gonzui

    1: /*      $OpenBSD: fgets.c,v 1.14 2009/11/09 00:18:27 kurt Exp $ */
    2: /*-
    3:  * Copyright (c) 1990, 1993
    4:  *      The Regents of the University of California.  All rights reserved.
    5:  *
    6:  * This code is derived from software contributed to Berkeley by
    7:  * Chris Torek.
    8:  *
    9:  * Redistribution and use in source and binary forms, with or without
   10:  * modification, are permitted provided that the following conditions
   11:  * are met:
   12:  * 1. Redistributions of source code must retain the above copyright
   13:  *    notice, this list of conditions and the following disclaimer.
   14:  * 2. Redistributions in binary form must reproduce the above copyright
   15:  *    notice, this list of conditions and the following disclaimer in the
   16:  *    documentation and/or other materials provided with the distribution.
   17:  * 3. Neither the name of the University nor the names of its contributors
   18:  *    may be used to endorse or promote products derived from this software
   19:  *    without specific prior written permission.
   20:  *
   21:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   22:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   23:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   24:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   25:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   26:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   27:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   28:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   29:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   30:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   31:  * SUCH DAMAGE.
   32:  */
   33: 
   34: #include <errno.h>
   35: #include <stdio.h>
   36: #include <string.h>
   37: #include "local.h"
   38: 
   39: /*
   40:  * Read at most n-1 characters from the given file.
   41:  * Stop when a newline has been read, or the count runs out.
   42:  * Return first argument, or NULL if no characters were read.
   43:  * Do not return NULL if n == 1.
   44:  */
   45: char *
   46: fgets(char *buf, int n, FILE *fp)
   47: {
   48:         size_t len;
   49:         char *s;
   50:         unsigned char *p, *t;
   51: 
   52:         if (n <= 0) {          /* sanity check */
   53:                 __sseterr(fp, EINVAL);
   54:                 return (NULL);
   55:         }
   56: 
   57:         FLOCKFILE(fp);
   58:         _SET_ORIENTATION(fp, -1);
   59:         s = buf;
   60:         n--;                   /* leave space for NUL */
   61:         while (n != 0) {
   62:                 /*
   63:                  * If the buffer is empty, refill it.
   64:                  */
   65:                 if (fp->_r <= 0) {
   66:                         if (__srefill(fp)) {
   67:                                 /* EOF/error: stop with partial or no line */
   68:                                 if (s == buf) {
   69:                                         FUNLOCKFILE(fp);
   70:                                         return (NULL);
   71:                                 }
   72:                                 break;
   73:                         }
   74:                 }
   75:                 len = fp->_r;
   76:                 p = fp->_p;
   77: 
   78:                 /*
   79:                  * Scan through at most n bytes of the current buffer,
   80:                  * looking for '\n'.  If found, copy up to and including
   81:                  * newline, and stop.  Otherwise, copy entire chunk
   82:                  * and loop.
   83:                  */
   84:                 if (len > n)
   85:                         len = n;
   86:                 t = memchr((void *)p, '\n', len);
   87:                 if (t != NULL) {
   88:                         len = ++t - p;
   89:                         fp->_r -= len;
   90:                         fp->_p = t;
   91:                         (void)memcpy((void *)s, (void *)p, len);
   92:                         s[len] = '\0';
   93:                         FUNLOCKFILE(fp);
   94:                         return (buf);
   95:                 }
   96:                 fp->_r -= len;
   97:                 fp->_p += len;
   98:                 (void)memcpy((void *)s, (void *)p, len);
   99:                 s += len;
  100:                 n -= len;
  101:         }
  102:         *s = '\0';
  103:         FUNLOCKFILE(fp);
  104:         return (buf);
  105: }