/*      $NetBSD: elf_next.c,v 1.5 2024/03/03 17:37:33 christos Exp $    */

/*-
* Copyright (c) 2006,2008 Joseph Koshy
* All rights reserved.
*
* 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 HAVE_NBTOOL_CONFIG_H
# include "nbtool_config.h"
#endif

#include <sys/cdefs.h>

#include <ar.h>
#include <assert.h>
#include <libelf.h>

#include "_libelf.h"

__RCSID("$NetBSD: elf_next.c,v 1.5 2024/03/03 17:37:33 christos Exp $");

Elf_Cmd
elf_next(Elf *e)
{
       off_t next;
       Elf *parent;

       if (e == NULL)
               return (ELF_C_NULL);

        if ((parent = e->e_parent) == NULL) {
                LIBELF_SET_ERROR(ARGUMENT, 0);
                return (ELF_C_NULL);
        }

       assert(parent->e_kind == ELF_K_AR);
       assert(parent->e_cmd == ELF_C_READ);
       assert(e->e_rawfile > parent->e_rawfile);

       next = e->e_rawfile - parent->e_rawfile + (off_t) e->e_rawsize;
       next = (next + 1) & ~1; /* round up to an even boundary */

       /*
        * Setup the 'e_next' field of the archive descriptor for the
        * next call to 'elf_begin()'.
        */
       parent->e_u.e_ar.e_next = (next >= (off_t) parent->e_rawsize) ?
           (off_t) 0 : next;

       /*
        * Return an error if the 'e_next' field falls outside the current
        * file.
        *
        * This check is performed after updating the parent descriptor's
        * 'e_next' field so that the next call to elf_begin(3) will terminate
        * traversal of a too-small archive even if client code forgets to
        * check the return value from elf_next(3).
        */
       if (next > (off_t) parent->e_rawsize) {
               LIBELF_SET_ERROR(ARGUMENT, 0);
               return (ELF_C_NULL);
       }

       return (ELF_C_READ);
}