/* p_sys.cpp -- dos/sys executable format

   This file is part of the UPX executable compressor.

   Copyright (C) Markus Franz Xaver Johannes Oberhumer
   Copyright (C) Laszlo Molnar
   All Rights Reserved.

   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.com>               <ezerotven+github@gmail.com>
 */

#include "conf.h"
#include "file.h"
#include "filter.h"
#include "packer.h"
#include "p_com.h"
#include "p_sys.h"
#define WANT_EHDR_ENUM 1
#include "p_elf_enum.h"
#include "linker.h"

static const CLANG_FORMAT_DUMMY_STATEMENT
#include "stub/i086-dos16.sys.h"

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

tribool PackSys::canPack() {
    byte buf[128];

    fi->readx(buf, sizeof(buf));
    if (memcmp(buf, "\xff\xff\xff\xff", 4) != 0)
        return false;
    if (!fn_has_ext(fi->getName(), "sys")) // query file name
        return false;
    checkAlreadyPacked(buf, sizeof(buf));
    if (file_size < 1024)
        throwCantPack("file is too small for dos/sys");
    if (file_size > 0x10000)
        throwCantPack("file is too large for dos/sys");
    return true;
}

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

void PackSys::buildLoader(const Filter *ft) {
    initLoader(EM_386, stub_i086_dos16_sys, sizeof(stub_i086_dos16_sys));
    // clang-format off
    addLoader("SYSMAIN1",
              opt->cpu_x86 == opt->CPU_8086 ? "SYSI0861" : "SYSI2861",
              "SYSMAIN2",
              ph.first_offset_found == 1 ? "SYSSBBBP" : "",
              ft->id ? "SYSCALLT" : "",
              "SYSMAIN3,UPX1HEAD,SYSCUTPO,NRV2B160,NRVDDONE,NRVDECO1",
              ph.max_offset_found <= 0xd00 ? "NRVLED00" : "NRVGTD00",
              "NRVDECO2");
    // clang-format on
    if (ft->id) {
        assert(ft->calls > 0);
        addFilter16(ft->id);
    }
    // clang-format off
    addLoader("SYSMAIN5",
              opt->cpu_x86 == opt->CPU_8086 ? "SYSI0862" : "SYSI2862",
              "SYSJUMP1");
    // clang-format on
}

void PackSys::patchLoader(OutputFile *fo, byte *loader, int lsize, unsigned calls) {
    const int e_len = getLoaderSectionStart("SYSCUTPO");
    const int d_len = lsize - e_len;
    assert(e_len > 0 && e_len < 128);
    assert(d_len > 0 && d_len < 256);

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

    // use some fields of the original file
    linker->defineSymbol("attribute", get_le16(ibuf + 4));
    linker->defineSymbol("interrupt", get_le16(ibuf + 8));

    unsigned copy_to = ph.u_len + d_len + ph.overlap_overhead;

    linker->defineSymbol("calltrick_calls", calls);
    linker->defineSymbol("copy_source", ph.c_len + lsize - 1);
    linker->defineSymbol("copy_destination", copy_to);
    linker->defineSymbol("neg_e_len", 0 - e_len);
    linker->defineSymbol("NRV2B160", ph.u_len + ph.overlap_overhead + 1);
    linker->defineSymbol("original_strategy", get_le16(ibuf + 6));

    relocateLoader();
    loader = getLoader();

    // some day we could use the relocation stuff for patchPackHeader too..
    patchPackHeader(loader, e_len);
    // write loader + compressed file
    fo->write(loader, e_len);         // entry
    fo->write(obuf, ph.c_len);        // compressed
    fo->write(loader + e_len, d_len); // decompressor
    NO_printf("%-13s: entry        : %8u bytes\n", getName(), e_len);
    NO_printf("%-13s: compressed   : %8u bytes\n", getName(), ph.c_len);
    NO_printf("%-13s: decompressor : %8u bytes\n", getName(), d_len);
}

/* vim:set ts=4 sw=4 et: */
