANDing.

So that could be both failbit and badbit or some other combination.

to see if badbit is on, you do xxx.rdstate() & ios::badbit
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Expert Comment

by:nietod
ID: 2192886
cum is right in that.  Although that doesn't explain the original problem.

It might help if you post your code so we might see what you are doing wrong.
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Expert Comment

by:KangaRoo
ID: 2193321
ios::badbit | ios::eofbit
Just checking, you did open in binary mode
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Accepted Solution

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tdubroff earned 150 total points
ID: 2291369
// This is an example of writing and reading binary data
#include <fstream.h>
void main()
{
    float f = 3.2;
    ofstream ofile("test.txt", ios::out | ios::binary);
    ofile.write((char*) &f, sizeof(f));
    ofile.close();

    ifstream ifile("test.txt", ios::in | ios::binary);
    ifile.read((char*) &f, sizeof(f));
    ifile.close();
}
   
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