[Mingw-users] ifstream read() results in wrong gcount and eof for CR+LF terminated files

[Ronald L. <R.L...@T-...>]

Hi,

Using the current mingw3.4.2 the following simple example used with a
Windows CR+LF lineterminated testfile of more than 512 bytes results in
wrong gcount() and eof():

     std::ifstream ifs("my_cr_lf_file.txt");
     std::vector<char> dest;
     int blocksize = 512;
     size_t len = 0;
     int nread=0;
     do {
         dest.resize(dest.size() + blocksize);
         is.read (&dest[len], blocksize);
         nread = is.gcount();
         len += nread;
     } while (nread == blocksize);

If the testfile consists of 17 lines within the first 512 bytes
gcount() will return 495 and eof() will be true after the first read()
call. Looks like a problem with CR+LF to LF convertion in read().

I found the following hint in this mailing list that was missing details
and code examples:

> From: John Gaughan <john@...>
> Subject: Re: [mingw - C/C++] why always read() file error?
> Newsgroups: gmane.comp.gnu.mingw.user
> Date: 2004-05-27 18:32:02 GMT (1 year, 32 weeks, 5 days, 15 hours and 11 minutes ago)
> 
> SourceForge.net said:
>> I compile a program to read a file, but the return of read() function
>> always
>> less than my willing, how to deal with it?
> 
> Could you show us what your code looks like and what the problem is?
> 
> ifstream.read() should return the number of bytes read, if my [failing]
> memory serves me correctly.
> 
> -- 
> John Gaughan