/*-
 * Copyright (c) 2006,2008-2011 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.
 */

#include <libelf.h>

#include "_libelf.h"

ELFTC_VCSID("$Id: elf_begin.c,v 1.1 2019/02/01 05:27:37 jsg Exp $");

Elf *
elf_begin(int fd, Elf_Cmd c, Elf *a)
{
        Elf *e;

        e = NULL;

        if (LIBELF_PRIVATE(version) == EV_NONE) {
                LIBELF_SET_ERROR(SEQUENCE, 0);
                return (NULL);
        }

        switch (c) {
        case ELF_C_NULL:
                return (NULL);

        case ELF_C_WRITE:
                /*
                 * The ELF_C_WRITE command is required to ignore the
                 * descriptor passed in.
                 */
                a = NULL;
                break;

        case ELF_C_RDWR:
                if (a != NULL) { /* not allowed for ar(1) archives. */
                        LIBELF_SET_ERROR(ARGUMENT, 0);
                        return (NULL);
                }
                /*FALLTHROUGH*/
        case ELF_C_READ:
                /*
                 * Descriptor `a' could be for a regular ELF file, or
                 * for an ar(1) archive.  If descriptor `a' was opened
                 * using a valid file descriptor, we need to check if
                 * the passed in `fd' value matches the original one.
                 */
                if (a &&
                    ((a->e_fd != -1 && a->e_fd != fd) || c != a->e_cmd)) {
                        LIBELF_SET_ERROR(ARGUMENT, 0);
                        return (NULL);
                }
                break;

        default:
                LIBELF_SET_ERROR(ARGUMENT, 0);
                return (NULL);

        }

        if (a == NULL)
                e = _libelf_open_object(fd, c, 1);
        else if (a->e_kind == ELF_K_AR)
                e = _libelf_ar_open_member(a->e_fd, c, a);
        else
                (e = a)->e_activations++;

        return (e);
}