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fgetln.c revision 1.3 
      1 /*	$NetBSD: fgetln.c,v 1.3 1997/07/13 20:14:54 christos Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1990, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * This code is derived from software contributed to Berkeley by
      8  * Chris Torek.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *	This product includes software developed by the University of
     21  *	California, Berkeley and its contributors.
     22  * 4. Neither the name of the University nor the names of its contributors
     23  *    may be used to endorse or promote products derived from this software
     24  *    without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     29  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     36  * SUCH DAMAGE.
     37  */
     38 
     39 #include <sys/cdefs.h>
     40 #if defined(LIBC_SCCS) && !defined(lint)
     41 #if 0
     42 static char sccsid[] = "@(#)fgetline.c	8.1 (Berkeley) 6/4/93";
     43 #else
     44 __RCSID("$NetBSD: fgetln.c,v 1.3 1997/07/13 20:14:54 christos Exp $");
     45 #endif
     46 #endif /* LIBC_SCCS and not lint */
     47 
     48 #include <stdio.h>
     49 #include <stdlib.h>
     50 #include <string.h>
     51 #include "local.h"
     52 
     53 int __slbexpand __P((FILE *, size_t));
     54 
     55 /*
     56  * Expand the line buffer.  Return -1 on error.
     57 #ifdef notdef
     58  * The `new size' does not account for a terminating '\0',
     59  * so we add 1 here.
     60 #endif
     61  */
     62 int
     63 __slbexpand(fp, newsize)
     64 	FILE *fp;
     65 	size_t newsize;
     66 {
     67 	void *p;
     68 
     69 #ifdef notdef
     70 	++newsize;
     71 #endif
     72 	if (fp->_lb._size >= newsize)
     73 		return (0);
     74 	if ((p = realloc(fp->_lb._base, newsize)) == NULL)
     75 		return (-1);
     76 	fp->_lb._base = p;
     77 	fp->_lb._size = newsize;
     78 	return (0);
     79 }
     80 
     81 /*
     82  * Get an input line.  The returned pointer often (but not always)
     83  * points into a stdio buffer.  Fgetline does not alter the text of
     84  * the returned line (which is thus not a C string because it will
     85  * not necessarily end with '\0'), but does allow callers to modify
     86  * it if they wish.  Thus, we set __SMOD in case the caller does.
     87  */
     88 char *
     89 fgetln(fp, lenp)
     90 	register FILE *fp;
     91 	size_t *lenp;
     92 {
     93 	register unsigned char *p;
     94 	register size_t len;
     95 	size_t off;
     96 
     97 	/* make sure there is input */
     98 	if (fp->_r <= 0 && __srefill(fp)) {
     99 		*lenp = 0;
    100 		return (NULL);
    101 	}
    102 
    103 	/* look for a newline in the input */
    104 	if ((p = memchr((void *)fp->_p, '\n', fp->_r)) != NULL) {
    105 		register char *ret;
    106 
    107 		/*
    108 		 * Found one.  Flag buffer as modified to keep fseek from
    109 		 * `optimising' a backward seek, in case the user stomps on
    110 		 * the text.
    111 		 */
    112 		p++;		/* advance over it */
    113 		ret = (char *)fp->_p;
    114 		*lenp = len = p - fp->_p;
    115 		fp->_flags |= __SMOD;
    116 		fp->_r -= len;
    117 		fp->_p = p;
    118 		return (ret);
    119 	}
    120 
    121 	/*
    122 	 * We have to copy the current buffered data to the line buffer.
    123 	 * As a bonus, though, we can leave off the __SMOD.
    124 	 *
    125 	 * OPTIMISTIC is length that we (optimistically) expect will
    126 	 * accomodate the `rest' of the string, on each trip through the
    127 	 * loop below.
    128 	 */
    129 #define OPTIMISTIC 80
    130 
    131 	for (len = fp->_r, off = 0;; len += fp->_r) {
    132 		register size_t diff;
    133 
    134 		/*
    135 		 * Make sure there is room for more bytes.  Copy data from
    136 		 * file buffer to line buffer, refill file and look for
    137 		 * newline.  The loop stops only when we find a newline.
    138 		 */
    139 		if (__slbexpand(fp, len + OPTIMISTIC))
    140 			goto error;
    141 		(void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
    142 		    len - off);
    143 		off = len;
    144 		if (__srefill(fp))
    145 			break;	/* EOF or error: return partial line */
    146 		if ((p = memchr((void *)fp->_p, '\n', fp->_r)) == NULL)
    147 			continue;
    148 
    149 		/* got it: finish up the line (like code above) */
    150 		p++;
    151 		diff = p - fp->_p;
    152 		len += diff;
    153 		if (__slbexpand(fp, len))
    154 			goto error;
    155 		(void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
    156 		    diff);
    157 		fp->_r -= diff;
    158 		fp->_p = p;
    159 		break;
    160 	}
    161 	*lenp = len;
    162 #ifdef notdef
    163 	fp->_lb._base[len] = 0;
    164 #endif
    165 	return ((char *)fp->_lb._base);
    166 
    167 error:
    168 	*lenp = 0;		/* ??? */
    169 	return (NULL);		/* ??? */
    170 }
    171