/*********************************************************************/
// dar - disk archive - a backup/restoration program
// Copyright (C) 2002-2022 Denis Corbin
//
// 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
//
// to contact the author, see the AUTHOR file
/*********************************************************************/

    /// \file real_infinint.hpp
    /// \brief the original infinint class implementation
    /// \ingroup API
    ///
    /// the infinint class implementation defined in this module can
    /// handle arbitrary large positive integer numbers

#ifndef REAL_INFININT_HPP
#define REAL_INFININT_HPP

#include "../my_config.h"

extern "C"
{
#if HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
} // end extern "C"

#include <typeinfo>

#include "integers.hpp"
#include "int_tools.hpp"
#include "proto_generic_file.hpp"
#include "storage.hpp"

#define ZEROED_SIZE 50

namespace libdar
{
	/// \addtogroup API
        /// @{

	/// the arbitrary large positive integer class

	/// can only handle positive integer numbers
	/// \note if you just want to convert an infinint
	/// integer to its decimal representation see the
	/// class libdar::deci
    class infinint
    {
    public :

#if SIZEOF_OFF_T > SIZEOF_TIME_T
#if SIZEOF_OFF_T > SIZEOF_SIZE_T
        infinint(off_t a = 0) { infinint_from(a); };
#else
        infinint(size_t a = 0) { infinint_from(a); };
#endif
#else
#if SIZEOF_TIME_T > SIZEOF_SIZE_T
        infinint(time_t a = 0) { infinint_from(a); };
#else
        infinint(size_t a = 0) { infinint_from(a); };
#endif
#endif
	    /// read an infinint from a file
	infinint(proto_generic_file & x);

        infinint(const infinint & ref) { copy_from(ref); }
	infinint(infinint && ref) noexcept { field = nullptr; move_from(std::move(ref)); };

	infinint & operator = (const infinint & ref) { detruit(); copy_from(ref); return *this; };
	infinint & operator = (infinint && ref) noexcept { move_from(std::move(ref)); return *this; }

        ~infinint() { detruit(); };

        void dump(proto_generic_file &x) const; // write byte sequence to file
        void read(proto_generic_file &f) { detruit(); build_from_file(f); };

        infinint & operator += (const infinint & ref);
        infinint & operator -= (const infinint & ref);
        infinint & operator *= (unsigned char arg);
        infinint & operator *= (const infinint & ref);
	template <class T> infinint power(const T & exponent) const;
        inline infinint & operator /= (const infinint & ref);
        inline infinint & operator %= (const infinint & ref);
	infinint & operator &= (const infinint & ref);
	infinint & operator |= (const infinint & ref);
	infinint & operator ^= (const infinint & ref);
        infinint & operator >>= (U_32 bit);
        infinint & operator >>= (infinint bit);
        infinint & operator <<= (U_32 bit);
        infinint & operator <<= (infinint bit);
        infinint operator ++(int a)
	{ infinint ret = *this; ++(*this); return ret; };
        infinint operator --(int a)
	{ infinint ret = *this; --(*this); return ret; };
        infinint & operator ++()
	{ return *this += 1; };
        infinint & operator --()
	{ return *this -= 1; };

        U_32 operator % (U_32 arg) const
	{ return modulo(arg); };

	    /// convert infinint to standard interger types

            /// \note increment the argument up to a legal value for
	    /// its storage type and decrement the object in consequence
            /// note that the initial value of the argument is not ignored!
            /// when the object is null the value of the argument is unchanged
        template <class T>void unstack(T &v)
	{ infinint_unstack_to(v); }

	    /// it returns number of byte of information necessary to store the integer
	infinint get_storage_size() const noexcept { return field->size(); };

	    /// return in little endian order the information byte storing the integer
	unsigned char operator [] (const infinint & position) const;

	    /// \return true when the object is zero (more efficient than integer comparison)
	bool is_zero() const;

        friend bool operator < (const infinint &, const infinint &);
        friend bool operator == (const infinint &, const infinint &);
        friend bool operator > (const infinint &, const infinint &);
        friend bool operator <= (const infinint &, const infinint &);
        friend bool operator != (const infinint &, const infinint &);
        friend bool operator >= (const infinint &, const infinint &);
        friend void euclide(infinint a, const infinint &b, infinint &q, infinint &r);

	static bool is_system_big_endian();

    private :
        static constexpr int TG = 4;

        enum endian { big_endian, little_endian, not_initialized };
	using group = unsigned char[TG];

        storage *field;

        bool is_valid() const noexcept;
        void build_from_file(proto_generic_file & x);
        void reduce(); // put the object in canonical form : no leading byte equal to zero
        void copy_from(const infinint & ref);
	void move_from(infinint && ref) noexcept { std::swap(field, ref.field); };
        void detruit();
        void make_at_least_as_wider_as(const infinint & ref);
        template <class T> void infinint_from(T a);
	template <class T> T max_val_of(T x);
        template <class T> void infinint_unstack_to(T &a);
        template <class T> T modulo(T arg) const;
        signed int difference(const infinint & b) const; // gives the sign of (*this - arg) but only the sign !

            /////////////////////////
            // static statments
            //
        static endian used_endian;
	static U_8 zeroed_field[ZEROED_SIZE];
        static void setup_endian();
    };


#define OPERATOR(OP) inline bool operator OP (const infinint &a, const infinint &b) \
    {									\
	return a.difference(b) OP 0;					\
    }

    OPERATOR(<)
    OPERATOR(>)
    OPERATOR(<=)
    OPERATOR(>=)
    OPERATOR(==)
    OPERATOR(!=)

    infinint operator + (const infinint &, const infinint &);
    infinint operator - (const infinint &, const infinint &);
    infinint operator * (const infinint &, const infinint &);
    infinint operator * (const infinint &, const unsigned char);
    infinint operator * (const unsigned char, const infinint &);
    infinint operator / (const infinint &, const infinint &);
    infinint operator % (const infinint &, const infinint &);
    infinint operator & (const infinint & a, const infinint & bit);
    infinint operator | (const infinint & a, const infinint & bit);
    infinint operator ^ (const infinint & a, const infinint & bit);
    infinint operator >> (const infinint & a, U_32 bit);
    infinint operator >> (const infinint & a, const infinint & bit);
    infinint operator << (const infinint & a, U_32 bit);
    infinint operator << (const infinint & a, const infinint & bit);
    void euclide(infinint a, const infinint &b, infinint &q, infinint &r);
    template <class T> inline void euclide(T a, T b, T & q, T &r)
    {
	q = a/b; r = a%b;
    }

    inline infinint & infinint::operator /= (const infinint & ref)
    {
	*this = *this / ref;
        return *this;
    }

    inline infinint & infinint::operator %= (const infinint & ref)
    {
	*this = *this % ref;
        return *this;
    }


	/////////////////////////////////////////////////////
	///////////////// TEMPLATE BODIES ///////////////////
	/////////////////////////////////////////////////////

    template <class T> infinint infinint::power(const T & exponent) const
    {
	infinint ret = 1;
	for(T count = 0; count < exponent; ++count)
	    ret *= *this;

	return ret;
    }

    template <class T> T infinint::modulo(T arg) const
    {
	infinint tmp = *this % infinint(arg);
        T ret = 0;
        unsigned char *debut = (unsigned char *)(&ret);
        unsigned char *ptr = debut + sizeof(T) - 1;
        storage::iterator it = tmp.field->rbegin();

        while(it != tmp.field->rend() && ptr >= debut)
	{
            *ptr = *it;
            --ptr;
            --it;
        }

	    // checking for overflow (should never occur, but for sanity, we check it anyway)

	while(it != tmp.field->rend()) // field may not be reduced (some zeros are leading)
	{
	    if(*it != 0)
		throw SRC_BUG; // could not put all the data in the returned value !
	    --it;
	}

        if(used_endian == little_endian)
            int_tools_swap_bytes(debut, sizeof(T));

        return ret;
    }


    template <class T> void infinint::infinint_from(T a)
    {
        U_I size = sizeof(a);
        S_I direction = +1;
        unsigned char *ptr, *fin;

        if(used_endian == not_initialized)
            setup_endian();

        if(used_endian == little_endian)
        {
            direction = -1;
            ptr = (unsigned char *)(&a) + (size - 1);
            fin = (unsigned char *)(&a) - 1;
        }
        else
        {
            direction = +1;
            ptr = (unsigned char *)(&a);
            fin = (unsigned char *)(&a) + size;
        }

        while(ptr != fin && *ptr == 0)
        {
            ptr += direction;
            --size;
        }

        if(size == 0)
        {
            size = 1;
            ptr -= direction;
        }

        field = new (std::nothrow) storage(size);
        if(field != nullptr)
        {
            storage::iterator it = field->begin();

            while(ptr != fin)
            {
                *it = *ptr;
                ++it;
                ptr += direction;
            }
            if(it != field->end())
                throw SRC_BUG; // size mismatch in this algorithm
        }
        else
            throw Ememory("template infinint::infinint_from");
    }

    template <class T> T infinint::max_val_of(T x)
    {
	x = 0;
	x = ~x;

	if(x <= 0) // T is a signed integer type. Note that it should be "x < 0" but to avoid compiler warning when T is unsigned it does not hurt having "x <= 0" here
	{
	    x = 1;
	    x = int_tools_rotate_right_one_bit(x);
	    x = ~x;
	}

	return x;
    }

    template <class T> void infinint::infinint_unstack_to(T & a)
    {
	    // T is supposed to be an unsigned "integer"
	    // (ie.: sizeof() returns the width of the storage bit field  and no sign bit is present)
	    // Note : static here avoids the recalculation of max_T at each call
	static const T max_T = max_val_of(a);
        infinint step = max_T - a;

        if(*this < step)
        {
            T transfert = 0;
            unsigned char *debut = (unsigned char *)&transfert;
            unsigned char *ptr = debut + sizeof(transfert) - 1;
            storage::iterator it = field->rbegin();

            while(ptr >= debut && it != field->rend())
            {
                *ptr = *it;
                --ptr;
                --it;
	    }

            if(used_endian == little_endian)
                int_tools_swap_bytes(debut, sizeof(transfert));
            a += transfert;
            *this -= *this;
        }
        else
        {
            *this -= step;
            a = max_T;
        }
    }

} // end of namespace

#endif
