要想进行二次开发，先进行分析之一：

我们开始介绍第一个类：HashTable

class HashTable {public:  virtual ~HashTable();  //以下必须由一个特定子类实现  static HashTable* create(int keyType);//静态方法主要是为了实现单例模式，一种数据只能实现一种特定的HashTable  virtual void* Add(char const* key, void* value) = 0;//虚方法，需子类实现  // Returns the old value if different, otherwise 0  virtual Boolean Remove(char const* key) = 0;  virtual void* Lookup(char const* key) const = 0;  // Returns 0 if not found  virtual unsigned numEntries() const = 0;  Boolean IsEmpty() const { return numEntries() == 0; }//是否为空  // Used to iterate through the members of the table:  class Iterator {//HashTable内的指针  public:    static Iterator* create(HashTable const& hashTable);    virtual ~Iterator();        virtual void* next(char const*& key) = 0; // returns 0 if none    protected:    Iterator(); // 子类能够使用  };  //可用于先后删除每个表中的条目  void* RemoveNext();  //返回表中的第一个条目。  void* getFirst();  protected:  HashTable(); // abstract base class};

第二个介绍 BasicHashTable

class BasicHashTable: public HashTable {private:class TableEntry; // forwardpublic:  BasicHashTable(int keyType);//创建基本的HashTable 有字符型也有字符串型的 还有别的类型，对最小表的清空  virtual ~BasicHashTable();//删除每个key对应的TableEntry，如果新建竖着的TableEntry*，就需要删除新建的大小  // Used to iterate through the members of the table:  class Iterator; friend class Iterator; // to make Sun's C++ compiler happy  class Iterator: public HashTable::Iterator {  public:    Iterator(BasicHashTable const& table);  private:    void* next(char const*& key); // returns 0 if none//初始时TableEntry*为空，index++找到下一个不为空的TableEntry，然后给下一个给fNextEntry，返回当前value  private:    BasicHashTable const& fTable;    unsigned fNextIndex; // 记录下一个的index    TableEntry* fNextEntry; // 在当前表中下一个TableEntry  };private:  virtual void* Add(char const* key, void* value);//向竖着的某key对应的TableEntry*中添加一个value，  //因多个key估计对应一个index，所以要遍历整个TableEntry*找到对应的key  // 如果在这HashTable，找到该key，返回以前数据，更新表；没有找到返回0，并在结尾添加新的TableEntry  virtual Boolean Remove(char const* key);//删除TableEntry  virtual void* Lookup(char const* key) const;//返回key的TableEntry的value  // Returns 0 if not found  virtual unsigned numEntries() const;private:  class TableEntry {  public:    TableEntry* fNext;//这是个链表，相当于HashTable里面的一个key所对应的离岸边    char const* key;    void* value;  };  TableEntry* lookupKey(char const* key, unsigned& index) const;    // returns entry matching "key", or NULL if none  Boolean keyMatches(char const* key1, char const* key2) const;    // used to implement "lookupKey()"  TableEntry* insertNewEntry(unsigned index, char const* key);    // creates a new entry, and inserts it in the table  void assignKey(TableEntry* entry, char const* key);    // used to implement "insertNewEntry()"  void deleteEntry(unsigned index, TableEntry* entry);  void deleteKey(TableEntry* entry);    // used to implement "deleteEntry()"  void rebuild(); // rebuilds the table as its size increases  unsigned hashIndexFromKey(char const* key) const;    // used to implement many of the routines above  unsigned randomIndex(uintptr_t i) const {    return (unsigned)(((i*1103515245) >> fDownShift) & fMask);  }private:  TableEntry** fBuckets; //形象化描述如下  // 2-3-4  // |  // 5-4-4-6  // |  // 7-2  TableEntry* fStaticBuckets[SMALL_HASH_TABLE_SIZE];// 最小的HashTable  unsigned fNumBuckets/*竖着的TableEntry链表长度*/, fNumEntries/*已存在实体个数*/, fRebuildSize/*重建竖着的TableEntry链表长度*/, fDownShift, fMask;  int fKeyType/*该元素数据类型*/;};