util.hpp

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/*
   Copyright (C) 2003 - 2016 by David White <[email protected]>
   Part of the Battle for Wesnoth Project http://www.wesnoth.org/

   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.

   See the COPYING file for more details.
*/

/**
 *  @file
 *  Templates and utility-routines for strings and numbers.
 */

#ifndef UTIL_H_INCLUDED
#define UTIL_H_INCLUDED

#include "global.hpp"
#include <cmath>
#include <cstddef>
#include <cstdint>
#include <limits>
#include <math.h> // cmath may not provide round()
#include <vector>
#include <sstream>
#include <algorithm>

template<typename T>
inline bool is_even(T num) { return num % 2 == 0; }

template<typename T>
inline bool is_odd(T num) { return !is_even(num); }

/**
 * Returns base + increment, but will not increase base above max_sum, nor
 * decrease it below min_sum.
 * (If base is already beyond the applicable limit, base will be returned.)
 */
inline int bounded_add(int base, int increment, int max_sum, int min_sum=0) {
    if ( increment >= 0 )
        return std::min(base+increment, std::max(base, max_sum));
    else
        return std::max(base+increment, std::min(base, min_sum));
}

/** Guarantees portable results for division by 100; round towards 0 */
inline int div100rounded(int num) {
    return (num < 0) ? -(((-num) + 50) / 100) : (num + 50) / 100;
}

/**
 *  round (base_damage * bonus / divisor) to the closest integer,
 *  but up or down towards base_damage
 */
inline int round_damage(int base_damage, int bonus, int divisor) {
    if (base_damage==0) return 0;
    const int rounding = divisor / 2 - (bonus < divisor || divisor==1 ? 0 : 1);
    return std::max<int>(1, (base_damage * bonus + rounding) / divisor);
}

// not guaranteed to have exactly the same result on different platforms
inline int round_double(double d) {
#ifdef HAVE_ROUND
    return static_cast<int>(round(d)); //surprisingly, not implemented everywhere
#else
    return static_cast<int>((d >= 0.0)? std::floor(d + 0.5) : std::ceil(d - 0.5));
#endif
}

// Guaranteed to have portable results across different platforms
inline double round_portable(double d) {
    return (d >= 0.0) ? std::floor(d + 0.5) : std::ceil(d - 0.5);
}

struct bad_lexical_cast : public std::exception
{
    const char *what() const throw()
    {
        return "bad_lexical_cast";
    }
};


template<typename To, typename From>
To lexical_cast(From a)
{
    To res = To();
    std::stringstream str;

    if(str << a && str >> res) {
        return res;
    } else {
        throw bad_lexical_cast();
    }
}

template<typename To, typename From>
To lexical_cast_default(From a, To def=To())
{
    To res = To();
    std::stringstream str;

    if(str << a && str >> res) {
        return res;
    } else {
        return def;
    }
}

template<>
size_t lexical_cast<size_t, const std::string&>(const std::string& a);

template<>
size_t lexical_cast<size_t, const char*>(const char* a);

template<>
size_t lexical_cast_default<size_t, const std::string&>(const std::string& a, size_t def);

template<>
size_t lexical_cast_default<size_t, const char*>(const char* a, size_t def);

template<>
long lexical_cast<long, const std::string&>(const std::string& a);

template<>
long lexical_cast<long, const char*>(const char* a);

template<>
long lexical_cast_default<long, const std::string&>(const std::string& a, long def);

template<>
long lexical_cast_default<long, const char*>(const char* a, long def);

template<>
int lexical_cast<int, const std::string&>(const std::string& a);

template<>
int lexical_cast<int, const char*>(const char* a);

template<>
int lexical_cast_default<int, const std::string&>(const std::string& a, int def);

template<>
int lexical_cast_default<int, const char*>(const char* a, int def);

template<>
double lexical_cast<double, const std::string&>(const std::string& a);

template<>
double lexical_cast<double, const char*>(const char* a);

template<>
double lexical_cast_default<double, const std::string&>(const std::string& a, double def);

template<>
double lexical_cast_default<double, const char*>(const char* a, double def);

template<>
float lexical_cast<float, const std::string&>(const std::string& a);

template<>
float lexical_cast<float, const char*>(const char* a);

template<>
float lexical_cast_default<float, const std::string&>(const std::string& a, float def);

template<>
float lexical_cast_default<float, const char*>(const char* a, float def);

template<typename To, typename From>
To lexical_cast_in_range(From a, To def, To min, To max)
{
    To res;
    std::stringstream str;

    if(str << a && str >> res) {
        if(res < min) {
            return min;
        }
        if(res > max) {
            return max;
        }
        return res;
    } else {
        return def;
    }
}

template<typename Cmp>
bool in_ranges(const Cmp c, const std::vector<std::pair<Cmp, Cmp> >&ranges) {
    typename std::vector<std::pair<Cmp,Cmp> >::const_iterator range,
        range_end = ranges.end();
    for (range = ranges.begin(); range != range_end; ++range) {
        if(range->first <= c && c <= range->second) {
            return true;
        }
    }
    return false;
}

inline bool chars_equal_insensitive(char a, char b) { return tolower(a) == tolower(b); }
inline bool chars_less_insensitive(char a, char b) { return tolower(a) < tolower(b); }

/**
 * Returns the size, in bits, of an instance of type `T`, providing a
 * convenient and self-documenting name for the underlying expression:
 *
 *     sizeof(T) * std::numeric_limits<unsigned char>::digits
 *
 * @tparam T The return value is the size, in bits, of an instance of this
 * type.
 *
 * @returns the size, in bits, of an instance of type `T`.
 */
template<typename T>
inline std::size_t bit_width() {
    return sizeof(T) * std::numeric_limits<unsigned char>::digits;
}

/**
 * Returns the size, in bits, of `x`, providing a convenient and
 * self-documenting name for the underlying expression:
 *
 *     sizeof(x) * std::numeric_limits<unsigned char>::digits
 *
 * @tparam T The type of `x`.
 *
 * @param x The return value is the size, in bits, of this object.
 *
 * @returns the size, in bits, of an instance of type `T`.
 */
template<typename T>
inline std::size_t bit_width(const T&) {
    return sizeof(T) * std::numeric_limits<unsigned char>::digits;
}

/**
 * Returns the quantity of `1` bits in `n` — i.e., `n`’s population count.
 *
 * Algorithm adapted from:
 * <https://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetKernighan>
 *
 * This algorithm was chosen for relative simplicity, not for speed.
 *
 * @tparam N The type of `n`. This should be a fundamental integer type no
 * greater than `UINT_MAX` bits in width; if it is not, the return value is
 * undefined.
 *
 * @param n An integer upon which to operate.
 *
 * @returns the quantity of `1` bits in `n`, if `N` is a fundamental integer
 * type.
 */
template<typename N>
inline unsigned int count_ones(N n) {
    unsigned int r = 0;
    while (n) {
        n &= n-1;
        ++r;
    }
    return r;
}

// Support functions for `count_leading_zeros`.
#if defined(__GNUC__) || defined(__clang__)
inline unsigned int count_leading_zeros_impl(
        unsigned char n, std::size_t w) {
    // Returns the result of the compiler built-in function, adjusted for
    // the difference between the width, in bits, of the built-in
    // function’s parameter’s type (which is `unsigned int`, at the
    // smallest) and the width, in bits, of the input to this function, as
    // specified at the call-site in `count_leading_zeros`.
    return static_cast<unsigned int>(__builtin_clz(n))
        - static_cast<unsigned int>(
            bit_width<unsigned int>() - w);
}
inline unsigned int count_leading_zeros_impl(
        unsigned short int n, std::size_t w) {
    return static_cast<unsigned int>(__builtin_clz(n))
        - static_cast<unsigned int>(
            bit_width<unsigned int>() - w);
}
inline unsigned int count_leading_zeros_impl(
        unsigned int n, std::size_t w) {
    return static_cast<unsigned int>(__builtin_clz(n))
        - static_cast<unsigned int>(
            bit_width<unsigned int>() - w);
}
inline unsigned int count_leading_zeros_impl(
        unsigned long int n, std::size_t w) {
    return static_cast<unsigned int>(__builtin_clzl(n))
        - static_cast<unsigned int>(
            bit_width<unsigned long int>() - w);
}
inline unsigned int count_leading_zeros_impl(
        unsigned long long int n, std::size_t w) {
    return static_cast<unsigned int>(__builtin_clzll(n))
        - static_cast<unsigned int>(
            bit_width<unsigned long long int>() - w);
}
inline unsigned int count_leading_zeros_impl(
        char n, std::size_t w) {
    return count_leading_zeros_impl(
        static_cast<unsigned char>(n), w);
}
inline unsigned int count_leading_zeros_impl(
        signed char n, std::size_t w) {
    return count_leading_zeros_impl(
        static_cast<unsigned char>(n), w);
}
inline unsigned int count_leading_zeros_impl(
        signed short int n, std::size_t w) {
    return count_leading_zeros_impl(
        static_cast<unsigned short int>(n), w);
}
inline unsigned int count_leading_zeros_impl(
        signed int n, std::size_t w) {
    return count_leading_zeros_impl(
        static_cast<unsigned int>(n), w);
}
inline unsigned int count_leading_zeros_impl(
        signed long int n, std::size_t w) {
    return count_leading_zeros_impl(
        static_cast<unsigned long int>(n), w);
}
inline unsigned int count_leading_zeros_impl(
        signed long long int n, std::size_t w) {
    return count_leading_zeros_impl(
        static_cast<unsigned long long int>(n), w);
}
#else
template<typename N>
inline unsigned int count_leading_zeros_impl(N n, std::size_t w) {
    // Algorithm adapted from:
    // <http://aggregate.org/MAGIC/#Leading%20Zero%20Count>
    for (unsigned int shift = 1; shift < w; shift *= 2) {
        n |= (n >> shift);
    }
    return static_cast<unsigned int>(w) - count_ones(n);
}
#endif

/**
 * Returns the quantity of leading `0` bits in `n` — i.e., the quantity of
 * bits in `n`, minus the 1-based bit index of the most significant `1` bit in
 * `n`, or minus 0 if `n` is 0.
 *
 * @tparam N The type of `n`. This should be a fundamental integer type that
 *  (a) is not wider than `unsigned long long int` (the GCC
 *   count-leading-zeros built-in functions are defined for `unsigned int`,
 *   `unsigned long int`, and `unsigned long long int`), and
 *  (b) is no greater than `INT_MAX` bits in width (the GCC built-in functions
 *   return instances of type `int`);
 * if `N` does not satisfy these constraints, the return value is undefined.
 *
 * @param n An integer upon which to operate.
 *
 * @returns the quantity of leading `0` bits in `n`, if `N` satisfies the
 * above constraints.
 *
 * @see count_leading_ones()
 */
template<typename N>
inline unsigned int count_leading_zeros(N n) {
#if defined(__GNUC__) || defined(__clang__)
    // GCC’s `__builtin_clz` returns an undefined value when called with 0
    // as argument.
    // [<http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html>]
    if (n == 0) {
        // Return the quantity of zero bits in `n` rather than
        // returning that undefined value.
        return static_cast<unsigned int>(bit_width(n));
    }
#endif
    // Dispatch, on the static type of `n`, to one of the
    // `count_leading_zeros_impl` functions.
    return count_leading_zeros_impl(n, bit_width(n));
    // The second argument to `count_leading_zeros_impl` specifies the
    // width, in bits, of `n`.
    //
    // This is necessary because `n` may be widened (or, alas, shrunk),
    // and thus the information of `n`’s true width may be lost.
    //
    // At least, this *was* necessary before there were so many overloads
    // of `count_leading_zeros_impl`, but I’ve kept it anyway as an extra
    // precautionary measure, that will (I hope) be optimized out.
    //
    // To be clear, `n` would only be shrunk in cases noted above as
    // having an undefined result.
}

/**
 * Returns the quantity of leading `1` bits in `n` — i.e., the quantity of
 * bits in `n`, minus the 1-based bit index of the most significant `0` bit in
 * `n`, or minus 0 if `n` contains no `0` bits.
 *
 * @tparam N The type of `n`. This should be a fundamental integer type that
 *  (a) is not wider than `unsigned long long int`, and
 *  (b) is no greater than `INT_MAX` bits in width;
 * if `N` does not satisfy these constraints, the return value is undefined.
 *
 * @param n An integer upon which to operate.
 *
 * @returns the quantity of leading `1` bits in `n`, if `N` satisfies the
 * above constraints.
 *
 * @see count_leading_zeros()
 */
template<typename N>
inline unsigned int count_leading_ones(N n) {
    // Explicitly specify the type for which to instantiate
    // `count_leading_zeros` in case `~n` is of a different type.
    return count_leading_zeros<N>(~n);
}

#ifdef __GNUC__
#define LIKELY(a)    __builtin_expect((a),1) // Tells GCC to optimize code so that if is likely to happen
#define UNLIKELY(a)  __builtin_expect((a),0) // Tells GCC to optimize code so that if is unlikely to happen
#else
#define LIKELY(a)    a
#define UNLIKELY(a)  a
#endif

namespace util {

template<class T>
class unique_ptr
{
    T *ptr_;
    // Neither copyable nor assignable.
    unique_ptr(const unique_ptr &);
    unique_ptr &operator=(const unique_ptr &);
public:
    unique_ptr(T *p = nullptr): ptr_(p) {}
    ~unique_ptr() { delete ptr_; }

    void reset(T *p = nullptr)
    {
        delete ptr_;
        ptr_ = p;
    }

    T *release()
    {
        T *p = ptr_;
        ptr_ = nullptr;
        return p;
    }

    T *get() { return ptr_; }
    T *operator->() const { return ptr_; }
    T &operator*() const { return *ptr_; }
};

namespace detail {
    /// A struct that exists to implement a generic wrapper for std::find.
    /// Container should "look like" an STL container of Values.
    template<typename Container, typename Value> struct contains_impl {
        static bool eval(const Container & container, const Value & value)
        {
            typename Container::const_iterator end = container.end();
            return std::find(container.begin(), end, value) != end;
        }
    };
    /// A struct that exists to implement a generic wrapper for the find()
    /// member of associative containers.
    /// Container should "look like" an STL associative container.
    template<typename Container>
    struct contains_impl<Container, typename Container::key_type>  {
        static bool eval(const Container & container,
                         const typename Container::key_type & value)
        {
            return container.find(value) != container.end();
        }
    };
}//namespace detail

/// Returns true iff @a value is found in @a container.
/// This should work whenever Container "looks like" an STL container of Values.
/// Normally this uses std::find(), but a simulated partial template specialization
/// exists when Value is Container::key_type. In this case, Container is assumed
/// an associative container, and the member function find() is used.
template<typename Container, typename Value>
inline bool contains(const Container & container, const Value & value)
{
    return detail::contains_impl<Container, Value>::eval(container, value);
}

}//namespace util


#if 1
typedef int32_t fixed_t;
# define fxp_shift 8
# define fxp_base (1 << fxp_shift)

/** IN: float or int - OUT: fixed_t */
# define ftofxp(x) (fixed_t((x) * fxp_base))

/** IN: unsigned and fixed_t - OUT: unsigned */
# define fxpmult(x,y) (((x)*(y)) >> fxp_shift)

/** IN: unsigned and int - OUT: fixed_t */
# define fxpdiv(x,y) (((x) << fxp_shift) / (y))

/** IN: fixed_t - OUT: int */
# define fxptoi(x) ( ((x)>0) ? ((x) >> fxp_shift) : (-((-(x)) >> fxp_shift)) )

#else
typedef float fixed_t;
# define ftofxp(x) (x)
# define fxpmult(x,y) ((x)*(y))
# define fxpdiv(x,y) (static_cast<float>(x) / static_cast<float>(y))
# define fxptoi(x) ( static_cast<int>(x) )
#endif

#endif