lib/libc/stdio/fgets.c

   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  * 4. Neither the name of the University nor the names of its contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  *
  32  * @(#)fgets.c  8.2 (Berkeley) 12/22/93
  33  * $FreeBSD: src/lib/libc/stdio/fgets.c,v 1.14 2007/01/09 00:28:06 imp Exp $
  34  * $DragonFly: src/lib/libc/stdio/fgets.c,v 1.7 2005/11/20 11:07:30 swildner Exp $
  35  */
  36
  37 #include "namespace.h"
  38 #include <stdio.h>
  39 #include <string.h>
  40 #include "un-namespace.h"
  41 #include "local.h"
  42 #include "libc_private.h"
  43 #include "priv_stdio.h"
  44
  45 /*
  46  * Read at most n-1 characters from the given file.
  47  * Stop when a newline has been read, or the count runs out.
  48  * Return first argument, or NULL if no characters were read.
  49  */
  50 char *
  51 fgets(char *buf, int n, FILE *fp)
  52 {
  53         size_t len;
  54         char *s;
  55         unsigned char *p, *t;
  56
  57         if (n <= 0)             /* sanity check */
  58                 return (NULL);
  59
  60         FLOCKFILE(fp);
  61         ORIENT(fp, -1);
  62         s = buf;
  63         n--;                    /* leave space for NUL */
  64         while (n != 0) {
  65                 /*
  66                  * If the buffer is empty, refill it.
  67                  */
  68                 if ((len = fp->pub._r) <= 0) {
  69                         if (__srefill(fp)) {
  70                                 /* EOF/error: stop with partial or no line */
  71                                 if (s == buf) {
  72                                         FUNLOCKFILE(fp);
  73                                         return (NULL);
  74                                 }
  75                                 break;
  76                         }
  77                         len = fp->pub._r;
  78                 }
  79                 p = fp->pub._p;
  80
  81                 /*
  82                  * Scan through at most n bytes of the current buffer,
  83                  * looking for '\n'.  If found, copy up to and including
  84                  * newline, and stop.  Otherwise, copy entire chunk
  85                  * and loop.
  86                  */
  87                 if (len > n)
  88                         len = n;
  89                 t = memchr((void *)p, '\n', len);
  90                 if (t != NULL) {
  91                         len = ++t - p;
  92                         fp->pub._r -= len;
  93                         fp->pub._p = t;
  94                         memcpy((void *)s, (void *)p, len);
  95                         s[len] = 0;
  96                         FUNLOCKFILE(fp);
  97                         return (buf);
  98                 }
  99                 fp->pub._r -= len;
 100                 fp->pub._p += len;
 101                 memcpy((void *)s, (void *)p, len);
 102                 s += len;
 103                 n -= len;
 104         }
 105         *s = 0;
 106         FUNLOCKFILE(fp);
 107         return (buf);
 108 }