Add a target in GN that generates a last_change.h file for the SVN revision.

build/util/lastchange.py

 #!/usr/bin/env python
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """
 lastchange.py -- Chromium revision fetching utility.
 """
 
 import re
@@ skipping 150 matching lines @@
                   FetchGitSVNRevision(directory, svn_url_regex) or
                   FetchGitRevision(directory))
   if not version_info:
     if default_lastchange and os.path.exists(default_lastchange):
       revision = open(default_lastchange, 'r').read().strip()
       version_info = VersionInfo(None, revision)
     else:
       version_info = VersionInfo(None, None)
   return version_info
 
+def GetHeaderGuard(path):
+  """
+  Returns the header #define guard for the given file path.
+  This treats everything after the last instance of "src/" as being a
+  relevant part of the guard. If there is no "src/", then the entire path
+  is used.
+  """
+  src_index = path.rfind('src/')
+  if src_index != -1:
+    guard = path[src_index + 4:]
+  else:
+    guard = path
+  guard = guard.upper()
+  return guard.replace('/', '_').replace('.', '_').replace('\\', '_') + '_'

[viettrungluu, 2013/11/06 18:39:22]

Maybe it'd be better to just replace all non-alphanumeric characters with
'_'.... <shrug>

[brettw, 2013/11/07 18:47:33]

I didn't do this because it doesn't come up, it's more work, and I'm lazy. Feel
free to argue if you feel strongly.

+
+def GetHeaderContents(path, define, version):
+  """
+  Returns what the contents of the header file should be that indicate the given
+  revision. Note that the #define is specified as a string, even though it's
+  currently always a SVN revision number, in case we need to move to git hashes.
+  """
+  header_guard = GetHeaderGuard(path)
+
+  header_contents = """/* Generated by lastchange.py, do not edit.*/
+
+#ifndef %(header_guard)s
+#define %(header_guard)s
+
+#define %(define)s "%(version)s"
+
+#endif  // %(header_guard)s
+"""
+  header_contents = header_contents % { 'header_guard': header_guard,
+                                        'define': define,
+                                        'version': version }
+  return header_contents
 
 def WriteIfChanged(file_name, contents):
   """
   Writes the specified contents to the specified file_name
   iff the contents are different than the current contents.
   """
   try:
     old_contents = open(file_name, 'r').read()
   except EnvironmentError:
     pass
   else:
     if contents == old_contents:
       return
     os.unlink(file_name)
   open(file_name, 'w').write(contents)
 
 
 def main(argv=None):
   if argv is None:
     argv = sys.argv
 
   parser = optparse.OptionParser(usage="lastchange.py [options]")
   parser.add_option("-d", "--default-lastchange", metavar="FILE",
-                    help="default last change input FILE")
+                    help="Default last change input FILE.")
+  parser.add_option("", "--define",

[viettrungluu, 2013/11/06 18:39:22]

Maybe this should be "--version-macro" or "--version-macro-name", instead of
"--define", which is a little vague. <shrug>

+                    help="Name of C #define when using --header. Defaults to " +
+                    "LASTCHANGE.",
+                    default="LASTCHANGE")

[viettrungluu, 2013/11/06 18:39:22]

Why is your default ("LASTCHANGE") something other than what you actually use
("LAST_CHANGE")?

   parser.add_option("-o", "--output", metavar="FILE",
-                    help="write last change to FILE")
+                    help="Write last change to FILE. " +
+                    "Can be combined with --header to write both files.")
+  parser.add_option("", "--header", metavar="FILE",
+                    help="Write last change to FILE as a C/C++ header. " +
+                    "Can be combined with --output to write both files.")
   parser.add_option("--revision-only", action='store_true',
-                    help="just print the SVN revision number")
+                    help="Just print the SVN revision number. Overrides any " +
+                    "file-output-related options.")
   parser.add_option("-s", "--source-dir", metavar="DIR",
-                    help="use repository in the given directory")
+                    help="Use repository in the given directory.")
   opts, args = parser.parse_args(argv[1:])
 
   out_file = opts.output
+  header = opts.header
 
   while len(args) and out_file is None:
     if out_file is None:
       out_file = args.pop(0)
   if args:
     sys.stderr.write('Unexpected arguments: %r\n\n' % args)
     parser.print_help()
     sys.exit(2)
 
   if opts.source_dir:
     src_dir = opts.source_dir
   else:
     src_dir = os.path.dirname(os.path.abspath(__file__))
 
   version_info = FetchVersionInfo(opts.default_lastchange, src_dir)
 
   if version_info.revision == None:
     version_info.revision = '0'
 
   if opts.revision_only:
     print version_info.revision
   else:
     contents = "LASTCHANGE=%s\n" % version_info.revision
-    if out_file:
-      WriteIfChanged(out_file, contents)
+    if not out_file and not opts.header:
+      sys.stdout.write(contents)
     else:
-      sys.stdout.write(contents)
+      if out_file:
+        WriteIfChanged(out_file, contents)
+      if header:
+        WriteIfChanged(header,
+                       GetHeaderContents(header, opts.define,
+                                         version_info.revision))
 
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(main())