basecode.h

// 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);
		BaseN_Encoder::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);
		BaseN_Decoder::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);
		Grouper::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