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[/] [openrisc/] [trunk/] [gnu-src/] [newlib-1.18.0/] [newlib/] [libc/] [stdio/] [ftell.c] - Rev 540
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/* * Copyright (c) 1990 The Regents of the University of California. * All rights reserved. * * Redistribution and use in source and binary forms are permitted * provided that the above copyright notice and this paragraph are * duplicated in all such forms and that any documentation, * advertising materials, and other materials related to such * distribution and use acknowledge that the software was developed * by the University of California, Berkeley. The name of the * University may not be used to endorse or promote products derived * from this software without specific prior written permission. * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. */ /* FUNCTION <<ftell>>, <<ftello>>---return position in a stream or file INDEX ftell INDEX ftello INDEX _ftell_r INDEX _ftello_r ANSI_SYNOPSIS #include <stdio.h> long ftell(FILE *<[fp]>); off_t ftello(FILE *<[fp]>); long _ftell_r(struct _reent *<[ptr]>, FILE *<[fp]>); off_t _ftello_r(struct _reent *<[ptr]>, FILE *<[fp]>); TRAD_SYNOPSIS #include <stdio.h> long ftell(<[fp]>) FILE *<[fp]>; off_t ftello(<[fp]>) FILE *<[fp]>; long _ftell_r(<[ptr]>, <[fp]>) struct _reent *<[ptr]>; FILE *<[fp]>; off_t _ftello_r(<[ptr]>, <[fp]>) struct _reent *<[ptr]>; FILE *<[fp]>; DESCRIPTION Objects of type <<FILE>> can have a ``position'' that records how much of the file your program has already read. Many of the <<stdio>> functions depend on this position, and many change it as a side effect. The result of <<ftell>>/<<ftello>> is the current position for a file identified by <[fp]>. If you record this result, you can later use it with <<fseek>>/<<fseeko>> to return the file to this position. The difference between <<ftell>> and <<ftello>> is that <<ftell>> returns <<long>> and <<ftello>> returns <<off_t>>. In the current implementation, <<ftell>>/<<ftello>> simply uses a character count to represent the file position; this is the same number that would be recorded by <<fgetpos>>. RETURNS <<ftell>>/<<ftello>> return the file position, if possible. If they cannot do this, they return <<-1L>>. Failure occurs on streams that do not support positioning; the global <<errno>> indicates this condition with the value <<ESPIPE>>. PORTABILITY <<ftell>> is required by the ANSI C standard, but the meaning of its result (when successful) is not specified beyond requiring that it be acceptable as an argument to <<fseek>>. In particular, other conforming C implementations may return a different result from <<ftell>> than what <<fgetpos>> records. <<ftello>> is defined by the Single Unix specification. No supporting OS subroutines are required. */ #if defined(LIBC_SCCS) && !defined(lint) static char sccsid[] = "%W% (Berkeley) %G%"; #endif /* LIBC_SCCS and not lint */ /* * ftell: return current offset. */ #include <_ansi.h> #include <reent.h> #include <stdio.h> #include <errno.h> #include "local.h" long _DEFUN(_ftell_r, (ptr, fp), struct _reent *ptr _AND register FILE * fp) { _fpos_t pos; /* Ensure stdio is set up. */ CHECK_INIT (ptr, fp); _flockfile (fp); if (fp->_seek == NULL) { ptr->_errno = ESPIPE; _funlockfile (fp); return -1L; } /* Find offset of underlying I/O object, then adjust for buffered bytes. Flush a write stream, since the offset may be altered if the stream is appending. Do not flush a read stream, since we must not lose the ungetc buffer. */ if (fp->_flags & __SWR) _fflush_r (ptr, fp); if (fp->_flags & __SOFF) pos = fp->_offset; else { pos = fp->_seek (ptr, fp->_cookie, (_fpos_t) 0, SEEK_CUR); if (pos == -1L) { _funlockfile (fp); return pos; } } if (fp->_flags & __SRD) { /* * Reading. Any unread characters (including * those from ungetc) cause the position to be * smaller than that in the underlying object. */ pos -= fp->_r; if (HASUB (fp)) pos -= fp->_ur; } else if ((fp->_flags & __SWR) && fp->_p != NULL) { /* * Writing. Any buffered characters cause the * position to be greater than that in the * underlying object. */ pos += fp->_p - fp->_bf._base; } _funlockfile (fp); if ((long)pos != pos) { pos = -1; ptr->_errno = EOVERFLOW; } return pos; } #ifndef _REENT_ONLY long _DEFUN(ftell, (fp), register FILE * fp) { return _ftell_r (_REENT, fp); } #endif /* !_REENT_ONLY */
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