stl_allocator.h

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#ifndef _STL_ALLOCATOR_H
#define _STL_ALLOCATOR_H
 
// @see https://github.com/endurodave/stl_allocator
// David Lafreniere
 
#include "xallocator.h"
#include <memory>  // For std::allocator and std::allocator_traits
 
// Forward declaration for stl_allocator<void>
template <typename T>
class stl_allocator;
 
// Specialization for `void`, but we no longer need to define `pointer` and `const_pointer`
template <>
class stl_allocator<void> 
{
public:
    typedef void value_type;
 
    template <class U>
    struct rebind { typedef stl_allocator<U> other; };
};
 
// Define the custom stl_allocator inheriting from std::allocator
template <typename T>
class stl_allocator : public std::allocator<T> 
{
public:
    typedef size_t size_type;
    typedef ptrdiff_t difference_type;
    typedef T* pointer;
    typedef const T* const_pointer;
    typedef T& reference;
    typedef const T& const_reference;
    typedef T value_type;
 
    // Default constructor
    stl_allocator() {}
 
    // Copy constructor
    template <class U>
    stl_allocator(const stl_allocator<U>&) {}
 
    // Rebind struct
    template <class U>
    struct rebind { typedef stl_allocator<U> other; };
 
    // Override allocate method to use custom allocation function
    pointer allocate(size_type n, typename std::allocator_traits<stl_allocator<void>>::const_pointer hint = 0) 
    {
        return static_cast<pointer>(xmalloc(n * sizeof(T)));
    }
 
    // Override deallocate method to use custom deallocation function
    void deallocate(pointer p, size_type n) 
    {
        xfree(p);
    }
 
    // You can inherit other methods like construct and destroy from std::allocator
};
 
// Comparison operators for compatibility
template <typename T, typename U>
inline bool operator==(const stl_allocator<T>&, const stl_allocator<U>) { return true; }
 
template <typename T, typename U>
inline bool operator!=(const stl_allocator<T>&, const stl_allocator<U>) { return false; }
 
#endif