BSD 4_3_Net_2 release

[unix-history] / usr / src / lib / libc / stdio / fgetline.c

/*-
* Copyright (c) 1990 The Regents of the University of California.
* All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Chris Torek.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
*    must display the following acknowledgement:
*      This product includes software developed by the University of
*      California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
*    may be used to endorse or promote products derived from this software
*    without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)fgetline.c  5.2 (Berkeley) 5/4/91";
#endif /* LIBC_SCCS and not lint */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "local.h"

/*
* Expand the line buffer.  Return -1 on error.
* The `new size' does not account for a terminating '\0',
* so we add 1 here.
*/
__slbexpand(fp, newsize)
       FILE *fp;
       size_t newsize;
{
       void *p;

       if (fp->_lb._size >= ++newsize)
               return (0);
       if ((p = realloc(fp->_lb._base, newsize)) == NULL)
               return (-1);
       fp->_lb._base = p;
       fp->_lb._size = newsize;
       return (0);
}

/*
* Get an input line.  The returned pointer often (but not always)
* points into a stdio buffer.  Fgetline smashes the newline (if any)
* in the stdio buffer; callers must not use it on streams that
* have `magic' setvbuf() games happening.
*/
char *
fgetline(fp, lenp)
       register FILE *fp;
       size_t *lenp;
{
       register unsigned char *p;
       register size_t len;
       size_t off;

       /* make sure there is input */
       if (fp->_r <= 0 && __srefill(fp)) {
               if (lenp != NULL)
                       *lenp = 0;
               return (NULL);
       }

       /* look for a newline in the input */
       if ((p = memchr((void *)fp->_p, '\n', fp->_r)) != NULL) {
               register char *ret;

               /*
                * Found one.  Flag buffer as modified to keep
                * fseek from `optimising' a backward seek, since
                * the newline is about to be trashed.  (We should
                * be able to get away with doing this only if
                * p is not pointing into an ungetc buffer, since
                * fseek discards ungetc data, but this is the
                * usual case anyway.)
                */
               ret = (char *)fp->_p;
               len = p - fp->_p;
               fp->_flags |= __SMOD;
               *p = 0;
               fp->_r -= len + 1;
               fp->_p = p + 1;
               if (lenp != NULL)
                       *lenp = len;
               return (ret);
       }

       /*
        * We have to copy the current buffered data to the line buffer.
        *
        * OPTIMISTIC is length that we (optimistically)
        * expect will accomodate the `rest' of the string,
        * on each trip through the loop below.
        */
#define OPTIMISTIC 80

       for (len = fp->_r, off = 0;; len += fp->_r) {
               register size_t diff;

               /*
                * Make sure there is room for more bytes.
                * Copy data from file buffer to line buffer,
                * refill file and look for newline.  The
                * loop stops only when we find a newline.
                */
               if (__slbexpand(fp, len + OPTIMISTIC))
                       goto error;
               (void) bcopy((void *)fp->_p, (void *)(fp->_lb._base + off),
                   len - off);
               off = len;
               if (__srefill(fp))
                       break;  /* EOF or error: return partial line */
               if ((p = memchr((void *)fp->_p, '\n', fp->_r)) == NULL)
                       continue;

               /* got it: finish up the line (like code above) */
               fp->_flags |= __SMOD;   /* soon */
               diff = p - fp->_p;
               len += diff;
               if (__slbexpand(fp, len))
                       goto error;
               (void) bcopy((void *)fp->_p, (void *)(fp->_lb._base + off),
                   diff);
               fp->_r -= diff + 1;
               fp->_p = p + 1;
               break;
       }
       if (lenp != NULL)
               *lenp = len;
       fp->_lb._base[len] = 0;
       return ((char *)fp->_lb._base);

error:
       if (lenp != NULL)
               *lenp = 0;      /* ??? */
       return (NULL);          /* ??? */
}