/*      $NetBSD: expandm.c,v 1.13 2024/10/04 08:37:20 rillig Exp $      */

/*-
* Copyright (c) 2019 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Christos Zoulas.
*
* 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
*/
#include <sys/cdefs.h>
__RCSID("$NetBSD: expandm.c,v 1.13 2024/10/04 08:37:20 rillig Exp $");

#include <limits.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>

#include "expandm.h"

#ifdef TEST
#undef INT_MAX
#define INT_MAX 31
#endif


const char * __attribute__((__format_arg__(1)))
expandm(const char *fmt, const char *sf, char **rbuf)
{
       const int err = errno;
       const char *e = NULL;
       char *buf, *nbuf;
       const char *ptr, *m;

       buf = NULL;
       for (ptr = fmt; (m = strstr(ptr, "%m")) != NULL; ptr = m + 2) {
               size_t cnt = 0;
               size_t nlen;

               for (const char *p = m; p >= ptr && *p == '%'; p--)
                       cnt++;

               nlen = (size_t)(m - ptr);
               /*
                * we can't exceed INT_MAX because int is used as
                * a format width
                */
               if (__predict_false(nlen >= INT_MAX)) {
                       size_t blen = buf ? strlen(buf) : 0;
                       size_t tlen;

                       /*
                        * if we would overflow a ptrdiff_t when computing
                        * tlen, then don't bother.  The format string is
                        * simply too large to be converted.
                        */
                       if (blen >= PTRDIFF_MAX ||
                           nlen >= PTRDIFF_MAX - blen ||
                           nlen >= SIZE_T_MAX - blen)
                               goto out;

                       tlen = nlen + blen;

                       nbuf = realloc(buf, tlen + 1);
                       if (nbuf == NULL)
                               goto out;

                       memcpy(nbuf + blen, ptr, nlen);
                       nbuf[tlen] = '\0';
                       ptr += nlen;
                       buf = nbuf;
               }

               if (__predict_true(e == NULL && (cnt & 1) != 0))
                       e = strerror(err);
               if (asprintf(&nbuf, "%s%.*s%s", buf ? buf : "",
                   (int)(m - ptr), ptr, (cnt & 1) ? e : "%m") == -1)
                       goto out;
               free(buf);
               buf = nbuf;
       }

       if (asprintf(&nbuf, "%s%s%s", buf ? buf : "", ptr, sf ? sf : "") == -1)
               goto out;

       free(buf);
       if (rbuf)
               *rbuf = nbuf;
       errno = err;
       return nbuf;
out:
       free(buf);
       if (rbuf)
               *rbuf = NULL;
       errno = err;
       return fmt;
}

#ifdef TEST
int
main(int argc, char *argv[])
{
       errno = ERANGE;
       printf("%s\n", expandm(argc > 1 ? argv[1] : "Message %%m=%m: %%%m%%",
           "...", NULL));
       return 0;
}
#endif