Add generation of filenames in the cache directory.

2 files changed, 53 insertions, 0 deletions

diff --git a/morphlib/cachedir.py b/morphlib/cachedir.py
index 88008547..7ee77222 100644
--- a/morphlib/cachedir.py
+++ b/morphlib/cachedir.py
@@ -15,6 +15,7 @@
 
 
 import hashlib
+import os
 
 
 class CacheDir(object):
@@ -40,3 +41,24 @@ class CacheDir(object):
         data = ''.join(key + value for key, value in dict_key.iteritems())
         return hashlib.sha256(data).hexdigest()
 
+    def name(self, dict_key):
+        '''Return a filename for an object described by dictionary key.
+        
+        It is the caller's responsibility to set the fields in the
+        dictionary key suitably. For example, if there is a field
+        specifying a commit id, it should be the full git SHA-1
+        identifier, not something ephemeral like HEAD.
+        
+        If the field 'kind' has a value, it is used as a suffix for
+        the filename.
+        
+        '''
+
+        key = self.key(dict_key)
+        if 'kind' in dict_key and dict_key['kind']:
+            suffix = '.%s' % dict_key['kind']
+        else:
+            suffix = ''
+
+        return os.path.join(self.dirname, key + suffix)
+
diff --git a/morphlib/cachedir_tests.py b/morphlib/cachedir_tests.py
index 17fa6e0f..b9f7c80b 100644
--- a/morphlib/cachedir_tests.py
+++ b/morphlib/cachedir_tests.py
@@ -56,3 +56,34 @@ class CacheDirTests(unittest.TestCase):
         self.assertNotEqual(self.cachedir.key(dict_key_1), 
                             self.cachedir.key(dict_key_2))
 
+    def test_returns_a_chunk_pathname_in_cache_directory(self):
+        dict_key = {
+            'kind': 'chunk',
+            'ref': 'DEADBEEF',
+            'repo': 'git://git.baserock.org/hello/',
+            'arch': 'armel',
+        }
+        pathname = self.cachedir.name(dict_key)
+        self.assert_(pathname.startswith(self.cachedir.dirname + '/'))
+        self.assert_(pathname.endswith('.chunk'))
+
+    def test_returns_a_stratum_pathname_in_cache_directory(self):
+        dict_key = {
+            'kind': 'stratum',
+            'ref': 'DEADBEEF',
+            'repo': 'git://git.baserock.org/hello/',
+            'arch': 'armel',
+        }
+        pathname = self.cachedir.name(dict_key)
+        self.assert_(pathname.startswith(self.cachedir.dirname + '/'))
+        self.assert_(pathname.endswith('.stratum'))
+
+    def test_returns_a_valid_pathname_in_cache_directory(self):
+        dict_key = {
+            'ref': 'DEADBEEF',
+            'repo': 'git://git.baserock.org/hello/',
+            'arch': 'armel',
+        }
+        pathname = self.cachedir.name(dict_key)
+        self.assert_(pathname.startswith(self.cachedir.dirname + '/'))
+