#!ruby
# -*- mode: ruby; coding: utf-8 -*-
# Last updated: <2022/08/17 02:06:52 +0900>
#
# ffi sample. use mutex.
#
# 二重起動の防止（１） - Advanced HSP
# http://chokuto.ifdef.jp/advanced/singleton1.html
#
# Windows10 x64 21H2 + Ruby 2.6.10 p210 i386-mingw32 + ffi 1.15.5 x86-mingw32
#
# not work Ruby 1.9.3 p551 i386-mingw32 + ffi 1.9.14 x86-mingw32

require "rubygems"
require "ffi"

module WinKernel
  extend FFI::Library
  ffi_lib :kernel32
  ffi_convention :stdcall

  attach_function :CreateMutexW, [:long, :bool, :pointer], :ulong
  attach_function :ReleaseMutex, [:ulong], :bool
  attach_function :CloseHandle, [:ulong], :long
  # attach_function :GetLastError, [], :ulong
end

mutex_name = "rubyffimutexsample"
ERROR_ALREADY_EXISTS = 183

mutex = WinKernel.CreateMutexW(0, false, mutex_name.encode("UTF-16LE"))

# Add API.last_error #55 - Github Lab
# https://githublab.com/repository/issues/cosmo0920/win32-api/55
#
# GetLastError() is reset when calling Win32 API from Ruby.
# FFI::LastError.winapi_error" is a good choice.

begin
  # err = WinKernel.GetLastError
  # err = FFI::LastError.error
  err = FFI::LastError.winapi_error
rescue => e
  puts "Error : This version of ffi does not support FFI::LastError.winapi_error."
  if mutex != 0
    WinKernel.ReleaseMutex(mutex)
    WininKernel.CloseHandle(mutex)
  end
  exit
end

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
  WinKernel.ReleaseMutex(mutex)
  WinKernel.CloseHandle(mutex)
end