SmartPtr.h

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// Copyright © 2008-2023 Pioneer Developers. See AUTHORS.txt for details
// Licensed under the terms of the GPL v3. See licenses/GPL-3.txt
 
#ifndef _SMARTPTR_H
#define _SMARTPTR_H
 
#include <cassert>
#include <cstddef> // for ptrdiff_t
#include <cstdlib> // for free()
 
#ifdef __GNUC__
#define WARN_UNUSED_RESULT(ret, decl) ret decl __attribute__((warn_unused_result))
#else
#define WARN_UNUSED_RESULT(ret, decl) ret decl
#endif
 
template <typename Derived, typename T>
class SmartPtrBase {
    typedef SmartPtrBase<Derived, T> this_type;
    typedef T *this_type::*safe_bool;
 
public:
    // copy & swap idiom
    // see http://stackoverflow.com/questions/3279543/what-is-the-copy-and-swap-idiom
    void Reset(T *p = 0) { Derived(p).Swap(*static_cast<Derived *>(this)); }
 
    T &operator*() const
    {
        assert(m_ptr);
        return *m_ptr;
    }
    T *operator->() const
    {
        assert(m_ptr);
        return m_ptr;
    }
    T *Get() const { return m_ptr; }
    bool Valid() const { return (m_ptr != 0); }
 
    // safe bool idiom; see http://www.artima.com/cppsource/safebool.html
    operator safe_bool() const { return (m_ptr == 0) ? 0 : &this_type::m_ptr; }
    bool operator!() const { return (m_ptr == 0); }
 
    friend void swap(this_type &a, this_type &b) { a.Swap(b); }
 
    void Swap(this_type &b)
    {
        T *p = m_ptr;
        m_ptr = b.m_ptr;
        b.m_ptr = p;
    }
 
    // comparisons directly with T* have to be defined here, because
    // if comparing with literal 0 (null pointer), the compiler can't
    // deduce the second pointer type for the more general templated
    // comparisons that are written to work on any <T1,T2> pair
    friend bool operator==(const this_type &a, const T *b) { return (a.Get() == b); }
    friend bool operator!=(const this_type &a, const T *b) { return (a.Get() != b); }
    friend bool operator<(const this_type &a, const T *b) { return (a.Get() < b); }
    friend bool operator<=(const this_type &a, const T *b) { return (a.Get() <= b); }
    friend bool operator>(const this_type &a, const T *b) { return (a.Get() > b); }
    friend bool operator>=(const this_type &a, const T *b) { return (a.Get() >= b); }
 
    friend bool operator==(const T *a, const this_type &b) { return (a == b.Get()); }
    friend bool operator!=(const T *a, const this_type &b) { return (a != b.Get()); }
    friend bool operator<(const T *a, const this_type &b) { return (a < b.Get()); }
    friend bool operator<=(const T *a, const this_type &b) { return (a <= b.Get()); }
    friend bool operator>(const T *a, const this_type &b) { return (a > b.Get()); }
    friend bool operator>=(const T *a, const this_type &b) { return (a >= b.Get()); }
 
protected:
    SmartPtrBase() :
        m_ptr(0) {}
    explicit SmartPtrBase(T *p) :
        m_ptr(p) {}
 
    // Release() doesn't make sense for all smart pointer types
    // (e.g., RefCountedPtr can't Release, it can only Reset)
    WARN_UNUSED_RESULT(T *, Release())
    {
        T *p = m_ptr;
        m_ptr = 0;
        return p;
    }
 
    T *m_ptr;
};
 
#define DEF_SMARTPTR_COMPARISON(op)                                                       \
    template <typename D1, typename T1, typename D2, typename T2>                         \
    inline bool operator op(const SmartPtrBase<D1, T1> &a, const SmartPtrBase<D2, T2> &b) \
    {                                                                                     \
        return (a.Get() op b.Get());                                                      \
    }                                                                                     \
    template <typename D, typename T1, typename T2>                                       \
    inline bool operator op(const SmartPtrBase<D, T1> &a, const T2 *b)                    \
    {                                                                                     \
        return (a.Get() op b);                                                            \
    }                                                                                     \
    template <typename D, typename T1, typename T2>                                       \
    inline bool operator op(const T1 *a, const SmartPtrBase<D, T2> &b)                    \
    {                                                                                     \
        return (a op b.Get());                                                            \
    }
DEF_SMARTPTR_COMPARISON(==)
DEF_SMARTPTR_COMPARISON(!=)
DEF_SMARTPTR_COMPARISON(<)
DEF_SMARTPTR_COMPARISON(<=)
DEF_SMARTPTR_COMPARISON(>)
DEF_SMARTPTR_COMPARISON(>=)
#undef DEF_SMARTPTR_COMPARISON
 
// a deleter type for use with std::unique_ptr
struct FreeDeleter {
    void operator()(void *p) { std::free(p); }
};
 
#endif