Add program to generate test data for backwards compatbility

1 files changed, 113 insertions, 0 deletions

diff --git a/test-backwards-compatibility b/test-backwards-compatibility
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+#!/usr/bin/python
+# Copyright 2012  Lars Wirzenius
+# 
+# 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, either version 3 of the License, or
+# (at your option) any later version.
+# 
+# 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, see <http://www.gnu.org/licenses/>.
+
+
+'''Test backwards compatibility of an on-disk B-tree.
+
+This program tests that a Larch on-disk B-tree is backwards compatible
+with previous versions, at least to the extent that it can be read from.
+This program operates in one of two modes:
+
+* it can generate a new B-tree to be stored as test data for the future
+* it can read an existing tree and verify that it can read it right
+
+The generated B-tree is actually a forest, and contains four trees.
+The first tree has the following keys:
+
+* key size is 4 bytes
+* keys are 0, 1, 2, ..., 1023, converted into binary strings with struct
+* values are 0, 1, 2, ..., 1023, converted into text strings with '%d' % i
+* node size is 128 bytes
+
+The second tree is a clone of the first one, but with all odd-numbered
+keys removed.
+
+The third tree is a clone of the second one, but with all odd-numbered
+keys and values added back.
+
+The fourth tree is a clone of the third one, but with all even-numbered
+keys removed.
+
+'''
+
+
+import cliapp
+import shutil
+import struct
+import tarfile
+import tempfile
+
+import larch
+
+
+class BackwardsCompatibilityTester(cliapp.Application):
+
+    key_size = 4
+    node_size = 128
+    num_keys = 1024
+    
+    def setup(self):
+        self.dirname = tempfile.mkdtemp()
+        
+    def teardown(self):
+        shutil.rmtree(self.dirname)
+
+    def key(self, i):
+        return struct.pack('!L', i)
+        
+    def value(self, i):
+        return '%d' % i
+
+    def cmd_generate(self, args):
+        '''Generate a Larch B-tree forest'''
+        
+        forest = larch.open_forest(key_size=self.key_size,
+                                   node_size=self.node_size,
+                                   dirname=self.dirname,
+                                   allow_writes=True)
+
+        # First tree.
+        t = forest.new_tree()
+        for i in range(self.num_keys):
+            t.insert(self.key(i), self.value(i))
+            
+        # Second tree.
+        t = forest.new_tree(t)
+        for i in range(self.num_keys):
+            if (i % 2) == 1:
+                t.remove(self.key(i))
+            
+        # Third tree.
+        t = forest.new_tree(t)
+        for i in range(self.num_keys):
+            if (i % 2) == 1:
+                t.insert(self.key(i), self.value(i))
+            
+        # Fourth tree.
+        t = forest.new_tree(t)
+        for i in range(self.num_keys):
+            if (i % 2) == 0:
+                t.remove(self.key(i))
+
+        # Commit and make into a tarball.
+        forest.commit()
+        tf = tarfile.open(fileobj=self.output, mode='w:gz')
+        tf.add(self.dirname, arcname='.')
+        tf.close()
+
+
+BackwardsCompatibilityTester().run()
+