stdio/FreeBSD/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
  33 #if defined(LIBC_SCCS) && !defined(lint)
  34 static char sccsid[] = "@(#)fgets.c     8.2 (Berkeley) 12/22/93";
  35 #endif /* LIBC_SCCS and not lint */
  36 #include <sys/cdefs.h>
  37 __FBSDID("$FreeBSD: src/lib/libc/stdio/fgets.c,v 1.14 2007/01/09 00:28:06 imp Exp $");
  38
  39 #include "namespace.h"
  40 #include <stdio.h>
  41 #include <string.h>
  42 #include "un-namespace.h"
  43 #include "local.h"
  44 #include "libc_private.h"
  45
  46 /*
  47  * Read at most n-1 characters from the given file.
  48  * Stop when a newline has been read, or the count runs out.
  49  * Return first argument, or NULL if no characters were read.
  50  */
  51 char *
  52 fgets(buf, n, fp)
  53         char *buf;
  54         int n;
  55         FILE *fp;
  56 {
  57         size_t len;
  58         char *s;
  59         unsigned char *p, *t;
  60
  61         if (n <= 0)             /* sanity check */
  62                 return (NULL);
  63
  64         FLOCKFILE(fp);
  65         ORIENT(fp, -1);
  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->_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->_r;
  82                 }
  83                 p = fp->_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->_r -= len;
  97                         fp->_p = t;
  98                         (void)memcpy((void *)s, (void *)p, len);
  99                         s[len] = 0;
 100                         FUNLOCKFILE(fp);
 101                         return (buf);
 102                 }
 103                 fp->_r -= len;
 104                 fp->_p += len;
 105                 (void)memcpy((void *)s, (void *)p, len);
 106                 s += len;
 107                 n -= len;
 108         }
 109         *s = 0;
 110         FUNLOCKFILE(fp);
 111         return (buf);
 112 }