GCC Code Coverage Report
Directory: ./ Exec Total Coverage
File: lib/libc/stdio/fseek.c Lines: 19 95 20.0 %
Date: 2017-11-13 Branches: 10 92 10.9 %

Line Branch Exec Source
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/*	$OpenBSD: fseek.c,v 1.12 2015/08/31 02:53:57 guenther Exp $ */
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/*-
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 * Copyright (c) 1990, 1993
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 *	The Regents of the University of California.  All rights reserved.
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 *
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 * This code is derived from software contributed to Berkeley by
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 * Chris Torek.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 * 1. Redistributions of source code must retain the above copyright
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 *    notice, this list of conditions and the following disclaimer.
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 * 2. Redistributions in binary form must reproduce the above copyright
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 *    notice, this list of conditions and the following disclaimer in the
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 *    documentation and/or other materials provided with the distribution.
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 * 3. Neither the name of the University nor the names of its contributors
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 *    may be used to endorse or promote products derived from this software
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 *    without specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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 * SUCH DAMAGE.
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 */
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <errno.h>
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#include "local.h"
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#define	POS_ERR	(-(fpos_t)1)
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/*
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 * Seek the given file to the given offset.
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 * `Whence' must be one of the three SEEK_* macros.
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 */
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int
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fseeko(FILE *fp, off_t offset, int whence)
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{
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	fpos_t (*seekfn)(void *, fpos_t, int);
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	fpos_t target, curoff;
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	size_t n;
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2076
	struct stat st;
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	int havepos;
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	/* make sure stdio is set up */
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1038
	if (!__sdidinit)
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		__sinit();
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	/*
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	 * Have to be able to seek.
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	 */
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1038
	if ((seekfn = fp->_seek) == NULL) {
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		errno = ESPIPE;			/* historic practice */
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		return (EOF);
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	}
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	/*
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	 * Change any SEEK_CUR to SEEK_SET, and check `whence' argument.
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	 * After this, whence is either SEEK_SET or SEEK_END.
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	 */
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1038
	FLOCKFILE(fp);
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1038
	switch (whence) {
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	case SEEK_CUR:
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		/*
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		 * In order to seek relative to the current stream offset,
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		 * we have to first find the current stream offset a la
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		 * ftell (see ftell for details).
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		 */
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		__sflush(fp);	/* may adjust seek offset on append stream */
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		if (fp->_flags & __SOFF)
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			curoff = fp->_offset;
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		else {
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			curoff = (*seekfn)(fp->_cookie, (fpos_t)0, SEEK_CUR);
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			if (curoff == (fpos_t)-1) {
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				FUNLOCKFILE(fp);
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				return (EOF);
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			}
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		}
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		if (fp->_flags & __SRD) {
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			curoff -= fp->_r;
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			if (HASUB(fp))
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				curoff -= fp->_ur;
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		} else if (fp->_flags & __SWR && fp->_p != NULL)
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			curoff += fp->_p - fp->_bf._base;
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		offset += curoff;
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		whence = SEEK_SET;
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		havepos = 1;
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		break;
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	case SEEK_SET:
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	case SEEK_END:
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		curoff = 0;		/* XXX just to keep gcc quiet */
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		havepos = 0;
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1038
		break;
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	default:
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		FUNLOCKFILE(fp);
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		errno = EINVAL;
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		return (EOF);
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	}
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	/*
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	 * Can only optimise if:
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	 *	reading (and not reading-and-writing);
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	 *	not unbuffered; and
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	 *	this is a `regular' Unix file (and hence seekfn==__sseek).
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	 * We must check __NBF first, because it is possible to have __NBF
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	 * and __SOPT both set.
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	 */
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1038
	if (fp->_bf._base == NULL)
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1038
		__smakebuf(fp);
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1038
	if (fp->_flags & (__SWR | __SRW | __SNBF | __SNPT))
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		goto dumb;
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	if ((fp->_flags & __SOPT) == 0) {
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		if (seekfn != __sseek ||
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		    fp->_file < 0 || fstat(fp->_file, &st) ||
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		    (st.st_mode & S_IFMT) != S_IFREG) {
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			fp->_flags |= __SNPT;
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			goto dumb;
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		}
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		fp->_blksize = st.st_blksize;
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		fp->_flags |= __SOPT;
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	}
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	/*
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	 * We are reading; we can try to optimise.
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	 * Figure out where we are going and where we are now.
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	 */
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	if (whence == SEEK_SET)
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		target = offset;
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	else {
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		if (fstat(fp->_file, &st))
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			goto dumb;
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		target = st.st_size + offset;
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	}
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	if (!havepos) {
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		if (fp->_flags & __SOFF)
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			curoff = fp->_offset;
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		else {
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			curoff = (*seekfn)(fp->_cookie, (fpos_t)0, SEEK_CUR);
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			if (curoff == POS_ERR)
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				goto dumb;
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		}
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		curoff -= fp->_r;
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		if (HASUB(fp))
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			curoff -= fp->_ur;
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	}
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164
	/*
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	 * Compute the number of bytes in the input buffer (pretending
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	 * that any ungetc() input has been discarded).  Adjust current
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	 * offset backwards by this count so that it represents the
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	 * file offset for the first byte in the current input buffer.
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	 */
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	if (HASUB(fp)) {
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		curoff += fp->_r;	/* kill off ungetc */
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		n = fp->_up - fp->_bf._base;
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		curoff -= n;
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		n += fp->_ur;
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	} else {
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		n = fp->_p - fp->_bf._base;
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		curoff -= n;
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		n += fp->_r;
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	}
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181
	/*
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	 * If the target offset is within the current buffer,
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	 * simply adjust the pointers, clear EOF, undo ungetc(),
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	 * and return.  (If the buffer was modified, we have to
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	 * skip this; see fgetln.c.)
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	 */
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	if ((fp->_flags & __SMOD) == 0 &&
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	    target >= curoff && target < curoff + n) {
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		int o = target - curoff;
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		fp->_p = fp->_bf._base + o;
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		fp->_r = n - o;
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		if (HASUB(fp))
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			FREEUB(fp);
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		fp->_flags &= ~__SEOF;
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		FUNLOCKFILE(fp);
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		return (0);
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	}
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200
	/*
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	 * The place we want to get to is not within the current buffer,
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	 * but we can still be kind to the kernel copyout mechanism.
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	 * By aligning the file offset to a block boundary, we can let
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	 * the kernel use the VM hardware to map pages instead of
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	 * copying bytes laboriously.  Using a block boundary also
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	 * ensures that we only read one block, rather than two.
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	 */
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	curoff = target & ~(fp->_blksize - 1);
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	if ((*seekfn)(fp->_cookie, curoff, SEEK_SET) == POS_ERR)
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		goto dumb;
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	fp->_r = 0;
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 	fp->_p = fp->_bf._base;
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	if (HASUB(fp))
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		FREEUB(fp);
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	fp->_flags &= ~__SEOF;
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	n = target - curoff;
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	if (n) {
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		if (__srefill(fp) || fp->_r < n)
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			goto dumb;
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		fp->_p += n;
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		fp->_r -= n;
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	}
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	FUNLOCKFILE(fp);
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	return (0);
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226
	/*
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	 * We get here if we cannot optimise the seek ... just
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	 * do it.  Allow the seek function to change fp->_bf._base.
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	 */
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dumb:
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2076
	if (__sflush(fp) ||
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1038
	    (*seekfn)(fp->_cookie, (fpos_t)offset, whence) == POS_ERR) {
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		FUNLOCKFILE(fp);
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		return (EOF);
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	}
236
	/* success: clear EOF indicator and discard ungetc() data */
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1038
	if (HASUB(fp))
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		FREEUB(fp);
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1038
	fp->_p = fp->_bf._base;
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1038
	fp->_r = 0;
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	/* fp->_w = 0; */	/* unnecessary (I think...) */
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1038
	fp->_flags &= ~__SEOF;
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1038
	FUNLOCKFILE(fp);
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1038
	return (0);
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1038
}
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DEF_WEAK(fseeko);
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248
int
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fseek(FILE *fp, long offset, int whence)
250
{
251
2076
	return (fseeko(fp, offset, whence));
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}
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DEF_STRONG(fseek);