/** @file utils.h
 *
 *  Interface to several small and furry utilities needed within GiNaC but not
 *  of any interest to the user of the library. */

/*
 *  GiNaC Copyright (C) 1999-2011 Johannes Gutenberg University Mainz, Germany
 *
 *  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
 */

#ifndef GINAC_UTILS_H
#define GINAC_UTILS_H

#include "assertion.h"
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <functional>
#ifdef HAVE_STDINT_H
#include <stdint.h> // for uintptr_t
#endif
#include <string>

namespace GiNaC {

/** Exception class thrown by functions to signal unimplemented functionality
 *  so the expression may just be .hold() */
class dunno {};

// some compilers (e.g. cygwin) define a macro log2, causing confusion
#ifdef log2
#undef log2
#endif

unsigned log2(unsigned n);

/** Rotate bits of unsigned value by one bit to the left.
  * This can be necesary if the user wants to define its own hashes. */
inline unsigned rotate_left(unsigned n)
{
	return (n & 0x80000000U) ? (n << 1 | 0x00000001U) : (n << 1);
}

/** Compare two pointers (just to establish some sort of canonical order).
 *  @return -1, 0, or 1 */
template <class T>
inline int compare_pointers(const T * a, const T * b)
{
	// '<' is not defined for pointers that don't point to the same array,
	// but std::less is.
	if (std::less<const T *>()(a, b))
		return -1;
	else if (std::less<const T *>()(b, a))
		return 1;
	return 0;
}

#ifdef HAVE_STDINT_H
typedef uintptr_t p_int;
#else
typedef unsigned long p_int;
#endif

/** Truncated multiplication with golden ratio, for computing hash values. */
inline unsigned golden_ratio_hash(p_int n)
{
	// This function works much better when fast arithmetic with at
	// least 64 significant bits is available.
	if (sizeof(long) >= 8) {
	// So 'long' has 64 bits.  Excellent!  We prefer it because it might be
	// more efficient than 'long long'.
	unsigned long l = n * 0x4f1bbcddUL;
	return (unsigned)l;
	}
#ifdef HAVE_LONG_LONG
	else if (sizeof(long long) >= 8) {
	// This requires 'long long' (or an equivalent 64 bit type)---which is,
	// unfortunately, not ANSI-C++-compliant.
	// (Yet C99 demands it, which is reason for hope.)
	unsigned long long l = n * 0x4f1bbcddULL;
	return (unsigned)l;
	}
#endif
	// Without a type with 64 significant bits do the multiplication manually
	// by splitting n up into the lower and upper two bytes.
	const unsigned n0 = (n & 0x0000ffffU);
	const unsigned n1 = (n & 0xffff0000U) >> 16;
	return (n0 * 0x0000bcddU) + ((n1 * 0x0000bcddU + n0 * 0x00004f1bU) << 16);
}

/* Compute the sign of a permutation of a container, with and without an
   explicitly supplied comparison function. If the sign returned is 1 or -1,
   the container is sorted after the operation. */
template <class It>
int permutation_sign(It first, It last)
{
	if (first == last)
		return 0;
	--last;
	if (first == last)
		return 0;
	It flag = first;
	int sign = 1;

	do {
		It i = last, other = last;
		--other;
		bool swapped = false;
		while (i != first) {
			if (*i < *other) {
				std::iter_swap(other, i);
				flag = other;
				swapped = true;
				sign = -sign;
			} else if (!(*other < *i))
				return 0;
			--i;
			if (i != first)
				--other;
		}
		if (!swapped)
			return sign;
		++flag;
		if (flag == last)
			return sign;
		first = flag;
		i = first; other = first;
		++other;
		swapped = false;
		while (i != last) {
			if (*other < *i) {
				std::iter_swap(i, other);
				flag = other;
				swapped = true;
				sign = -sign;
			} else if (!(*i < *other))
				return 0;
			++i;
			if (i != last)
				++other;
		}
		if (!swapped)
			return sign;
		last = flag;
		--last;
	} while (first != last);

	return sign;
}

template <class It, class Cmp, class Swap>
int permutation_sign(It first, It last, Cmp comp, Swap swapit)
{
	if (first == last)
		return 0;
	--last;
	if (first == last)
		return 0;
	It flag = first;
	int sign = 1;

	do {
		It i = last, other = last;
		--other;
		bool swapped = false;
		while (i != first) {
			if (comp(*i, *other)) {
				swapit(*other, *i);
				flag = other;
				swapped = true;
				sign = -sign;
			} else if (!comp(*other, *i))
				return 0;
			--i;
			if (i != first)
				--other;
		}
		if (!swapped)
			return sign;
		++flag;
		if (flag == last)
			return sign;
		first = flag;
		i = first; other = first;
		++other;
		swapped = false;
		while (i != last) {
			if (comp(*other, *i)) {
				swapit(*i, *other);
				flag = other;
				swapped = true;
				sign = -sign;
			} else if (!comp(*i, *other))
				return 0;
			++i; 
			if (i != last)
				++other;
		}
		if (!swapped)
			return sign;
		last = flag;
		--last;
	} while (first != last);

	return sign;
}

/* Implementation of shaker sort, only compares adjacent elements. */
template <class It, class Cmp, class Swap>
void shaker_sort(It first, It last, Cmp comp, Swap swapit)
{
	if (first == last)
		return;
	--last;
	if (first == last)
		return;
	It flag = first;

	do {
		It i = last, other = last;
		--other;
		bool swapped = false;
		while (i != first) {
			if (comp(*i, *other)) {
				swapit(*other, *i);
				flag = other;
				swapped = true;
			}
			--i;
			if (i != first)
				--other;
		}
		if (!swapped)
			return;
		++flag;
		if (flag == last)
			return;
		first = flag;
		i = first; other = first;
		++other;
		swapped = false;
		while (i != last) {
			if (comp(*other, *i)) {
				swapit(*i, *other);
				flag = other;
				swapped = true;
			}
			++i;
			if (i != last)
				++other;
		}
		if (!swapped)
			return;
		last = flag;
		--last;
	} while (first != last);
}

/* In-place cyclic permutation of a container (no copying, only swapping). */
template <class It, class Swap>
void cyclic_permutation(It first, It last, It new_first, Swap swapit)
{
	unsigned num = last - first;
again:
	if (first == new_first || num < 2)
		return;

	unsigned num1 = new_first - first, num2 = last - new_first;
	if (num1 >= num2) {
		It a = first, b = new_first;
		while (b != last) {
			swapit(*a, *b);
			++a; ++b;
		}
		if (num1 > num2) {
			first += num2;
			num = num1;
			goto again;
		}
	} else {
		It a = new_first, b = last;
		do {
			--a; --b;
			swapit(*a, *b);
		} while (a != first);
		last -= num1;
		num = num2;
		goto again;
	}
}


// Collection of `construct on first use' wrappers for safely avoiding
// internal object replication without running into the `static
// initialization order fiasco'.  This chest of numbers helps speed up
// the library but should not be used outside it since it is
// potentially confusing.

class ex;

extern const numeric *_num_120_p;
extern const ex _ex_120;
extern const numeric *_num_60_p;
extern const ex _ex_60;
extern const numeric *_num_48_p;
extern const ex _ex_48;
extern const numeric *_num_30_p;
extern const ex _ex_30;
extern const numeric *_num_25_p;
extern const ex _ex_25;
extern const numeric *_num_24_p;
extern const ex _ex_24;
extern const numeric *_num_20_p;
extern const ex _ex_20;
extern const numeric *_num_18_p;
extern const ex _ex_18;
extern const numeric *_num_15_p;
extern const ex _ex_15;
extern const numeric *_num_12_p;
extern const ex _ex_12;
extern const numeric *_num_11_p;
extern const ex _ex_11;
extern const numeric *_num_10_p;
extern const ex _ex_10;
extern const numeric *_num_9_p;
extern const ex _ex_9;
extern const numeric *_num_8_p;
extern const ex _ex_8;
extern const numeric *_num_7_p;
extern const ex _ex_7;
extern const numeric *_num_6_p;
extern const ex _ex_6;
extern const numeric *_num_5_p;
extern const ex _ex_5;
extern const numeric *_num_4_p;
extern const ex _ex_4;
extern const numeric *_num_3_p;
extern const ex _ex_3;
extern const numeric *_num_2_p;
extern const ex _ex_2;
extern const numeric *_num_1_p;
extern const ex _ex_1;
extern const numeric *_num_1_2_p;
extern const ex _ex_1_2;
extern const numeric *_num_1_3_p;
extern const ex _ex_1_3;
extern const numeric *_num_1_4_p;
extern const ex _ex_1_4;
extern const numeric *_num0_p;
extern const basic *_num0_bp;
extern const ex _ex0;
extern const numeric *_num1_4_p;
extern const ex _ex1_4;
extern const numeric *_num1_3_p;
extern const ex _ex1_3;
extern const numeric *_num1_2_p;
extern const ex _ex1_2;
extern const numeric *_num1_p;
extern const ex _ex1;
extern const numeric *_num2_p;
extern const ex _ex2;
extern const numeric *_num3_p;
extern const ex _ex3;
extern const numeric *_num4_p;
extern const ex _ex4;
extern const numeric *_num5_p;
extern const ex _ex5;
extern const numeric *_num6_p;
extern const ex _ex6;
extern const numeric *_num7_p;
extern const ex _ex7;
extern const numeric *_num8_p;
extern const ex _ex8;
extern const numeric *_num9_p;
extern const ex _ex9;
extern const numeric *_num10_p;
extern const ex _ex10;
extern const numeric *_num11_p;
extern const ex _ex11;
extern const numeric *_num12_p;
extern const ex _ex12;
extern const numeric *_num15_p;
extern const ex _ex15;
extern const numeric *_num18_p;
extern const ex _ex18;
extern const numeric *_num20_p;
extern const ex _ex20;
extern const numeric *_num24_p;
extern const ex _ex24;
extern const numeric *_num25_p;
extern const ex _ex25;
extern const numeric *_num30_p;
extern const ex _ex30;
extern const numeric *_num48_p;
extern const ex _ex48;
extern const numeric *_num60_p;
extern const ex _ex60;
extern const numeric *_num120_p;
extern const ex _ex120;


// Helper macros for class implementations (mostly useful for trivial classes)

#define DEFAULT_CTOR(classname) \
classname::classname() { setflag(status_flags::evaluated | status_flags::expanded); }

#define DEFAULT_COMPARE(classname) \
int classname::compare_same_type(const basic & other) const \
{ \
	/* by default, the objects are always identical */ \
	return 0; \
}

#define DEFAULT_PRINT(classname, text) \
void classname::do_print(const print_context & c, unsigned level) const \
{ \
	c.s << text; \
}

#define DEFAULT_PRINT_LATEX(classname, text, latex) \
DEFAULT_PRINT(classname, text) \
void classname::do_print_latex(const print_latex & c, unsigned level) const \
{ \
	c.s << latex; \
}

} // namespace GiNaC

#endif // ndef GINAC_UTILS_H