Поиск строки текста в наследниках TCustomEdit

{ПРИМЕР :

[...]

implementation

uses Search;}
{$R *.DFM}

{procedure TForm1.Button1Click(Sender: TObject);
begin

SearchMemo(RichEdit1, "Найди меня", [frDown]);
end;

В опции поиска можно подключать, отключать, комбинировать следующие
параметры:
frDown - указывает на то, что происходит поиск вниз по тексту от курсора(при
отключенном frDown"е будет происходит поиск вверх по тексту).
frMatchCase - указывает на то, что следует проводить поиск с учетом
регистра.
frWholeWord - указывает на то, что следует искать только слово целиком.

[...]

Авторские права на этот юнит пренадлежат неизвесно кому.

В каком виде этот юнит попал мне, практически в этом же
виде я отдаю его вам. Пользуйтесь и благодарите неизвесного
героя.}

unit Search;

interface

uses

  WinProcs, SysUtils, StdCtrls, Dialogs;

const
  {****************************************************************************

  * Default word delimiters are any character except the core alphanumerics. *
  ****************************************************************************}
  WordDelimiters: set of Char = [#0..#255] - ["a".."z", "A".."Z", "1".."9",
    "0"];
  {******************************************************************************

  * SearchMemo scans the text of a TEdit, TMemo, or other TCustomEdit-derived  *
  * component for a given search string. The search starts at the current      *
  * caret position in the control.  The Options parameter determines whether   *
  * the search runs forward (frDown) or backward from the caret position,      *
  * whether or not the text comparison is case sensitive, and whether the      *
  * matching string must be a whole word.  If text is already selected in the  *
  * control, the search starts at the "far end" of the selection (SelStart if  *
  * searching backwards, SelEnd if searching forwards).  If a match is found,  *
  * the control"s text selection is changed to select the found text and the   *
  * function returns True.  If no match is found, the function returns False.  *
  ******************************************************************************}
function SearchMemo(Memo: TCustomEdit;

  const SearchString: string;
  Options: TFindOptions): Boolean;
{******************************************************************************

* SearchBuf is a lower-level search routine for arbitrary text buffers.      *
* Same rules as SearchMemo above. If a match is found, the function returns  *
* a pointer to the start of the matching string in the buffer. If no match,  *
* the function returns nil.                                                  *
******************************************************************************}
function SearchBuf(Buf: PChar; BufLen: Integer;

  SelStart, SelLength: Integer;
  SearchString: string;
  Options: TFindOptions): PChar;

implementation

function SearchMemo(Memo: TCustomEdit;

  const SearchString: string;
  Options: TFindOptions): Boolean;
var

  Buffer, P: PChar;
  Size: Word;
begin

  Result := False;
  if (Length(SearchString) = 0) then
    Exit;
  Size := Memo.GetTextLen;
  if Size = 0 then
    Exit;
  Buffer := StrAlloc(Size + 1);
  try
    Memo.GetTextBuf(Buffer, Size + 1);
    P := SearchBuf(Buffer, Size, Memo.SelStart, Memo.SelLength, SearchString,
      Options);
    if P <> nil then
    begin
      Memo.SelStart := P - Buffer;
      Memo.SelLength := Length(SearchString);
      Result := True;
    end;
  finally
    StrDispose(Buffer);
  end;
end;

function SearchBuf(Buf: PChar; BufLen: Integer;

  SelStart, SelLength: Integer;
  SearchString: string;
  Options: TFindOptions): PChar;
var

  SearchCount, I: Integer;
  C: Char;
  Direction: Shortint;
  CharMap: array[Char] of Char;

  function FindNextWordStart(var BufPtr: PChar): Boolean;
  begin { (True XOR N) is equivalent to (not N) }
    //    Result := False;      { (False XOR N) is equivalent to (N)    }

    { When Direction is forward (1), skip non delimiters, then skip delimiters. }
    { When Direction is backward (-1), skip delims, then skip non delims }

    while (SearchCount > 0) and
      ((Direction = 1) xor
      (BufPtr^ in WordDelimiters)) do
    begin
      Inc(BufPtr, Direction);
      Dec(SearchCount);
    end;

    while (SearchCount > 0) and
      ((Direction = -1) xor
      (BufPtr^ in WordDelimiters)) do
    begin
      Inc(BufPtr, Direction);
      Dec(SearchCount);
    end;

    Result := SearchCount > 0;
    if Direction = -1 then
    begin {back up one char, to leave ptr on first non delim}
      Dec(BufPtr, Direction);
      Inc(SearchCount);
    end;
  end;

begin

  Result := nil;

  if BufLen <= 0 then
    Exit;

  if frDown in Options then
  begin {if frDown...}
    Direction := 1;
    Inc(SelStart, SelLength); { start search past end of selection }
    SearchCount := BufLen - SelStart - Length(SearchString);

    if SearchCount < 0 then
      Exit;

    if Longint(SelStart) + SearchCount > BufLen then
      Exit;

  end {if frDown...}
  else
  begin {else}
    Direction := -1;
    Dec(SelStart, Length(SearchString));
    SearchCount := SelStart;
  end; {else}

  if (SelStart < 0) or (SelStart > BufLen) then
    Exit;

  Result := @Buf[SelStart];
  { Using a Char map array is faster than calling AnsiUpper on every character }

  for C := Low(CharMap) to High(CharMap) do
    CharMap[C] := C;

  if not (frMatchCase in Options) then
  begin {if not (frMatchCase}
    AnsiUpperBuff(PChar(@CharMap), sizeof(CharMap));
    AnsiUpperBuff(@SearchString[1], Length(SearchString));
  end; {if not (frMatchCase}

  while SearchCount > 0 do
  begin {while SearchCount}
    if frWholeWord in Options then
    begin
      if not FindNextWordStart(Result) then
        Break;
    end;
    I := 0;

    while (CharMap[Result[I]] = SearchString[I + 1]) do
    begin {while (CharMap...}
      Inc(I);
      if I >= Length(SearchString) then
      begin {if I >=...}
        if (not (frWholeWord in Options)) or
          (SearchCount = 0) or
          (Result[I] in WordDelimiters) then
          Exit;
        Break;
      end; {if I >=...}
    end; {while (CharMap...}

    Inc(Result, Direction);
    Dec(SearchCount);
  end; {while SearchCount}

  Result := nil;
end;

end.