module SimpleCov::ResultMerger::ResultsetStore

def resultset_path 

def resultset_path
  File.join(SimpleCov.coverage_path, ".resultset.json")
end

def synchronize(&)

call no matter how deeply nested.
any given time. Reentrant: the lock is acquired once per outer
Ensure only one process is reading or writing the resultset at 
def synchronize(&)
  return yield if @locked
  @locked = true
  with_flock(&)
ensure
  @locked = false
end

def with_flock 

def with_flock
  FileUtils.mkdir_p(SimpleCov.coverage_path)
  File.open(writelock_path, "w+") do |f|
    f.flock(File::LOCK_EX)
    yield
  end
end

def write(resultset) 

def write(resultset)
  FileUtils.mkdir_p(SimpleCov.coverage_path)
  temp_path = "#{resultset_path}.#{Process.pid}.tmp"
  File.open(temp_path, "w") { |f| f.puts JSON.pretty_generate(resultset) }
  File.rename(temp_path, resultset_path)
end

def writelock_path 

def writelock_path
  File.join(SimpleCov.coverage_path, ".resultset.json.lock")
end