make sure the md5_tstamp module can be imported multiple times without causing problems

waflib/extras/md5_tstamp.py

@@ -2,6 +2,9 @@
 # encoding: utf-8
 
 """
+This module assumes that only one build context is running at a given time, which
+is not the case if you want to execute configuration tests in parallel.
+
 Store some values on the buildcontext mapping file paths to
 stat values and md5 values (timestamp + md5)
 this way the md5 hashes are computed only when timestamp change (can be faster)
@@ -18,52 +21,57 @@ except: import pickle as cPickle
 from waflib import Utils, Build, Context
 
 STRONGEST = True
-Context.DBFILE += '_md5tstamp'
 
-Build.hashes_md5_tstamp = {}
-Build.SAVED_ATTRS.append('hashes_md5_tstamp')
-def store(self):
-	# save the hash cache as part of the default pickle file
-	self.hashes_md5_tstamp = Build.hashes_md5_tstamp
-	self.store_real()
-Build.BuildContext.store_real = Build.BuildContext.store
-Build.BuildContext.store      = store
+try:
+	Build.BuildContext.store_real
+except AttributeError:
 
-def restore(self):
-	# we need a module variable for h_file below
-	self.restore_real()
-	try:
-		Build.hashes_md5_tstamp = self.hashes_md5_tstamp or {}
-	except Exception as e:
-		Build.hashes_md5_tstamp = {}
-Build.BuildContext.restore_real = Build.BuildContext.restore
-Build.BuildContext.restore      = restore
+	Context.DBFILE += '_md5tstamp'
 
-def h_file(filename):
-	st = os.stat(filename)
-	if stat.S_ISDIR(st[stat.ST_MODE]): raise IOError('not a file')
+	Build.hashes_md5_tstamp = {}
+	Build.SAVED_ATTRS.append('hashes_md5_tstamp')
+	def store(self):
+		# save the hash cache as part of the default pickle file
+		self.hashes_md5_tstamp = Build.hashes_md5_tstamp
+		self.store_real()
+	Build.BuildContext.store_real = Build.BuildContext.store
+	Build.BuildContext.store      = store
 
-	if filename in Build.hashes_md5_tstamp:
-		if Build.hashes_md5_tstamp[filename][0] == str(st.st_mtime):
-			return Build.hashes_md5_tstamp[filename][1]
-	m = Utils.md5()
-
-	if STRONGEST:
-		f = open(filename, 'rb')
-		read = 1
+	def restore(self):
+		# we need a module variable for h_file below
+		self.restore_real()
 		try:
-			while read:
-				read = f.read(100000)
-				m.update(read)
-		finally:
-			f.close()
-	else:
-		m.update(str(st.st_mtime))
-		m.update(str(st.st_size))
-		m.update(filename)
+			Build.hashes_md5_tstamp = self.hashes_md5_tstamp or {}
+		except Exception as e:
+			Build.hashes_md5_tstamp = {}
+	Build.BuildContext.restore_real = Build.BuildContext.restore
+	Build.BuildContext.restore      = restore
 
-	# ensure that the cache is overwritten
-	Build.hashes_md5_tstamp[filename] = (str(st.st_mtime), m.digest())
-	return m.digest()
-Utils.h_file = h_file
+	def h_file(filename):
+		st = os.stat(filename)
+		if stat.S_ISDIR(st[stat.ST_MODE]): raise IOError('not a file')
+
+		if filename in Build.hashes_md5_tstamp:
+			if Build.hashes_md5_tstamp[filename][0] == str(st.st_mtime):
+				return Build.hashes_md5_tstamp[filename][1]
+		m = Utils.md5()
+
+		if STRONGEST:
+			f = open(filename, 'rb')
+			read = 1
+			try:
+				while read:
+					read = f.read(100000)
+					m.update(read)
+			finally:
+				f.close()
+		else:
+			m.update(str(st.st_mtime))
+			m.update(str(st.st_size))
+			m.update(filename)
+
+		# ensure that the cache is overwritten
+		Build.hashes_md5_tstamp[filename] = (str(st.st_mtime), m.digest())
+		return m.digest()
+	Utils.h_file = h_file
 

waflib/extras/win32_opts.py

@@ -3,6 +3,8 @@
 
 """
 Windows-specific optimizations
+
+This module can help reducing the overhead of listing files on windows (more than 10000 files).
 """
 
 import os
@@ -11,37 +13,9 @@ except: import pickle as cPickle
 from waflib import Utils, Build, Context, Node, Logs
 
 if Utils.is_win32:
+	from waflib.extras import md5_tstamp
 	import ctypes, ctypes.wintypes
 
-	Context.DBFILE += '_md5tstamp'
-
-	try:
-		Build.BuildContext.store_real
-	except AttributeError:
-		pass
-	else:
-		raise ValueError('win32opts has been loaded twice (or the incompatible md5_tstamp tool was loaded before)')
-
-	Build.hashes_md5_tstamp = {}
-	Build.SAVED_ATTRS.append('hashes_md5_tstamp')
-	def store(self):
-		# save the hash cache as part of the default pickle file
-		self.hashes_md5_tstamp = Build.hashes_md5_tstamp
-		self.store_real()
-	Build.BuildContext.store_real = Build.BuildContext.store
-	Build.BuildContext.store      = store
-
-	def restore(self):
-		# we need a module variable for h_file below
-		self.restore_real()
-		try:
-			Build.hashes_md5_tstamp = self.hashes_md5_tstamp or {}
-		except Exception as e:
-			Build.hashes_md5_tstamp = {}
-
-	Build.BuildContext.restore_real = Build.BuildContext.restore
-	Build.BuildContext.restore      = restore
-
 	FindFirstFile        = ctypes.windll.kernel32.FindFirstFileW
 	FindNextFile         = ctypes.windll.kernel32.FindNextFileW
 	FindClose            = ctypes.windll.kernel32.FindClose