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fgetln.c revision 1.2 
      1 /*	$NetBSD: fgetln.c,v 1.2 1995/02/02 02:09:10 jtc 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 #if defined(LIBC_SCCS) && !defined(lint)
     40 /* from: static char sccsid[] = "@(#)fgetline.c	8.1 (Berkeley) 6/4/93"; */
     41 static char *rcsid = "$Id: fgetln.c,v 1.2 1995/02/02 02:09:10 jtc Exp $";
     42 #endif /* LIBC_SCCS and not lint */
     43 
     44 #include <stdio.h>
     45 #include <stdlib.h>
     46 #include <string.h>
     47 #include "local.h"
     48 
     49 /*
     50  * Expand the line buffer.  Return -1 on error.
     51 #ifdef notdef
     52  * The `new size' does not account for a terminating '\0',
     53  * so we add 1 here.
     54 #endif
     55  */
     56 int
     57 __slbexpand(fp, newsize)
     58 	FILE *fp;
     59 	size_t newsize;
     60 {
     61 	void *p;
     62 
     63 #ifdef notdef
     64 	++newsize;
     65 #endif
     66 	if (fp->_lb._size >= newsize)
     67 		return (0);
     68 	if ((p = realloc(fp->_lb._base, newsize)) == NULL)
     69 		return (-1);
     70 	fp->_lb._base = p;
     71 	fp->_lb._size = newsize;
     72 	return (0);
     73 }
     74 
     75 /*
     76  * Get an input line.  The returned pointer often (but not always)
     77  * points into a stdio buffer.  Fgetline does not alter the text of
     78  * the returned line (which is thus not a C string because it will
     79  * not necessarily end with '\0'), but does allow callers to modify
     80  * it if they wish.  Thus, we set __SMOD in case the caller does.
     81  */
     82 char *
     83 fgetln(fp, lenp)
     84 	register FILE *fp;
     85 	size_t *lenp;
     86 {
     87 	register unsigned char *p;
     88 	register size_t len;
     89 	size_t off;
     90 
     91 	/* make sure there is input */
     92 	if (fp->_r <= 0 && __srefill(fp)) {
     93 		*lenp = 0;
     94 		return (NULL);
     95 	}
     96 
     97 	/* look for a newline in the input */
     98 	if ((p = memchr((void *)fp->_p, '\n', fp->_r)) != NULL) {
     99 		register char *ret;
    100 
    101 		/*
    102 		 * Found one.  Flag buffer as modified to keep fseek from
    103 		 * `optimising' a backward seek, in case the user stomps on
    104 		 * the text.
    105 		 */
    106 		p++;		/* advance over it */
    107 		ret = (char *)fp->_p;
    108 		*lenp = len = p - fp->_p;
    109 		fp->_flags |= __SMOD;
    110 		fp->_r -= len;
    111 		fp->_p = p;
    112 		return (ret);
    113 	}
    114 
    115 	/*
    116 	 * We have to copy the current buffered data to the line buffer.
    117 	 * As a bonus, though, we can leave off the __SMOD.
    118 	 *
    119 	 * OPTIMISTIC is length that we (optimistically) expect will
    120 	 * accomodate the `rest' of the string, on each trip through the
    121 	 * loop below.
    122 	 */
    123 #define OPTIMISTIC 80
    124 
    125 	for (len = fp->_r, off = 0;; len += fp->_r) {
    126 		register size_t diff;
    127 
    128 		/*
    129 		 * Make sure there is room for more bytes.  Copy data from
    130 		 * file buffer to line buffer, refill file and look for
    131 		 * newline.  The loop stops only when we find a newline.
    132 		 */
    133 		if (__slbexpand(fp, len + OPTIMISTIC))
    134 			goto error;
    135 		(void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
    136 		    len - off);
    137 		off = len;
    138 		if (__srefill(fp))
    139 			break;	/* EOF or error: return partial line */
    140 		if ((p = memchr((void *)fp->_p, '\n', fp->_r)) == NULL)
    141 			continue;
    142 
    143 		/* got it: finish up the line (like code above) */
    144 		p++;
    145 		diff = p - fp->_p;
    146 		len += diff;
    147 		if (__slbexpand(fp, len))
    148 			goto error;
    149 		(void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
    150 		    diff);
    151 		fp->_r -= diff;
    152 		fp->_p = p;
    153 		break;
    154 	}
    155 	*lenp = len;
    156 #ifdef notdef
    157 	fp->_lb._base[len] = 0;
    158 #endif
    159 	return ((char *)fp->_lb._base);
    160 
    161 error:
    162 	*lenp = 0;		/* ??? */
    163 	return (NULL);		/* ??? */
    164 }
    165