Article ID: 246934
Article Last Modified on 7/30/2001
This article was previously published under Q246934
SYMPTOMS
The istream::readsome function does not read correct data from a file.
CAUSE
The basic_istream::readsome function has some limitations when used on certain streams. Moreover, the MSDN documentation for basic_istream::readsome states that internally basic_istream::readsome calls the read function. However, in the basic_istream::readsome implementation, the read function is never called.
RESOLUTION
Give preference to basic_istream::read.
STATUS
Microsoft has confirmed that this is a bug in the Microsoft products that are listed at the beginning of this article.
MORE INFORMATION
Here is a code sample that illustrates the problem and provides a workaround:
#include <iostream>
#include <fstream>
using namespace std;
int main()
{
ifstream file("c:\\config.sys",ios::in|ios::binary);
static char buffer[10];
buffer[10] = 0;
if ( !file )
cout << "unable to open file" << endl;
else
{
file.readsome(buffer,10); // It does not work properly.
//file.read( buffer, 10 ); // Uncomment this line for work around.
cout << buffer << endl;
cout << endl << "File contents are:" << endl;
file.seekg( 0 ); // Rewind file.
while( file.good() )
{
file.getline( buffer, 10 );
cout << buffer << endl;
}
}
return 0;
}
Additional query words: stl
Keywords: kbbug KB246934
