3D游戏引擎底层数据结构的封装之Dictionary
来源：互联网 发布：电影后期特效制作软件 编辑：程序博客网 时间：2024/06/07 12:14
笔者介绍：姜雪伟，IT公司技术合伙人，IT高级讲师，CSDN社区专家，特邀编辑，畅销书作者，国家专利发明人;已出版书籍：《手把手教你架构3D游戏引擎》电子工业出版社和《Unity3D实战核心技术详解》电子工业出版社等。
本章主要给读者介绍Dictionary的封装，Dictionary在游戏开发中使用的非常多，开发者通常的做法是直接使用系统提供的Dictionary去做操作，不知道大家在使用Dictionary时，自己想没想过，它内部是如何实现的？换句话说，如果自己写应该怎样写出来，还有Dictionary都有哪些特性？在使用的过程中应该注意哪些问题？以前做端游的时候面试时，我也会经常提问一些关于Dictionary的用法，很多人对此掌握的并不是特别好。Dictionary在游戏开发中功能主要处理的是游戏数据信息。下面给读者分析一下商业引擎中是如何封装的？Dictionary它本身也是Key／Value值对。所以我们首先定义的是封装一个Key／Value类，因为它可以使用任何对象，封装也是用模版的方式，完整代码详情见下文：
template<class KEYTYPE, class VALUETYPE> class KeyValuePair{public: /// default constructor KeyValuePair(); /// constructor with key and value KeyValuePair(const KEYTYPE& k, const VALUETYPE& v); /// constructor with key and undefined value KeyValuePair(const KEYTYPE& k); /// copy constructor KeyValuePair(const KeyValuePair<KEYTYPE, VALUETYPE>& rhs); /// assignment operator void operator=(const KeyValuePair<KEYTYPE, VALUETYPE>& rhs); /// equality operator bool operator==(const KeyValuePair<KEYTYPE, VALUETYPE>& rhs) const; /// inequality operator bool operator!=(const KeyValuePair<KEYTYPE, VALUETYPE>& rhs) const; /// greater operator bool operator>(const KeyValuePair<KEYTYPE, VALUETYPE>& rhs) const; /// greater-or-equal operator bool operator>=(const KeyValuePair<KEYTYPE, VALUETYPE>& rhs) const; /// lesser operator bool operator<(const KeyValuePair<KEYTYPE, VALUETYPE>& rhs) const; /// lesser-or-equal operator bool operator<=(const KeyValuePair<KEYTYPE, VALUETYPE>& rhs) const; /// read/write access to value VALUETYPE& Value(); /// read access to key const KEYTYPE& Key() const; /// read access to key const VALUETYPE& Value() const;protected: KEYTYPE keyData; VALUETYPE valueData;};//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE>KeyValuePair<KEYTYPE, VALUETYPE>::KeyValuePair(){ // empty}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE>KeyValuePair<KEYTYPE, VALUETYPE>::KeyValuePair(const KEYTYPE& k, const VALUETYPE& v) : keyData(k), valueData(v){ // empty}//------------------------------------------------------------------------------/** This strange constructor is useful for search-by-key if the key-value-pairs are stored in a Util::Array.*/template<class KEYTYPE, class VALUETYPE>KeyValuePair<KEYTYPE, VALUETYPE>::KeyValuePair(const KEYTYPE& k) : keyData(k){ // empty}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE>KeyValuePair<KEYTYPE, VALUETYPE>::KeyValuePair(const KeyValuePair<KEYTYPE, VALUETYPE>& rhs) : keyData(rhs.keyData), valueData(rhs.valueData){ // empty}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE>voidKeyValuePair<KEYTYPE, VALUETYPE>::operator=(const KeyValuePair<KEYTYPE, VALUETYPE>& rhs){ this->keyData = rhs.keyData; this->valueData = rhs.valueData;}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE>boolKeyValuePair<KEYTYPE, VALUETYPE>::operator==(const KeyValuePair<KEYTYPE, VALUETYPE>& rhs) const{ return (this->keyData == rhs.keyData);}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE>boolKeyValuePair<KEYTYPE, VALUETYPE>::operator!=(const KeyValuePair<KEYTYPE, VALUETYPE>& rhs) const{ return (this->keyData != rhs.keyData);}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE>boolKeyValuePair<KEYTYPE, VALUETYPE>::operator>(const KeyValuePair<KEYTYPE, VALUETYPE>& rhs) const{ return (this->keyData > rhs.keyData);}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE>boolKeyValuePair<KEYTYPE, VALUETYPE>::operator>=(const KeyValuePair<KEYTYPE, VALUETYPE>& rhs) const{ return (this->keyData >= rhs.keyData);}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE>boolKeyValuePair<KEYTYPE, VALUETYPE>::operator<(const KeyValuePair<KEYTYPE, VALUETYPE>& rhs) const{ return (this->keyData < rhs.keyData);}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE>boolKeyValuePair<KEYTYPE, VALUETYPE>::operator<=(const KeyValuePair<KEYTYPE, VALUETYPE>& rhs) const{ return (this->keyData <= rhs.keyData);}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE>VALUETYPE&KeyValuePair<KEYTYPE, VALUETYPE>::Value(){ return this->valueData;}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE>const KEYTYPE&KeyValuePair<KEYTYPE, VALUETYPE>::Key() const{ return this->keyData;}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE>const VALUETYPE&KeyValuePair<KEYTYPE, VALUETYPE>::Value() const{ return this->valueData;}这个也是封装Dictionary所需要的类，封装一个对象首先要知道封装它用来做什么？我们自己封装就要首先知道它经常使用的方法，比如获取某个值，它的大小，清空Dictionary，向Dictionary增加元素，查找元素，是否存在某个元素等等，下面就把它的真实内容显示出来，它的内部其实按照一个有序列表执行的。封装的代码中会用到Array类，完整代码如下所示：
template<class KEYTYPE, class VALUETYPE> class Dictionary{public: /// default constructor Dictionary(); /// copy constructor Dictionary(const Dictionary<KEYTYPE, VALUETYPE>& rhs); /// assignment operator void operator=(const Dictionary<KEYTYPE, VALUETYPE>& rhs); /// read/write [] operator VALUETYPE& operator[](const KEYTYPE& key); /// read-only [] operator const VALUETYPE& operator[](const KEYTYPE& key) const; /// return number of key/value pairs in the dictionary SizeT Size() const; /// clear the dictionary void Clear(); /// return true if empty bool IsEmpty() const; /// reserve space (useful if number of elements is known beforehand) void Reserve(SizeT numElements); /// begin a bulk insert (array will be sorted at End) void BeginBulkAdd(); /// add a key/value pair void Add(const KeyValuePair<KEYTYPE, VALUETYPE>& kvp); /// add a key and associated value void Add(const KEYTYPE& key, const VALUETYPE& value); /// end a bulk insert (this will sort the internal array) void EndBulkAdd(); /// erase a key and its associated value void Erase(const KEYTYPE& key); /// erase a key at index void EraseAtIndex(IndexT index); /// find index of key/value pair (InvalidIndex if doesn't exist) IndexT FindIndex(const KEYTYPE& key) const; /// return true if key exists in the array bool Contains(const KEYTYPE& key) const; /// get a key at given index const KEYTYPE& KeyAtIndex(IndexT index) const; /// access to value at given index VALUETYPE& ValueAtIndex(IndexT index); /// get a value at given index const VALUETYPE& ValueAtIndex(IndexT index) const; /// get key/value pair at index KeyValuePair<KEYTYPE, VALUETYPE>& KeyValuePairAtIndex(IndexT index) const; /// get all keys as an Util::Array Array<KEYTYPE> KeysAsArray() const; /// get all keys as an Util::Array Array<VALUETYPE> ValuesAsArray() const; /// get all keys as (typically) an array template<class RETURNTYPE> RETURNTYPE KeysAs() const; /// get all keys as (typically) an array template<class RETURNTYPE> RETURNTYPE ValuesAs() const;protected: /// make sure the key value pair array is sorted void SortIfDirty() const; Array<KeyValuePair<KEYTYPE, VALUETYPE> > keyValuePairs; bool inBulkInsert;};//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE>Dictionary<KEYTYPE, VALUETYPE>::Dictionary() : inBulkInsert(false){ // empty}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE>Dictionary<KEYTYPE, VALUETYPE>::Dictionary(const Dictionary<KEYTYPE, VALUETYPE>& rhs) : keyValuePairs(rhs.keyValuePairs), inBulkInsert(false){ #if NEBULA3_BOUNDSCHECKS n_assert(!rhs.inBulkInsert); #endif}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE> voidDictionary<KEYTYPE, VALUETYPE>::operator=(const Dictionary<KEYTYPE, VALUETYPE>& rhs){ #if NEBULA3_BOUNDSCHECKS n_assert(!this->inBulkInsert); n_assert(!rhs.inBulkInsert); #endif this->keyValuePairs = rhs.keyValuePairs;}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE> voidDictionary<KEYTYPE, VALUETYPE>::Clear(){ #if NEBULA3_BOUNDSCHECKS n_assert(!this->inBulkInsert); #endif this->keyValuePairs.Clear();}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE> SizeTDictionary<KEYTYPE, VALUETYPE>::Size() const{ return this->keyValuePairs.Size();}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE> boolDictionary<KEYTYPE, VALUETYPE>::IsEmpty() const{ return (0 == this->keyValuePairs.Size());}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE> voidDictionary<KEYTYPE, VALUETYPE>::Add(const KeyValuePair<KEYTYPE, VALUETYPE>& kvp){ if (this->inBulkInsert) { this->keyValuePairs.Append(kvp); } else { this->keyValuePairs.InsertSorted(kvp); }}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE> voidDictionary<KEYTYPE, VALUETYPE>::Reserve(SizeT numElements){ this->keyValuePairs.Reserve(numElements);}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE> voidDictionary<KEYTYPE, VALUETYPE>::BeginBulkAdd(){ #if NEBULA3_BOUNDSCHECKS n_assert(!this->inBulkInsert); #endif this->inBulkInsert = true;}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE> voidDictionary<KEYTYPE, VALUETYPE>::EndBulkAdd(){ #if NEBULA3_BOUNDSCHECKS n_assert(this->inBulkInsert); #endif this->keyValuePairs.Sort(); this->inBulkInsert = false;}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE> voidDictionary<KEYTYPE, VALUETYPE>::Add(const KEYTYPE& key, const VALUETYPE& value){ //n_assert(!this->Contains(key)); KeyValuePair<KEYTYPE, VALUETYPE> kvp(key, value); if (this->inBulkInsert) { this->keyValuePairs.Append(kvp); } else { this->keyValuePairs.InsertSorted(kvp); }}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE> voidDictionary<KEYTYPE, VALUETYPE>::Erase(const KEYTYPE& key){ #if NEBULA3_BOUNDSCHECKS n_assert(!this->inBulkInsert); #endif IndexT eraseIndex = this->keyValuePairs.BinarySearchIndex(key); #if NEBULA3_BOUNDSCHECKS n_assert(InvalidIndex != eraseIndex); #endif this->keyValuePairs.EraseIndex(eraseIndex);}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE> voidDictionary<KEYTYPE, VALUETYPE>::EraseAtIndex(IndexT index){ #if NEBULA3_BOUNDSCHECKS n_assert(!this->inBulkInsert); #endif this->keyValuePairs.EraseIndex(index);}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE> IndexTDictionary<KEYTYPE, VALUETYPE>::FindIndex(const KEYTYPE& key) const{ #if NEBULA3_BOUNDSCHECKS n_assert(!this->inBulkInsert); #endif return this->keyValuePairs.BinarySearchIndex(key);}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE> boolDictionary<KEYTYPE, VALUETYPE>::Contains(const KEYTYPE& key) const{ #if NEBULA3_BOUNDSCHECKS n_assert(!this->inBulkInsert); #endif return (InvalidIndex != this->keyValuePairs.BinarySearchIndex(key));}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE> const KEYTYPE&Dictionary<KEYTYPE, VALUETYPE>::KeyAtIndex(IndexT index) const{ #if NEBULA3_BOUNDSCHECKS n_assert(!this->inBulkInsert); #endif return this->keyValuePairs[index].Key();}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE> VALUETYPE&Dictionary<KEYTYPE, VALUETYPE>::ValueAtIndex(IndexT index){ #if NEBULA3_BOUNDSCHECKS n_assert(!this->inBulkInsert); #endif return this->keyValuePairs[index].Value();}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE> const VALUETYPE&Dictionary<KEYTYPE, VALUETYPE>::ValueAtIndex(IndexT index) const{ #if NEBULA3_BOUNDSCHECKS n_assert(!this->inBulkInsert); #endif return this->keyValuePairs[index].Value();}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE> KeyValuePair<KEYTYPE, VALUETYPE>&Dictionary<KEYTYPE, VALUETYPE>::KeyValuePairAtIndex(IndexT index) const{ #if NEBULA3_BOUNDSCHECKS n_assert(!this->inBulkInsert); #endif return this->keyValuePairs[index];}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE> VALUETYPE&Dictionary<KEYTYPE, VALUETYPE>::operator[](const KEYTYPE& key){ int keyValuePairIndex = this->FindIndex(key); #if NEBULA3_BOUNDSCHECKS n_assert(InvalidIndex != keyValuePairIndex); #endif return this->keyValuePairs[keyValuePairIndex].Value();}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE> const VALUETYPE&Dictionary<KEYTYPE, VALUETYPE>::operator[](const KEYTYPE& key) const{ int keyValuePairIndex = this->FindIndex(key); #if NEBULA3_BOUNDSCHECKS n_assert(InvalidIndex != keyValuePairIndex); #endif return this->keyValuePairs[keyValuePairIndex].Value();}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE>template<class RETURNTYPE>RETURNTYPEDictionary<KEYTYPE, VALUETYPE>::ValuesAs() const{ #if NEBULA3_BOUNDSCHECKS n_assert(!this->inBulkInsert); #endif RETURNTYPE result(this->Size(),this->Size()); IndexT i; for (i = 0; i < this->keyValuePairs.Size(); i++) { result.Append(this->keyValuePairs[i].Value()); } return result;}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE>Array<VALUETYPE>Dictionary<KEYTYPE, VALUETYPE>::ValuesAsArray() const{ return this->ValuesAs<Array<VALUETYPE> >();}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE> template<class RETURNTYPE>RETURNTYPEDictionary<KEYTYPE, VALUETYPE>::KeysAs() const{ #if NEBULA3_BOUNDSCHECKS n_assert(!this->inBulkInsert); #endif RETURNTYPE result(this->Size(),this->Size()); IndexT i; for (i = 0; i < this->keyValuePairs.Size(); i++) { result.Append(this->keyValuePairs[i].Key()); } return result;}//------------------------------------------------------------------------------/***/template<class KEYTYPE, class VALUETYPE>Array<KEYTYPE>Dictionary<KEYTYPE, VALUETYPE>::KeysAsArray() const{ return this->KeysAs<Array<KEYTYPE> >();}虽然代码看着很多，但是读者仔细琢磨一下，并不难的，这些代码如果读者看不懂的话，很难能看懂像虚幻4那样的引擎代码，模版在引擎开发中使用的非常广泛，不论是客户端还是服务器端，读者要做的首先要能看懂别人的代码，而且这种写法现在使用的非常多。
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