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/*-
 * Copyright (c) 1990, 1993
 *      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)
#if 0
static char sccsid[] = "@(#)fgetln.c    8.2 (Berkeley) 1/2/94";
#endif
static const char rcsid[] =
                "$\Id: fgetln.c,v 1.3 1996/06/22 10:33:08 jraynard Exp $";
#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.
#ifdef notdef
 * The `new size' does not account for a terminating '\0',
 * so we add 1 here.
#endif
 */
int
__slbexpand(fp, newsize)
        FILE *fp;
        size_t newsize;
{
        void *p;

#ifdef notdef
        ++newsize;
#endif
        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.  Fgetln does not alter the text of
 * the returned line (which is thus not a C string because it will
 * not necessarily end with '\0'), but does allow callers to modify
 * it if they wish.  Thus, we set __SMOD in case the caller does.
 */
char *
fgetln(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)) {
                *lenp = 0;
                return (NULL);
        }

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

                /*
                 * Found one.  Flag buffer as modified to keep fseek from
                 * `optimising' a backward seek, in case the user stomps on
                 * the text.
                 */
                p++;            /* advance over it */
                ret = (char *)fp->_p;
                *lenp = len = p - fp->_p;
                fp->_flags |= __SMOD;
                fp->_r -= len;
                fp->_p = p;
                return (ret);
        }

        /*
         * We have to copy the current buffered data to the line buffer.
         * As a bonus, though, we can leave off the __SMOD.
         *
         * 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)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
                    len - off);
                off = len;
                if (__srefill(fp))
                        break;  /* EOF or error: return partial line */
                if ((p = memchr((void *)fp->_p, '\n', (size_t)fp->_r)) == NULL)
                        continue;

                /* got it: finish up the line (like code above) */
                p++;
                diff = p - fp->_p;
                len += diff;
                if (__slbexpand(fp, len))
                        goto error;
                (void)memcpy((void *)(fp->_lb._base + off), (void *)fp->_p,
                    diff);
                fp->_r -= diff;
                fp->_p = p;
                break;
        }
        *lenp = len;
#ifdef notdef
        fp->_lb._base[len] = 0;
#endif
        return ((char *)fp->_lb._base);

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