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fgetln.c revision 1.1.1.1 
      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 static char sccsid[] = "@(#)fgetln.c	8.2 (Berkeley) 1/2/94";
     39 #endif /* LIBC_SCCS and not lint */
     40 
     41 #include <stdio.h>
     42 #include <stdlib.h>
     43 #include <string.h>
     44 #include "local.h"
     45 
     46 /*
     47  * Expand the line buffer.  Return -1 on error.
     48 #ifdef notdef
     49  * The `new size' does not account for a terminating '\0',
     50  * so we add 1 here.
     51 #endif
     52  */
     53 __slbexpand(fp, newsize)
     54 	FILE *fp;
     55 	size_t newsize;
     56 {
     57 	void *p;
     58 
     59 #ifdef notdef
     60 	++newsize;
     61 #endif
     62 	if (fp->_lb._size >= newsize)
     63 		return (0);
     64 	if ((p = realloc(fp->_lb._base, newsize)) == NULL)
     65 		return (-1);
     66 	fp->_lb._base = p;
     67 	fp->_lb._size = newsize;
     68 	return (0);
     69 }
     70 
     71 /*
     72  * Get an input line.  The returned pointer often (but not always)
     73  * points into a stdio buffer.  Fgetln does not alter the text of
     74  * the returned line (which is thus not a C string because it will
     75  * not necessarily end with '\0'), but does allow callers to modify
     76  * it if they wish.  Thus, we set __SMOD in case the caller does.
     77  */
     78 char *
     79 fgetln(fp, lenp)
     80 	register FILE *fp;
     81 	size_t *lenp;
     82 {
     83 	register unsigned char *p;
     84 	register size_t len;
     85 	size_t off;
     86 
     87 	/* make sure there is input */
     88 	if (fp->_r <= 0 && __srefill(fp)) {
     89 		*lenp = 0;
     90 		return (NULL);
     91 	}
     92 
     93 	/* look for a newline in the input */
     94 	if ((p = memchr((void *)fp->_p, '\n', fp->_r)) != NULL) {
     95 		register char *ret;
     96 
     97 		/*
     98 		 * Found one.  Flag buffer as modified to keep fseek from
     99 		 * `optimising' a backward seek, in case the user stomps on
    100 		 * the text.
    101 		 */
    102 		p++;		/* advance over it */
    103 		ret = (char *)fp->_p;
    104 		*lenp = len = p - fp->_p;
    105 		fp->_flags |= __SMOD;
    106 		fp->_r -= len;
    107 		fp->_p = p;
    108 		return (ret);
    109 	}
    110 
    111 	/*
    112 	 * We have to copy the current buffered data to the line buffer.
    113 	 * As a bonus, though, we can leave off the __SMOD.
    114 	 *
    115 	 * OPTIMISTIC is length that we (optimistically) expect will
    116 	 * accomodate the `rest' of the string, on each trip through the
    117 	 * loop below.
    118 	 */
    119 #define OPTIMISTIC 80
    120 
    121 	for (len = fp->_r, off = 0;; len += fp->_r) {
    122 		register size_t diff;
    123 
    124 		/*
    125 		 * Make sure there is room for more bytes.  Copy data from
    126 		 * file buffer to line buffer, refill file and look for
    127 		 * newline.  The loop stops only when we find a newline.
    128 		 */
    129 		if (__slbexpand(fp, len + OPTIMISTIC))
    130 			goto error;
    131 		(void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
    132 		    len - off);
    133 		off = len;
    134 		if (__srefill(fp))
    135 			break;	/* EOF or error: return partial line */
    136 		if ((p = memchr((void *)fp->_p, '\n', fp->_r)) == NULL)
    137 			continue;
    138 
    139 		/* got it: finish up the line (like code above) */
    140 		p++;
    141 		diff = p - fp->_p;
    142 		len += diff;
    143 		if (__slbexpand(fp, len))
    144 			goto error;
    145 		(void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
    146 		    diff);
    147 		fp->_r -= diff;
    148 		fp->_p = p;
    149 		break;
    150 	}
    151 	*lenp = len;
    152 #ifdef notdef
    153 	fp->_lb._base[len] = 0;
    154 #endif
    155 	return ((char *)fp->_lb._base);
    156 
    157 error:
    158 	*lenp = 0;		/* ??? */
    159 	return (NULL);		/* ??? */
    160 }
    161