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      1 /*	$OpenBSD: fgetln.c,v 1.13 2015/01/05 21:58:52 millert Exp $ */
      2 /*-
      3  * Copyright (c) 1990, 1993
      4  *	The Regents of the University of California.  All rights reserved.
      5  *
      6  * This code is derived from software contributed to Berkeley by
      7  * Chris Torek.
      8  *
      9  * Redistribution and use in source and binary forms, with or without
     10  * modification, are permitted provided that the following conditions
     11  * are met:
     12  * 1. Redistributions of source code must retain the above copyright
     13  *    notice, this list of conditions and the following disclaimer.
     14  * 2. Redistributions in binary form must reproduce the above copyright
     15  *    notice, this list of conditions and the following disclaimer in the
     16  *    documentation and/or other materials provided with the distribution.
     17  * 3. Neither the name of the University nor the names of its contributors
     18  *    may be used to endorse or promote products derived from this software
     19  *    without specific prior written permission.
     20  *
     21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     31  * SUCH DAMAGE.
     32  */
     33 
     34 #include <stdio.h>
     35 #include <stdlib.h>
     36 #include <string.h>
     37 #include "local.h"
     38 
     39 /*
     40  * Expand the line buffer.  Return -1 on error.
     41  */
     42 static int
     43 __slbexpand(FILE *fp, size_t newsize)
     44 {
     45 	void *p;
     46 
     47 	if (fp->_lb._size >= newsize)
     48 		return (0);
     49 	if ((p = realloc(fp->_lb._base, newsize)) == NULL)
     50 		return (-1);
     51 	fp->_lb._base = p;
     52 	fp->_lb._size = newsize;
     53 	return (0);
     54 }
     55 
     56 /*
     57  * Get an input line.  The returned pointer often (but not always)
     58  * points into a stdio buffer.  Fgetline does not alter the text of
     59  * the returned line (which is thus not a C string because it will
     60  * not necessarily end with '\0'), but does allow callers to modify
     61  * it if they wish.  Thus, we set __SMOD in case the caller does.
     62  */
     63 char *
     64 fgetln(FILE *fp, size_t *lenp)
     65 {
     66 	unsigned char *p;
     67 	char *ret;
     68 	size_t len;
     69 	size_t off;
     70 
     71 	FLOCKFILE(fp);
     72 	_SET_ORIENTATION(fp, -1);
     73 
     74 	/* make sure there is input */
     75 	if (fp->_r <= 0 && __srefill(fp))
     76 		goto error;
     77 
     78 	/* look for a newline in the input */
     79 	if ((p = memchr((void *)fp->_p, '\n', fp->_r)) != NULL) {
     80 		/*
     81 		 * Found one.  Flag buffer as modified to keep fseek from
     82 		 * `optimising' a backward seek, in case the user stomps on
     83 		 * the text.
     84 		 */
     85 		p++;		/* advance over it */
     86 		ret = (char *)fp->_p;
     87 		*lenp = len = p - fp->_p;
     88 		fp->_flags |= __SMOD;
     89 		fp->_r -= len;
     90 		fp->_p = p;
     91 		FUNLOCKFILE(fp);
     92 		return (ret);
     93 	}
     94 
     95 	/*
     96 	 * We have to copy the current buffered data to the line buffer.
     97 	 * As a bonus, though, we can leave off the __SMOD.
     98 	 *
     99 	 * OPTIMISTIC is length that we (optimistically) expect will
    100 	 * accommodate the `rest' of the string, on each trip through the
    101 	 * loop below.
    102 	 */
    103 #define OPTIMISTIC 80
    104 
    105 	for (len = fp->_r, off = 0;; len += fp->_r) {
    106 		size_t diff;
    107 
    108 		/*
    109 		 * Make sure there is room for more bytes.  Copy data from
    110 		 * file buffer to line buffer, refill file and look for
    111 		 * newline.  The loop stops only when we find a newline.
    112 		 */
    113 		if (__slbexpand(fp, len + OPTIMISTIC))
    114 			goto error;
    115 		(void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
    116 		    len - off);
    117 		off = len;
    118 		if (__srefill(fp))
    119 			break;	/* EOF or error: return partial line */
    120 		if ((p = memchr((void *)fp->_p, '\n', fp->_r)) == NULL)
    121 			continue;
    122 
    123 		/* got it: finish up the line (like code above) */
    124 		p++;
    125 		diff = p - fp->_p;
    126 		len += diff;
    127 		if (__slbexpand(fp, len))
    128 			goto error;
    129 		(void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
    130 		    diff);
    131 		fp->_r -= diff;
    132 		fp->_p = p;
    133 		break;
    134 	}
    135 	*lenp = len;
    136 	ret = (char *)fp->_lb._base;
    137 	FUNLOCKFILE(fp);
    138 	return (ret);
    139 
    140 error:
    141 	FUNLOCKFILE(fp);
    142 	*lenp = 0;
    143 	return (NULL);
    144 }
    145