在TFileStream

Question

我试图找到mykeyword的位置并从加载的文件中提取字符串（最多200 MB）。

procedure TForm5.Button4Click(Sender: TObject);
var
  Stream: TFileStream; 
  Buffer: array [0 .. 1023] of AnsiChar;
  i: Integer;
  myKeyword: string;
  pullStr: AnsiString;
begin
myKeyword :='anything';
  Stream := TFileStream.Create(edtTarget.Text, fmOpenRead);
    while Stream.Position < Stream.Size do
    begin
      Stream.Read(Buffer, 1024);
      m1.Lines.Add(Buffer); // no need, just display to evaluate
      (* 1. Get address of given keyword *)
      // i := Stream.PositionOf(myKeyword);   < how to do this?
      (* 2. Stream Exract *)
      // pullStr := Stream.copy(i,1000); < how to do this ?
    end;
end;

我已阅读有关文件和字符串的其他主题。我找到了一个非常好的答案from here。我想我想扩展这些功能。 像

这样的东西

TFileSearchReplace.GetStrPos(const KeyWord: string) : Integer;
TFileSearchReplace.ExtractStr (const KeyWord: string; Len : Integer) ;  

Answer 1

procedure TForm5.Button4Click(Sender: TObject);
var
  Stream: TFileStream; 
  Buffer: AnsiString;
  i, BytesRead, SearchPos: Integer;
  myKeyword: string;
  pullStr: AnsiString;
  Found: Boolean;
begin
  myKeyword :='anything';
  Found := False;
  SetLength(Buffer, 1024);
  Stream := TFileStream.Create(edtTarget.Text, fmOpenRead);
    while Stream.Position < Stream.Size do
    begin
      // read some bytes and remember, how many bytes been read actually
      BytesRead := Stream.Read(Buffer[1], 1024);
      // glue new bytes to the end of the pullStr
      pullStr := pullStr + copy(Buffer, 1, BytesRead);
      // file is divided to two parts: before myKeyword, and after
      // if myKeyword alreay found, there is nothing to do, just repeat reading to pullStr
      if Found then
        continue;
      // if myKeyword is not found yet, pullStr acts like temporary buffer
      // search for myKeyword in buffer
      SearchPos := Pos(myKeyword, pullStr);
      if SearchPos > 0 then
      begin //keyword was found, delete from beginning up to and icluding myKeyword
        // from now on, pullStr is not tmp buffer, but result
        Found := True;
        Delete(pullStr, 1, SearchPos + Length(myKeyWord) - 1);
        continue;
      end;
      // myKeyword still not found. Find last line end in buffer
      SearchPos := LastDelimiter(#13#10, pullStr);
      // and delete everything before it
      if SearchPos > 0 then
        Delete(pullStr, 1, SearchPos);
      // so if myKeyword spans across two reads, it still will be found in next iteration
    end;
    // if there is no myKeyword in file, clear buffer
    if not Found then
      pullStr := '';
end;