[Boost-users] [iostreams] problem with bzip2_decompressor and incomplete files

2 Oct 2005

      Hello.

I've been experiencing a problem with the bzip2_decompressor filter when
reading from a stream attached to an incomplete file. Instead of
throwing an exception or reaching EOF, the program just hangs.

Consider the following example code (hello.cc) taken from the documentation:

-----------------------------------------------------------
#include <fstream>
#include <iostream>
#include <boost/iostreams/filtering_streambuf.hpp>
#include <boost/iostreams/copy.hpp>
#include <boost/iostreams/filter/bzip2.hpp>

int main()
{
  using namespace std;
  using namespace boost;
  using namespace boost::iostreams;

  ifstream file("hello.bz2", ios_base::in | ios_base::binary);
  filtering_streambuf<input> in;
  in.push(bzip2_decompressor());
  in.push(file);
  boost::iostreams::copy(in, cout);
}
-----------------------------------------------------------

Suppose this is compiled as "hello". The following command will generate
a simple bzip2-compressed file:

$ echo -e "Hello world\n" | bzip2 > hello-complete.bz2

The next line will copy everything but the last byte from
"hello-complete.bz2" to "hello.bz2":

$ dd if=hello-complete.bz2 of=hello.bz2 bs=1 count=53

So now if the program is run:

$ ./hello

It just hangs in an infinite loop, instead of throwing an exception or
reaching EOF. In the same situation, gzip_decompressor throws an
exception... Is there a reason for this not happening in this case, or
is this just a bug?

I'm using boost 1.33.0 with GCC 4.0.1 on an i686 with GNU/Linux.

Thanks for any help.
-- 
Tiago de Paula Peixoto <tiago@forked.de>