/*- * 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. * 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. */ #if defined(LIBC_SCCS) && !defined(lint) static char sccsid[] = "@(#)fseek.c 8.3 (Berkeley) 1/2/94"; #endif /* LIBC_SCCS and not lint */ #include <sys/cdefs.h> __FBSDID("$FreeBSD: src/lib/libc/stdio/fseek.c,v 1.44 2008/04/17 22:17:54 jhb Exp $"); #include "namespace.h" #include <sys/types.h> #include <sys/stat.h> #include <errno.h> #include <fcntl.h> #include <limits.h> #include <stdio.h> #include <stdlib.h> #include "un-namespace.h" #include "local.h" #include "libc_private.h" #define POS_ERR (-(fpos_t)1) int fseek(fp, offset, whence) FILE *fp; long offset; int whence; { int ret; int serrno = errno; /* make sure stdio is set up */ if (!__sdidinit) __sinit(); FLOCKFILE(fp); ret = _fseeko(fp, (off_t)offset, whence, 1); FUNLOCKFILE(fp); if (ret == 0) errno = serrno; return (ret); } int fseeko(fp, offset, whence) FILE *fp; off_t offset; int whence; { int ret; int serrno = errno; /* make sure stdio is set up */ if (!__sdidinit) __sinit(); FLOCKFILE(fp); ret = _fseeko(fp, offset, whence, 0); FUNLOCKFILE(fp); if (ret == 0) errno = serrno; return (ret); } /* * Seek the given file to the given offset. * `Whence' must be one of the three SEEK_* macros. */ int _fseeko(fp, offset, whence, ltest) FILE *fp; off_t offset; int whence; int ltest; { fpos_t (*seekfn)(void *, fpos_t, int); fpos_t target, curoff, ret; size_t n; struct stat st; int havepos; /* * Have to be able to seek. */ if ((seekfn = fp->_seek) == NULL) { errno = ESPIPE; /* historic practice */ return (-1); } /* * 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 via * ftell (see ftell for details). */ if (_ftello(fp, &curoff)) return (-1); if (curoff < 0) { /* Unspecified position because of ungetc() at 0 */ errno = ESPIPE; return (-1); } if (offset > 0 && curoff > OFF_MAX - offset) { errno = EOVERFLOW; return (-1); } offset += curoff; if (offset < 0) { errno = EINVAL; return (-1); } if (ltest && offset > LONG_MAX) { errno = EOVERFLOW; return (-1); } whence = SEEK_SET; havepos = 1; break; case SEEK_SET: if (offset < 0) { errno = EINVAL; return (-1); } case SEEK_END: curoff = 0; /* XXX just to keep gcc quiet */ havepos = 0; break; default: errno = EINVAL; return (-1); } /* * 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; if (offset > 0 && st.st_size > OFF_MAX - offset) { errno = EOVERFLOW; return (-1); } target = st.st_size + offset; if ((off_t)target < 0) { errno = EINVAL; return (-1); } if (ltest && (off_t)target > LONG_MAX) { errno = EOVERFLOW; return (-1); } } if (!havepos && _ftello(fp, &curoff)) goto dumb; /* * (If the buffer was modified, we have to * skip this; see fgetln.c.) */ if (fp->_flags & __SMOD) goto abspos; /* * 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 (target >= curoff && target < curoff + n) { size_t o = target - curoff; fp->_p = fp->_bf._base + o; fp->_r = n - o; if (HASUB(fp)) FREEUB(fp); fp->_flags &= ~__SEOF; memset(&fp->_mbstate, 0, sizeof(mbstate_t)); return (0); } abspos: /* * 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 (_sseek(fp, curoff, SEEK_SET) == POS_ERR) goto dumb; fp->_r = 0; fp->_p = fp->_bf._base; if (HASUB(fp)) FREEUB(fp); n = target - curoff; if (n) { if (__srefill(fp) || fp->_r < n) goto dumb; fp->_p += n; fp->_r -= n; } fp->_flags &= ~__SEOF; memset(&fp->_mbstate, 0, sizeof(mbstate_t)); 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) || (ret = _sseek(fp, (fpos_t)offset, whence)) == POS_ERR) return (-1); if (ltest && ret > LONG_MAX) { fp->_flags |= __SERR; errno = EOVERFLOW; return (-1); } /* 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; memset(&fp->_mbstate, 0, sizeof(mbstate_t)); return (0); }