1 files changed, 60 insertions, 0 deletions
diff --git a/tool/lib/atomic_write.rb b/tool/lib/atomic_write.rb
new file mode 100644
index 0000000000..12a8e12a8a
--- /dev/null
+++ b/tool/lib/atomic_write.rb
@@ -0,0 +1,60 @@
+require 'optparse'
+require_relative 'vpath'
+require_relative 'colorize'
+
+class AtomicWrite
+  attr_accessor :vpath, :timestamp, :output, :compare :color
+
+  def initialize
+    @vpath = nil
+    @timestamp = nil
+    @output = nil
+    @compare = nil
+    @color = nil
+  end
+
+  def def_options(opt)
+    opt.on('-t', '--timestamp[=PATH]') {|v| @timestamp = v || true}
+    opt.on('-o', '--output=PATH') {|v| @output = v}
+    opt.on('-c', '--[no-]if-change') {|v| @compare = v}
+    opt.on('--color') {@color = true}
+    @vpath.def_options(opt) if @vpath
+    opt
+  end
+
+  def emit(result)
+    output = @output
+    if output
+      update output, result
+      stamp output
+    else
+      print result
+    end
+  end
+
+  def update(output, result)
+    color = Colorize.new(@color)
+    unchanged = color.pass("unchanged")
+    updated = color.fail("updated")
+    vpath = @vpath || File
+    if @compare and (vpath.open(output, "rb") {|f| f.read} rescue nil) == result
+      puts "#{output} #{unchanged}"
+      false
+    else
+      open(output, "wb") {|f| f.print result}
+      puts "#{output} #{updated}"
+      true
+    end
+  end
+
+  def stamp(output, timestamp = @timestamp)
+    if timestamp
+      if timestamp == true
+        dir, base = File.split(output)
+        timestamp = File.join(dir, ".time." + base)
+      end
+      File.open(timestamp, 'a') {}
+      File.utime(nil, nil, timestamp)
+    end
+  end
+end