faststrings.pas

自己写的一个 RSS 阅读器

    //Go back to findind the first char
          POP  ECX
          Jmp  @NextChar

    @Matches:
          Dec  ECX
          Jnz  @CompareNext

    @FullMatch:
          POP  ECX

          mov  EAX, EDI
          sub  EAX, aSourceString
          inc  EAX
          mov  Result, EAX
          jmp  @TheEnd
    @NextChar:
          dec  EDI
          dec  ECX
          jnz  @ScaSB

          mov  Result,0

    @TheEnd:
          pop  EBX
          pop  EDI
          pop  ESI
  end;
end;

//My move is not as fast as MOVE when source and destination are both
//DWord aligned, but certainly faster when they are not.
//As we are moving characters in a string, it is not very likely at all that
//both source and destination are DWord aligned, so moving bytes avoids the
//cycle penality of reading/writing DWords across physical boundaries
procedure FastCharMove(const Source; var Dest; Count : Integer);
asm
//Note:  When this function is called, delphi passes the parameters as follows
//ECX = Count
//EAX = Const Source
//EDX = Var Dest

        //If no bytes to copy, just quit altogether, no point pushing registers
        cmp   ECX,0
        Je    @JustQuit

        //Preserve the critical delphi registers
        push  ESI
        push  EDI

        //move Source into ESI  (generally the SOURCE register)
        //move Dest into EDI (generally the DEST register for string commands)
        //This may not actually be neccessary, as I am not using MOVsb etc
        //I may be able just to use EAX and EDX, there may be a penalty for
        //not using ESI, EDI but I doubt it, this is another thing worth trying !
        mov   ESI, EAX
        mov   EDI, EDX

        //The following loop is the same as repNZ MovSB, but oddly quicker !
    @Loop:
        //Get the source byte
        Mov   AL, [ESI]
        //Point to next byte
        Inc   ESI
        //Put it into the Dest
        mov   [EDI], AL
        //Point dest to next position
        Inc   EDI
        //Dec ECX to note how many we have left to copy
        Dec   ECX
        //If ECX <> 0 then loop
        Jnz   @Loop

        //Another optimization note.
        //Many people like to do this

        //Mov AL, [ESI]
        //Mov [EDI], Al
        //Inc ESI
        //Inc ESI

        //There is a hidden problem here, I wont go into too much detail, but
        //the pentium can continue processing instructions while it is still
        //working out the result of INC ESI or INC EDI
        //(almost like a multithreaded CPU)
        //if, however, you go to use them while they are still being calculated
        //the processor will stop until they are calculated (a penalty)
        //Therefore I alter ESI and EDI as far in advance as possible of using them

        //Pop the critical Delphi registers that we have altered
        pop   EDI
        pop   ESI
    @JustQuit:
end;

function FastAnsiReplace(const S, OldPattern, NewPattern: string;
  Flags: TReplaceFlags): string;
var
  BufferSize, BytesWritten: Integer;
  SourceString, FindString: string;
  ResultPChar: PChar;
  FindPChar, ReplacePChar: PChar;
  SPChar, SourceStringPChar, PrevSourceStringPChar: PChar;
  FinalSourceMarker: PChar;
  SourceLength, FindLength, ReplaceLength, CopySize: Integer;
  FinalSourcePosition: Integer;
begin
  //Set up string lengths
  BytesWritten := 0;
  SourceLength := Length(S);
  FindLength := Length(OldPattern);
  ReplaceLength := Length(NewPattern);
  //Quick exit
  if (SourceLength = 0) or (FindLength = 0) or
    (FindLength > SourceLength) then
  begin
    Result := S;
    Exit;
  end;

  //Set up the source string and find string
  if rfIgnoreCase in Flags then
  begin
    SourceString := AnsiUpperCase(S);
    FindString := AnsiUpperCase(OldPattern);
  end else
  begin
    SourceString := S;
    FindString := OldPattern;
  end;

  //Set up the result buffer size and pointers
  try
    if ReplaceLength <= FindLength then
      //Result cannot be larger, only same size or smaller
      BufferSize := SourceLength
    else
      //Assume a source string made entired of the sub string
      BufferSize := (SourceLength * ReplaceLength) div
    FindLength;

    //10 times is okay for starters. We don't want to
    //go allocating much more than we need.
    if BufferSize > (SourceLength * 10) then
      BufferSize := SourceLength * 10;
  except
    //Oops, integer overflow! Better start with a string
    //of the same size as the source.
    BufferSize := SourceLength;
  end;
  SetLength(Result, BufferSize);
  ResultPChar := @Result[1];

  //Set up the pointers to S and SourceString
  SPChar := @S[1];
  SourceStringPChar := @SourceString[1];
  PrevSourceStringPChar := SourceStringPChar;
  FinalSourceMarker := @SourceString[SourceLength - (FindLength - 1)];

  //Set up the pointer to FindString
  FindPChar := @FindString[1];

  //Set the pointer to ReplaceString
  if ReplaceLength > 0 then
    ReplacePChar := @NewPattern[1]
  else
    ReplacePChar := nil;

  //Replace routine
  repeat
    //Find the sub string
    SourceStringPChar := AnsiStrPos(PrevSourceStringPChar,
    FindPChar);
    if SourceStringPChar = nil then Break;
    //How many characters do we need to copy before
    //the string occurs
    CopySize := SourceStringPChar - PrevSourceStringPChar;

    //Check we have enough space in our Result buffer
    if CopySize + ReplaceLength > BufferSize - BytesWritten then
    begin
      BufferSize := Trunc((BytesWritten + CopySize + ReplaceLength) * cDeltaSize);
      SetLength(Result, BufferSize);
      ResultPChar := @Result[BytesWritten + 1];
    end;

    //Copy the preceeding characters to our result buffer
    Move(SPChar^, ResultPChar^, CopySize);
    Inc(BytesWritten, CopySize);
    //Advance the copy position of S
    Inc(SPChar, CopySize + FindLength);
    //Advance the Result pointer
    Inc(ResultPChar, CopySize);
    //Copy the replace string into the Result buffer
    if Assigned(ReplacePChar) then
    begin
      Move(ReplacePChar^, ResultPChar^, ReplaceLength);
      Inc(ResultPChar, ReplaceLength);
      Inc(BytesWritten, ReplaceLength);
    end;

    //Fake delete the start of the source string
    PrevSourceStringPChar := SourceStringPChar + FindLength;
  until (PrevSourceStringPChar > FinalSourceMarker) or
    not (rfReplaceAll in Flags);

  FinalSourcePosition := Integer(SPChar - @S[1]);
  CopySize := SourceLength - FinalSourcePosition;
  SetLength(Result, BytesWritten + CopySize);
  if CopySize > 0 then
    Move(SPChar^, Result[BytesWritten + 1], CopySize);
end;

function FastReplace(const aSourceString : string; const aFindString, aReplaceString : string;
   CaseSensitive : Boolean = False) : string;
var
  PResult                     : PChar;
  PReplace                    : PChar;
  PSource                     : PChar;
  PFind                       : PChar;
  PPosition                   : PChar;
  CurrentPos,
  BytesUsed,
  lResult,
  lReplace,
  lSource,
  lFind                       : Integer;
  Find                        : TFastPosProc;
  CopySize                    : Integer;
  JumpTable                   : TBMJumpTable;
begin
  LSource := Length(aSourceString);
  if LSource = 0 then begin
    Result := aSourceString;
    exit;
  end;
  PSource := @aSourceString[1];

  LFind := Length(aFindString);
  if LFind = 0 then exit;
  PFind := @aFindString[1];

  LReplace := Length(aReplaceString);

  //Here we may get an Integer Overflow, or OutOfMemory, if so, we use a Delta
  try
    if LReplace <= LFind then
      SetLength(Result,lSource)
    else
      SetLength(Result, (LSource *LReplace) div  LFind);
  except
    SetLength(Result,0);
  end;

  LResult := Length(Result);
  if LResult = 0 then begin
    LResult := Trunc((LSource + LReplace) * cDeltaSize);
    SetLength(Result, LResult);
  end;


  PResult := @Result[1];


  if CaseSensitive then
  begin
    MakeBMTable(PChar(AFindString), lFind, JumpTable);
    Find := BMPos;
  end else
  begin
    MakeBMTableNoCase(PChar(AFindString), lFind, JumpTable);
    Find := BMPosNoCase;
  end;


  BytesUsed := 0;
  if LReplace > 0 then begin
    PReplace := @aReplaceString[1];
    repeat
      PPosition := Find(PSource,PFind,lSource, lFind, JumpTable);
      if PPosition = nil then break;

      CopySize := PPosition - PSource;
      Inc(BytesUsed, CopySize + LReplace);

      if BytesUsed >= LResult then begin
        //We have run out of space
        CurrentPos := Integer(PResult) - Integer(@Result[1]) +1;
        LResult := Trunc(LResult * cDeltaSize);
        SetLength(Result,LResult);
        PResult := @Result[CurrentPos];
      end;

      FastCharMove(PSource^,PResult^,CopySize);
      Dec(lSource,CopySize + LFind);
      Inc(PSource,CopySize + LFind);
      Inc(PResult,CopySize);

      FastCharMove(PReplace^,PResult^,LReplace);
      Inc(PResult,LReplace);

    until lSource < lFind;
  end else begin
    repeat
      PPosition := Find(PSource,PFind,lSource, lFind, JumpTable);
      if PPosition = nil then break;

      CopySize := PPosition - PSource;
      FastCharMove(PSource^,PResult^,CopySize);
      Dec(lSource,CopySize + LFind);
      Inc(PSource,CopySize + LFind);
      Inc(PResult,CopySize);
      Inc(BytesUsed, CopySize);
    until lSource < lFind;
  end;

  SetLength(Result, (PResult+LSource) - @Result[1]);
  if LSource > 0 then
    FastCharMove(PSource^, Result[BytesUsed + 1], LSource);
end;

function FastTagReplace(const SourceString, TagStart, TagEnd: string;
  FastTagReplaceProc: TFastTagReplaceProc; const UserData: Integer): string;
var
  TagStartPChar: PChar;
  TagEndPChar: PChar;
  SourceStringPChar: PChar;
  TagStartFindPos: PChar;
  TagEndFindPos: PChar;
  TagStartLength: Integer;
  TagEndLength: Integer;
  DestPChar: PChar;
  FinalSourceMarkerStart: PChar;
  FinalSourceMarkerEnd: PChar;
  BytesWritten: Integer;
  BufferSize: Integer;
  CopySize: Integer;
  ReplaceString: string;

  procedure AddBuffer(const Buffer: Pointer; Size: Integer);
  begin
    if BytesWritten + Size > BufferSize then
    begin
      BufferSize := Trunc(BufferSize * cDeltaSize);
      if BufferSize <= (BytesWritten + Size) then
        BufferSize := Trunc((BytesWritten + Size) * cDeltaSize);
      SetLength(Result, BufferSize);
      DestPChar := @Result[BytesWritten + 1];
    end;
    Inc(BytesWritten, Size);
    FastCharMove(Buffer^, DestPChar^, Size);
    DestPChar := DestPChar + Size;
  end;

begin
  Assert(Assigned(@FastTagReplaceProc));
  TagStartPChar := PChar(TagStart);
  TagEndPChar := PChar(TagEnd);
  if (SourceString = '') or (TagStart = '') or (TagEnd = '') then
  begin
    Result := SourceString;
    Exit;
  end;

  SourceStringPChar := PChar(SourceString);
  TagStartLength := Length(TagStart);
  TagEndLength := Length(TagEnd);
  FinalSourceMarkerEnd := SourceStringPChar + Length(SourceString) - TagEndLength;
  FinalSourceMarkerStart := FinalSourceMarkerEnd - TagStartLength;

  BytesWritten := 0;
  BufferSize := Length(SourceString);
  SetLength(Result, BufferSize);
  DestPChar := @Result[1];

  repeat
    TagStartFindPos := AnsiStrPos(SourceStringPChar, TagStartPChar);
    if (TagStartFindPos = nil) or (TagStartFindPos > FinalSourceMarkerStart) then Break;
    TagEndFindPos := AnsiStrPos(TagStartFindPos + TagStartLength, TagEndPChar);
    if (TagEndFindPos = nil) or (TagEndFindPos > FinalSourceMarkerEnd) then Break;
    CopySize := TagStartFindPos - SourceStringPChar;
    AddBuffer(SourceStringPChar, CopySize);
    CopySize := TagEndFindPos - (TagStartFindPos + TagStartLength);
    SetLength(ReplaceString, CopySize);
    if CopySize > 0 then
      Move((TagStartFindPos + TagStartLength)^, ReplaceString[1], CopySize);
    FastTagReplaceProc(ReplaceString, UserData);
    if Length(ReplaceString) > 0 then
      AddBuffer(@ReplaceString[1], Length(ReplaceString));
    SourceStringPChar := TagEndFindPos + TagEndLength;
  until SourceStringPChar > FinalSourceMarkerStart;
  CopySize := PChar(@SourceString[Length(SourceString)]) - (SourceStringPChar - 1);
  if CopySize > 0 then
    AddBuffer(SourceStringPChar, CopySize);
  SetLength(Result, BytesWritten);
end;

function SmartPos(const SearchStr,SourceStr : string;
                  const CaseSensitive : Boolean = TRUE;
                  const StartPos : Integer = 1;
                  const ForwardSearch : Boolean = TRUE) : Integer;
begin
  // NOTE:  When using StartPos, the returned value is absolute!
  if (CaseSensitive) then
    if (ForwardSearch) then
      Result:=
        FastPos(SourceStr,SearchStr,Length(SourceStr),Length(SearchStr),StartPos)
    else
      Result:=
        FastPosBack(SourceStr,SearchStr,Length(SourceStr),Length(SearchStr),StartPos)
  else
    if (ForwardSearch) then
      Result:=
        FastPosNoCase(SourceStr,SearchStr,Length(SourceStr),Length(SearchStr),StartPos)
    else
      Result:=
        FastPosBackNoCase(SourceStr,SearchStr,Length(SourceStr),Length(SearchStr),StartPos)
end;

function SplitString(const Source,ch:string):TStringList;
var
  temp:String;
  i:Integer;
begin
  Result:=TStringList.Create;
  //如果是空自符串则返回空列表
  if Source=''
  then exit;
  temp:=Source;
  i:=pos(ch,Source);
  while i<>0 do
  begin
     Result.add(copy(temp,0,i-1));
     Delete(temp,1,i);
     i:=pos(ch,temp);
  end;
  Result.add(temp);
end;

function CreateGuid: string;
var
  ID: TGUID;
begin
  Result := '';
  if CoCreateGuid(ID) = S_OK then
    Result := GUIDToString(ID);
end;

function ExtractURLPath(aURL:WideString):WideString;
var i,r:Integer;
begin
  r := Length(aURL);
  for  i:= Length(aURL) - 1 downto 0 do    // Iterate
  begin
    if aURL[i]='/' then
    begin
      r:=i;
      Break;
    end;
  end;    // for
  Result := Copy(aURL,0,r);
end;

function CheckSpecialChar(AText:string):Boolean;
begin
  Result :=not (
  (Pos('&',AText)>0) or
  (Pos('<',AText)>0) or
  (Pos('>',AText)>0) or
  (Pos('?',AText)>0) or
  (Pos('"',AText)>0) or
  (Pos('/',AText)>0) or
  (Pos('!',AText)>0) or
  (Pos('\',AText)>0) );
end;

var
  I: Integer;
initialization
  {$IFNDEF LINUX}
    for I:=0 to 255 do GUpcaseTable[I] := Chr(I);
    CharUpperBuff(@GUpcaseTable[0], 256);
  {$ELSE}
    for I:=0 to 255 do GUpcaseTable[I] := UpCase(Chr(I));
  {$ENDIF}
  GUpcaseLUT := @GUpcaseTable[0];
end.