stdio/fgetln.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 <stdlib.h>
  64 #include <string.h>
  65 #include "local.h"
  66
  67 /*
  68  * Expand the line buffer.  Return -1 on error.
  69 #ifdef notdef
  70  * The `new size' does not account for a terminating '\0',
  71  * so we add 1 here.
  72 #endif
  73  */
  74 int
  75 __slbexpand(fp, newsize)
  76         FILE *fp;
  77         size_t newsize;
  78 {
  79         void *p;
  80
  81 #ifdef notdef
  82         ++newsize;
  83 #endif
  84         if (fp->_lb._size >= newsize)
  85                 return (0);
  86         if ((p = realloc(fp->_lb._base, newsize)) == NULL)
  87                 return (-1);
  88         fp->_lb._base = p;
  89         fp->_lb._size = newsize;
  90         return (0);
  91 }
  92
  93 /*
  94  * Get an input line.  The returned pointer often (but not always)
  95  * points into a stdio buffer.  Fgetln does not alter the text of
  96  * the returned line (which is thus not a C string because it will
  97  * not necessarily end with '\0'), but does allow callers to modify
  98  * it if they wish.  Thus, we set __SMOD in case the caller does.
  99  */
 100 char *
 101 fgetln(fp, lenp)
 102         register FILE *fp;
 103         size_t *lenp;
 104 {
 105         register unsigned char *p;
 106         register size_t len;
 107         size_t off;
 108
 109         /* make sure there is input */
 110         if (fp->_r <= 0 && __srefill(fp)) {
 111                 *lenp = 0;
 112                 return (NULL);
 113         }
 114
 115         /* look for a newline in the input */
 116         if ((p = memchr((void *)fp->_p, '\n', fp->_r)) != NULL) {
 117                 register char *ret;
 118
 119                 /*
 120                  * Found one.  Flag buffer as modified to keep fseek from
 121                  * `optimising' a backward seek, in case the user stomps on
 122                  * the text.
 123                  */
 124                 p++;            /* advance over it */
 125                 ret = (char *)fp->_p;
 126                 *lenp = len = p - fp->_p;
 127                 fp->_flags |= __SMOD;
 128                 fp->_r -= len;
 129                 fp->_p = p;
 130                 return (ret);
 131         }
 132
 133         /*
 134          * We have to copy the current buffered data to the line buffer.
 135          * As a bonus, though, we can leave off the __SMOD.
 136          *
 137          * OPTIMISTIC is length that we (optimistically) expect will
 138          * accomodate the `rest' of the string, on each trip through the
 139          * loop below.
 140          */
 141 #define OPTIMISTIC 80
 142
 143         for (len = fp->_r, off = 0;; len += fp->_r) {
 144                 register size_t diff;
 145
 146                 /*
 147                  * Make sure there is room for more bytes.  Copy data from
 148                  * file buffer to line buffer, refill file and look for
 149                  * newline.  The loop stops only when we find a newline.
 150                  */
 151                 if (__slbexpand(fp, len + OPTIMISTIC))
 152                         goto error;
 153                 (void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
 154                     len - off);
 155                 off = len;
 156                 if (__srefill(fp))
 157                         break;  /* EOF or error: return partial line */
 158                 if ((p = memchr((void *)fp->_p, '\n', fp->_r)) == NULL)
 159                         continue;
 160
 161                 /* got it: finish up the line (like code above) */
 162                 p++;
 163                 diff = p - fp->_p;
 164                 len += diff;
 165                 if (__slbexpand(fp, len))
 166                         goto error;
 167                 (void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
 168                     diff);
 169                 fp->_r -= diff;
 170                 fp->_p = p;
 171                 break;
 172         }
 173         *lenp = len;
 174 #ifdef notdef
 175         fp->_lb._base[len] = 0;
 176 #endif
 177         return ((char *)fp->_lb._base);
 178
 179 error:
 180         *lenp = 0;              /* ??? */
 181         return (NULL);          /* ??? */
 182 }