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  * 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
  33 #if defined(LIBC_SCCS) && !defined(lint)
  34 static char sccsid[] = "@(#)fgetln.c    8.2 (Berkeley) 1/2/94";
  35 #endif /* LIBC_SCCS and not lint */
  36 #include <sys/cdefs.h>
  37 __FBSDID("$FreeBSD: src/lib/libc/stdio/fgetln.c,v 1.11 2007/01/09 00:28:06 imp Exp $");
  38
  39 #include "namespace.h"
  40 #include <errno.h>
  41 #include <stdio.h>
  42 #include <stdlib.h>
  43 #include <string.h>
  44 #include "un-namespace.h"
  45 #include "libc_private.h"
  46 #include "local.h"
  47
  48 /*
  49  * Expand the line buffer.  Return -1 on error.
  50 #ifdef notdef
  51  * The `new size' does not account for a terminating '\0',
  52  * so we add 1 here.
  53 #endif
  54  */
  55 int
  56 __slbexpand(FILE *fp, size_t newsize)
  57 {
  58         void *p;
  59
  60 #ifdef notdef
  61         ++newsize;
  62 #endif
  63         if (fp->_lb._size >= newsize)
  64                 return (0);
  65         if (newsize > INT_MAX) {
  66                 errno = ENOMEM;
  67                 return (-1);
  68         }
  69         if ((p = realloc(fp->_lb._base, newsize)) == NULL)
  70                 return (-1);
  71         fp->_lb._base = p;
  72         fp->_lb._size = newsize;
  73         return (0);
  74 }
  75
  76 /*
  77  * Get an input line.  The returned pointer often (but not always)
  78  * points into a stdio buffer.  Fgetln does not alter the text of
  79  * the returned line (which is thus not a C string because it will
  80  * not necessarily end with '\0'), but does allow callers to modify
  81  * it if they wish.  Thus, we set __SMOD in case the caller does.
  82  */
  83 char *
  84 fgetln(FILE *fp, size_t *lenp)
  85 {
  86         unsigned char *p;
  87         size_t len;
  88         size_t off;
  89
  90         FLOCKFILE(fp);
  91         ORIENT(fp, -1);
  92         /* make sure there is input */
  93         if (fp->_r <= 0 && __srefill(fp)) {
  94                 *lenp = 0;
  95                 FUNLOCKFILE(fp);
  96                 return (NULL);
  97         }
  98
  99         /* look for a newline in the input */
 100         if ((p = memchr((void *)fp->_p, '\n', (size_t)fp->_r)) != NULL) {
 101                 char *ret;
 102
 103                 /*
 104                  * Found one.  Flag buffer as modified to keep fseek from
 105                  * `optimising' a backward seek, in case the user stomps on
 106                  * the text.
 107                  */
 108                 p++;            /* advance over it */
 109                 ret = (char *)fp->_p;
 110                 *lenp = len = p - fp->_p;
 111                 fp->_flags |= __SMOD;
 112                 fp->_r -= len;
 113                 fp->_p = p;
 114                 FUNLOCKFILE(fp);
 115                 return (ret);
 116         }
 117
 118         /*
 119          * We have to copy the current buffered data to the line buffer.
 120          * As a bonus, though, we can leave off the __SMOD.
 121          *
 122          * OPTIMISTIC is length that we (optimistically) expect will
 123          * accomodate the `rest' of the string, on each trip through the
 124          * loop below.
 125          */
 126 #define OPTIMISTIC 80
 127
 128         for (len = fp->_r, off = 0;; len += fp->_r) {
 129                 size_t diff;
 130
 131                 /*
 132                  * Make sure there is room for more bytes.  Copy data from
 133                  * file buffer to line buffer, refill file and look for
 134                  * newline.  The loop stops only when we find a newline.
 135                  */
 136                 if (__slbexpand(fp, len + OPTIMISTIC))
 137                         goto error;
 138                 (void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
 139                     len - off);
 140                 off = len;
 141                 if (__srefill(fp))
 142                         break;  /* EOF or error: return partial line */
 143                 if ((p = memchr((void *)fp->_p, '\n', (size_t)fp->_r)) == NULL)
 144                         continue;
 145
 146                 /* got it: finish up the line (like code above) */
 147                 p++;
 148                 diff = p - fp->_p;
 149                 len += diff;
 150                 if (__slbexpand(fp, len))
 151                         goto error;
 152                 (void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
 153                     diff);
 154                 fp->_r -= diff;
 155                 fp->_p = p;
 156                 break;
 157         }
 158         *lenp = len;
 159 #ifdef notdef
 160         fp->_lb._base[len] = 0;
 161 #endif
 162         FUNLOCKFILE(fp);
 163         return ((char *)fp->_lb._base);
 164
 165 error:
 166         *lenp = 0;              /* ??? */
 167         fp->_flags |= __SERR;
 168         FUNLOCKFILE(fp);
 169         return (NULL);          /* ??? */
 170 }