lib/libc/stdio/fgetln.c

   1 /*-
   2  * Copyright (c) 1990, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Chris Torek.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  *
  36  * @(#)fgetln.c 8.2 (Berkeley) 1/2/94
  37  * $FreeBSD: src/lib/libc/stdio/fgetln.c,v 1.6 1999/08/28 00:00:59 peter Exp $
  38  * $DragonFly: src/lib/libc/stdio/fgetln.c,v 1.7 2005/11/20 11:07:30 swildner Exp $
  39  */
  40
  41 #include <stdio.h>
  42 #include <stdlib.h>
  43 #include <string.h>
  44 #include "local.h"
  45 #include "priv_stdio.h"
  46
  47 /*
  48  * Expand the line buffer.  Return -1 on error.
  49 #ifdef notdef
  50  * The `new size' does not account for a terminating '\0',
  51  * so we add 1 here.
  52 #endif
  53  */
  54 int
  55 __slbexpand(FILE *fp, size_t newsize)
  56 {
  57         void *p;
  58
  59 #ifdef notdef
  60         ++newsize;
  61 #endif
  62         if (fp->_lb._size >= newsize)
  63                 return (0);
  64         if ((p = realloc(fp->_lb._base, newsize)) == NULL)
  65                 return (-1);
  66         fp->_lb._base = p;
  67         fp->_lb._size = newsize;
  68         return (0);
  69 }
  70
  71 /*
  72  * Get an input line.  The returned pointer often (but not always)
  73  * points into a stdio buffer.  Fgetln does not alter the text of
  74  * the returned line (which is thus not a C string because it will
  75  * not necessarily end with '\0'), but does allow callers to modify
  76  * it if they wish.  Thus, we set __SMOD in case the caller does.
  77  */
  78 char *
  79 fgetln(FILE *fp, size_t *lenp)
  80 {
  81         unsigned char *p;
  82         size_t len;
  83         size_t off;
  84
  85         /* make sure there is input */
  86         if (fp->pub._r <= 0 && __srefill(fp)) {
  87                 *lenp = 0;
  88                 return (NULL);
  89         }
  90
  91         /* look for a newline in the input */
  92         if ((p = memchr((void *)fp->pub._p, '\n', (size_t)fp->pub._r)) != NULL) {
  93                 char *ret;
  94
  95                 /*
  96                  * Found one.  Flag buffer as modified to keep fseek from
  97                  * `optimising' a backward seek, in case the user stomps on
  98                  * the text.
  99                  */
 100                 p++;            /* advance over it */
 101                 ret = (char *)fp->pub._p;
 102                 *lenp = len = p - fp->pub._p;
 103                 fp->pub._flags |= __SMOD;
 104                 fp->pub._r -= len;
 105                 fp->pub._p = p;
 106                 return (ret);
 107         }
 108
 109         /*
 110          * We have to copy the current buffered data to the line buffer.
 111          * As a bonus, though, we can leave off the __SMOD.
 112          *
 113          * OPTIMISTIC is length that we (optimistically) expect will
 114          * accomodate the `rest' of the string, on each trip through the
 115          * loop below.
 116          */
 117 #define OPTIMISTIC 80
 118
 119         for (len = fp->pub._r, off = 0;; len += fp->pub._r) {
 120                 size_t diff;
 121
 122                 /*
 123                  * Make sure there is room for more bytes.  Copy data from
 124                  * file buffer to line buffer, refill file and look for
 125                  * newline.  The loop stops only when we find a newline.
 126                  */
 127                 if (__slbexpand(fp, len + OPTIMISTIC))
 128                         goto error;
 129                 memcpy((void *)(fp->_lb._base + off), (void *)fp->pub._p,
 130                     len - off);
 131                 off = len;
 132                 if (__srefill(fp))
 133                         break;  /* EOF or error: return partial line */
 134                 if ((p = memchr((void *)fp->pub._p, '\n', (size_t)fp->pub._r))
 135                     == NULL)
 136                         continue;
 137
 138                 /* got it: finish up the line (like code above) */
 139                 p++;
 140                 diff = p - fp->pub._p;
 141                 len += diff;
 142                 if (__slbexpand(fp, len))
 143                         goto error;
 144                 memcpy((void *)(fp->_lb._base + off), (void *)fp->pub._p,
 145                     diff);
 146                 fp->pub._r -= diff;
 147                 fp->pub._p = p;
 148                 break;
 149         }
 150         *lenp = len;
 151 #ifdef notdef
 152         fp->_lb._base[len] = 0;
 153 #endif
 154         return ((char *)fp->_lb._base);
 155
 156 error:
 157         *lenp = 0;              /* ??? */
 158         return (NULL);          /* ??? */
 159 }