sl@0: /* FTELL.C
sl@0:  * 
sl@0:  * Portions Copyright (c) 1990-1999 Nokia Corporation and/or its subsidiary(-ies).
sl@0:  * All rights reserved.
sl@0:  */
sl@0: 
sl@0: /*
sl@0:  * Copyright (c) 1990 The Regents of the University of California.
sl@0:  * All rights reserved.
sl@0:  *
sl@0:  * Redistribution and use in source and binary forms are permitted
sl@0:  * provided that the above copyright notice and this paragraph are
sl@0:  * duplicated in all such forms and that any documentation,
sl@0:  * advertising materials, and other materials related to such
sl@0:  * distribution and use acknowledge that the software was developed
sl@0:  * by the University of California, Berkeley.  The name of the
sl@0:  * University may not be used to endorse or promote products derived
sl@0:  * from this software without specific prior written permission.
sl@0:  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
sl@0:  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
sl@0:  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
sl@0:  */
sl@0: 
sl@0: /*
sl@0: FUNCTION
sl@0: <<ftell>>---return position in a stream or file
sl@0: 
sl@0: INDEX
sl@0: 	ftell
sl@0: 
sl@0: ANSI_SYNOPSIS
sl@0: 	#include <stdio.h>
sl@0: 	long ftell(FILE *<[fp]>);
sl@0: 
sl@0: TRAD_SYNOPSIS
sl@0: 	#include <stdio.h>
sl@0: 	long ftell(<[fp]>)
sl@0: 	FILE *<[fp]>;
sl@0: 
sl@0: DESCRIPTION
sl@0: Objects of type <<FILE>> can have a ``position'' that records how much
sl@0: of the file your program has already read.  Many of the <<stdio>> functions
sl@0: depend on this position, and many change it as a side effect.
sl@0: 
sl@0: The result of <<ftell>> is the current position for a file
sl@0: identified by <[fp]>.  If you record this result, you can later
sl@0: use it with <<fseek>> to return the file to this
sl@0: position.
sl@0: 
sl@0: In the current implementation, <<ftell>> simply uses a character
sl@0: count to represent the file position; this is the same number that
sl@0: would be recorded by <<fgetpos>>.
sl@0: 
sl@0: RETURNS
sl@0: <<ftell>> returns the file position, if possible.  If it cannot do
sl@0: this, it returns <<-1L>>.  Failure occurs on streams that do not support
sl@0: positioning; the global <<errno>> indicates this condition with the
sl@0: value <<ESPIPE>>.
sl@0: 
sl@0: PORTABILITY
sl@0: <<ftell>> is required by the ANSI C standard, but the meaning of its
sl@0: result (when successful) is not specified beyond requiring that it be
sl@0: acceptable as an argument to <<fseek>>.  In particular, other
sl@0: conforming C implementations may return a different result from
sl@0: <<ftell>> than what <<fgetpos>> records.
sl@0: 
sl@0: No supporting OS subroutines are required.
sl@0: */
sl@0: 
sl@0: /*
sl@0:  * ftell: return current offset.
sl@0:  */
sl@0: 
sl@0: #include <stdio_r.h>
sl@0: #include <errno.h>
sl@0: 
sl@0: #include "LOCAL.H"
sl@0: 
sl@0: /**
sl@0: Return the current position in a stream.
sl@0: Returns the current position pointed by the position indicator of the stream. 
sl@0: When a file has been opened in binary mode the value obtained corresponds to 
sl@0: the number of bytes from the beginning of the file. In files opened in 
sl@0: text-mode this is not granted because of carriage-return translations under that mode.
sl@0: @return On success, the current file pointer position is returned.
sl@0: If an error occurs -1 is returned.
sl@0: @param Pointer to an open file.
sl@0: */
sl@0: EXPORT_C long
sl@0: ftell (FILE * fp)
sl@0: {
sl@0:   fpos_t pos;
sl@0: 
sl@0:   /* Ensure stdio is set up.  */
sl@0: 
sl@0:   CHECK_INIT (fp);
sl@0: 
sl@0:   if (fp->_seek == NULL)
sl@0:     {
sl@0:       __errno_r(fp->_data) = ESPIPE;
sl@0:       return -1L;
sl@0:     }
sl@0: 
sl@0:   /* Find offset of underlying I/O object, then
sl@0:      adjust for buffered bytes.  */
sl@0: 
sl@0:   if (fp->_flags & __SOFF)
sl@0:     pos = fp->_offset;
sl@0:   else
sl@0:     {
sl@0:       pos = (*fp->_seek) (fp->_cookie, (fpos_t) 0, SEEK_CUR);
sl@0:       if (pos == -1L)
sl@0: 	return pos;
sl@0:     }
sl@0:   if (fp->_flags & __SRD)
sl@0:     {
sl@0:       /*
sl@0:        * Reading.  Any unread characters (including
sl@0:        * those from ungetc) cause the position to be
sl@0:        * smaller than that in the underlying object.
sl@0:        */
sl@0:       pos -= fp->_r;
sl@0:       if (HASUB (fp))
sl@0: 	pos -= fp->_ur;
sl@0:     }
sl@0:   else if (fp->_flags & __SWR && fp->_p != NULL)
sl@0:     {
sl@0:       /*
sl@0:        * Writing.  Any buffered characters cause the
sl@0:        * position to be greater than that in the
sl@0:        * underlying object.
sl@0:        */
sl@0:       pos += fp->_p - fp->_bf._base;
sl@0:     }
sl@0: 
sl@0:   return pos;
sl@0: }