DouKaku?

:: gcd.bat
@echo off
  setlocal
    set n=0

    echo %1%2|findstr /r "[^0-9]" >NUL 2>&1
    if %ERRORLEVEL% equ 0 (echo %~n0 [NUMBER] [NUMBER]) & goto :EOF

    call :gcd %1 %2 n
  endlocal & echo %n%
goto :EOF

:gcd
  setlocal enabledelayedexpansion
    set a=%1
    set b=%2
    set m=0
    set q=0

    if %a% lss %b% (
      set /a a=%b%-%a%
      set /a b-=!a!
      set /a a+=!b!
    )

    :loop_gcd
      call :mod %a% %b% m
      if %m% equ 0 (endlocal & set %3=%b%) & goto :EOF
      :: 剰余を除数の半分未満にして演算効率を向上
      call :div %b% 2 q
      if %q% lss %m% set /a m=%b%-%m%
      set a=%b%
      set b=%m%
    goto loop_gcd
  endlocal
goto :EOF

:mod
  setlocal
    set m=0
    set q=0

    call :div %1 %2 q

    set /a m=%2*%q%
  endlocal & set /a %3=%1-%m%
goto :EOF

:div
  setlocal enabledelayedexpansion
    set i=0
    set m=%1
    set m_=0
    set n=%2
    set n_=0
    set q=0

    if %n% gtr %m% (endlocal & set %3=%q%) & goto :EOF

    call :msb %m% m_
    call :msb %n% n_
    set /a i=%m_%-%n_%

    :loop_div
      if %i% lss 0 (endlocal & set %3=%q%) & goto :EOF
      set /a "q<<=1"
      set /a "m_=%m%>>%i%"
      if %m_% geq %n% (
        set /a "n_=%n%<<%i%"
        set /a m-=!n_!
        set /a q+=1
      )
      set /a i-=1
    goto loop_div
  endlocal
goto :EOF

:: 最上位ビットを取得(most significant bit)
:msb
  setlocal
    set i=%1
    set n=0

    :loop_msb
      set /a "i>>=1"
      set /a n+=1
    if %i% neq 0 goto loop_msb
  endlocal & set %2=%n%
goto :EOF