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fgetln.c revision 1.1 
      1 /*-
      2  * Copyright (c) 1990, 1993
      3  *	The Regents of the University of California.  All rights reserved.
      4  *
      5  * This code is derived from software contributed to Berkeley by
      6  * Chris Torek.
      7  *
      8  * Redistribution and use in source and binary forms, with or without
      9  * modification, are permitted provided that the following conditions
     10  * are met:
     11  * 1. Redistributions of source code must retain the above copyright
     12  *    notice, this list of conditions and the following disclaimer.
     13  * 2. Redistributions in binary form must reproduce the above copyright
     14  *    notice, this list of conditions and the following disclaimer in the
     15  *    documentation and/or other materials provided with the distribution.
     16  * 3. All advertising materials mentioning features or use of this software
     17  *    must display the following acknowledgement:
     18  *	This product includes software developed by the University of
     19  *	California, Berkeley and its contributors.
     20  * 4. Neither the name of the University nor the names of its contributors
     21  *    may be used to endorse or promote products derived from this software
     22  *    without specific prior written permission.
     23  *
     24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     34  * SUCH DAMAGE.
     35  */
     36 
     37 #if defined(LIBC_SCCS) && !defined(lint)
     38 /* from: static char sccsid[] = "@(#)fgetline.c	8.1 (Berkeley) 6/4/93"; */
     39 static char *rcsid = "$Id: fgetln.c,v 1.1 1994/01/04 05:13:18 cgd Exp $";
     40 #endif /* LIBC_SCCS and not lint */
     41 
     42 #include <stdio.h>
     43 #include <stdlib.h>
     44 #include <string.h>
     45 #include "local.h"
     46 
     47 /*
     48  * Expand the line buffer.  Return -1 on error.
     49 #ifdef notdef
     50  * The `new size' does not account for a terminating '\0',
     51  * so we add 1 here.
     52 #endif
     53  */
     54 int
     55 __slbexpand(fp, newsize)
     56 	FILE *fp;
     57 	size_t newsize;
     58 {
     59 	void *p;
     60 
     61 #ifdef notdef
     62 	++newsize;
     63 #endif
     64 	if (fp->_lb._size >= newsize)
     65 		return (0);
     66 	if ((p = realloc(fp->_lb._base, newsize)) == NULL)
     67 		return (-1);
     68 	fp->_lb._base = p;
     69 	fp->_lb._size = newsize;
     70 	return (0);
     71 }
     72 
     73 /*
     74  * Get an input line.  The returned pointer often (but not always)
     75  * points into a stdio buffer.  Fgetline does not alter the text of
     76  * the returned line (which is thus not a C string because it will
     77  * not necessarily end with '\0'), but does allow callers to modify
     78  * it if they wish.  Thus, we set __SMOD in case the caller does.
     79  */
     80 char *
     81 fgetln(fp, lenp)
     82 	register FILE *fp;
     83 	size_t *lenp;
     84 {
     85 	register unsigned char *p;
     86 	register size_t len;
     87 	size_t off;
     88 
     89 	/* make sure there is input */
     90 	if (fp->_r <= 0 && __srefill(fp)) {
     91 		*lenp = 0;
     92 		return (NULL);
     93 	}
     94 
     95 	/* look for a newline in the input */
     96 	if ((p = memchr((void *)fp->_p, '\n', fp->_r)) != NULL) {
     97 		register char *ret;
     98 
     99 		/*
    100 		 * Found one.  Flag buffer as modified to keep fseek from
    101 		 * `optimising' a backward seek, in case the user stomps on
    102 		 * the text.
    103 		 */
    104 		p++;		/* advance over it */
    105 		ret = (char *)fp->_p;
    106 		*lenp = len = p - fp->_p;
    107 		fp->_flags |= __SMOD;
    108 		fp->_r -= len;
    109 		fp->_p = p;
    110 		return (ret);
    111 	}
    112 
    113 	/*
    114 	 * We have to copy the current buffered data to the line buffer.
    115 	 * As a bonus, though, we can leave off the __SMOD.
    116 	 *
    117 	 * OPTIMISTIC is length that we (optimistically) expect will
    118 	 * accomodate the `rest' of the string, on each trip through the
    119 	 * loop below.
    120 	 */
    121 #define OPTIMISTIC 80
    122 
    123 	for (len = fp->_r, off = 0;; len += fp->_r) {
    124 		register size_t diff;
    125 
    126 		/*
    127 		 * Make sure there is room for more bytes.  Copy data from
    128 		 * file buffer to line buffer, refill file and look for
    129 		 * newline.  The loop stops only when we find a newline.
    130 		 */
    131 		if (__slbexpand(fp, len + OPTIMISTIC))
    132 			goto error;
    133 		(void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
    134 		    len - off);
    135 		off = len;
    136 		if (__srefill(fp))
    137 			break;	/* EOF or error: return partial line */
    138 		if ((p = memchr((void *)fp->_p, '\n', fp->_r)) == NULL)
    139 			continue;
    140 
    141 		/* got it: finish up the line (like code above) */
    142 		p++;
    143 		diff = p - fp->_p;
    144 		len += diff;
    145 		if (__slbexpand(fp, len))
    146 			goto error;
    147 		(void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
    148 		    diff);
    149 		fp->_r -= diff;
    150 		fp->_p = p;
    151 		break;
    152 	}
    153 	*lenp = len;
    154 #ifdef notdef
    155 	fp->_lb._base[len] = 0;
    156 #endif
    157 	return ((char *)fp->_lb._base);
    158 
    159 error:
    160 	*lenp = 0;		/* ??? */
    161 	return (NULL);		/* ??? */
    162 }
    163