unit H62;

interface

uses SysUtils;

function IntToH62(N: UInt64): string; //整数转到 62 进制字符串

function H62ToInt(S: string): UInt64; //62 进制字符串转到整数

implementation

function _C2B(C: Char): Byte; inline;

begin

  Result := 0;

  if C in ['0'..'9'] then Result:=Byte(C) - 48;      //0..9

  if C in ['a'..'z'] then Result:=Byte(C) - 97 + 10; //a..z

  if C in ['A'..'Z'] then Result:=Byte(C) - 65 + 36; //A..Z

end;

function _B2C(B: Byte): Char; inline;

begin

  Result := #0;

  if B <= 9 then Result:=Char(B + 48);                       //0..9

  if (B >= 10) and (B <= 35) then Result:=Char(B - 10 + 97); //a..z

  if (B >= 36) and (B <= 61) then Result:=Char(B - 36 + 65); //A..Z

end;

function _Power(B,P: Cardinal): UInt64; inline;

var

  i: Integer;

begin

  Result := B;

  for i := 1 to P-1 do Result := Result * B;

end;

function _C2V(C: Char; N: Byte): UInt64; inline;

begin

  Result := 0;

  if (N = 0) then Result:=_C2B(C);

  if (N > 0) then Result := _C2B(C) * _Power(62, N);

end;

function IntToH62(N: UInt64): string;

var

  C: Char;

begin

  Result := '';

  repeat

    C := _B2C(N mod 62);

    Result := C + Result;

    N := N div 62;

  until (N = 0);

end;

function H62ToInt(S: string): UInt64;

var

  C: Char;

  L,N,I: Cardinal;

begin

  Result := 0;

  L := Length(S);

  if L > 11 then raise Exception.Create('Err: H62ToInt'); //不能多于 11 位

  for I := L downto 1 do

  begin

    C := S[I];

    N := L - I;

    Result := Result + _C2V(C, N);

  end;

end;

end.