/*
 * Copyright 2013-2014, Haiku, Inc.
 * Distributed under the terms of the MIT License.
 *
 * Authors:
 *      Alexander von Gluck IV, <kallisti5@unixzen.com>
 */


#include "pe.h"

#include <ctype.h>
#include <dlfcn.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>


static status_t
parse_mz_header(MzHeader* mzHeader, off_t* peOffset)
{
        if (memcmp(&mzHeader->magic, MZ_MAGIC, 2) != 0)
                return B_NOT_AN_EXECUTABLE;

        *peOffset = (off_t)mzHeader->lfaNew;
        return B_OK;
}


static status_t
parse_pe_header(PeHeader* peHeader)
{
        if (memcmp(&peHeader->magic, PE_MAGIC, 2) != 0)
                return B_NOT_AN_EXECUTABLE;

        // Looks like an old BeOS R3 x86 program
        if (peHeader->characteristics == 0x10E)
                return B_LEGACY_EXECUTABLE;

        return B_OK;
}


/*! Read and verify the PE header */
status_t
pe_verify_header(void *header, size_t length)
{
        if (length < sizeof(MzHeader))
                return B_NOT_AN_EXECUTABLE;

        // Verify MZ header, pull PE header offset
        off_t peOffset = 0;
        if (parse_mz_header((MzHeader*)header, &peOffset) != B_OK)
                return B_NOT_AN_EXECUTABLE;

        // MS-DOS program
        if (peOffset == 0)
                return B_UNKNOWN_EXECUTABLE;

        // Something is wrong with the binary
        if (peOffset + sizeof(PeHeader) > length)
                return B_UNKNOWN_EXECUTABLE;

        // Find the PE header based on MZ provided offset
        uint8* pePtr = (uint8*)header;
        pePtr += peOffset;

        // Win32 program or old BeOS R3 x86 program
        return parse_pe_header((PeHeader*)pePtr);
}