Source code of Windows XP (NT5)
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#ifndef __STRING_TABLE_H
#define __STRING_TABLE_H
///////////////////////////////////////////////////////////////////////////////
// Class: StringTable
//
// This class implements a simple hash table for storing text strings.
// The purpose of the table is to store strings and then verify later
// if the table contains a given string. Since there is no data associated
// with the string, the stored strings act as both key and data. Therefore,
// there is no requirement for string retrieval. Only existence checks
// are required.
// The structure maintains a fixed-length array of pointers, each pointing
// to a linked list structure (List). These lists are used to handle the
// problem of hash collisions (sometimes known as "separate chaining").
//
// Note that these classes do not contain all the stuff that is usually
// considered necessary in C++ classes. Things like copy constructors,
// assignment operator, type conversion etc are excluded. The classes
// are very specialized for the Font Folder application and these things
// would be considered "fat". Should this hash table class be later used
// in a situation where these things are needed, they can be added then.
//
// The public interfaces to the table are:
//
// Initialize - Initialize a new string table.
// Add - Add a new string to a table.
// Exists - Determine if a string exists in a table.
// Count - Return the number of strings in a table.
//
// Destruction of the object automatically releases all memory associated
// with the table.
//
// BrianAu - 4/11/96
///////////////////////////////////////////////////////////////////////////////
#include <windows.h>
#include <tchar.h>
//
// Hash table containing text strings.
//
class StringTable {
private:
//
// Linked list for hash collisions.
//
class List {
private:
//
// Element in hash collision list.
//
class Element {
public:
LPTSTR m_pszText; // Pointer to string text.
Element *m_pNext; // Pointer to next in list.
Element(void);
~Element(void);
BOOL Initialize(LPCTSTR pszItem);
BOOL operator == (const Element& ele) const;
BOOL operator != (const Element& ele) const;
#ifdef DEBUG
void DebugOut(void) const;
#endif
};
Element *m_pHead; // Ptr to head of list;
DWORD m_dwCount; // Count of elements in list.
public:
List(void);
~List(void);
BOOL Add(LPCTSTR pszText, BOOL bAllowDuplicates = TRUE);
BOOL Exists(LPCTSTR pszText) const;
DWORD Count(void) const { return m_dwCount; }
#ifdef DEBUG
void DebugOut(void) const;
#endif
};
CRITICAL_SECTION m_cs; // Protect from concurrent access.
List **m_apLists; // Array of ptrs to collision lists.
DWORD m_dwItemCount; // Number of items in table.
DWORD m_dwHashBuckets; // Number of pointers in hash array.
BOOL m_bCaseSensitive; // Key strings treated case-sensitive?
BOOL m_bAllowDuplicates; // Allow duplicate strings?
DWORD Hash(LPCTSTR pszText) const;
LPTSTR StringTable::CreateUpperCaseString(LPCTSTR pszText) const;
BOOL Exists(DWORD dwHashCode, LPCTSTR pszText);
public:
StringTable(void);
~StringTable(void);
BOOL Initialize(DWORD dwHashBuckets,
BOOL bCaseSensitive = TRUE,
BOOL bAllowDuplicates = FALSE);
BOOL IsInitialized(void);
void Destroy(void);
BOOL Add(LPCTSTR pszText);
BOOL Exists(LPCTSTR pszText);
DWORD Count(void) const { return m_dwItemCount; }
#ifdef DEBUG
void DebugOut(void) const;
#endif
};
#endif