1 files changed, 47 insertions, 0 deletions
diff --git a/tool/lib/test/jobserver.rb b/tool/lib/test/jobserver.rb
new file mode 100644
index 0000000000..7b889163b0
--- /dev/null
+++ b/tool/lib/test/jobserver.rb
@@ -0,0 +1,47 @@
+module Test
+  module JobServer
+  end
+end
+
+class << Test::JobServer
+  def connect(makeflags = ENV["MAKEFLAGS"])
+    return unless /(?:\A|\s)--jobserver-(?:auth|fds)=(?:(\d+),(\d+)|fifo:((?:\\.|\S)+))/ =~ makeflags
+    begin
+      if fifo = $3
+        fifo.gsub!(/\\(?=.)/, '')
+        r = File.open(fifo, IO::RDONLY|IO::NONBLOCK|IO::BINARY)
+        w = File.open(fifo, IO::WRONLY|IO::NONBLOCK|IO::BINARY)
+      else
+        r = IO.for_fd($1.to_i(10), "rb", autoclose: false)
+        w = IO.for_fd($2.to_i(10), "wb", autoclose: false)
+      end
+    rescue
+      r&.close
+      nil
+    else
+      return r, w
+    end
+  end
+
+  def acquire_possible(r, w, max)
+    return unless tokens = r.read_nonblock(max - 1, exception: false)
+    if (jobs = tokens.size) > 0
+      jobserver, w = w, nil
+      at_exit do
+        jobserver.print(tokens)
+        jobserver.close
+      end
+    end
+    return jobs + 1
+  rescue Errno::EBADF
+  ensure
+    r&.close
+    w&.close
+  end
+
+  def max_jobs(max = 2, makeflags = ENV["MAKEFLAGS"])
+    if max > 1 and (r, w = connect(makeflags))
+      acquire_possible(r, w, max)
+    end
+  end
+end