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delph HASH类

作者:admin 来源:未知 日期:2010/10/9 0:16:24 人气: 标签:

HASH类是我在学习《DELPHI算法与数据结构》的时候按照上面的文字和例子重新整理的,就是为了自己看起来比较方便。这个HASH类使用的是线性探测的方式来消除冲突。希望这个HASH类对大家编写代码有一定的帮助。同时希望大家在发现代码中的错误或者问题后能给我留言。
{
类名 :线性探测HASH表
作者 :张超
创建时间 :2008-07-06
说明 :此HASH表使用线性探测方法实现。
修改说明 :
2008-07-06 创建
测试说明 :
}
unit Hash_Unit;

interface
uses
RecordList_Unit,Windows;
type
TOnRomveHash = procedure(Buf:Pointer) of object;
//槽结构
THashSlot = record
FKey : String; //Hash的Key
FItem : Pointer; //内容
FInUse: Boolean; //是否在使用
end;
PHashSlot = ^THashSlot;
type
THashClass = class
private
FHashCS:TRTLCriticalSection;
FCount:Integer;
FTable : TRecordList;
FOnRomve: TOnRomveHash;
function HashFunc(FKey:String;FTableSize:Integer):Integer;
function IndexOf(FKey:String;var FItem:Pointer):Integer;
procedure SetTableSize(FTableSize:Integer);
function GetPrime(N:Integer):Integer; //得到最接近的质数
procedure SetOnRomve(const Value: TOnRomveHash);
public
constructor Create(TableSize:Integer = 1024);
destructor Destroy; override;
(****方法****)
function Delete(FKey:String):Boolean;
function Find(FKey:String;var FItem:Pointer):Boolean;
function Insert(const FKey:String;FItem:Pointer):Boolean;
procedure Clear;
published
property OnRomve:TOnRomveHash read FOnRomve write SetOnRomve;
property Count:Integer read FCount;
end;
implementation
{ THashClass }
procedure THashClass.Clear;
var
Inx : integer;
begin
EnterCriticalSection(FHashCS);
try
if FCount<>0 then
begin
for Inx := 0 to pred(FTable.Count) do
begin
if PHashSlot(FTable[Inx])^.FInUse then
begin
PHashSlot(FTable[Inx])^.FKey:='';
//抛出清空Hash中有数据的槽事件
if Assigned(OnRomve) then
begin
OnRomve(PHashSlot(FTable[Inx])^.FItem);
end;
end;
PHashSlot(FTable[Inx])^.FInUse:=false;
end;
FCount := 0;
end;
finally
LeaveCriticalSection(FHashCS);
end;
end;
constructor THashClass.Create(TableSize:Integer);
begin
InitializeCriticalSection(FHashCS);
FTable:=TRecordList.Create(SizeOf(THashSlot));
FTable.Name:='';
FTable.Count:=GetPrime(TableSize);
end;
function THashClass.Delete(FKey: String):Boolean;
var
Inx:Integer;
ItemSlot : Pointer;
Slot : PHashSlot;
Key : string;
Item : pointer;
begin
EnterCriticalSection(FHashCS);
try
Result:=true;
Inx := IndexOf(FKey, ItemSlot);
if (Inx = -1) then
begin
//没有找到
Result:=false;
Exit;
end;
//Dispose(PHashSlot(ItemSlot).FItem);
PHashSlot(ItemSlot).FInUse:=False;
PHashSlot(ItemSlot).FKey:='';
dec(FCount);
inc(Inx);
if (Inx = FTable.Count) then
begin
Inx := 0;
end;
Slot := PHashSlot(FTable[Inx]);
while Slot^.FInUse do
begin
Item := Slot^.FItem;
Key := Slot^.FKey;
Slot^.FKey := '';
Slot^.FInUse := False;
dec(FCount);
Insert(Key, Item);
{move to the next slot}
inc(Inx);
if (Inx = FTable.Count) then
begin
Inx := 0;
end;
Slot := PHashSlot(FTable[Inx]);
end;
finally
LeaveCriticalSection(FHashCS);
end;
end;
destructor THashClass.Destroy;
begin
if (FTable <> nil) then
begin
Clear;
FTable.Destroy;
end;
DeleteCriticalSection(FHashCS);
inherited Destroy;
end;
function THashClass.Find(FKey: String; var FItem: Pointer): Boolean;
var
Slot : Pointer;
begin
EnterCriticalSection(FHashCS);
try
if IndexOf(FKey,Slot)<>-1 then
begin
Result:=true;
FItem:=PHashSlot(Slot).FItem;
end
else
begin
Result:=False;
FItem:=nil;
end;
finally
LeaveCriticalSection(FHashCS);
end;
end;
function THashClass.GetPrime(N: Integer): Integer;
{$I TDPrimes.inc}
const
Forever = true;
var
L, R, M : integer;
RootN : integer;
IsPrime : boolean;
DivisorIndex : integer;
begin
EnterCriticalSection(FHashCS);
try
if (N = 2) then
begin
Result := N;
Exit;
end;
if Odd(N) then
begin
Result := N;
end
else
begin
Result := succ(N);
end;
if (Result <= MaxPrime) then
begin
L := 0;
R := pred(PrimeCount);
while (L <= R) do
begin
M := (L + R) div 2;
if (Result = Primes[M]) then
begin
Exit;
end
else if (Result < Primes[M]) then
begin
R := pred(M);
end
else
begin
L := succ(M);
end;
end;
Result := Primes[L];
Exit;
end;
if (Result <= (MaxPrime * MaxPrime)) then
begin
while Forever do
begin
RootN := round(Sqrt(Result));
DivisorIndex := 1; {ignore the prime number 2}
IsPrime := true;
while (DivisorIndex < PrimeCount) and (RootN > Primes[DivisorIndex]) do
begin
if ((Result div Primes[DivisorIndex]) * Primes[DivisorIndex] = Result) then
begin
IsPrime := false;
Break;
end;
inc(DivisorIndex);
end;
if IsPrime then
begin
Exit;
end;
inc(Result, 2);
end;
end;
finally
LeaveCriticalSection(FHashCS);
end;
end;
function THashClass.HashFunc(FKey: String; FTableSize: Integer): Integer;
var
G:Longint;
I:Integer;
Hash:Longint;
begin
Result:=0;
Hash:=0;
for I:=0 to Length(FKey) do
begin
Hash:=(Hash shl 4) + Ord(FKey[I]);
G:=Hash and $F0000000;
if (G<>0) then
begin
Hash:=Hash xor (G shr 24) xor G;
end;
Result:=Hash mod FTableSize;
end;
end;
function THashClass.IndexOf(FKey: String; var FItem: Pointer): Integer;
var
Inx:Integer;
CurSlot : PHashSlot;
FirstInx : integer;
begin
EnterCriticalSection(FHashCS);
try
//计算此KEY的Index
Inx:=HashFunc(FKey,FTable.Count);
FirstInx := Inx;
while True do
begin
CurSlot := PHashSlot(FTable[Inx]);
if not CurSlot.FInUse then
begin
FItem:=CurSlot;
Result:=-1;
Exit;
end
else
begin
if CurSlot^.FKey = FKey then
begin
FItem:=CurSlot;
Result:=Inx;
Exit;
end;
end;
//没有找到,需要循环
Inc(Inx);
if (Inx = FTable.Count) then
begin
Inx := 0;
end
else if (Inx = FirstInx) then
begin
FItem := nil;
Result := -1;
Exit;
end;
end;
finally
LeaveCriticalSection(FHashCS);
end;
end;
function THashClass.Insert(const FKey: String; FItem: Pointer):Boolean;
var
Slot:Pointer;
begin
EnterCriticalSection(FHashCS);
try
//加入HASH表中
Result:=true;
if IndexOf(FKey,Slot)<>-1 then
begin
//已经存在
Result:=false;
Exit;
end;
if Slot = nil then
begin
//Hash表已经满了
Result:=false;
Exit;
end;
PHashSlot(Slot).FKey:=FKey;
PHashSlot(Slot).FItem:=FItem;
PHashSlot(Slot).FInUse:=true;
Inc(FCount);
if FCount * 3 > (FTable.Count * 2) then
begin
//已经大于2/3需要扩展Hash表
SetTableSize(GetPrime(succ(FTable.Count * 2)))
end;
finally
LeaveCriticalSection(FHashCS);
end;
end;
procedure THashClass.SetOnRomve(const Value: TOnRomveHash);
begin
FOnRomve := Value;
end;
procedure THashClass.SetTableSize(FTableSize: Integer);
var
Inx:Integer;
OldTable:TRecordList;
begin
OldTable := FTable;
FTable := TRecordList.Create(sizeof(THashSlot));
try
FTable.Count := FTableSize;
FCount := 0;
for Inx := 0 to pred(OldTable.Count) do
begin
with PHashSlot(OldTable[Inx])^ do
begin
if FInUse then
begin
Insert(FKey, FItem);
FKey := '';
end;
end;
end;
except
FTable.Free;
FTable := OldTable;
raise;
end;
OldTable.Free;
end;
end.
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