src/system/libroot/posix/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
  37 #if defined(LIBC_SCCS) && !defined(lint)
  38 static char *rcsid = "$OpenBSD: fgetln.c,v 1.2 1996/08/19 08:32:29 tholo Exp $";
  39 #endif /* LIBC_SCCS and not lint */
  40
  41 #include <stdio.h>
  42 #include <stdlib.h>
  43 #include <string.h>
  44 #include "local.h"
  45
  46 /*
  47  * Expand the line buffer.  Return -1 on error.
  48 #ifdef notdef
  49  * The `new size' does not account for a terminating '\0',
  50  * so we add 1 here.
  51 #endif
  52  */
  53 static int
  54 __slbexpand(fp, newsize)
  55         FILE *fp;
  56         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 ((p = realloc(fp->_lb._base, newsize)) == NULL)
  66                 return (-1);
  67         fp->_lb._base = p;
  68         fp->_lb._size = newsize;
  69         return (0);
  70 }
  71
  72 /*
  73  * Get an input line.  The returned pointer often (but not always)
  74  * points into a stdio buffer.  Fgetline does not alter the text of
  75  * the returned line (which is thus not a C string because it will
  76  * not necessarily end with '\0'), but does allow callers to modify
  77  * it if they wish.  Thus, we set __SMOD in case the caller does.
  78  */
  79 char *
  80 fgetln(fp, lenp)
  81         register FILE *fp;
  82         size_t *lenp;
  83 {
  84         register unsigned char *p;
  85         register size_t len;
  86         size_t off;
  87
  88         /* make sure there is input */
  89         if (fp->_r <= 0 && __srefill(fp)) {
  90                 *lenp = 0;
  91                 return (NULL);
  92         }
  93
  94         /* look for a newline in the input */
  95         if ((p = memchr((void *)fp->_p, '\n', fp->_r)) != NULL) {
  96                 register 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->_p;
 105                 *lenp = len = p - fp->_p;
 106                 fp->_flags |= __SMOD;
 107                 fp->_r -= len;
 108                 fp->_p = p;
 109                 return (ret);
 110         }
 111
 112         /*
 113          * We have to copy the current buffered data to the line buffer.
 114          * As a bonus, though, we can leave off the __SMOD.
 115          *
 116          * OPTIMISTIC is length that we (optimistically) expect will
 117          * accomodate the `rest' of the string, on each trip through the
 118          * loop below.
 119          */
 120 #define OPTIMISTIC 80
 121
 122         for (len = fp->_r, off = 0;; len += fp->_r) {
 123                 register size_t diff;
 124
 125                 /*
 126                  * Make sure there is room for more bytes.  Copy data from
 127                  * file buffer to line buffer, refill file and look for
 128                  * newline.  The loop stops only when we find a newline.
 129                  */
 130                 if (__slbexpand(fp, len + OPTIMISTIC))
 131                         goto error;
 132                 (void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
 133                     len - off);
 134                 off = len;
 135                 if (__srefill(fp))
 136                         break;  /* EOF or error: return partial line */
 137                 if ((p = memchr((void *)fp->_p, '\n', fp->_r)) == NULL)
 138                         continue;
 139
 140                 /* got it: finish up the line (like code above) */
 141                 p++;
 142                 diff = p - fp->_p;
 143                 len += diff;
 144                 if (__slbexpand(fp, len))
 145                         goto error;
 146                 (void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
 147                     diff);
 148                 fp->_r -= diff;
 149                 fp->_p = p;
 150                 break;
 151         }
 152         *lenp = len;
 153 #ifdef notdef
 154         fp->_lb._base[len] = 0;
 155 #endif
 156         return ((char *)fp->_lb._base);
 157
 158 error:
 159         *lenp = 0;              /* ??? */
 160         return (NULL);          /* ??? */
 161 }