peerplays-fc/include/boost/atomic/detail/builder.hpp

#ifndef BOOST_DETAIL_ATOMIC_BUILDER_HPP
#define BOOST_DETAIL_ATOMIC_BUILDER_HPP

//  Copyright (c) 2009 Helge Bahmann
//
//  Distributed under the Boost Software License, Version 1.0.
//  See accompanying file LICENSE_1_0.txt or copy at
//  http://www.boost.org/LICENSE_1_0.txt)

#include <boost/detail/endian.hpp>
#include <boost/atomic/detail/valid_integral_types.hpp>

namespace boost {
namespace detail {
namespace atomic {

/*
given a Base that implements:

- load(memory_order order)
- compare_exchange_weak(integral_type &expected, integral_type desired, memory_order order)

generates exchange and compare_exchange_strong
*/
template<typename Base>
class build_exchange : public Base {
public:
    typedef typename Base::integral_type integral_type;
    
    using Base::load;
    using Base::compare_exchange_weak;
    
    bool compare_exchange_strong(
        integral_type &expected,
        integral_type desired,
        memory_order success_order,
        memory_order failure_order) volatile
    {
        integral_type expected_save=expected;
        while(true) {
            if (compare_exchange_weak(expected, desired, success_order, failure_order)) return true;
            if (expected_save!=expected) return false;
            expected=expected_save;
        }
    }
    
    integral_type exchange(integral_type replacement, memory_order order=memory_order_seq_cst) volatile
    {
        integral_type o=load(memory_order_relaxed);
        do {} while(!compare_exchange_weak(o, replacement, order, memory_order_relaxed));
        return o;
    }
    
    build_exchange() {}
    explicit build_exchange(integral_type i) : Base(i) {}
};

/*
given a Base that implements:

- fetch_add_var(integral_type c, memory_order order)
- fetch_inc(memory_order order)
- fetch_dec(memory_order order)

creates a fetch_add method that delegates to fetch_inc/fetch_dec if operand
is constant +1/-1, and uses fetch_add_var otherwise

the intention is to allow optimizing the incredibly common case of +1/-1
*/
template<typename Base>
class build_const_fetch_add : public Base {
public:
    typedef typename Base::integral_type integral_type;
    
    integral_type fetch_add(
        integral_type c,
        memory_order order=memory_order_seq_cst) volatile
    {
        if (__builtin_constant_p(c)) {
            switch(c) {
                case -1: return fetch_dec(order);
                case 1: return fetch_inc(order);
            }
        }
        return fetch_add_var(c, order);
    }
    
    build_const_fetch_add() {}
    explicit build_const_fetch_add(integral_type i) : Base(i) {}
protected:
    using Base::fetch_add_var;
    using Base::fetch_inc;
    using Base::fetch_dec;
};

/*
given a Base that implements:

- load(memory_order order)
- compare_exchange_weak(integral_type &expected, integral_type desired, memory_order order)

generates a -- not very efficient, but correct -- fetch_add operation
*/
template<typename Base>
class build_fetch_add : public Base {
public:
    typedef typename Base::integral_type integral_type;
    
    using Base::compare_exchange_weak;
    
    integral_type fetch_add(
        integral_type c, memory_order order=memory_order_seq_cst) volatile
    {
        integral_type o=Base::load(memory_order_relaxed), n;
        do {n=o+c;} while(!compare_exchange_weak(o, n, order, memory_order_relaxed));
        return o;
    }
    
    build_fetch_add() {}
    explicit build_fetch_add(integral_type i) : Base(i) {}
};

/*
given a Base that implements:

- fetch_add(integral_type c, memory_order order)

generates fetch_sub and post/pre- increment/decrement operators
*/
template<typename Base>
class build_arithmeticops : public Base {
public:
    typedef typename Base::integral_type integral_type;
    
    using Base::fetch_add;
    
    integral_type fetch_sub(
        integral_type c,
        memory_order order=memory_order_seq_cst) volatile
    {
#if defined(BOOST_MSVC)
#pragma warning(push)
#pragma warning(disable: 4146)    // unary minus operator applied to unsigned type, result still unsigned
#endif
        return fetch_add(-c, order);
#if defined(BOOST_MSVC)
#pragma warning(pop)
#endif
    }
    
    build_arithmeticops() {}
    explicit build_arithmeticops(integral_type i) : Base(i) {}
};

/*
given a Base that implements:

- load(memory_order order)
- compare_exchange_weak(integral_type &expected, integral_type desired, memory_order order)

generates -- not very efficient, but correct -- fetch_and, fetch_or and fetch_xor operators
*/
template<typename Base>
class build_logicops : public Base {
public:
    typedef typename Base::integral_type integral_type;
    
    using Base::compare_exchange_weak;
    using Base::load;
    
    integral_type fetch_and(integral_type c, memory_order order=memory_order_seq_cst) volatile
    {
        integral_type o=load(memory_order_relaxed), n;
        do {n=o&c;} while(!compare_exchange_weak(o, n, order, memory_order_relaxed));
        return o;
    }
    integral_type fetch_or(integral_type c, memory_order order=memory_order_seq_cst) volatile
    {
        integral_type o=load(memory_order_relaxed), n;
        do {n=o|c;} while(!compare_exchange_weak(o, n, order, memory_order_relaxed));
        return o;
    }
    integral_type fetch_xor(integral_type c, memory_order order=memory_order_seq_cst) volatile
    {
        integral_type o=load(memory_order_relaxed), n;
        do {n=o^c;} while(!compare_exchange_weak(o, n, order, memory_order_relaxed));
        return o;
    }
    
    build_logicops() {}
    build_logicops(integral_type i) : Base(i) {}
};

/*
given a Base that implements:

- load(memory_order order)
- store(integral_type i, memory_order order)
- compare_exchange_weak(integral_type &expected, integral_type desired, memory_order order)

generates the full set of atomic operations for integral types
*/
template<typename Base>
class build_atomic_from_minimal : public build_logicops< build_arithmeticops< build_fetch_add< build_exchange<Base> > > > {
public:
    typedef build_logicops< build_arithmeticops< build_fetch_add< build_exchange<Base> > > > super;
    typedef typename super::integral_type integral_type;
    
    build_atomic_from_minimal(void) {}
    build_atomic_from_minimal(typename super::integral_type i) : super(i) {}
};

/*
given a Base that implements:

- load(memory_order order)
- store(integral_type i, memory_order order)
- compare_exchange_weak(integral_type &expected, integral_type desired, memory_order order)
- compare_exchange_strong(integral_type &expected, integral_type desired, memory_order order)
- exchange(integral_type replacement, memory_order order)
- fetch_add_var(integral_type c, memory_order order)
- fetch_inc(memory_order order)
- fetch_dec(memory_order order)

generates the full set of atomic operations for integral types
*/
template<typename Base>
class build_atomic_from_typical : public build_logicops< build_arithmeticops< build_const_fetch_add<Base> > > {
public:
    typedef build_logicops< build_arithmeticops< build_const_fetch_add<Base> > > super;
    typedef typename super::integral_type integral_type;
    
    build_atomic_from_typical(void) {}
    build_atomic_from_typical(typename super::integral_type i) : super(i) {}
};

/*
given a Base that implements:

- load(memory_order order)
- store(integral_type i, memory_order order)
- compare_exchange_weak(integral_type &expected, integral_type desired, memory_order order)
- compare_exchange_strong(integral_type &expected, integral_type desired, memory_order order)
- exchange(integral_type replacement, memory_order order)
- fetch_add(integral_type c, memory_order order)

generates the full set of atomic operations for integral types
*/
template<typename Base>
class build_atomic_from_add : public build_logicops< build_arithmeticops<Base> > {
public:
    typedef build_logicops< build_arithmeticops<Base> > super;
    typedef typename super::integral_type integral_type;
    
    build_atomic_from_add(void) {}
    build_atomic_from_add(typename super::integral_type i) : super(i) {}
};

/*
given a Base that implements:

- load(memory_order order)
- store(integral_type i, memory_order order)
- compare_exchange_weak(integral_type &expected, integral_type desired, memory_order order)
- compare_exchange_strong(integral_type &expected, integral_type desired, memory_order order)
- exchange(integral_type replacement, memory_order order)

generates the full set of atomic operations for integral types
*/
template<typename Base>
class build_atomic_from_exchange : public build_logicops< build_arithmeticops< build_fetch_add<Base> > > {
public:
    typedef build_logicops< build_arithmeticops< build_fetch_add<Base> > > super;
    typedef typename super::integral_type integral_type;
    
    build_atomic_from_exchange(void) {}
    build_atomic_from_exchange(typename super::integral_type i) : super(i) {}
};


/*
given a Base that implements:

- compare_exchange_weak()

generates load, store and compare_exchange_weak for a smaller
data type (e.g. an atomic "byte" embedded into a temporary
and properly aligned atomic "int").
*/
template<typename Base, typename Type>
class build_base_from_larger_type {
public:
    typedef Type integral_type;
    
    build_base_from_larger_type() {}
    build_base_from_larger_type(integral_type t) {store(t, memory_order_relaxed);}
    
    integral_type load(memory_order order=memory_order_seq_cst) const volatile
    {
        larger_integral_type v=get_base().load(order);
        return extract(v);
    }
    bool compare_exchange_weak(integral_type &expected,
        integral_type desired,
        memory_order success_order,
        memory_order failure_order) volatile
    {
        larger_integral_type expected_;
        larger_integral_type desired_;
        
        expected_=get_base().load(memory_order_relaxed);
        expected_=insert(expected_, expected);
        desired_=insert(expected_, desired);
        bool success=get_base().compare_exchange_weak(expected_, desired_, success_order, failure_order);
        expected=extract(expected_);
        return success;
    }
    void store(integral_type v,
        memory_order order=memory_order_seq_cst) volatile
    {
        larger_integral_type expected, desired;
        expected=get_base().load(memory_order_relaxed);
        do {
            desired=insert(expected, v);
        } while(!get_base().compare_exchange_weak(expected, desired, order, memory_order_relaxed));
    }
    
    bool is_lock_free(void)
    {
        return get_base().is_lock_free();
    }
private:
    typedef typename Base::integral_type larger_integral_type;
    
    const Base &get_base(void) const volatile
    {
        intptr_t address=(intptr_t)this;
        address&=~(sizeof(larger_integral_type)-1);
        return *reinterpret_cast<const Base *>(address);
    }
    Base &get_base(void) volatile
    {
        intptr_t address=(intptr_t)this;
        address&=~(sizeof(larger_integral_type)-1);
        return *reinterpret_cast<Base *>(address);
    }
    unsigned int get_offset(void) const volatile
    {
        intptr_t address=(intptr_t)this;
        address&=(sizeof(larger_integral_type)-1);
        return address;
    }
    
    unsigned int get_shift(void) const volatile
    {
#if defined(BOOST_LITTLE_ENDIAN)
        return get_offset()*8;
#elif  defined(BOOST_BIG_ENDIAN)
        return (sizeof(larger_integral_type)-sizeof(integral_type)-get_offset())*8;
#else
    #error "Unknown endian"
#endif
    }
    
    integral_type extract(larger_integral_type v) const volatile
    {
        return v>>get_shift();
    }
    
    larger_integral_type insert(larger_integral_type target, integral_type source) const volatile
    {
        larger_integral_type tmp=source;
        larger_integral_type mask=(larger_integral_type)-1;
        
        mask=~(mask<<(8*sizeof(integral_type)));
        
        mask=mask<<get_shift();
        tmp=tmp<<get_shift();
        
        tmp=(tmp & mask) | (target & ~mask);
        
        return tmp;
    }
    
    integral_type i;
};

/*
given a Base that implements:

- compare_exchange_weak()

generates the full set of atomic ops for a smaller
data type (e.g. an atomic "byte" embedded into a temporary
and properly aligned atomic "int").
*/
template<typename Base, typename Type>
class build_atomic_from_larger_type : public build_atomic_from_minimal< build_base_from_larger_type<Base, Type> > {
public:
    typedef build_atomic_from_minimal< build_base_from_larger_type<Base, Type> > super;
    //typedef typename super::integral_type integral_type;
    typedef Type integral_type;
    
    build_atomic_from_larger_type() {}
    build_atomic_from_larger_type(integral_type v) : super(v) {}
};

}
}
}

#endif