basecode.h

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

/// \file
/// \brief Base classes for working with encoders and decoders.

#ifndef CRYPTOPP_BASECODE_H
#define CRYPTOPP_BASECODE_H

#include "cryptlib.h"
#include "filters.h"
#include "algparam.h"
#include "argnames.h"

NAMESPACE_BEGIN(CryptoPP)

/// \brief Encoder for bases that are a power of 2
class CRYPTOPP_DLL BaseN_Encoder : public Unflushable<Filter>
{
public:
    /// \brief Construct a BaseN_Encoder
    /// \param attachment a BufferedTransformation to attach to this object
    BaseN_Encoder(BufferedTransformation *attachment=NULLPTR)
        : m_alphabet(NULLPTR), m_padding(0), m_bitsPerChar(0)
        , m_outputBlockSize(0), m_bytePos(0), m_bitPos(0)
            {Detach(attachment);}

    /// \brief Construct a BaseN_Encoder
    /// \param alphabet table of ASCII characters to use as the alphabet
    /// \param log2base the log<sub>2</sub>base
    /// \param attachment a BufferedTransformation to attach to this object
    /// \param padding the character to use as padding
    /// \pre log2base must be between 1 and 7 inclusive
    /// \throws InvalidArgument if log2base is not between 1 and 7
    BaseN_Encoder(const byte *alphabet, int log2base, BufferedTransformation *attachment=NULLPTR, int padding=-1)
        : m_alphabet(NULLPTR), m_padding(0), m_bitsPerChar(0)
        , m_outputBlockSize(0), m_bytePos(0), m_bitPos(0)
    {
        Detach(attachment);
        IsolatedInitialize(MakeParameters(Name::EncodingLookupArray(), alphabet)
            (Name::Log2Base(), log2base)
            (Name::Pad(), padding != -1)
            (Name::PaddingByte(), byte(padding)));
    }

    void IsolatedInitialize(const NameValuePairs &parameters);
    size_t Put2(const byte *begin, size_t length, int messageEnd, bool blocking);

private:
    const byte *m_alphabet;
    int m_padding, m_bitsPerChar, m_outputBlockSize;
    int m_bytePos, m_bitPos;
    SecByteBlock m_outBuf;
};

/// \brief Decoder for bases that are a power of 2
class CRYPTOPP_DLL BaseN_Decoder : public Unflushable<Filter>
{
public:
    /// \brief Construct a BaseN_Decoder
    /// \param attachment a BufferedTransformation to attach to this object
    /// \details padding is set to -1, which means use default padding. If not
    ///   required, then the value must be set via IsolatedInitialize().
    BaseN_Decoder(BufferedTransformation *attachment=NULLPTR)
        : m_lookup(NULLPTR), m_bitsPerChar(0)
        , m_outputBlockSize(0), m_bytePos(0), m_bitPos(0)
            {Detach(attachment);}

    /// \brief Construct a BaseN_Decoder
    /// \param lookup table of values
    /// \param log2base the log<sub>2</sub>base
    /// \param attachment a BufferedTransformation to attach to this object
    /// \details log2base is the exponent (like 5 in 2<sup>5</sup>), and not
    ///   the number of elements (like 32).
    /// \details padding is set to -1, which means use default padding. If not
    ///   required, then the value must be set via IsolatedInitialize().
    BaseN_Decoder(const int *lookup, int log2base, BufferedTransformation *attachment=NULLPTR)
        : m_lookup(NULLPTR), m_bitsPerChar(0)
        , m_outputBlockSize(0), m_bytePos(0), m_bitPos(0)
    {
        Detach(attachment);
        IsolatedInitialize(MakeParameters(Name::DecodingLookupArray(), lookup)(Name::Log2Base(), log2base));
    }

    void IsolatedInitialize(const NameValuePairs &parameters);
    size_t Put2(const byte *begin, size_t length, int messageEnd, bool blocking);

    /// \brief Initializes BaseN lookup array
    /// \param lookup table of values
    /// \param alphabet table of ASCII characters
    /// \param base the base for the encoder
    /// \param caseInsensitive flag indicating whether the alphabet is case sensitivie
    /// \pre COUNTOF(lookup) == 256
    /// \pre COUNTOF(alphabet) == base
    /// \details Internally, the function sets the first 256 elements in the lookup table to
    ///  their value from the alphabet array or -1. base is the number of element (like 32),
    ///  and not an exponent (like 5 in 2<sup>5</sup>)
    static void CRYPTOPP_API InitializeDecodingLookupArray(int *lookup, const byte *alphabet, unsigned int base, bool caseInsensitive);

private:
    const int *m_lookup;
    int m_bitsPerChar, m_outputBlockSize;
    int m_bytePos, m_bitPos;
    SecByteBlock m_outBuf;
};

/// \brief Filter that breaks input stream into groups of fixed size
class CRYPTOPP_DLL Grouper : public Bufferless<Filter>
{
public:
    /// \brief Construct a Grouper
    /// \param attachment a BufferedTransformation to attach to this object
    Grouper(BufferedTransformation *attachment=NULLPTR)
        : m_groupSize(0), m_counter(0) {Detach(attachment);}

    /// \brief Construct a Grouper
    /// \param groupSize the size of the grouping
    /// \param separator the separator to use between groups
    /// \param terminator the terminator appeand after processing
    /// \param attachment a BufferedTransformation to attach to this object
    Grouper(int groupSize, const std::string &separator, const std::string &terminator, BufferedTransformation *attachment=NULLPTR)
        : m_groupSize(0), m_counter(0)
    {
        Detach(attachment);
        IsolatedInitialize(MakeParameters(Name::GroupSize(), groupSize)
            (Name::Separator(), ConstByteArrayParameter(separator))
            (Name::Terminator(), ConstByteArrayParameter(terminator)));
    }

    void IsolatedInitialize(const NameValuePairs &parameters);
    size_t Put2(const byte *begin, size_t length, int messageEnd, bool blocking);

private:
    SecByteBlock m_separator, m_terminator;
    size_t m_groupSize, m_counter;
};

NAMESPACE_END

#endif