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HashTableKey_String.cpp

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//*** HashTableKey_String.cpp ***

#include "HashTableKey_String.h"
#include "StandardLibrary.h"



HashTableKey_String::HashTableKey_String():
   string_(0),
   hash_(0)
   {
   }

HashTableKey_String::HashTableKey_String(const HashTableKey_String& string):
   string_(0),
   hash_(0)
   {
   if (string.string_)
      {
      string_=StrDup(string.string_);
      }
   hash_=string.hash_;
   }

const HashTableKey_String& HashTableKey_String::operator =(const HashTableKey_String& string )
   {
   // Get rid of the copy of the string
   if (string_)
      {
      Free(string_);
      string_=0;
      }
   if (string.string_)
      {
      string_=StrDup(string.string_);
      }
   hash_=string.hash_;
   return *this;
   }


//*** Constructor ***

HashTableKey_String::HashTableKey_String(const char* string):
   string_(0),
   hash_(0)
   {
   
   // Keep a copy of the string
   if (string)
      {
      string_=StrDup(string);
      }
   
   // Calculate the hash value for the string
   hash_=CalculateHash(string);
   }


//*** Destructor ***

HashTableKey_String::~HashTableKey_String()
   {
   // Get rid of the copy of the string
   if (string_)
      {
      Free(string_);
      string_=0;
      }
   }


//*** GetHash ***

unsigned int HashTableKey_String::GetHash() const 
   { 
   return hash_; 
   }
   

//*** GetString ***

const char* HashTableKey_String::GetString() const
   {
   return string_;
   }

//*** Compare ***

bool HashTableKey_String::Compare(const HashTableKey* key) const
   {
   // Make sure key is of the correct type
   if (key->GetType()!=GetType())
      {
      return false;
      }

   if (string_==0 || (static_cast<const HashTableKey_String*>(key))->string_==0)
      {
      if (string_==(static_cast<const HashTableKey_String*>(key))->string_)
         {
         return true;
         }
      return false;
      }
   // The keys are only the same if the two strings are the same (two
   // different strings might have the same hash value)
   return (StrICmp(string_,(static_cast<const HashTableKey_String*>(key))->string_)==0);
   }


//*** CalculateHash ***

unsigned int HashTableKey_String::CalculateHash(const char* key) const
   {
   unsigned long hash = 5381; // Seed value

   // Modify hash for each character in the string
   const char* stringData=key;
   while (*stringData)
      {
      // A little bit-manipulation magic to get a nice distribution of values
      hash = ((hash << 5) + hash) ^ ToUpper(*stringData);
      stringData++;
      }

   // Return the final hash value
   return hash;

   }
   

//*** GetType ***

StringId HashTableKey_String::GetType() const
   {
   static StringId type("HashTableKey_String");
   return type;
   }

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