Add a class to manage the staging area for builds

3 files changed, 136 insertions, 0 deletions

diff --git a/morphlib/__init__.py b/morphlib/__init__.py
index 6c74082c..e6040af1 100644
--- a/morphlib/__init__.py
+++ b/morphlib/__init__.py
@@ -40,6 +40,7 @@ import savefile
 import source
 import sourcemanager
 import sourcepool
+import stagingarea
 import stopwatch
 import tempdir
 import util
diff --git a/morphlib/stagingarea.py b/morphlib/stagingarea.py
new file mode 100644
index 00000000..126d7d91
--- /dev/null
+++ b/morphlib/stagingarea.py
@@ -0,0 +1,60 @@
+# Copyright (C) 2012  Codethink Limited
+# 
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; version 2 of the License.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License along
+# with this program; if not, write to the Free Software Foundation, Inc.,
+# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+
+import shutil
+import tarfile
+
+
+class StagingArea(object):
+
+    '''Represent the staging area for building software.
+    
+    The build dependencies of what will be built will be installed in the
+    staging area. The staging area may be a dedicated part of the
+    filesystem, used with chroot, or it can be the actual root of the
+    filesystem, which is needed when bootstrap building Baserock. The
+    caller chooses this by providing the root directory of the staging
+    area when the object is created. The directory must already exist.
+    
+    The staging area can also install build artifacts.
+    
+    '''
+    
+    def __init__(self, dirname):
+        self.dirname = dirname
+
+    def install_artifact(self, handle):
+        '''Install a build artifact into the staging area.
+        
+        We access the artifact via an open file handle. For now, we assume
+        the artifact is a tarball.
+        
+        '''
+        
+        tf = tarfile.TarFile(fileobj=handle)
+        tf.extractall(path=self.dirname)
+
+    def remove(self):
+        '''Remove the entire staging area.
+        
+        Do not expect anything with the staging area to work after this
+        method is called. Be careful about calling this method if
+        the filesystem root directory was given as the dirname.
+        
+        '''
+        
+        shutil.rmtree(self.dirname)
+
diff --git a/morphlib/stagingarea_tests.py b/morphlib/stagingarea_tests.py
new file mode 100644
index 00000000..c6b17610
--- /dev/null
+++ b/morphlib/stagingarea_tests.py
@@ -0,0 +1,75 @@
+# Copyright (C) 2012  Codethink Limited
+# 
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; version 2 of the License.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License along
+# with this program; if not, write to the Free Software Foundation, Inc.,
+# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+
+import os
+import shutil
+import tarfile
+import tempfile
+import unittest
+
+import morphlib
+
+
+class StagingAreaTests(unittest.TestCase):
+
+    def setUp(self):
+        self.tempdir = tempfile.mkdtemp()
+        self.staging = os.path.join(self.tempdir, 'staging')
+        self.sa = morphlib.stagingarea.StagingArea(self.staging)
+
+    def tearDown(self):
+        shutil.rmtree(self.tempdir)
+        
+    def create_chunk(self):
+        chunkdir = os.path.join(self.tempdir, 'chunk')
+        os.mkdir(chunkdir)
+        with open(os.path.join(chunkdir, 'file.txt'), 'w'):
+            pass
+        chunk_tar = os.path.join(self.tempdir, 'chunk.tar')
+        tf = tarfile.TarFile(name=chunk_tar, mode='w')
+        tf.add(chunkdir, arcname='.')
+        tf.close()
+        
+        return chunk_tar
+        
+    def list_tree(self, root):
+        files = []
+        for dirname, subdirs, basenames in os.walk(root):
+            paths = [os.path.join(dirname, x) for x in basenames]
+            for x in [dirname] + sorted(paths):
+                files.append(x[len(root):] or '/')
+        return files
+
+    def test_remembers_specified_directory(self):
+        self.assertEqual(self.sa.dirname, self.staging)
+
+    def test_accepts_root_directory(self):
+        sa = morphlib.stagingarea.StagingArea('/')
+        self.assertEqual(sa.dirname, '/')
+        
+    def test_installs_artifact(self):
+        chunk_tar = self.create_chunk()
+        with open(chunk_tar, 'rb') as f:
+            self.sa.install_artifact(f)
+        self.assertEqual(self.list_tree(self.staging), ['/', '/file.txt'])
+
+    def test_removes_everything(self):
+        chunk_tar = self.create_chunk()
+        with open(chunk_tar, 'rb') as f:
+            self.sa.install_artifact(f)
+        self.sa.remove()
+        self.assertFalse(os.path.exists(self.staging))
+