Delphi中扩展的字符串操作函数

{*****************************扩展的字符串操作函数*****************************}
procedure SwapStr(var s1, s2: string); // 交换字串
function StrRight(Str: String; Len: Integer): String; //返回字符串右边的字符 Examples: StrRight('ABCEDFG',3);返回:'DFG'
function StrLeft(Str: string; Len: Integer): string; //返回字符串左边的字符
function StrNum(ShortStr:string;LongString:string):Integer; //返回某个字符串中某个字符串中出现的次数
function FindStr(ShortStr:String;LongStrIng:String):Integer; //返回某个字符串中查找某个字符串的位置
function SubStr(psInput:String; BeginPlace,CutLeng:Integer):String;//返回从位置BeginPlace开始切取长度为CatLeng字符串
function RandomStr(aLength : Longint) : String; //随机字符串函数
function RandomSys(Num: Integer): integer; //利用系统时间产生随机数
function RandomGuid:string;//用GUID得到一个永远不会重复的随机序列

 方法主体：

procedure SwapStr(var s1, s2: string);
var
  tempstr: string;
begin
  tempstr := s1;
  s1 := s2;
  s2 := tempstr;
end;

function StrRight(Str: string; Len: Integer): string;
begin
  if Len >= Length(Str) then
    Result := Str
  else
    Result := Copy(Str, Length(Str) - Len + 1, Len);
end;

function StrLeft(Str: string; Len: Integer): string;
begin
  if Len >= Length(Str) then
    Result := Str
  else
    Result := Copy(Str, 1, Len);
end;

function StrNum(ShortStr:string;LongString:string):Integer;
var
   i:Integer;
begin
   i:=0;
   while pos(ShortStr,LongString)>0 do
      begin
         i:=i+1;
         LongString:=Substr(LongString,(FindStr(ShortStr,LongString))+1,Length(LongString)-FindStr(ShortStr,LongString))
      end;
   Result:=i;
end;

function FindStr(ShortStr:String;LongStrIng:String):Integer;//在一个字符串中找某个字符的位置
var
   locality:integer;
begin
   locality:=Pos(ShortStr,LongStrIng);
   if locality=0 then
      Result:=0
   else
      Result:=locality;
end;

function SubStr(psInput:String; BeginPlace,CutLeng:Integer):String;
begin
	Result:=Copy(psInput,BeginPlace,CutLeng)
end;

function RandomStr(aLength : Longint) : String;
var
  X : Longint;
begin
  if aLength <= 0 then exit;
  SetLength(Result, aLength);
  for X:=1 to aLength do
    Result[X] := Chr(Random(26) + 65);
end;

function RandomSys(Num: Integer): integer;
var
   T: _SystemTime;
   X: integer;
   I: integer;
begin
   Result := 0;
   If Num = 0 then Exit;;
      GetSystemTime(T);
      X := Trunc(T.wMilliseconds/10) * T.wSecond * 1231;
      X := X + random(1);
      if X<>0 then
         X := -X;
      X := Random(X);
      X := X mod num;
      for I := 0 to X do
         X := Random(Num);
      Result := X;
end;

function RandomGuid:string;
var
  ID: TGUID;
begin
  if CreateGuid(ID) =0 then
  begin
    Result := GUIDToString(ID);
  end;
end;