stdio/fgets.c

   1 /*
   2  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
   7  *
   8  * This file contains Original Code and/or Modifications of Original Code
   9  * as defined in and that are subject to the Apple Public Source License
  10  * Version 2.0 (the 'License'). You may not use this file except in
  11  * compliance with the License. Please obtain a copy of the License at
  12  * http://www.opensource.apple.com/apsl/ and read it before using this
  13  * file.
  14  *
  15  * The Original Code and all software distributed under the License are
  16  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  17  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  18  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  20  * Please see the License for the specific language governing rights and
  21  * limitations under the License.
  22  *
  23  * @APPLE_LICENSE_HEADER_END@
  24  */
  25 /*
  26  * Copyright (c) 1990, 1993
  27  *      The Regents of the University of California.  All rights reserved.
  28  *
  29  * This code is derived from software contributed to Berkeley by
  30  * Chris Torek.
  31  *
  32  * Redistribution and use in source and binary forms, with or without
  33  * modification, are permitted provided that the following conditions
  34  * are met:
  35  * 1. Redistributions of source code must retain the above copyright
  36  *    notice, this list of conditions and the following disclaimer.
  37  * 2. Redistributions in binary form must reproduce the above copyright
  38  *    notice, this list of conditions and the following disclaimer in the
  39  *    documentation and/or other materials provided with the distribution.
  40  * 3. All advertising materials mentioning features or use of this software
  41  *    must display the following acknowledgement:
  42  *      This product includes software developed by the University of
  43  *      California, Berkeley and its contributors.
  44  * 4. Neither the name of the University nor the names of its contributors
  45  *    may be used to endorse or promote products derived from this software
  46  *    without specific prior written permission.
  47  *
  48  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  49  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  50  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  51  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  52  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  53  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  54  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  55  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  56  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  57  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  58  * SUCH DAMAGE.
  59  */
  60
  61
  62 #include <stdio.h>
  63 #include <string.h>
  64
  65 /*
  66  * Read at most n-1 characters from the given file.
  67  * Stop when a newline has been read, or the count runs out.
  68  * Return first argument, or NULL if no characters were read.
  69  */
  70 char *
  71 fgets(buf, n, fp)
  72         char *buf;
  73         register int n;
  74         register FILE *fp;
  75 {
  76         register size_t len;
  77         register char *s;
  78         register unsigned char *p, *t;
  79
  80         if (n == 0)             /* sanity check */
  81                 return (NULL);
  82
  83         s = buf;
  84         n--;                    /* leave space for NUL */
  85         while (n != 0) {
  86                 /*
  87                  * If the buffer is empty, refill it.
  88                  */
  89                 if ((len = fp->_r) <= 0) {
  90                         if (__srefill(fp)) {
  91                                 /* EOF/error: stop with partial or no line */
  92                                 if (s == buf)
  93                                         return (NULL);
  94                                 break;
  95                         }
  96                         len = fp->_r;
  97                 }
  98                 p = fp->_p;
  99
 100                 /*
 101                  * Scan through at most n bytes of the current buffer,
 102                  * looking for '\n'.  If found, copy up to and including
 103                  * newline, and stop.  Otherwise, copy entire chunk
 104                  * and loop.
 105                  */
 106                 if (len > n)
 107                         len = n;
 108                 t = memchr((void *)p, '\n', len);
 109                 if (t != NULL) {
 110                         len = ++t - p;
 111                         fp->_r -= len;
 112                         fp->_p = t;
 113                         (void)memcpy((void *)s, (void *)p, len);
 114                         s[len] = 0;
 115                         return (buf);
 116                 }
 117                 fp->_r -= len;
 118                 fp->_p += len;
 119                 (void)memcpy((void *)s, (void *)p, len);
 120                 s += len;
 121                 n -= len;
 122         }
 123         *s = 0;
 124         return (buf);
 125 }