path: root/src/corelib/fpg_stringhashlist.pas

{
    fpGUI  -  Free Pascal GUI Library

    Copyright (C) 2006 - 2008 See the file AUTHORS.txt, included in this
    distribution, for details of the copyright.

    See the file COPYING.modifiedLGPL, included in this distribution,
    for details about redistributing fpGUI.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

    Description:
      This file was originally part of the Lazarus Component Library (LCL).
      Thanks to Markus Waldenburg.

      Ported this unit to fpGUI by Graeme Geldenhuys.
      TStringHashList is supposed to be faster than FPC's TFPObjectHashTable.
      This unit is used in fpg_pofile unit.
}

unit fpg_stringhashlist;

{$mode objfpc}{$H+}

interface

uses
  Classes, SysUtils, fpg_constants;

type
  PStringHashItem = ^TStringHashItem;
  TStringHashItem = record
    HashValue: Cardinal;
    Key: String;
    Data: Pointer;
  end;

  PStringHashItemList = ^PStringHashItem;

  TStringHashList = class(TObject)
  private
    FList: PStringHashItemList;
    FCount: Integer;
    fCaseSensitive: Boolean;
    function CompareString(const Value1, Value2: String): Boolean;
    function CompareValue(const Value1, Value2: Cardinal): Integer;
    function GetData(const S: String): Pointer;
    procedure SetCaseSensitive(const Value: Boolean);
    procedure Delete(Index: Integer);
    procedure SetData(const S: String; const AValue: Pointer);
  protected
    function HashOf(const Key: string): Cardinal;
    procedure Insert(Index: Integer; Item: PStringHashItem);
  public
    constructor Create(CaseSensitivity: boolean);
    destructor Destroy; override;
    function Add(const S: String): Integer;
    function Add(const S: String; ItemData: Pointer): Integer;
    procedure Clear;
    function Find(const S: String): Integer;
    function Remove(const S: String): Integer;
    property CaseSensitive: Boolean read fCaseSensitive write SetCaseSensitive;
    property Count: Integer read FCount;
    property Data[const S: String]: Pointer read GetData write SetData; default;
    property List: PStringHashItemList read FList;
  end;


implementation

var
  UpperCaseChars: array[char] of char;

{ TStringHashList }

function TStringHashList.Add(const S: String): Integer;
begin
  Result:=Add(S,nil);
end;

function TStringHashList.Add(const S: String; ItemData: Pointer): Integer;
var
  Item: PStringHashItem;
  First, Last, I: Integer;
  Val: Cardinal;
  Larger: boolean;
begin
  New(Item);
  Val:= HashOf(S);
  Item^.HashValue := Val;
  Item^.Key := S;
  Item^.Data := ItemData;
  if FCount > 0 then
  begin
    First:=0;
    Last:= FCount-1;
    Larger:=False;
    while First<=Last do
    begin
      I:=(First+Last)shr 1;
      Case CompareValue(Val, fList[I]^.HashValue)<=0 of
        True:
          begin
            Last:=I-1;
            Larger:=False;
          end;
        False:
          begin
            First:=I+1;
            Larger:=True;
          end;
      end;
    end;
    Case Larger of
      True: Result:=I+1;
      False: Result:=I;
    end;
  end else
    Result:=0;
  Insert(Result,Item);
end;

procedure TStringHashList.Clear;
var
  I: Integer;
begin
  if fCount = 0 then exit;
  for I:= 0 to fCount -1 do
    Dispose(fList[I]);
  if FList<>nil then begin
    FreeMem(FList);
    FList:=nil;
  end;
  fCount:= 0;
end;

function TStringHashList.CompareString(const Value1, Value2: String): Boolean;
var
  I, Len: Integer;
  P1,P2: PChar;
begin
  Result:= False;
  P1:= PChar(Value1);
  Len:= Length(Value1);
  P2:= PChar(Value2);
  if Len = Length(Value2) then
  begin
    Result:= True;
    case fCaseSensitive of
    True:
      for I:= Len -1 downto 0 do
        if P1[I] <> P2[I] then begin
          Result:= False;
          break;
        end;
    False:
      for I:= Len -1 downto 0 do
        if UpperCaseChars[P1[I]] <> UpperCaseChars[P2[I]] then begin
          Result:= False;
          break;
        end;
    end;
  end;
end;

function TStringHashList.CompareValue(const Value1, Value2: Cardinal): Integer;
begin
  Result:= 0;
  if Value1 > Value2 then
    Result:= 1
  else if Value1 < Value2 then
    Result:= -1;
end;

function TStringHashList.GetData(const S: String): Pointer;
var i: integer;
begin
  i:=Find(S);
  if i>=0 then
    Result:=FList[i]^.Data
  else
    Result:=nil;
end;

procedure TStringHashList.Delete(Index: Integer);
begin
  if (Index >= 0) and (Index < FCount) then
  begin
    dec(FCount);
    if Index < FCount then
      System.Move(FList[Index + 1], FList[Index],
        (FCount - Index) * SizeOf(PStringHashItem));
  end;
end;

procedure TStringHashList.SetData(const S: String; const AValue: Pointer);
var i: integer;
begin
  i:=Find(S);
  if i>=0 then
    FList[i]^.Data:=AValue
  else
    Add(S,AValue);
end;

destructor TStringHashList.Destroy;
begin
  Clear;
  inherited Destroy;
end;

function TStringHashList.Find(const S: String): Integer;
var
  Value: Integer;
  First, Last, Temp, I: Integer;
begin
  Value:= HashOf(s);
  Result:= -1;
  First:= 0;
  Last:= Count -1;
  while First <= Last do
  begin
    Temp:= (First + Last) div 2;
    case CompareValue(Value, FList[Temp]^.HashValue) of
     1: First:= Temp +1;
     0:
       begin
         Result:= Temp;
         if CompareString(S, FList[Temp]^.Key) then
           exit
         else
           break;
       end;
     -1: Last:= Temp-1;
    end;
    end;
  if Result <> -1 then
  begin
    Result:= -1;
    First:= Temp -1;
    if First > 0 then
    while CompareValue(Value, FList[First]^.HashValue) = 0 do
      dec(First);
    inc(First);
    Last:= Temp +1;
    if Last < Count -1 then
    while CompareValue(Value, FList[Last]^.HashValue) = 0 do
      inc(Last);
    dec(Last);
    for I:= First to Last do
      if CompareString(S, FList[I]^.Key) then
      begin
        Result:= I;
        Exit;
      end;
  end;
end;

function TStringHashList.HashOf(const Key: string): Cardinal;
var
  P: PChar;
  I, Len: Integer;
begin
  P:= PChar(Key);
  Len:= Length(Key);
  Result := Len;
  // use the last 30 characters to compute the hash
  case fCaseSensitive of
  True:
    for I:= Len -1 downto 0 do
      inc(Result, cardinal(ord(P[I])) shl I);
  False:
    for I:= Len -1 downto 0 do
      inc(Result, cardinal(ord(UpperCaseChars[P[I]])) shl I);
  end;
end;

procedure TStringHashList.Insert(Index: Integer; Item: PStringHashItem);
begin
  ReallocMem(FList, (fCount +1) * SizeOf(PStringHashItem));
  if Index > fCount then Index:= fCount;
  if Index < 0 then Index:= 0;
  if Index < FCount then
    System.Move(FList[Index], FList[Index + 1],
      (FCount - Index) * SizeOf(PStringHashItem));
  FList[Index] := Item;
  Inc(FCount);
end;

constructor TStringHashList.Create(CaseSensitivity: boolean);
begin
  fCaseSensitive:=CaseSensitivity;
  inherited Create;
end;

function TStringHashList.Remove(const S: String): Integer;
begin
  Result:= Find(S);
  if Result > -1 then
  begin
    Dispose(fList[Result]);
    Delete(Result);
  end;
end;

procedure TStringHashList.SetCaseSensitive(const Value: Boolean);
begin
  if fCaseSensitive <> Value then
  begin
    if Count > 0 then
    begin
      raise EListError.Create(rsErrListMustBeEmpty);
      exit;
    end;
    fCaseSensitive := Value;
  end;
end;

//------------------------------------------------------------------------------
procedure InternalInit;
var c: char;
begin
  for c:=Low(char) to High(char) do begin
    UpperCaseChars[c]:=upcase(c);
  end;
end;

initialization
  InternalInit;

end.