stdio.subproj/fgets.c

   1 /*
   2  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1 (the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22 /*
  23  * Copyright (c) 1990, 1993
  24  *      The Regents of the University of California.  All rights reserved.
  25  *
  26  * This code is derived from software contributed to Berkeley by
  27  * Chris Torek.
  28  *
  29  * Redistribution and use in source and binary forms, with or without
  30  * modification, are permitted provided that the following conditions
  31  * are met:
  32  * 1. Redistributions of source code must retain the above copyright
  33  *    notice, this list of conditions and the following disclaimer.
  34  * 2. Redistributions in binary form must reproduce the above copyright
  35  *    notice, this list of conditions and the following disclaimer in the
  36  *    documentation and/or other materials provided with the distribution.
  37  * 3. All advertising materials mentioning features or use of this software
  38  *    must display the following acknowledgement:
  39  *      This product includes software developed by the University of
  40  *      California, Berkeley and its contributors.
  41  * 4. Neither the name of the University nor the names of its contributors
  42  *    may be used to endorse or promote products derived from this software
  43  *    without specific prior written permission.
  44  *
  45  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  46  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  47  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  48  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  49  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  50  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  51  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  52  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  53  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  54  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  55  * SUCH DAMAGE.
  56  */
  57
  58
  59 #include <stdio.h>
  60 #include <string.h>
  61
  62 /*
  63  * Read at most n-1 characters from the given file.
  64  * Stop when a newline has been read, or the count runs out.
  65  * Return first argument, or NULL if no characters were read.
  66  */
  67 char *
  68 fgets(buf, n, fp)
  69         char *buf;
  70         register size_t n;
  71         register FILE *fp;
  72 {
  73         register size_t len;
  74         register char *s;
  75         register unsigned char *p, *t;
  76
  77         if (n == 0)             /* sanity check */
  78                 return (NULL);
  79
  80         s = buf;
  81         n--;                    /* leave space for NUL */
  82         while (n != 0) {
  83                 /*
  84                  * If the buffer is empty, refill it.
  85                  */
  86                 if ((len = fp->_r) <= 0) {
  87                         if (__srefill(fp)) {
  88                                 /* EOF/error: stop with partial or no line */
  89                                 if (s == buf)
  90                                         return (NULL);
  91                                 break;
  92                         }
  93                         len = fp->_r;
  94                 }
  95                 p = fp->_p;
  96
  97                 /*
  98                  * Scan through at most n bytes of the current buffer,
  99                  * looking for '\n'.  If found, copy up to and including
 100                  * newline, and stop.  Otherwise, copy entire chunk
 101                  * and loop.
 102                  */
 103                 if (len > n)
 104                         len = n;
 105                 t = memchr((void *)p, '\n', len);
 106                 if (t != NULL) {
 107                         len = ++t - p;
 108                         fp->_r -= len;
 109                         fp->_p = t;
 110                         (void)memcpy((void *)s, (void *)p, len);
 111                         s[len] = 0;
 112                         return (buf);
 113                 }
 114                 fp->_r -= len;
 115                 fp->_p += len;
 116                 (void)memcpy((void *)s, (void *)p, len);
 117                 s += len;
 118                 n -= len;
 119         }
 120         *s = 0;
 121         return (buf);
 122 }