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  * 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  * @(#)fgets.c  8.2 (Berkeley) 12/22/93
  37  * $FreeBSD: src/lib/libc/stdio/fgets.c,v 1.9 1999/08/28 00:01:00 peter Exp $
  38  * $DragonFly: src/lib/libc/stdio/fgets.c,v 1.7 2005/11/20 11:07:30 swildner Exp $
  39  */
  40
  41 #include "namespace.h"
  42 #include <stdio.h>
  43 #include <string.h>
  44 #include "un-namespace.h"
  45 #include "local.h"
  46
  47 #include "libc_private.h"
  48 #include "priv_stdio.h"
  49
  50 /*
  51  * Read at most n-1 characters from the given file.
  52  * Stop when a newline has been read, or the count runs out.
  53  * Return first argument, or NULL if no characters were read.
  54  */
  55 char *
  56 fgets(char *buf, int n, FILE *fp)
  57 {
  58         size_t len;
  59         char *s;
  60         unsigned char *p, *t;
  61
  62         if (n <= 0)             /* sanity check */
  63                 return (NULL);
  64
  65         FLOCKFILE(fp);
  66         s = buf;
  67         n--;                    /* leave space for NUL */
  68         while (n != 0) {
  69                 /*
  70                  * If the buffer is empty, refill it.
  71                  */
  72                 if ((len = fp->pub._r) <= 0) {
  73                         if (__srefill(fp)) {
  74                                 /* EOF/error: stop with partial or no line */
  75                                 if (s == buf) {
  76                                         FUNLOCKFILE(fp);
  77                                         return (NULL);
  78                                 }
  79                                 break;
  80                         }
  81                         len = fp->pub._r;
  82                 }
  83                 p = fp->pub._p;
  84
  85                 /*
  86                  * Scan through at most n bytes of the current buffer,
  87                  * looking for '\n'.  If found, copy up to and including
  88                  * newline, and stop.  Otherwise, copy entire chunk
  89                  * and loop.
  90                  */
  91                 if (len > n)
  92                         len = n;
  93                 t = memchr((void *)p, '\n', len);
  94                 if (t != NULL) {
  95                         len = ++t - p;
  96                         fp->pub._r -= len;
  97                         fp->pub._p = t;
  98                         memcpy((void *)s, (void *)p, len);
  99                         s[len] = 0;
 100                         FUNLOCKFILE(fp);
 101                         return (buf);
 102                 }
 103                 fp->pub._r -= len;
 104                 fp->pub._p += len;
 105                 memcpy((void *)s, (void *)p, len);
 106                 s += len;
 107                 n -= len;
 108         }
 109         *s = 0;
 110         FUNLOCKFILE(fp);
 111         return (buf);
 112 }