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. 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  */
  35
  36 #include "namespace.h"
  37 #include <stdio.h>
  38 #include <stdlib.h>
  39 #include <string.h>
  40 #include "un-namespace.h"
  41
  42 #include "libc_private.h"
  43 #include "local.h"
  44
  45 /*
  46  * Expand the line buffer.  Return -1 on error.
  47 #ifdef notdef
  48  * The `new size' does not account for a terminating '\0',
  49  * so we add 1 here.
  50 #endif
  51  */
  52 int
  53 __slbexpand(FILE *fp, size_t newsize)
  54 {
  55         void *p;
  56
  57 #ifdef notdef
  58         ++newsize;
  59 #endif
  60         if (fp->_lb._size >= newsize)
  61                 return (0);
  62         if ((p = realloc(fp->_lb._base, newsize)) == NULL)
  63                 return (-1);
  64         fp->_lb._base = p;
  65         fp->_lb._size = newsize;
  66         return (0);
  67 }
  68
  69 /*
  70  * Get an input line.  The returned pointer often (but not always)
  71  * points into a stdio buffer.  Fgetln does not alter the text of
  72  * the returned line (which is thus not a C string because it will
  73  * not necessarily end with '\0'), but does allow callers to modify
  74  * it if they wish.  Thus, we set __SMOD in case the caller does.
  75  */
  76 char *
  77 fgetln(FILE *fp, size_t *lenp)
  78 {
  79         unsigned char *p;
  80         size_t len;
  81         size_t off;
  82
  83         FLOCKFILE(fp);
  84         ORIENT(fp, -1);
  85         /* make sure there is input */
  86         if (fp->pub._r <= 0 && __srefill(fp)) {
  87                 *lenp = 0;
  88                 FUNLOCKFILE(fp);
  89                 return (NULL);
  90         }
  91
  92         /* look for a newline in the input */
  93         if ((p = memchr((void *)fp->pub._p, '\n', (size_t)fp->pub._r)) != NULL) {
  94                 char *ret;
  95
  96                 /*
  97                  * Found one.  Flag buffer as modified to keep fseek from
  98                  * `optimising' a backward seek, in case the user stomps on
  99                  * the text.
 100                  */
 101                 p++;            /* advance over it */
 102                 ret = (char *)fp->pub._p;
 103                 *lenp = len = p - fp->pub._p;
 104                 fp->pub._flags |= __SMOD;
 105                 fp->pub._r -= len;
 106                 fp->pub._p = p;
 107                 FUNLOCKFILE(fp);
 108                 return (ret);
 109         }
 110
 111         /*
 112          * We have to copy the current buffered data to the line buffer.
 113          * As a bonus, though, we can leave off the __SMOD.
 114          *
 115          * OPTIMISTIC is length that we (optimistically) expect will
 116          * accomodate the `rest' of the string, on each trip through the
 117          * loop below.
 118          */
 119 #define OPTIMISTIC 80
 120
 121         for (len = fp->pub._r, off = 0;; len += fp->pub._r) {
 122                 size_t diff;
 123
 124                 /*
 125                  * Make sure there is room for more bytes.  Copy data from
 126                  * file buffer to line buffer, refill file and look for
 127                  * newline.  The loop stops only when we find a newline.
 128                  */
 129                 if (__slbexpand(fp, len + OPTIMISTIC))
 130                         goto error;
 131                 memcpy((void *)(fp->_lb._base + off), (void *)fp->pub._p,
 132                     len - off);
 133                 off = len;
 134                 if (__srefill(fp))
 135                         break;  /* EOF or error: return partial line */
 136                 if ((p = memchr((void *)fp->pub._p, '\n', (size_t)fp->pub._r))
 137                     == NULL)
 138                         continue;
 139
 140                 /* got it: finish up the line (like code above) */
 141                 p++;
 142                 diff = p - fp->pub._p;
 143                 len += diff;
 144                 if (__slbexpand(fp, len))
 145                         goto error;
 146                 memcpy((void *)(fp->_lb._base + off), (void *)fp->pub._p, diff);
 147                 fp->pub._r -= diff;
 148                 fp->pub._p = p;
 149                 break;
 150         }
 151         *lenp = len;
 152 #ifdef notdef
 153         fp->_lb._base[len] = 0;
 154 #endif
 155         FUNLOCKFILE(fp);
 156         return ((char *)fp->_lb._base);
 157
 158 error:
 159         *lenp = 0;              /* ??? */
 160         FUNLOCKFILE(fp);
 161         return (NULL);          /* ??? */
 162 }