basecode.cpp

// basecode.cpp - originally written and placed in the public domain by Wei Dai

#include "pch.h"
#include "config.h"

#ifndef CRYPTOPP_IMPORTS

#include "basecode.h"
#include "fltrimpl.h"
#include <ctype.h>

NAMESPACE_BEGIN(CryptoPP)

void BaseN_Encoder::IsolatedInitialize(const NameValuePairs &parameters)
{
    parameters.GetRequiredParameter("BaseN_Encoder", Name::EncodingLookupArray(), m_alphabet);

    parameters.GetRequiredIntParameter("BaseN_Encoder", Name::Log2Base(), m_bitsPerChar);
    if (m_bitsPerChar <= 0 || m_bitsPerChar >= 8)
        throw InvalidArgument("BaseN_Encoder: Log2Base must be between 1 and 7 inclusive");

    byte padding;
    bool pad;
    if (parameters.GetValue(Name::PaddingByte(), padding))
        pad = parameters.GetValueWithDefault(Name::Pad(), true);
    else
        pad = false;
    m_padding = pad ? padding : -1;

    m_bytePos = m_bitPos = 0;

    int i = 8;
    while (i%m_bitsPerChar != 0)
        i += 8;
    m_outputBlockSize = i/m_bitsPerChar;

    m_outBuf.New(m_outputBlockSize);
}

size_t BaseN_Encoder::Put2(const byte *begin, size_t length, int messageEnd, bool blocking)
{
    FILTER_BEGIN;
    while (m_inputPosition < length)
    {
        if (m_bytePos == 0)
            std::memset(m_outBuf, 0, m_outputBlockSize);

        {
        unsigned int b = begin[m_inputPosition++], bitsLeftInSource = 8;
        while (true)
        {
            CRYPTOPP_ASSERT(m_bitsPerChar-m_bitPos >= 0);
            unsigned int bitsLeftInTarget = (unsigned int)(m_bitsPerChar-m_bitPos);
            m_outBuf[m_bytePos] |= b >> (8-bitsLeftInTarget);
            if (bitsLeftInSource >= bitsLeftInTarget)
            {
                m_bitPos = 0;
                ++m_bytePos;
                bitsLeftInSource -= bitsLeftInTarget;
                if (bitsLeftInSource == 0)
                    break;
                b <<= bitsLeftInTarget;
                b &= 0xff;
            }
            else
            {
                m_bitPos += bitsLeftInSource;
                break;
            }
        }
        }

        CRYPTOPP_ASSERT(m_bytePos <= m_outputBlockSize);
        if (m_bytePos == m_outputBlockSize)
        {
            int i;
            for (i=0; i<m_bytePos; i++)
            {
                CRYPTOPP_ASSERT(m_outBuf[i] < (1 << m_bitsPerChar));
                m_outBuf[i] = m_alphabet[m_outBuf[i]];
            }
            FILTER_OUTPUT(1, m_outBuf, m_outputBlockSize, 0);

            m_bytePos = m_bitPos = 0;
        }
    }
    if (messageEnd)
    {
        if (m_bitPos > 0)
            ++m_bytePos;

        int i;
        for (i=0; i<m_bytePos; i++)
            m_outBuf[i] = m_alphabet[m_outBuf[i]];

        if (m_padding != -1 && m_bytePos > 0)
        {
            std::memset(m_outBuf+m_bytePos, m_padding, m_outputBlockSize-m_bytePos);
            m_bytePos = m_outputBlockSize;
        }
        FILTER_OUTPUT(2, m_outBuf, m_bytePos, messageEnd);
        m_bytePos = m_bitPos = 0;
    }
    FILTER_END_NO_MESSAGE_END;
}

void BaseN_Decoder::IsolatedInitialize(const NameValuePairs &parameters)
{
    parameters.GetRequiredParameter("BaseN_Decoder", Name::DecodingLookupArray(), m_lookup);

    parameters.GetRequiredIntParameter("BaseN_Decoder", Name::Log2Base(), m_bitsPerChar);
    if (m_bitsPerChar <= 0 || m_bitsPerChar >= 8)
        throw InvalidArgument("BaseN_Decoder: Log2Base must be between 1 and 7 inclusive");

    m_bytePos = m_bitPos = 0;

    int i = m_bitsPerChar;
    while (i%8 != 0)
        i += m_bitsPerChar;
    m_outputBlockSize = i/8;

    m_outBuf.New(m_outputBlockSize);
}

size_t BaseN_Decoder::Put2(const byte *begin, size_t length, int messageEnd, bool blocking)
{
    FILTER_BEGIN;
    while (m_inputPosition < length)
    {
        unsigned int value;
        value = m_lookup[begin[m_inputPosition++]];
        if (value >= 256)
            continue;

        if (m_bytePos == 0 && m_bitPos == 0)
            std::memset(m_outBuf, 0, m_outputBlockSize);

        {
            int newBitPos = m_bitPos + m_bitsPerChar;
            if (newBitPos <= 8)
                m_outBuf[m_bytePos] |= value << (8-newBitPos);
            else
            {
                m_outBuf[m_bytePos] |= value >> (newBitPos-8);
                m_outBuf[m_bytePos+1] |= value << (16-newBitPos);
            }

            m_bitPos = newBitPos;
            while (m_bitPos >= 8)
            {
                m_bitPos -= 8;
                ++m_bytePos;
            }
        }

        if (m_bytePos == m_outputBlockSize)
        {
            FILTER_OUTPUT(1, m_outBuf, m_outputBlockSize, 0);
            m_bytePos = m_bitPos = 0;
        }
    }
    if (messageEnd)
    {
        FILTER_OUTPUT(2, m_outBuf, m_bytePos, messageEnd);
        m_bytePos = m_bitPos = 0;
    }
    FILTER_END_NO_MESSAGE_END;
}

void BaseN_Decoder::InitializeDecodingLookupArray(int *lookup, const byte *alphabet, unsigned int base, bool caseInsensitive)
{
    std::fill(lookup, lookup+256, -1);

    for (unsigned int i=0; i<base; i++)
    {
        // Debug asserts for 'lookup[alphabet[i]] == -1' removed because the self tests
        // have unusual tests that try to break the encoders and decoders. Tests include
        // a string of the same characters. I.,e., a string of stars like '********...'.
        if (caseInsensitive && isalpha(alphabet[i]))
        {
            lookup[toupper(alphabet[i])] = i;
            lookup[tolower(alphabet[i])] = i;
        }
        else
        {
            lookup[alphabet[i]] = i;
        }
    }
}

void Grouper::IsolatedInitialize(const NameValuePairs &parameters)
{
    m_groupSize = parameters.GetIntValueWithDefault(Name::GroupSize(), 0);
    ConstByteArrayParameter separator, terminator;
    if (m_groupSize)
        parameters.GetRequiredParameter("Grouper", Name::Separator(), separator);
    else
        parameters.GetValue(Name::Separator(), separator);
    parameters.GetValue(Name::Terminator(), terminator);

    m_separator.Assign(separator.begin(), separator.size());
    m_terminator.Assign(terminator.begin(), terminator.size());
    m_counter = 0;
}

size_t Grouper::Put2(const byte *begin, size_t length, int messageEnd, bool blocking)
{
    FILTER_BEGIN;
    if (m_groupSize)
    {
        while (m_inputPosition < length)
        {
            if (m_counter == m_groupSize)
            {
                FILTER_OUTPUT(1, m_separator, m_separator.size(), 0);
                m_counter = 0;
            }

            size_t len;
            FILTER_OUTPUT2(2, (len = STDMIN(length-m_inputPosition, m_groupSize-m_counter)),
                begin+m_inputPosition, len, 0);
            m_inputPosition += len;
            m_counter += len;
        }
    }
    else
        FILTER_OUTPUT(3, begin, length, 0);

    if (messageEnd)
    {
        FILTER_OUTPUT(4, m_terminator, m_terminator.size(), messageEnd);
        m_counter = 0;
    }
    FILTER_END_NO_MESSAGE_END
}

NAMESPACE_END

#endif