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. 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  */
  35
  36 #include "namespace.h"
  37 #include <stdio.h>
  38 #include <string.h>
  39 #include "un-namespace.h"
  40 #include "local.h"
  41 #include "libc_private.h"
  42
  43 /*
  44  * Read at most n-1 characters from the given file.
  45  * Stop when a newline has been read, or the count runs out.
  46  * Return first argument, or NULL if no characters were read.
  47  */
  48 char *
  49 fgets(char *buf, int n, FILE *fp)
  50 {
  51         size_t len;
  52         char *s;
  53         unsigned char *p, *t;
  54
  55         if (n <= 0)             /* sanity check */
  56                 return (NULL);
  57
  58         FLOCKFILE(fp);
  59         ORIENT(fp, -1);
  60         s = buf;
  61         n--;                    /* leave space for NUL */
  62         while (n != 0) {
  63                 /*
  64                  * If the buffer is empty, refill it.
  65                  */
  66                 if ((len = fp->pub._r) <= 0) {
  67                         if (__srefill(fp)) {
  68                                 /* EOF/error: stop with partial or no line */
  69                                 if (s == buf) {
  70                                         FUNLOCKFILE(fp);
  71                                         return (NULL);
  72                                 }
  73                                 break;
  74                         }
  75                         len = fp->pub._r;
  76                 }
  77                 p = fp->pub._p;
  78
  79                 /*
  80                  * Scan through at most n bytes of the current buffer,
  81                  * looking for '\n'.  If found, copy up to and including
  82                  * newline, and stop.  Otherwise, copy entire chunk
  83                  * and loop.
  84                  */
  85                 if (len > n)
  86                         len = n;
  87                 t = memchr((void *)p, '\n', len);
  88                 if (t != NULL) {
  89                         len = ++t - p;
  90                         fp->pub._r -= len;
  91                         fp->pub._p = t;
  92                         memcpy((void *)s, (void *)p, len);
  93                         s[len] = 0;
  94                         FUNLOCKFILE(fp);
  95                         return (buf);
  96                 }
  97                 fp->pub._r -= len;
  98                 fp->pub._p += len;
  99                 memcpy((void *)s, (void *)p, len);
 100                 s += len;
 101                 n -= len;
 102         }
 103         *s = 0;
 104         FUNLOCKFILE(fp);
 105         return (buf);
 106 }