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+++ Libc/Libc-262/stdio/fseek.c
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+/*
+ * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
+ *
+ * @APPLE_LICENSE_HEADER_START@
+ *
+ * The contents of this file constitute Original Code as defined in and
+ * are subject to the Apple Public Source License Version 1.1 (the
+ * "License"). You may not use this file except in compliance with the
+ * License. Please obtain a copy of the License at
+ * http://www.apple.com/publicsource and read it before using this file.
+ *
+ * This Original Code and all software distributed under the License are
+ * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
+ * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT. Please see the
+ * License for the specific language governing rights and limitations
+ * under the License.
+ *
+ * @APPLE_LICENSE_HEADER_END@
+ */
+/*
+ * Copyright (c) 1990, 1993
+ * The Regents of the University of California. All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Chris Torek.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ * must display the following acknowledgement:
+ * This product includes software developed by the University of
+ * California, Berkeley and its contributors.
+ * 4. Neither the name of the University nor the names of its contributors
+ * may be used to endorse or promote products derived from this software
+ * without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+
+#include <sys/types.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include "local.h"
+
+#define POS_ERR (-(fpos_t)1)
+
+int
+fseek(fp, offset, whence)
+ register FILE *fp;
+ long offset;
+ int whence;
+{
+ return (fseeko(fp, offset, whence));
+}
+
+
+/*
+ * Seek the given file to the given offset.
+ * `Whence' must be one of the three SEEK_* macros.
+ */
+int
+fseeko(fp, offset, whence)
+ register FILE *fp;
+ off_t offset;
+ int whence;
+{
+ register fpos_t (*seekfn) __P((void *, fpos_t, int));
+ fpos_t target, curoff;
+ size_t n;
+ struct stat st;
+ int havepos;
+
+ /* make sure stdio is set up */
+ if (!__sdidinit)
+ __sinit();
+
+ /* FLOCKFILE(fp); */
+ /*
+ * Have to be able to seek.
+ */
+ if ((seekfn = fp->_seek) == NULL) {
+ errno = ESPIPE; /* historic practice */
+ /* FUNLOCKFILE(fp); */
+ return (EOF);
+ }
+
+ /*
+ * Change any SEEK_CUR to SEEK_SET, and check `whence' argument.
+ * After this, whence is either SEEK_SET or SEEK_END.
+ */
+ switch (whence) {
+
+ case SEEK_CUR:
+ /*
+ * In order to seek relative to the current stream offset,
+ * we have to first find the current stream offset a la
+ * ftell (see ftell for details).
+ */
+ if (fp->_flags & __SOFF)
+ curoff = fp->_offset;
+ else {
+ curoff = (*seekfn)(fp->_cookie, (fpos_t)0, SEEK_CUR);
+ if (curoff == -1) {
+ /* FUNLOCKFILE(fp); */
+ return (EOF);
+ }
+ }
+ if (fp->_flags & __SRD) {
+ curoff -= fp->_r;
+ if (HASUB(fp))
+ curoff -= fp->_ur;
+ } else if (fp->_flags & __SWR && fp->_p != NULL)
+ curoff += fp->_p - fp->_bf._base;
+
+ offset += curoff;
+ whence = SEEK_SET;
+ havepos = 1;
+ break;
+
+ case SEEK_SET:
+ case SEEK_END:
+ curoff = 0; /* XXX just to keep gcc quiet */
+ havepos = 0;
+ break;
+
+ default:
+ errno = EINVAL;
+ /* FUNLOCKFILE(fp); */
+ return (EOF);
+ }
+
+ /*
+ * Can only optimise if:
+ * reading (and not reading-and-writing);
+ * not unbuffered; and
+ * this is a `regular' Unix file (and hence seekfn==__sseek).
+ * We must check __NBF first, because it is possible to have __NBF
+ * and __SOPT both set.
+ */
+ if (fp->_bf._base == NULL)
+ __smakebuf(fp);
+ if (fp->_flags & (__SWR | __SRW | __SNBF | __SNPT))
+ goto dumb;
+ if ((fp->_flags & __SOPT) == 0) {
+ if (seekfn != __sseek ||
+ fp->_file < 0 || fstat(fp->_file, &st) ||
+ (st.st_mode & S_IFMT) != S_IFREG) {
+ fp->_flags |= __SNPT;
+ goto dumb;
+ }
+ fp->_blksize = st.st_blksize;
+ fp->_flags |= __SOPT;
+ }
+
+ /*
+ * We are reading; we can try to optimise.
+ * Figure out where we are going and where we are now.
+ */
+ if (whence == SEEK_SET)
+ target = offset;
+ else {
+ if (fstat(fp->_file, &st))
+ goto dumb;
+ target = st.st_size + offset;
+ }
+
+ if (!havepos) {
+ if (fp->_flags & __SOFF)
+ curoff = fp->_offset;
+ else {
+ curoff = (*seekfn)(fp->_cookie, (fpos_t)0, SEEK_CUR);
+ if (curoff == POS_ERR)
+ goto dumb;
+ }
+ curoff -= fp->_r;
+ if (HASUB(fp))
+ curoff -= fp->_ur;
+ }
+
+ /*
+ * Compute the number of bytes in the input buffer (pretending
+ * that any ungetc() input has been discarded). Adjust current
+ * offset backwards by this count so that it represents the
+ * file offset for the first byte in the current input buffer.
+ */
+ if (HASUB(fp)) {
+ curoff += fp->_r; /* kill off ungetc */
+ n = fp->_up - fp->_bf._base;
+ curoff -= n;
+ n += fp->_ur;
+ } else {
+ n = fp->_p - fp->_bf._base;
+ curoff -= n;
+ n += fp->_r;
+ }
+
+ /*
+ * If the target offset is within the current buffer,
+ * simply adjust the pointers, clear EOF, undo ungetc(),
+ * and return. (If the buffer was modified, we have to
+ * skip this; see fgetln.c.)
+ */
+ if ((fp->_flags & __SMOD) == 0 &&
+ target >= curoff && target < curoff + n) {
+ register int o = target - curoff;
+
+ fp->_p = fp->_bf._base + o;
+ fp->_r = n - o;
+ if (HASUB(fp))
+ FREEUB(fp);
+ fp->_flags &= ~__SEOF;
+ /* FUNLOCKFILE(fp); */
+ return (0);
+ }
+
+ /*
+ * The place we want to get to is not within the current buffer,
+ * but we can still be kind to the kernel copyout mechanism.
+ * By aligning the file offset to a block boundary, we can let
+ * the kernel use the VM hardware to map pages instead of
+ * copying bytes laboriously. Using a block boundary also
+ * ensures that we only read one block, rather than two.
+ */
+ curoff = target & ~(fp->_blksize - 1);
+ if ((*seekfn)(fp->_cookie, curoff, SEEK_SET) == POS_ERR)
+ goto dumb;
+ fp->_r = 0;
+ fp->_p = fp->_bf._base;
+ if (HASUB(fp))
+ FREEUB(fp);
+ fp->_flags &= ~__SEOF;
+ n = target - curoff;
+ if (n) {
+ if (__srefill(fp) || fp->_r < n)
+ goto dumb;
+ fp->_p += n;
+ fp->_r -= n;
+ }
+ /* FUNLOCKFILE(fp); */
+ return (0);
+
+ /*
+ * We get here if we cannot optimise the seek ... just
+ * do it. Allow the seek function to change fp->_bf._base.
+ */
+dumb:
+ if (__sflush(fp) ||
+ (*seekfn)(fp->_cookie, (fpos_t)offset, whence) == POS_ERR) {
+ /* FUNLOCKFILE(fp); */
+ return (EOF);
+ }
+ /* success: clear EOF indicator and discard ungetc() data */
+ if (HASUB(fp))
+ FREEUB(fp);
+ fp->_p = fp->_bf._base;
+ fp->_r = 0;
+ /* fp->_w = 0; */ /* unnecessary (I think...) */
+ fp->_flags &= ~__SEOF;
+ /* FUNLOCKFILE(fp); */
+ return (0);
+}