stdio.subproj/fgetln.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 <stdlib.h>
  61 #include <string.h>
  62 #include "local.h"
  63
  64 /*
  65  * Expand the line buffer.  Return -1 on error.
  66 #ifdef notdef
  67  * The `new size' does not account for a terminating '\0',
  68  * so we add 1 here.
  69 #endif
  70  */
  71 int
  72 __slbexpand(fp, newsize)
  73         FILE *fp;
  74         size_t newsize;
  75 {
  76         void *p;
  77
  78 #ifdef notdef
  79         ++newsize;
  80 #endif
  81         if (fp->_lb._size >= newsize)
  82                 return (0);
  83         if ((p = realloc(fp->_lb._base, newsize)) == NULL)
  84                 return (-1);
  85         fp->_lb._base = p;
  86         fp->_lb._size = newsize;
  87         return (0);
  88 }
  89
  90 /*
  91  * Get an input line.  The returned pointer often (but not always)
  92  * points into a stdio buffer.  Fgetln does not alter the text of
  93  * the returned line (which is thus not a C string because it will
  94  * not necessarily end with '\0'), but does allow callers to modify
  95  * it if they wish.  Thus, we set __SMOD in case the caller does.
  96  */
  97 char *
  98 fgetln(fp, lenp)
  99         register FILE *fp;
 100         size_t *lenp;
 101 {
 102         register unsigned char *p;
 103         register size_t len;
 104         size_t off;
 105
 106         /* make sure there is input */
 107         if (fp->_r <= 0 && __srefill(fp)) {
 108                 *lenp = 0;
 109                 return (NULL);
 110         }
 111
 112         /* look for a newline in the input */
 113         if ((p = memchr((void *)fp->_p, '\n', fp->_r)) != NULL) {
 114                 register char *ret;
 115
 116                 /*
 117                  * Found one.  Flag buffer as modified to keep fseek from
 118                  * `optimising' a backward seek, in case the user stomps on
 119                  * the text.
 120                  */
 121                 p++;            /* advance over it */
 122                 ret = (char *)fp->_p;
 123                 *lenp = len = p - fp->_p;
 124                 fp->_flags |= __SMOD;
 125                 fp->_r -= len;
 126                 fp->_p = p;
 127                 return (ret);
 128         }
 129
 130         /*
 131          * We have to copy the current buffered data to the line buffer.
 132          * As a bonus, though, we can leave off the __SMOD.
 133          *
 134          * OPTIMISTIC is length that we (optimistically) expect will
 135          * accomodate the `rest' of the string, on each trip through the
 136          * loop below.
 137          */
 138 #define OPTIMISTIC 80
 139
 140         for (len = fp->_r, off = 0;; len += fp->_r) {
 141                 register size_t diff;
 142
 143                 /*
 144                  * Make sure there is room for more bytes.  Copy data from
 145                  * file buffer to line buffer, refill file and look for
 146                  * newline.  The loop stops only when we find a newline.
 147                  */
 148                 if (__slbexpand(fp, len + OPTIMISTIC))
 149                         goto error;
 150                 (void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
 151                     len - off);
 152                 off = len;
 153                 if (__srefill(fp))
 154                         break;  /* EOF or error: return partial line */
 155                 if ((p = memchr((void *)fp->_p, '\n', fp->_r)) == NULL)
 156                         continue;
 157
 158                 /* got it: finish up the line (like code above) */
 159                 p++;
 160                 diff = p - fp->_p;
 161                 len += diff;
 162                 if (__slbexpand(fp, len))
 163                         goto error;
 164                 (void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
 165                     diff);
 166                 fp->_r -= diff;
 167                 fp->_p = p;
 168                 break;
 169         }
 170         *lenp = len;
 171 #ifdef notdef
 172         fp->_lb._base[len] = 0;
 173 #endif
 174         return ((char *)fp->_lb._base);
 175
 176 error:
 177         *lenp = 0;              /* ??? */
 178         return (NULL);          /* ??? */
 179 }