Delphi 转换大小写字符（UpperCase、LowerCase）

function UpperCase(const S: string): string;
var
  Ch: Char;
  L: Integer;
  Source, Dest: PChar;
begin
  L := Length(S);
  SetLength(Result, L);
  Source := Pointer(S);
  Dest := Pointer(Result);
  while L <> 0 do
  begin
    Ch := Source^;
    if (Ch >= 'a') and (Ch <= 'z') then Dec(Ch, 32);
    Dest^ := Ch;
    Inc(Source);
    Inc(Dest);
    Dec(L);
  end;
end;

function LowerCase(const S: string): string;
var
  Ch: Char;
  L: Integer;
  Source, Dest: PChar;
begin
  L := Length(S);
  SetLength(Result, L);
  Source := Pointer(S);
  Dest := Pointer(Result);
  while L <> 0 do
  begin
    Ch := Source^;
    if (Ch >= 'A') and (Ch <= 'Z') then Inc(Ch, 32);
    Dest^ := Ch;
    Inc(Source);
    Inc(Dest);
    Dec(L);
  end;
end;