binary file parsing in C++

binary file parsing in C++

[Justin Findlay]

Is there any way to read through a file bit by bit, instead of character 
by character?

ifstream::read(), ifstream::readsome(), and ifstream::get() deal only in
chars (bytes).


Justin

Re: binary file parsing in C++

[Segher Boessenkool]

On 11-dec-03, at 0:20, Justin Findlay wrote:
> I am perplexed at what is happening here.  This is a simple script that
> reads a file one byte at a time, and writes it to another file one 
> byte at
> a time, but somehow there is an extra character at the end of the 
> output
> file.

end-of-file only gets set after you try to read past the end of the 
file,
not when you are _at_ the end of the file.


Segher

Re: binary file parsing in C++

[Justin Findlay]

On Wed, 10 Dec 2003, Eljay Love-Jensen wrote:

>> Is there any way to read through a file bit by bit, instead of character by character?
> 
> You'll have to write your own bit-by-bit reader.
> 
> A class that HAS-A ifstream, and whose "get" method returns a bit (via bool or int or enum Bit { Zero, One }).
> 
> Shouldn't be very hard.


I am perplexed at what is happening here.  This is a simple script that 
reads a file one byte at a time, and writes it to another file one byte at 
a time, but somehow there is an extra character at the end of the output 
file.

$ g++ --version
g++ (GCC) 3.3.2 20031022 (Red Hat Linux 3.3.2-1)
$ g++ binary.cpp
$ ./a.out
$ ls -ls
 8 -rw-rw-r--    1 justin   justin       4258 Dec  9 20:11 bin
 8 -rw-rw-r--    1 justin   justin       4259 Dec 10 16:14 bout
$ cat binary.cpp
//binary.cpp
#include <fstream>

  using namespace std;

int main()
{
  char b[ 1 ];
  ifstream fin( "bin" );
  ofstream fout( "bout" );
  while ( fin.good() && ! fin.eof() )
  {
    fin.read( b, 1 );
    fout.write( b, 1 );
  }
  return 0;
}


Justin

Re: binary file parsing in C++

[Eljay Love-Jensen]

Hi Justin,

>Is there any way to read through a file bit by bit, instead of character by character?

You'll have to write your own bit-by-bit reader.

A class that HAS-A ifstream, and whose "get" method returns a bit (via bool or int or enum Bit { Zero, One }).

Shouldn't be very hard.

HTH,
--Eljay