zero_after_free_allocator.h

#ifndef ZERO_AFTER_FREE_ALLOCATOR_H
#define ZERO_AFTER_FREE_ALLOCATOR_H

#include <openssl/crypto.h> // for OPENSSL_cleanse()

//
// Allocator that clears its contents before deletion.
//
template <typename T>
struct zero_after_free_allocator : public std::allocator<T> {
    // MSVC8 default copy constructor is broken
    typedef std::allocator<T> base;
    typedef typename base::size_type size_type;
    typedef typename base::difference_type difference_type;
    typedef typename base::pointer pointer;
    typedef typename base::const_pointer const_pointer;
    typedef typename base::reference reference;
    typedef typename base::const_reference const_reference;
    typedef typename base::value_type value_type;
    zero_after_free_allocator() throw() {}
    zero_after_free_allocator(const zero_after_free_allocator& a) throw() : base(a) {}
    template <typename U>
    zero_after_free_allocator(const zero_after_free_allocator<U>& a) throw() : base(a)
    {
    }
    ~zero_after_free_allocator() throw() {}
    template <typename _Other>
    struct rebind {
        typedef zero_after_free_allocator<_Other> other;
    };

    void deallocate(T* p, std::size_t n)
    {
        if (p != NULL)
            OPENSSL_cleanse(p, sizeof(T) * n);
        std::allocator<T>::deallocate(p, n);
    }
};

#endif