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/*
** PJL C++ Library
** fdbuf.h
**
** Copyright (C) 2001 Paul J. Lucas
**
** This program is free software; you can redistribute it and/or modify
** it under the terms of the GNU General Public License as published by
** the Free Software Foundation; either version 2 of the License, or
** (at your option) any later version.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
** GNU General Public License for more details.
**
** You should have received a copy of the GNU General Public License
** along with this program; if not, write to the Free Software
** Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
// standard
#include <cerrno>
#include <cstring>
#include <unistd.h>
// local
#include "fdbuf.h"
using namespace std;
namespace PJL {
//*****************************************************************************
//
// SYNOPSIS
//
void fdbuf::init( int fd )
//
// DESCRIPTION
//
// Initialize an fdbuf.
//
//*****************************************************************************
{
fd_ = fd;
setg( rbuf_, rbuf_ + buf_size, rbuf_ + buf_size );
setp( wbuf_, wbuf_ + buf_size );
}
//*****************************************************************************
//
// SYNOPSIS
//
int fdbuf::sync()
//
// DESCRIPTION
//
// Synchronize the write buffer by writing it out.
//
// RETURN VALUE
//
// On success, returns 0; on failure, returns -1.
//
//*****************************************************************************
{
int const len = pptr() - pbase();
if ( write_buf( wbuf_, len ) != len )
return -1;
pbump( -len );
return 0;
}
//*****************************************************************************
//
// SYNOPSIS
//
fdbuf::int_type fdbuf::overflow( int_type c )
//
// DESCRIPTION
//
// This function is called when a single character is to be output.
//
// PARAMETERS
//
// c The single character to be stuffed into the buffer unless it is
// EOF.
//
// RETURN VALUE
//
// On success, returns the passed-in character; on failure, returns EOF.
//
//*****************************************************************************
{
if ( sync() )
return EOF;
if ( c != EOF ) {
*pptr() = c;
pbump( 1 );
}
return c;
}
//*****************************************************************************
//
// SYNOPSIS
//
fdbuf::int_type fdbuf::underflow()
//
// DESCRIPTION
//
// This function is called when the buffer is underflowed, i.e., more
// characters need to be read from the source.
//
// RETURN VALUE
//
// Returns the next character from the source or EOF on error.
//
//*****************************************************************************
{
if ( gptr() == egptr() ) {
//
// The get-pointer is at the end-pointer meaning that the read-buffer
// is exhausted: read more.
//
ssize_t bytes;
while ( true ) {
if ( (bytes = ::read( fd_, rbuf_, buf_size )) > 0 ) {
//
// We read some bytes so stop.
//
break;
}
if ( bytes < 0 && (errno == EAGAIN || errno == EINTR) )
continue;
return EOF;
}
setg( rbuf_, rbuf_, rbuf_ + bytes );
}
return *gptr();
}
//*****************************************************************************
//
// SYNOPSIS
//
streamsize fdbuf::write_buf( char const *buf, streamsize len )
//
// DESCRIPTION
//
// Write a buffer to a Unix file descriptor.
//
// PARAMETERS
//
// buf The buffer to be written.
//
// len The length of the buffer.
//
// RETURN VALUE
//
// On success, returns the number of bytes written; on failure, returns
// -1.
//
// SEE ALSO
//
// W. Richard Stevens. "Unix Network Programming, Vol 1, 2nd ed."
// Prentice-Hall, Upper Saddle River, NJ, 1998.
//
//*****************************************************************************
{
streamsize total_bytes_written = 0;
while ( true ) {
ssize_t const bytes_written = ::write( fd_, buf, len );
if ( bytes_written >= 0 ) {
//
// Account for partial-writes in case the Unix file descriptor
// happens to be attached to a socket. From [Stevens 1998], p. 77:
//
// Stream sockets (e.g., TCP sockets) exhibit a behavior with
// the read and write functions that differs from normal file
// I/O. A read or write on a stream socket might input or
// output fewer bytes than requested, but this is not an error
// condition. The reason is that buffer limits might be
// reached for the kernel. All that is required is for the
// caller to invoke the read or write function again, to input
// or output the remaining bytes.
//
// Note that if the file descriptor isn't attached to a socket, the
// entire buffer will be written, so the loop will exit.
//
total_bytes_written += bytes_written;
if ( bytes_written == len )
return total_bytes_written;
len -= bytes_written;
buf += bytes_written;
continue;
}
if ( errno == EINTR ) // interrupt-proof
continue;
return -1;
}
}
//*****************************************************************************
//
// SYNOPSIS
//
streamsize fdbuf::xsputn( char const *buf, streamsize len )
//
// DESCRIPTION
//
// This function is called to output an entire buffer (as opposed to a
// single character).
//
// RETURN VALUE
//
// On success, returns the number of bytes written; on failure, returns
// -1.
//
//*****************************************************************************
{
if ( epptr() - pptr() >= len ) {
//
// The contents of buf will fit into the existing put-buffer so just
// put it there.
//
::memcpy( pptr(), buf, len );
pbump( len );
return len;
}
//
// The contents of buf will not fit into the existing put-buffer so
// syncronize what's currently there then write out the contents of buf
// directly.
//
return sync() ? -1 : write_buf( buf, len );
}
} // namespace PJL
/* vim:set et sw=4 ts=4: */
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