tbits.cpp

研读AxCrypt对加解密的处理方法

/*! \file
    \brief Implementation of AxPipe::Stock::TBits

    @(#) $Id: TBits.cpp,v 1.2 2004/01/01 20:05:54 svante Exp $

    AxPipe - Binary Stream Framework

    Copyright (C) 2003 Svante Seleborg/Axon Data, All rights reserved.

    This program is free software; you can redistribute it and/or modify it 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;
    if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
    Boston, MA 02111-1307 USA

    The author may be reached at mailto:[e-mail] and http://axpipe.sourceforge.net

    Why is this framework released as GPL and not LGPL? See http://www.gnu.org/philosophy/why-not-lgpl.html

----
\verbatim
    E-mail                          YYYY-MM-DD              Reason
    [e-mail]              2003-12-15              Initial
\endverbatim
*/
#include "stdafx.h"
#include "TBits.h"

// Can't use this for convenient notation below:
// using AxPipe::Stock::TBits;
// because the Doxygen get's confused.

namespace AxPipe {
    namespace Stock {

        // Instantiate explicitly to generate code for supported bit-lengths.
        template TBits<128>;                ///< 128-bit instantiation of bit-block
        template TBits<160>;                ///< 160-bit instantiation of bit-block
        template TBits<256>;                ///< 256-bit instantiation of bit-block

        /// Zero-initialize
        /// the Bit buffer
        template<int iBits> TBits<iBits>::TBits() {
	        ZeroMemory(m_Bits, sizeof m_Bits);
        }

        /// If shorter, pad on the right, i.e. with the Least
        /// Signifcant Bytes (sic!)
        /// \param bpInit Pointer to a sequence of bytes to initalize with
        /// \param cb Number of bytes in the init sequence (to use)
        template<int iBits> TBits<iBits>::TBits(unsigned char *bpInit, int cb) {
	        ZeroMemory(m_Bits, sizeof m_Bits);
            CopyMemory(m_Bits, bpInit, cb < sizeof m_Bits ? cb : sizeof m_Bits);
        }

        /// Get the left-most n bits. This is actually sort of a dummy function,
        /// as we return a pointer, and the left-most always start at the beginning
        /// of the byte buffer where the bits are.
        /// \param n The number of bits to get.
        /// \return A pointer to the left-most n bits of the buffer.
        template<int iBits> void *
        TBits<iBits>::GetLeft(const int n) {
            return &m_Bits;
        }

        /// Get the right-most n bits. Assume that this is a multiple by 8 value,
        /// otherwise the function fails silently.
        /// \return A pointer to the right-most n bits of the buffer.
        template<int iBits> void *
        TBits<iBits>::GetRight(const int n) {
            return &m_Bits[sizeof m_Bits - n/8];
        }

        /// Arbitrary precision add, endian independent, inefficient...
        /// Note that the byte arrays is presumed to be stored big-endian!
        /// \param rhs A TBits
        /// \return A reference to the destination result, as it should.
        template<int iBits> TBits<iBits>&
        TBits<iBits>::operator += (const TBits<iBits>& rhs) {
            bool bCarry = false;
            for (int i = sizeof m_Bits; i >= 0; i--) {
                bCarry = (m_Bits[i] += rhs.m_Bits[i] + (unsigned char)bCarry) < rhs.m_Bits[i];
            }
            return *this;
        }

        /// Arbitrary precision XOR, inefficient. Don't use if you're in a hurry.
        /// \param rhs A TBits
        /// \return A reference to the destination result, as it should.
        template<int iBits> TBits<iBits>&
        TBits<iBits>::operator ^=(const TBits<iBits>& rhs) {
            size_t cb = sizeof m_Bits;
            unsigned char *dst = m_Bits;
            const unsigned char *src = rhs.m_Bits;
            while (cb--) {
                *dst++ ^= *src++;
            }
            return *this;
        }

        /// Copy-Assign
        /// \param rhs A TBits
        /// \return A reference to the destination result, as it should.
        template<int iBits> TBits<iBits>&
        TBits<iBits>::operator =(const TBits<iBits>& rhs) {
            CopyMemory(&m_Bits, &rhs.m_Bits, sizeof m_Bits);
            return *this;
        }
    }
}