memory_lock.rb

require 'ffi'

module MemoryLock
  extend FFI::Library
  ffi_lib FFI::Library::LIBC

  # int mlockall(int flags);
  attach_function :mlockall, [:int], :int
  # int munlockall(void);
  attach_function :munlockall, [], :int

  MCL_CURRENT = 1
  #MCL_FUTURE = 2

  def self.lock!
    ret = MemoryLock.mlockall MemoryLock::MCL_CURRENT
    if ret.zero?
      warn "mlockall locked current process #{$$}"
    else
      err = SystemCallError.new('mlockall', FFI.errno)
      warn "mlockall failed with #{err.inspect} (#{FFI.errno})"
    end
    ret
  end

  def self.unlock!
    ret = MemoryLock.munlockall
    if ret.zero?
      warn "munlockall un-locked current process #{$$}"
    else
      err = SystemCallError.new('munlockall', FFI.errno)
      warn "munlockall failed with #{err.inspect} (#{FFI.errno})"
    end
    ret
  end
end