Add ExtractedTarball class and method to extract/mount an artifact

ExtractedTarball is more or less the equivalent to MountableImage for
artifacts that are not mountable images. So in order to inspect root
file system tarballs, ExtractedTarball can be used, for disk images,
MountableImage can be used.

The morphlib.bins.call_in_artifact_directory() method combines these
two classes and provides a way to extract/mount an artifact and call
a callback with the temporary directory / mount point as its first
argument. Using this, a plugin that runs a command relative to an
artifact's root directory can be written easily.

1 files changed, 28 insertions, 1 deletions

diff --git a/morphlib/bins.py b/morphlib/bins.py
index 622aa165..ba5f713f 100644
--- a/morphlib/bins.py
+++ b/morphlib/bins.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2011-2012  Codethink Limited
+# Copyright (C) 2011-2013  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
@@ -21,6 +21,7 @@ Binaries are chunks, strata, and system images.
 '''
 
 
+import cliapp
 import logging
 import os
 import re
@@ -29,6 +30,11 @@ import stat
 import shutil
 import tarfile
 
+import morphlib
+
+from morphlib.extractedtarball import ExtractedTarball
+from morphlib.mountableimage import MountableImage
+
 
 # Work around http://bugs.python.org/issue16477
 def safe_makefile(self, tarinfo, targetpath):
@@ -211,3 +217,24 @@ def unpack_binary_from_file(f, dirname):  # pragma: no cover
 def unpack_binary(filename, dirname):
     with open(filename, "rb") as f:
         unpack_binary_from_file(f, dirname)
+
+
+class ArtifactNotMountableError(cliapp.AppException): # pragma: no cover
+
+    def __init__(self, filename):
+        cliapp.AppException.__init__(
+                self, 'Artifact %s cannot be extracted or mounted' % filename)
+
+
+def call_in_artifact_directory(app, filename, callback): # pragma: no cover
+    '''Call a function in a directory the artifact is extracted/mounted in.'''
+
+    try:
+        with ExtractedTarball(app, filename) as dirname:
+            callback(dirname)
+    except tarfile.TarError:
+        try:
+            with MountableImage(app, filename) as dirname:
+                callback(dirname)
+        except (IOError, OSError):
+            raise ArtifactNotMountableError(filename)