#!ruby
# -*- mode: ruby; coding: utf-8 -*-
# Last updated: <2022/08/17 02:06:34 +0900>
#
# win32api sample. use mutex.
#
# 二重起動の防止（１） - Advanced HSP
# http://chokuto.ifdef.jp/advanced/singleton1.html
#
# Windows10 x64 21H2 + Ruby 1.8.7 p330 i386-mswin32

require "Win32API"

create_mutex = Win32API.new("kernel32", "CreateMutex", "llp", "l")
release_mutex = Win32API.new("kernel32", "ReleaseMutex", "l", "l")
close_handle = Win32API.new("kernel32", "CloseHandle", "l", "l")
get_last_error = Win32API.new("kernel32", "GetLastError", "", "l")

MUTEX_NAME = "ruby_win32api_mutex_sample"
ERROR_ALREADY_EXISTS = 183

mutex = create_mutex.call(0, 1, MUTEX_NAME)
err = get_last_error.call()
puts "Mutex : #{mutex}"
puts "GetLastError : #{err}"

if mutex == 0 or err == ERROR_ALREADY_EXISTS
  puts "already exists"
  exit
else
  10.times do |i|
    puts i
    sleep 1
  end
end

if mutex != 0
  release_mutex.call(mutex)
  close_handle.call(mutex)
end