stdio/FreeBSD/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
  37 #if defined(LIBC_SCCS) && !defined(lint)
  38 static char sccsid[] = "@(#)fgetln.c    8.2 (Berkeley) 1/2/94";
  39 #endif /* LIBC_SCCS and not lint */
  40 #include <sys/cdefs.h>
  41 __FBSDID("$FreeBSD: src/lib/libc/stdio/fgetln.c,v 1.10 2004/07/16 05:52:51 tjr Exp $");
  42
  43 #include "namespace.h"
  44 #include <stdio.h>
  45 #include <stdlib.h>
  46 #include <string.h>
  47 #include "un-namespace.h"
  48 #include "libc_private.h"
  49 #include "local.h"
  50
  51 /*
  52  * Expand the line buffer.  Return -1 on error.
  53 #ifdef notdef
  54  * The `new size' does not account for a terminating '\0',
  55  * so we add 1 here.
  56 #endif
  57  */
  58 int
  59 __slbexpand(FILE *fp, size_t newsize)
  60 {
  61         void *p;
  62
  63 #ifdef notdef
  64         ++newsize;
  65 #endif
  66         if (fp->_lb._size >= newsize)
  67                 return (0);
  68         if ((p = realloc(fp->_lb._base, newsize)) == NULL)
  69                 return (-1);
  70         fp->_lb._base = p;
  71         fp->_lb._size = newsize;
  72         return (0);
  73 }
  74
  75 /*
  76  * Get an input line.  The returned pointer often (but not always)
  77  * points into a stdio buffer.  Fgetln does not alter the text of
  78  * the returned line (which is thus not a C string because it will
  79  * not necessarily end with '\0'), but does allow callers to modify
  80  * it if they wish.  Thus, we set __SMOD in case the caller does.
  81  */
  82 char *
  83 fgetln(FILE *fp, size_t *lenp)
  84 {
  85         unsigned char *p;
  86         size_t len;
  87         size_t off;
  88
  89         FLOCKFILE(fp);
  90         ORIENT(fp, -1);
  91         /* make sure there is input */
  92         if (fp->_r <= 0 && __srefill(fp)) {
  93                 *lenp = 0;
  94                 FUNLOCKFILE(fp);
  95                 return (NULL);
  96         }
  97
  98         /* look for a newline in the input */
  99         if ((p = memchr((void *)fp->_p, '\n', (size_t)fp->_r)) != NULL) {
 100                 char *ret;
 101
 102                 /*
 103                  * Found one.  Flag buffer as modified to keep fseek from
 104                  * `optimising' a backward seek, in case the user stomps on
 105                  * the text.
 106                  */
 107                 p++;            /* advance over it */
 108                 ret = (char *)fp->_p;
 109                 *lenp = len = p - fp->_p;
 110                 fp->_flags |= __SMOD;
 111                 fp->_r -= len;
 112                 fp->_p = p;
 113                 FUNLOCKFILE(fp);
 114                 return (ret);
 115         }
 116
 117         /*
 118          * We have to copy the current buffered data to the line buffer.
 119          * As a bonus, though, we can leave off the __SMOD.
 120          *
 121          * OPTIMISTIC is length that we (optimistically) expect will
 122          * accomodate the `rest' of the string, on each trip through the
 123          * loop below.
 124          */
 125 #define OPTIMISTIC 80
 126
 127         for (len = fp->_r, off = 0;; len += fp->_r) {
 128                 size_t diff;
 129
 130                 /*
 131                  * Make sure there is room for more bytes.  Copy data from
 132                  * file buffer to line buffer, refill file and look for
 133                  * newline.  The loop stops only when we find a newline.
 134                  */
 135                 if (__slbexpand(fp, len + OPTIMISTIC))
 136                         goto error;
 137                 (void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
 138                     len - off);
 139                 off = len;
 140                 if (__srefill(fp))
 141                         break;  /* EOF or error: return partial line */
 142                 if ((p = memchr((void *)fp->_p, '\n', (size_t)fp->_r)) == NULL)
 143                         continue;
 144
 145                 /* got it: finish up the line (like code above) */
 146                 p++;
 147                 diff = p - fp->_p;
 148                 len += diff;
 149                 if (__slbexpand(fp, len))
 150                         goto error;
 151                 (void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
 152                     diff);
 153                 fp->_r -= diff;
 154                 fp->_p = p;
 155                 break;
 156         }
 157         *lenp = len;
 158 #ifdef notdef
 159         fp->_lb._base[len] = 0;
 160 #endif
 161         FUNLOCKFILE(fp);
 162         return ((char *)fp->_lb._base);
 163
 164 error:
 165         *lenp = 0;              /* ??? */
 166         FUNLOCKFILE(fp);
 167         return (NULL);          /* ??? */
 168 }