function QuickPos(const Substr, S: WideString; MatchesIndex: Integer = 1): Integer; function QuickPosBack(const Substr, S: WideString; MatchesReverseIndex: Integer = 1): Integer; 主要用途是搜索字符串中第n个Substr。 经过测试,这2个函数的速度比直接用Pos+Copy快好几倍(如果字符串够长,可能10几倍) 比Pos+Delete(如JVCL的函数NPos)处理要快(至少2-3倍以上)。 说明1:虽然说速度上的差异是微秒级别的,但是一个快速方便的Pos函数,还是会给编程带来很多方便。 说明2:经过大量测试和FastString作者的承认,FastString的速度还没有DELPHI标准函数快。 ======================================================================== // Compares a substring with a string. *for inline use" // C: 2004-07-05 | M: 2004-07-05 function _InlineCompareText(const Substr, S: WideString; StartIndex: Integer = 1; LenOfSubstr: Integer = -1; LenOfS: Integer = -1): Boolean; var I: Integer; begin if LenOfSubstr = -1 then LenOfSubstr := Length(Substr); if LenOfS = -1 then LenOfS := Length(S); if LenOfSubstr > LenOfS then begin Result := False; Exit; end; for I := 1 to LenOfSubstr do if Substr[I] <> S[I + StartIndex - 1] then begin Result := False; Exit; end; Result := True; end; // Returns the 1. index of a substring within a string start at a certain index. // C: 2004-07-05 | M: 2004-07-05 | P: 1.0+ function _PosForward(const Substr, S: WideString; StartIndex: Integer; LenOfSubstr: Integer = -1; LenOfS: Integer = -1): Integer; var I: Integer; begin Result := 0; case LenOfSubstr of 0: Exit; -1: LenOfSubstr := Length(Substr); end; if LenOfS = -1 then LenOfS := Length(S); for I := StartIndex to LenOfS do begin if (S[I] = Substr[1]) and _InlineCompareText(Substr, S, I, LenOfSubstr, LenOfS) then begin Result := I; Exit; end; end; end; // Returns the 1. index of a substring within a string. // Note: Searching time will increase when MatchesIndex increased. // C: 2004-04-09 | M: 2004-07-05 | P: 1.0+ function QuickPos(const Substr, S: WideString; MatchesIndex: Integer = 1): Integer; var LenOfS, LenOfSubstr: Integer; begin Result := Pos{Pos}(Substr, S); if (MatchesIndex = 1) or (Result = 0) then Exit; LenOfS := Length(S); LenOfSubstr := Length(Substr); while (MatchesIndex > 1) and (Result > 0) do begin Result := _PosForward{Pos}(Substr, S, Result + 1, LenOfSubstr, LenOfS); // Tip!! Do not use func.Copy!! if Result = 0 then Exit; Dec(MatchesIndex); end; end; // Returns the last index of a substring within a string. // Todo: Using asm to rewrite this function. The asm-code looks very like func.Pos! // C: 2004-04-09 | M: 2004-07-03 | P: n/a function _PosBack(const Substr, S: WideString; StopIndex: Integer = -1; LenOfSubstr: Integer = -1): Integer; var I: Integer; begin Result := 0; case LenOfSubstr of 0: Exit; -1: LenOfSubstr := Length(Substr); end; if StopIndex = -1 then StopIndex := Length(S); for I := StopIndex - LenOfSubstr + 1 downto 1 do begin if (S[I] = Substr[1]) and _InlineCompareText(Substr, S, I, LenOfSubstr) then begin Result := I; Exit; end; end; end; // Returns the last index of a substring within a string. // C: 2004-04-09 | M: 2004-07-03 | P: n/a function QuickPosBack(const Substr, S: WideString; MatchesReverseIndex: Integer = 1): Integer; var LenOfSubstr: Integer; begin Result := _PosBack{Pos}(Substr, S); if (MatchesReverseIndex = 1) or (Result = 0) then Exit; LenOfSubstr := Length(Substr); while (MatchesReverseIndex > 1) and (Result > 0) do begin Result := _PosBack{Pos}(Substr, S, Result + LenOfSubstr - 2, LenOfSubstr); Dec(MatchesReverseIndex); end; end;