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/*-
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 * Copyright (c) 1996  Peter Wemm <peter@freebsd.org>
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 * 1. Redistributions of source code must retain the above copyright
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 *    notice, this list of conditions and the following disclaimer.
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 * 2. Redistributions in binary form must reproduce the above copyright
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 *    notice, this list of conditions and the following disclaimer in the
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 *    documentation and/or other materials provided with the distribution.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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 * SUCH DAMAGE.
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 */
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#if defined(LIBC_RCS) && !defined(lint)
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static char rcsid[] = "$\Id: vasprintf.c,v 1.3 1996/07/28 16:16:11 peter Exp $";
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#endif /* LIBC_RCS and not lint */
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#include <stdio.h>
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#include <stdlib.h>
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#if __STDC__
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#include <stdarg.h>
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#else
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#include <varargs.h>
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#endif
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#define CHUNK_SPARE 128 /* how much spare to allocate to avoid realloc calls */
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struct bufcookie {
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        char    *base;  /* start of buffer */
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        size_t  size;
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        size_t  left;
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};
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static int      writehook __P((void *cookie, const char *, int));
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static int
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writehook(cookie, buf, len)
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        void *cookie;
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        const char *buf;
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        int   len;
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{
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        struct bufcookie *h = (struct bufcookie *)cookie;
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        char *newbuf;
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        if (len == 0)
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                return 0;
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        if (len > h->left) {
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                /* grow malloc region */
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                /*
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                 * XXX this is linearly expanded, which is slow for obscenely
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                 * large strings.
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                 */
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                h->left = h->left + len + CHUNK_SPARE;
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                h->size = h->size + len + CHUNK_SPARE;
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                newbuf = realloc(h->base, h->size);
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                if (newbuf == NULL) {
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                        free(h->base);
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                        h->base = NULL;
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                        return (-1);
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                } else
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                        h->base = newbuf;
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        }
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        /* "write" it */
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        (void)memcpy(h->base + h->size - h->left, buf, (size_t)len);
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        h->left -= len;
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        return (len);
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}
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int
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vasprintf(str, fmt, ap)
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        char **str;
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        const char *fmt;
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        va_list ap;
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{
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        int ret;
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        FILE *f;
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        struct bufcookie h;
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        h.base = malloc(CHUNK_SPARE);
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        if (h.base == NULL)
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                return (-1);
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        h.size = CHUNK_SPARE;
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        h.left = CHUNK_SPARE;
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        f = funopen(&h, NULL, writehook, NULL, NULL);
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        if (f == NULL) {
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                free(h.base);
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                return (-1);
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        }
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        ret = vfprintf(f, fmt, ap);
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        fclose(f);
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        if (ret < 0) {
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                free(h.base);
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                return (-1);
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        }
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        if (h.base == NULL)     /* failed to realloc in writehook */
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                return (-1);
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        h.base[h.size - h.left] = '\0';
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        *str = realloc(h.base, (size_t)(h.size - h.left + 1));
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        if (*str == NULL)       /* failed to realloc it to actual size */
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                *str = h.base;  /* return oversize buffer */
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        return (ret);
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}