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/*-
 * Copyright (c) 1996  Peter Wemm <peter@freebsd.org>
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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_RCS) && !defined(lint)
static char rcsid[] = "$\Id: vasprintf.c,v 1.3 1996/07/28 16:16:11 peter Exp $";
#endif /* LIBC_RCS and not lint */

#include <stdio.h>
#include <stdlib.h>

#if __STDC__
#include <stdarg.h>
#else
#include <varargs.h>
#endif

#define CHUNK_SPARE 128 /* how much spare to allocate to avoid realloc calls */

struct bufcookie {
        char    *base;  /* start of buffer */
        size_t  size;
        size_t  left;
};

static int      writehook __P((void *cookie, const char *, int));

static int
writehook(cookie, buf, len)
        void *cookie;
        const char *buf;
        int   len;
{
        struct bufcookie *h = (struct bufcookie *)cookie;
        char *newbuf;

        if (len == 0)
                return 0;

        if (len > h->left) {
                /* grow malloc region */
                /*
                 * XXX this is linearly expanded, which is slow for obscenely
                 * large strings.
                 */
                h->left = h->left + len + CHUNK_SPARE;
                h->size = h->size + len + CHUNK_SPARE;
                newbuf = realloc(h->base, h->size);
                if (newbuf == NULL) {
                        free(h->base);
                        h->base = NULL;
                        return (-1);
                } else
                        h->base = newbuf;
        }
        /* "write" it */
        (void)memcpy(h->base + h->size - h->left, buf, (size_t)len);
        h->left -= len;
        return (len);
}


int
vasprintf(str, fmt, ap)
        char **str;
        const char *fmt;
        va_list ap;
{
        int ret;
        FILE *f;
        struct bufcookie h;

        h.base = malloc(CHUNK_SPARE);
        if (h.base == NULL)
                return (-1);
        h.size = CHUNK_SPARE;
        h.left = CHUNK_SPARE;

        f = funopen(&h, NULL, writehook, NULL, NULL);
        if (f == NULL) {
                free(h.base);
                return (-1);
        }
        ret = vfprintf(f, fmt, ap);
        fclose(f);
        if (ret < 0) {
                free(h.base);
                return (-1);
        }
        if (h.base == NULL)     /* failed to realloc in writehook */
                return (-1);

        h.base[h.size - h.left] = '\0';
        *str = realloc(h.base, (size_t)(h.size - h.left + 1));
        if (*str == NULL)       /* failed to realloc it to actual size */
                *str = h.base;  /* return oversize buffer */
        return (ret);
}