BSD 4.4 Lite Lib Sources

1 files changed, 245 insertions, 0 deletions

diff --git a/lib/libc/stdio/fseek.c b/lib/libc/stdio/fseek.c
new file mode 100644
index 0000000..6b0cc8b
--- /dev/null
+++ b/lib/libc/stdio/fseek.c
@@ -0,0 +1,245 @@
+/*-
+ * 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.
+ */
+
+#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/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)
+
+/*
+ * Seek the given file to the given offset.
+ * `Whence' must be one of the three SEEK_* macros.
+ */
+int
+fseek(fp, offset, whence)
+	register FILE *fp;
+	long 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();
+
+	/*
+	 * Have to be able to seek.
+	 */
+	if ((seekfn = fp->_seek) == NULL) {
+		errno = ESPIPE;			/* historic practice */
+		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 == -1L)
+				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;
+		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;
+		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;
+	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;
+	}
+	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) {
+		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;
+	return (0);
+}