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  * 4. Neither the name of the University nor the names of its contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  *
  32  * @(#)fgetln.c 8.2 (Berkeley) 1/2/94
  33  * $FreeBSD: src/lib/libc/stdio/fgetln.c,v 1.11 2007/01/09 00:28:06 imp Exp $
  34  * $DragonFly: src/lib/libc/stdio/fgetln.c,v 1.7 2005/11/20 11:07:30 swildner Exp $
  35  */
  36
  37 #include "namespace.h"
  38 #include <stdio.h>
  39 #include <stdlib.h>
  40 #include <string.h>
  41 #include "un-namespace.h"
  42
  43 #include "libc_private.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         FLOCKFILE(fp);
  86         ORIENT(fp, -1);
  87         /* make sure there is input */
  88         if (fp->pub._r <= 0 && __srefill(fp)) {
  89                 *lenp = 0;
  90                 FUNLOCKFILE(fp);
  91                 return (NULL);
  92         }
  93
  94         /* look for a newline in the input */
  95         if ((p = memchr((void *)fp->pub._p, '\n', (size_t)fp->pub._r)) != NULL) {
  96                 char *ret;
  97
  98                 /*
  99                  * Found one.  Flag buffer as modified to keep fseek from
 100                  * `optimising' a backward seek, in case the user stomps on
 101                  * the text.
 102                  */
 103                 p++;            /* advance over it */
 104                 ret = (char *)fp->pub._p;
 105                 *lenp = len = p - fp->pub._p;
 106                 fp->pub._flags |= __SMOD;
 107                 fp->pub._r -= len;
 108                 fp->pub._p = p;
 109                 FUNLOCKFILE(fp);
 110                 return (ret);
 111         }
 112
 113         /*
 114          * We have to copy the current buffered data to the line buffer.
 115          * As a bonus, though, we can leave off the __SMOD.
 116          *
 117          * OPTIMISTIC is length that we (optimistically) expect will
 118          * accomodate the `rest' of the string, on each trip through the
 119          * loop below.
 120          */
 121 #define OPTIMISTIC 80
 122
 123         for (len = fp->pub._r, off = 0;; len += fp->pub._r) {
 124                 size_t diff;
 125
 126                 /*
 127                  * Make sure there is room for more bytes.  Copy data from
 128                  * file buffer to line buffer, refill file and look for
 129                  * newline.  The loop stops only when we find a newline.
 130                  */
 131                 if (__slbexpand(fp, len + OPTIMISTIC))
 132                         goto error;
 133                 memcpy((void *)(fp->_lb._base + off), (void *)fp->pub._p,
 134                     len - off);
 135                 off = len;
 136                 if (__srefill(fp))
 137                         break;  /* EOF or error: return partial line */
 138                 if ((p = memchr((void *)fp->pub._p, '\n', (size_t)fp->pub._r))
 139                     == NULL)
 140                         continue;
 141
 142                 /* got it: finish up the line (like code above) */
 143                 p++;
 144                 diff = p - fp->pub._p;
 145                 len += diff;
 146                 if (__slbexpand(fp, len))
 147                         goto error;
 148                 memcpy((void *)(fp->_lb._base + off), (void *)fp->pub._p, diff);
 149                 fp->pub._r -= diff;
 150                 fp->pub._p = p;
 151                 break;
 152         }
 153         *lenp = len;
 154 #ifdef notdef
 155         fp->_lb._base[len] = 0;
 156 #endif
 157         FUNLOCKFILE(fp);
 158         return ((char *)fp->_lb._base);
 159
 160 error:
 161         *lenp = 0;              /* ??? */
 162         FUNLOCKFILE(fp);
 163         return (NULL);          /* ??? */
 164 }