Table of Contents
    Extensions allowing filebufs to be constructed from
    "C" types like  FILE*s and file descriptors.
  
The v2 library included non-standard extensions to construct
      std::filebufs from C stdio types such as
      FILE*s and POSIX file descriptors.
      Today the recommended way to use stdio types with libstdc++
      IOStreams is via the stdio_filebuf class (see below),
      but earlier releases provided slightly different mechanisms.
   
3.0.x filebufs have another ctor with this signature:
	basic_filebuf(__c_file_type*, ios_base::openmode, int_type);
	
	 This comes in very handy in a number of places, such as
	 attaching Unix sockets, pipes, and anything else which uses file
	 descriptors, into the IOStream buffering classes.  The three
	 arguments are as follows:
	 
__c_file_type*      F   
	      // the __c_file_type typedef usually boils down to stdio's FILE
	  
ios_base::openmode  M   
	      // same as all the other uses of openmode
	  
int_type            B   
	      // buffer size, defaults to BUFSIZ if not specified
	  
	 For those wanting to use file descriptors instead of FILE*'s, I
	 invite you to contemplate the mysteries of C's fdopen().
     
In library snapshot 3.0.95 and later, filebufs bring
	 back an old extension:  the fd() member function.  The
	 integer returned from this function can be used for whatever file
	 descriptors can be used for on your platform.  Naturally, the
	 library cannot track what you do on your own with a file descriptor,
	 so if you perform any I/O directly, don't expect the library to be
	 aware of it.
     
Beginning with 3.1, the extra
	 basic_filebuf constructor and
	 the fd() function were removed from the standard
	 filebuf.  Instead,
	 <ext/stdio_filebuf.h>
	 contains a derived class template called
	 __gnu_cxx::stdio_filebuf.
	 This class can be constructed from a C FILE* or a file
	 descriptor, and provides the fd() function.