bluflame/meshToolsV5/src/Lib/mt/common/Map.h

#pragma once
#if _DEBUG
//#include <assert.h>
#define assert(a) if (!(a)) { throw #a; }
#endif


template<typename T>
struct equality { static bool Equals(T a, T b) { return a == b; } };

template<typename T>
struct hashing
{
	static int Generate(T a) 
	{
		return (int)a;
	} 
};

// Finetune this value for better performance.
#define MAXBUCKETSIZE 10

template<typename TKey, typename TValue>
class Map
{
public:
	struct Pair
	{
		int Hash;
		TKey Key;
		TValue Value;
	};

private:
	class HashBucket
	{
	public:
		HashBucket(const List<Pair*> pairs)
			: left{ nullptr }
			, right{ nullptr }
			, pairs { pairs }
		{
			if (pairs.Count() > 0)
				centerHash = pairs[0]->Hash;

		}

		HashBucket()
			: left{ nullptr }
			, right{ nullptr }
		{
		}

		~HashBucket()
		{
			delete left;
			delete right;
		}

		HashBucket* GetValue(const TKey& key, int hash, bool& success, TValue*& result) const
		{
			if ((hash == centerHash || left == nullptr) && pairs.Count() != 0)
			{
				for (const auto& pair : pairs)
					if (equality<const TKey&>::Equals(pair->Key, key))
					{
						success = true;
						result = &pair->Value;
						return nullptr;
					}
				return nullptr;
			}
			else if (left != nullptr)
				return hash < centerHash ? left : right;
			else
				return nullptr;
		}

		HashBucket* Remove(const TKey key, int hash, Pair*& pairResult)
		{
			if (left == nullptr || hash == centerHash)
			{
				for (int i = 0, iLength = pairs.Count(); i < iLength; ++i)
				{
					auto pair = pairs[i];
					if (equality<const TKey&>::Equals(pair->Key, key))
					{
						pairs.RemoveAt(i);
						pairResult = pair;
						return nullptr;
					}
				}
				return nullptr;
			}
			else if (left != nullptr)
				return hash < centerHash ? left : right;
			else
				return nullptr;
		}

		HashBucket* Add(Pair* pair)
		{
			if (pairs.Count() == 0)
				centerHash = pair->Hash;
			if (centerHash == pair->Hash || (left == nullptr && pairs.Count() < MAXBUCKETSIZE))
			{
#ifdef _DEBUG
				for (const auto& oldPair : pairs)
					if (equality<const TKey&>::Equals(oldPair->Key, pair->Key))
						assert("Key already exists in map" && false);
#endif
				pairs.Add(pair);
			}
			else if (left == nullptr)
			{
				centerHash = pairs[pairs.Count() / 2]->Hash;

				List<Pair*> leftPairs;
				List<Pair*> centerPairs;
				List<Pair*> rightPairs;

				for (const auto& oldPair : pairs)
				{
					if (oldPair->Hash < centerHash)
						leftPairs.Add(oldPair);
					if (oldPair->Hash > centerHash)
						rightPairs.Add(oldPair);
					else
						centerPairs.Add(oldPair);
				}

				left = new HashBucket(leftPairs);
				right = new HashBucket(rightPairs);
				pairs = centerPairs;

				return Add(pair);
			}
			else
				return pair->Hash < centerHash ? left : right;
			return nullptr;
		}

	private:
		int centerHash;
		HashBucket* left;
		HashBucket* right;
		List<Pair*> pairs;
	};

public:
	Map()
		: rootBucket{ new HashBucket() }
	{
	}

	Map(Map&& other)
		: pairs{ other.pairs }
		, rootBucket{ other.rootBucket }
	{
		other.rootBucket = nullptr;
		other.pairs.Clear();
	}

	Map(const Map& other)
	{
		throw "Implement me bitch!";
	}

	~Map()
	{
		for (int i = 0, iLength = pairs.Count(); i < iLength; ++i)
			delete pairs[i];

		delete rootBucket;
	}

	Map& operator=(Map&& other)
	{
		if (this != &other)
		{
			delete rootBucket;
			pairs = other.pairs;
			rootBucket = other.rootBucket;
			other.rootBucket = nullptr;
			other.pairs.Clear();
		}
		return *this;
	}
	

	void Add(const TKey& key, const TValue& value)
	{
		auto pair = new Pair();
		pair->Key = key;
		pair->Value = value;
		pair->Hash = hashing<const TKey&>::Generate(key);

		auto bucket = rootBucket;
		do
		{
			bucket = bucket->Add(pair);
		} while (bucket != nullptr);
		
		pairs.Add(pair);
	}

	bool TryGetValue(const TKey& key, TValue& value) const
	{
		bool success = false;
		auto hash = hashing<const TKey&>::Generate(key);
		TValue* result;

		auto bucket = rootBucket;
		do
		{
			bucket = bucket->GetValue(key, hash, success, result);
		} while (bucket != nullptr);
		if (success)
			value = *result;
		return success;
	}

	bool TryGetValue(const TKey& key, TValue*& value) const
	{
		bool success = false;
		auto hash = hashing<const TKey&>::Generate(key);
		TValue* result;

		auto bucket = rootBucket;
		do
		{
			bucket = bucket->GetValue(key, hash, success, result);
		} while (bucket != nullptr);
		if (success)
			value = result;
		return success;
	}

	void Remove(const TKey& key)
	{
		auto hash = hashing<const TKey&>::Generate(key);

		auto bucket = rootBucket;
		Pair* pair;
		do
		{
			bucket = bucket->Remove(key, hash, pair);
		} while (bucket != nullptr);

		if (pair != nullptr)
		{
			pairs.Remove(pair);
		}
	}

	TValue& GetValue(const TKey& key) const
	{
		TValue* result;
		bool success = false;
		auto hash = hashing<const TKey&>::Generate(key);

		auto bucket = rootBucket;
		do
		{
			bucket = bucket->GetValue(key, hash, success, result);
		} while (bucket != nullptr);

#if _DEBUG
		assert("No value found!" && success);
#endif
		return *result;
	}

	Pair** begin() const
	{
		return pairs.begin();
	}

	Pair** end() const
	{
		return pairs.end();
	}

	int Count() const
	{
		return pairs.Count();
	}

	bool ContainsKey(const TKey& key) const
	{
		TValue tmp;
		return TryGetValue(key, tmp);
	}

	TValue& operator[](const TKey& key)
	{
		return GetValue(key);
	}

	const TValue& operator[](const TKey& key) const
	{
		return GetValue(key);
	}

	List<TValue> GetValues() const
	{
		List<TValue> result;
		for (const auto& pair : pairs)
			result.Add(pair->Value);

		return result;
	}

private:
	HashBucket* rootBucket;
	List<Pair*> pairs;
};