/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/*

 * This file is part of the libqxp project.

 *

 * This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/.

 */

#include "QXP4Deobfuscator.h"

namespace libqxp

{

namespace

{

uint16_t fill(uint16_t value, uint16_t shift, uint16_t mask)

{

  uint16_t r = shift;

  uint16_t v = value;

  while ((v & 1) == 0 && r > 0)

  {

    v >>= 1;

    r--;

  }

  const uint16_t s = shift - r;

  const uint16_t m = (0xffff >> s) << s;

  return (value | m) & mask;

}

uint16_t shift(uint16_t value, uint16_t count)

{

  const uint16_t mask = 0xffff >> (16 - count);

  const uint16_t highinit = value & mask;

  const uint16_t high = fill(highinit | (value >> 15), count, mask) << (16 - count);

  return high | (value >> count);

}

}

QXP4Deobfuscator::QXP4Deobfuscator(uint16_t seed, uint16_t increment)

  : QXPDeobfuscator(seed)

  , m_increment(increment)

{

}

void QXP4Deobfuscator::next(uint16_t block)

{

  m_seed += m_increment;

  m_increment = shift(m_increment, block & 0xf);

}

void QXP4Deobfuscator::nextRev()

{

  m_seed += 0xffff - m_increment;

}

void QXP4Deobfuscator::nextShift(uint16_t count)

{

  m_seed = shift(m_seed, count & 0xf);

}

}

/* vim:set shiftwidth=2 softtabstop=2 expandtab: */