Change the forest factory to be a function, instead.

No point in a class, since every call needs all parameters
anyway.

9 files changed, 80 insertions, 25 deletions

diff --git a/btree/__init__.py b/btree/__init__.py
index 7da1e5a..313c84d 100644
--- a/btree/__init__.py
+++ b/btree/__init__.py
@@ -20,7 +20,7 @@ version = '0.18'
 from nodes import FrozenNode, LeafNode, IndexNode
 from codec import NodeCodec, CodecError
 from tree import BTree, KeySizeMismatch, ValueTooLarge
-from forest import Forest, ForestFactory
+from forest import Forest, open_forest, BadKeySize, BadNodeSize
 from nodestore import (NodeStore, NodeStoreTests, NodeMissing, NodeTooBig, 
                        NodeExists, NodeCannotBeModified)
 from refcountstore import RefcountStore
diff --git a/btree/forest.py b/btree/forest.py
index 055ce98..8fcf4fe 100644
--- a/btree/forest.py
+++ b/btree/forest.py
@@ -17,6 +17,26 @@
 import btree
 
 
+class BadKeySize(Exception):
+
+    def __init__(self, store_key_size, wanted_key_size):
+        self.msg = ('Node store has key size %s, program wanted %s' %
+                    (store_key_size, wanted_key_size))
+    
+    def __str__(self):
+        return self.msg
+
+
+class BadNodeSize(Exception):
+
+    def __init__(self, store_node_size, wanted_node_size):
+        self.msg = ('Node store has node size %s, program wanted %s' %
+                    (store_node_size, wanted_node_size))
+    
+    def __str__(self):
+        return self.msg
+
+
 class Forest(object):
 
     '''A collection of BTrees in the same node store.'''
@@ -85,20 +105,27 @@ class Forest(object):
         self.node_store.save_refcounts()
 
 
+def open_forest(key_size=None, node_size=None, codec=None, node_store=None, 
+                **kwargs):
+    '''Create a new Factory instance.
+    
+    key_size, node_size must be given with every call.
+    codec is the class to be used for the node codec, defaults to
+    btree.NodeCodec. Similarly, node_store is the node store class,
+    defaults to btree.NodeStoreDisk.
+    
+    All other keyword arguments are given the thoe node_store
+    class initializer.
+    
+    '''
 
-class ForestFactory(object):
+    assert key_size is not None
+    assert node_size is not None
 
-    '''Create new Forest objects.'''
-    
-    def __init__(self, codec=None, node_store=None):
-        assert codec != None
-        assert node_store != None
-        
-        self.codec = codec
-        self.node_store = node_store
-        
-    def new(self, key_size, node_size):
-        codec = self.codec(key_size)
-        ns = self.node_store(node_size, codec)
-        return Forest(ns)
+    codec = codec or btree.NodeCodec
+    node_store = node_store or btree.NodeStoreDisk
+
+    c = codec(key_size)
+    ns = node_store(node_size, c, **kwargs)
+    return Forest(ns)
 
diff --git a/btree/forest_tests.py b/btree/forest_tests.py
index 90e7e07..c2127cb 100644
--- a/btree/forest_tests.py
+++ b/btree/forest_tests.py
@@ -14,6 +14,8 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 
+import shutil
+import tempfile
 import unittest
 
 import btree
@@ -123,11 +125,36 @@ class ForestFactoryTests(unittest.TestCase):
     def setUp(self):
         self.key_size = 3
         self.node_size = 64
-        self.factory = btree.ForestFactory(codec=btree.NodeCodec,
-                                           node_store=btree.NodeStoreMemory)
+        self.tempdir = tempfile.mkdtemp()
+        
+    def tearDown(self):
+        shutil.rmtree(self.tempdir)
         
     def test_creates_new_forest(self):
-        f = self.factory.new(self.key_size, self.node_size)
+        f = btree.open_forest(key_size=self.key_size, node_size=self.node_size,
+                              dirname=self.tempdir)
         self.assertEqual(f.node_store.codec.key_bytes, self.key_size)
         self.assertEqual(f.node_store.node_size, self.node_size)
 
+    def test_fail_if_existing_tree_has_incompatible_key_size(self):
+        f = btree.open_forest(key_size=self.key_size, node_size=self.node_size,
+                              dirname=self.tempdir)
+        f.commit()
+        
+        self.assertRaises(btree.BadNodeSize, 
+                          btree.open_forest,
+                          key_size=self.key_size + 1, 
+                          node_size=self.node_size,
+                          dirname=self.tempdir)
+
+    def test_fail_if_existing_tree_has_incompatible_node_size(self):
+        f = btree.open_forest(key_size=self.key_size, node_size=self.node_size,
+                              dirname=self.tempdir)
+        f.commit()
+        
+        self.assertRaises(btree.BadNodeSize, 
+                          btree.open_forest,
+                          key_size=self.key_size, 
+                          node_size=self.node_size + 1,
+                          dirname=self.tempdir)
+
diff --git a/btree/nodestore_disk.py b/btree/nodestore_disk.py
index 801f10f..01ce88f 100644
--- a/btree/nodestore_disk.py
+++ b/btree/nodestore_disk.py
@@ -74,8 +74,9 @@ class NodeStoreDisk(btree.NodeStore):
 
     nodedir = 'nodes'
 
-    def __init__(self, dirname, node_size, codec, upload_max=1024, 
+    def __init__(self, node_size, codec, dirname=None, upload_max=1024, 
                  lru_size=100, vfs=None):
+        assert dirname is not None
         btree.NodeStore.__init__(self, node_size, codec)
         self.dirname = dirname
         self.metadata_name = os.path.join(dirname, 'metadata')
diff --git a/btree/nodestore_disk_tests.py b/btree/nodestore_disk_tests.py
index 9aabfe4..63d54bc 100644
--- a/btree/nodestore_disk_tests.py
+++ b/btree/nodestore_disk_tests.py
@@ -36,8 +36,8 @@ class NodeStoreDiskTests(unittest.TestCase, btree.NodeStoreTests):
         shutil.rmtree(self.tempdir)
 
     def new_ns(self):
-        return nodestore_disk.NodeStoreDisk(self.tempdir, self.node_size,
-                                            self.codec)
+        return nodestore_disk.NodeStoreDisk(self.node_size, self.codec,
+                                            dirname=self.tempdir)
 
     def test_has_persistent_metadata(self):
         self.ns.set_metadata('foo', 'bar')
diff --git a/example.py b/example.py
index 9feb5e3..eae007f 100644
--- a/example.py
+++ b/example.py
@@ -38,7 +38,7 @@ def open_tree(dirname):
     node_size = 4096
     
     codec = btree.NodeCodec(key_size)
-    ns = btree.NodeStoreDisk(dirname, node_size, codec)
+    ns = btree.NodeStoreDisk(node_size, codec, dirname=dirname)
     forest = btree.Forest(ns)
     if forest.trees:
         tree = forest.trees[0]
diff --git a/fsck-btree b/fsck-btree
index 9e4c144..c7b50b0 100755
--- a/fsck-btree
+++ b/fsck-btree
@@ -32,7 +32,7 @@ class BtreeFsck(object):
         self.node_size = node_size
         self.key_size = key_size
         codec = btree.NodeCodec(key_size)
-        self.ns = btree.NodeStoreDisk(dirname, node_size, codec)
+        self.ns = btree.NodeStoreDisk(node_size, codec, dirname=dirname)
         self.minkey = '\x00' * key_size
         self.maxkey = '\xff' * key_size
 
diff --git a/insert-remove-test b/insert-remove-test
index 3f81c73..b88b016 100755
--- a/insert-remove-test
+++ b/insert-remove-test
@@ -95,7 +95,7 @@ def main():
         if os.path.exists(location):
             raise Exception('%s exists already' % location)
         os.mkdir(location)
-        ns = btree.NodeStoreDisk(location, node_size, codec)
+        ns = btree.NodeStoreDisk(node_size, codec, dirname=location)
 
     forest = btree.Forest(ns)
     tree = forest.new_tree()
diff --git a/speed-test b/speed-test
index b14b95c..599ed18 100755
--- a/speed-test
+++ b/speed-test
@@ -74,7 +74,7 @@ class SpeedTest(cliapp.Application):
             if os.path.exists(location):
                 raise Exception('%s exists already' % location)
             os.mkdir(location)
-            ns = btree.NodeStoreDisk(location, node_size, codec)
+            ns = btree.NodeStoreDisk(node_size, codec, dirname=location)
 
         forest = btree.Forest(ns)
         tree = forest.new_tree()