it-works/nd_array/nd_array.hpp

//
//  nd_array.hpp
//
//  Created by Joshua Moerman on 10/25/11.
//  Copyright 2011 Vadovas. All rights reserved.
//

/*
 Dynamic multi-dimensional array.
 With the usual c-syntax: v[x][y][z].
 Memory is allocated as one big block, instead of multiple smaller blocks (which is the case with std::vector<std::vector<...>>).
 Showed no difference in speed compared to std::vector<std::vector<...>> (in release build), so you better can use std::vector.
 
 This class can be used te reinterpret a big chunk of memory as a n-dimensional array. (Could be useful if your legacy-code gives you somthing like that).
 
 It is templated in number of dimensions (and of course type). With extra effort you could make the dimension dynamic (ie not compile-time, but run-time), I leave that as an excercise to the reader.
 */

#ifndef ND_ARRAY_HPP
#define ND_ARRAY_HPP

#include <stdexcept>
#include <numeric>
#include <iterator>
#include <array>		// C++11, right here :D (if this fails, try using tr1)

template <typename T, size_t dimension>
class nd_array{
public:
	typedef T &				reference;
	typedef T const &		const_reference;
	typedef T *				iterator;
	typedef T const *		const_iterator;
	typedef size_t			size_type;
	typedef ptrdiff_t		difference_type;
	typedef T				value_type;
	typedef T *				pointer;
	typedef T const *		const_pointer;
	typedef std::reverse_iterator<iterator> reverse_iterator;
	typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
	
	/*
	 NOTE: I actually wanted to make a specialisation for N = 0, but this is not possible in class scope, so it had to be in namespace-scope. Problem with the specialisation then is that the outer-class isn't specialised, while the inner is, this is also not possible. So either I had to make this class completly out of the nd_array class (which would require a lot of templating), OR I check things in an non-templated way. I chose for the latter, since it was easier to make. The first one is actually beter (it would have better types, which make dimensionality-errors a type-error, instead of an exception).
	 */
	template <size_type N>
	struct proxy {
		nd_array * const data;
		size_t const offset;
		
		proxy(nd_array * const c, size_t o)
		: data(c)
		, offset(o)
		{}

		proxy<N-1> operator[](size_t y){
			if (N == 0) throw std::logic_error("called operator[] on a value");
			return proxy<N-1>(data, data->sizes[dimension - N]*offset + y);
		}
		
		operator reference(){
			if (N != 0) throw std::logic_error("using a non-value");
			return *(data->data + offset);
		}
		
		reference operator=(T const & n){
			if (N != 0) throw std::logic_error("assignment to a non-value");
			return *(data->data + offset) = n;
		}
	};
	
	template <size_type N>
	struct const_proxy {
		nd_array const * const data;
		size_t const offset;
		
		const_proxy(nd_array const * const c, size_t o)
		: data(c)
		, offset(o)
		{}
		
		const_proxy<N-1> operator[](size_t y) const {
			if (N == 0) throw std::logic_error("called operator[] on a value");
			return const_proxy<N-1>(data, data->sizes[dimension - N]*offset + y);
		}
		
		operator const_reference() const {
			if (N != 0) throw std::logic_error("using a non-value");
				return *(data->data + offset);
		}
	};
	
	nd_array(size_type width, size_type height)
	: data(0)
	, sizes()
	{
		if (dimension != 2) throw std::logic_error("wrong constructor");
		sizes[0] = width;
		sizes[1] = height;
		data = new T[width*height];
	}
	
	nd_array(size_type width, size_type height, size_type depth)
	: data(0)
	, sizes()
	{
		if (dimension != 3) throw std::logic_error("wrong constructor");
		sizes[0] = width;
		sizes[1] = height;
		sizes[2] = depth;
		data = new T[width*height*depth];
	}
	
	~nd_array(){
		delete[] data;
	}
	
	size_type get_size(size_type d) const {
		return sizes[d];
	}
	
	size_type size() const {
		return std::accumulate(sizes.begin(), sizes.end(), 1, std::multiplies<size_type>());
	}
	
	proxy<dimension-1> operator[](size_t x){
		return proxy<dimension-1>(this, x);
	}
	
	const_proxy<dimension-1> operator[](size_t x) const {
		return const_proxy<dimension-1>(this, x);
	}
	
	iterator begin(){
		return data;
	}
	
	iterator end(){
		size_type length = size();
		return data + length;
	}
	
	const_iterator cbegin() const {
		return data;
	}
	
	const_iterator cend() const {
		size_type length = size();
		return data + length;
	}
	
private:
	T * data;
	std::array<size_type, dimension> sizes;
};

#endif	// ND_ARRAY_HPP