source: git/src-cryptopp/basecode.h

// basecode.h - 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)

//! \class BaseN_Encoder
//! \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=NULL)
                : m_alphabet(NULL), 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=NULL, int padding=-1)
                : m_alphabet(NULL), 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;
};

//! \class BaseN_Decoder
//! \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=NULL)
                : m_lookup(0), m_padding(0), 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=NULL)
                : m_lookup(0), m_padding(0), 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 Intializes 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 alpabet 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_padding, m_bitsPerChar, m_outputBlockSize;
        int m_bytePos, m_bitPos;
        SecByteBlock m_outBuf;
};

//! \class Grouper
//! \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=NULL)
                : 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=NULL)
                : 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