From c7ec3c338c327c60c32d7f6680a6860a843aeb45 Mon Sep 17 00:00:00 2001
From: Tim Diels <limyreth@gmail.com>
Date: Tue, 31 May 2011 10:47:36 +0200
Subject: [PATCH] Made DownloadSource and UnpackArchive stateless using a
 'StepCommand'

---
 zeroinstall/injector/fetch.py | 12 +++++-----
 zeroinstall/injector/model.py | 53 +++++++++++++++++++++++++------------------
 2 files changed, 37 insertions(+), 28 deletions(-)

diff --git a/zeroinstall/injector/fetch.py b/zeroinstall/injector/fetch.py
index 11c4cbd..94c616b 100644
--- a/zeroinstall/injector/fetch.py
+++ b/zeroinstall/injector/fetch.py
@@ -104,7 +104,7 @@ class Fetcher(object):
 		# Maybe we're taking this metaphor too far?
 
 		# Start preparing all steps
-		blockers = [step.prepare(self, force, impl_hint) for step in recipe.steps]
+		step_commands = [step.prepare(self, force, impl_hint) for step in recipe.steps]
 
 		# Create an empty directory for the new implementation
 		store = stores.stores[0]
@@ -112,13 +112,13 @@ class Fetcher(object):
 
 		try:
 			# Run steps
-			valid_blockers = [b for b in blockers if b is not None]
-			for step, blocker in zip(recipe.steps, blockers):
-				if blocker:
-					while not blocker.happened:
+			valid_blockers = [s.blocker for s in step_commands if s.blocker is not None]
+			for step_command in step_commands:
+				if step_command.blocker:
+					while not step_command.blocker.happened:
 						yield valid_blockers
 						tasks.check(valid_blockers)
-				step.run(tmpdir)
+				step_command.run(tmpdir)
 
 			# Check that the result is correct and store it in the cache
 			store.check_manifest_and_rename(required_digest, tmpdir)
diff --git a/zeroinstall/injector/model.py b/zeroinstall/injector/model.py
index 4bb9315..ec30ba3 100644
--- a/zeroinstall/injector/model.py
+++ b/zeroinstall/injector/model.py
@@ -404,7 +404,7 @@ class RetrievalMethod(object):
 
 class DownloadSource(RetrievalMethod):
 	"""A DownloadSource provides a way to fetch an implementation."""
-	__slots__ = ['implementation', 'url', 'size', 'extract', 'start_offset', 'type', '_stream']
+	__slots__ = ['implementation', 'url', 'size', 'extract', 'start_offset', 'type']
 
 	def __init__(self, implementation, url, size, extract, start_offset = 0, type = None):
 		self.implementation = implementation
@@ -413,20 +413,23 @@ class DownloadSource(RetrievalMethod):
 		self.extract = extract
 		self.start_offset = start_offset
 		self.type = type		# MIME type - see unpack.py
-		self._stream = None
 
 	def prepare(self, fetcher, force, impl_hint):
-		blocker, self._stream = fetcher.download_archive(self, force = force, impl_hint = impl_hint)
-		assert self._stream, 'lol'
-		return blocker
-
-	def run(self, tmpdir):
-		assert self._stream, 'You must prepare the download step first'
-		self._stream.seek(0)
-		unpack.unpack_archive_over(self.url, self._stream, tmpdir,
-			extract = self.extract,
-			type = self.type,
-			start_offset = self.start_offset or 0)
+
+		class StepCommand(object):
+			__slots__ = ['blocker', '_stream']
+
+			def __init__(s):
+				s.blocker, s._stream = fetcher.download_archive(self, force = force, impl_hint = impl_hint)
+
+			def run(s, tmpdir):
+				s._stream.seek(0)
+				unpack.unpack_archive_over(self.url, s._stream, tmpdir,
+					extract = self.extract,
+					type = self.type,
+					start_offset = self.start_offset or 0)
+		return StepCommand()
+
 
 class UnpackArchive(object):
 	"""An UnpackArchive step provides unpacks/extracts an archive.
@@ -440,17 +443,23 @@ class UnpackArchive(object):
 		self.type = type
 
 	def prepare(self, fetcher, force, impl_hint):
-		return None
 
-	def run(self, tmpdir):
-		path = os.path.join(tmpdir, self.path)
-		stream = open(path, 'rb')
-		stream.seek(0)
+		class StepCommand(object):
+			__slots__ = ['blocker']
+
+			def __init__(s):
+				s.blocker = None
+
+			def run(s, tmpdir):
+				path = os.path.join(tmpdir, self.path)
+				stream = open(path, 'rb')
+				stream.seek(0)
 
-		unpack.unpack_archive_over(path, stream, tmpdir,
-		extract = self.extract,
-		type = self.type,
-		start_offset = 0)
+				unpack.unpack_archive_over(path, stream, tmpdir,
+					extract = self.extract,
+					type = self.type,
+					start_offset = 0)
+		return StepCommand()
 
 class Recipe(RetrievalMethod):
 	"""Get an implementation by following a series of steps.
-- 
2.11.4.GIT