/* p_sys.cpp --

   This file is part of the UPX executable compressor.

   Copyright (C) 1996-2000 Markus Franz Xaver Johannes Oberhumer
   Copyright (C) 1996-2000 Laszlo Molnar

   UPX and the UCL library are free software; you can redistribute them
   and/or modify them under the terms of the GNU General Public License as
   published by the Free Software Foundation; either version 2 of
   the License, or (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; see the file COPYING.
   If not, write to the Free Software Foundation, Inc.,
   59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

   Markus F.X.J. Oberhumer                   Laszlo Molnar
   markus.oberhumer@jk.uni-linz.ac.at        ml1050@cdata.tvnet.hu
 */


#include "conf.h"
#include "file.h"
#include "filter.h"
#include "packer.h"
#include "p_com.h"
#include "p_sys.h"

static const
#include "stub/l_sys.h"


/*************************************************************************
//
**************************************************************************/

bool PackSys::canPack()
{
    unsigned char buf[128];

    fi->readx(buf,128);
    if (memcmp (buf,"\xff\xff\xff\xff",4) != 0)
        return false;
    if (!fn_has_ext(fi->getName(),"sys"))
        return false;
    if (find_le32(buf,128,UPX_MAGIC_LE32))
        throwAlreadyPacked();
    if (file_size < 1024)
        throwCantPack("file is too small");
    if (file_size > 0x10000)
        throwCantPack("file is too big for dos/sys");
    return true;
}


/*************************************************************************
//
**************************************************************************/

void PackSys::patchLoader(OutputFile *fo,
                          upx_byte *loader, int lsize,
                          unsigned calls, unsigned overlapoh)
{
    const int filter_id = ph.filter;
    const int e_len = getLoaderSection("SYSCUTPO");
    const int d_len = lsize - e_len;
    assert(e_len > 0 && e_len < 256);
    assert(d_len > 0 && d_len < 256);

    if (ph.u_len + d_len + overlapoh > 0xfffe)
        throwNotCompressible();

    memcpy(loader,ibuf,6);              // copy from orig. header
    memcpy(loader+8,ibuf+8,2);          // opendos wants this word too

    unsigned copy_to = ph.u_len + d_len + overlapoh;

    patch_le16(loader,lsize,"JO",get_le16(ibuf+6)-copy_to-1);
    if (filter_id)
    {
        assert(calls > 0);
        patch_le16(loader,lsize,"CT",calls);
    }

    unsigned jmp_pos;
    jmp_pos = find_le16(loader,e_len,get_le16("JM")) - loader;
    patch_le16(loader,e_len,"JM",ph.u_len+overlapoh+2-jmp_pos-2);
    loader[getLoaderSection("SYSSUBSI") - 1] = (upx_byte) -e_len;
    patch_le16(loader,e_len,"DI",copy_to);
    patch_le16(loader,e_len,"SI",ph.c_len+e_len+d_len-1);

    // write loader + compressed file
    fo->write(loader,e_len);            // entry
    fo->write(obuf,ph.c_len);
    fo->write(loader+e_len,d_len);      // decompressor
}


int PackSys::buildLoader(const Filter *ft)
{
    const int filter_id = ft->id;
    initLoader(nrv2b_loader,sizeof(nrv2b_loader));
    addLoader("SYSMAIN1",
              opt->cpu == opt->CPU_8086 ? "SYSI0861" : "SYSI2861",
              "SYSMAIN2""SYSSUBSI",
              filter_id ? "SYSCALLT" : "",
              "SYSMAIN3""UPX1HEAD""SYSCUTPO""NRV2B160""NRVDDONE""NRVDECO1",
              ph.max_offset_found <= 0xd00 ? "NRVLED00" : "NRVGTD00",
              "NRVDECO2""NRV2B169",
              NULL
             );
    if (filter_id)
        addFilter16(filter_id);
    addLoader("SYSMAIN5",
              opt->cpu == opt->CPU_8086 ? "SYSI0862" : "SYSI2862",
              "SYSJUMP1",
              NULL
             );
    return getLoaderSize();
}


/*
vi:ts=4:et
*/