From fffef7bbc408b753b6d61699b800224ab77f18c4 Mon Sep 17 00:00:00 2001
From: "Edward Z. Yang" <ezyang@mit.edu>
Date: Sun, 11 Oct 2009 16:30:07 -0400
Subject: [PATCH] Implement sqlite dict.  We might not actually use this.

Signed-off-by: Edward Z. Yang <ezyang@mit.edu>
---
 doc/index.rst               |  1 +
 doc/module/wizard.cache.rst | 11 ++++++
 wizard/cache.py             | 69 +++++++++++++++++++++++++++++++++++++
 3 files changed, 81 insertions(+)
 create mode 100644 doc/module/wizard.cache.rst
 create mode 100644 wizard/cache.py

diff --git a/doc/index.rst b/doc/index.rst
index a5ba181..48f7038 100644
--- a/doc/index.rst
+++ b/doc/index.rst
@@ -62,6 +62,7 @@ Modules
     :maxdepth: 1
 
     module/wizard
+    module/wizard.cache
     module/wizard.deploy
     module/wizard.install
     module/wizard.shell
diff --git a/doc/module/wizard.cache.rst b/doc/module/wizard.cache.rst
new file mode 100644
index 0000000..a7cef06
--- /dev/null
+++ b/doc/module/wizard.cache.rst
@@ -0,0 +1,11 @@
+:mod:`wizard.cache`
+===================
+
+.. automodule:: wizard.cache
+
+Classes
+-------
+.. autoclass:: make
+    :members:
+.. autoclass:: SerializedDict
+    :members:
diff --git a/wizard/cache.py b/wizard/cache.py
new file mode 100644
index 0000000..82de819
--- /dev/null
+++ b/wizard/cache.py
@@ -0,0 +1,69 @@
+"""
+Provides caching of old results from mass commands, so that
+we don't have to do them again.  Successes are cached as
+the string "OK"; errors are stored as the string exception name.
+Entries are indexed by location.
+
+.. testsetup:: *
+
+    from wizard.cache import *
+"""
+
+import sqlite3
+
+def make(file):
+    if file:
+        return SerializedDict(file)
+    else:
+        return {}
+
+class SerializedDict(object):
+    """
+    Implements a dictionary that serializes itself to disk.  We
+    use sqlite in order to implement relatively efficient updates.
+
+        >>> import os
+        >>> f = "/tmp/wizard-cache-test.db"
+        >>> if os.path.exists(f): os.unlink(f)
+        >>> d = SerializedDict(f)
+        >>> try:
+        ...   d["foo"]
+        ...   raise Exception("didn't raise")
+        ... except KeyError:
+        ...   pass
+        >>> d["foo"] = "baz"
+        >>> d["foo"]
+        'baz'
+        >>> d["foo"] = "bar"
+        >>> d["foo"]
+        'bar'
+        >>> e = SerializedDict(f)
+        >>> e["foo"]
+        'bar'
+        >>> del e["foo"]
+        >>> "foo" in e
+        False
+        >>> os.unlink(f)
+    """
+    #: Connection to sqlite database
+    conn = None
+    def __init__(self, file):
+        self.conn = sqlite3.connect(file)
+        try:
+            self.conn.execute('create table dict(key string primary key, value string)')
+        except sqlite3.OperationalError as e:
+            if e.args[0] != "table dict already exists":
+                raise
+        self.conn.isolation_level = None
+    def __getitem__(self, key):
+        row = self.conn.execute('select value from dict where key = ?', (key,)).fetchone()
+        if row:
+            return str(row[0])
+        else:
+            raise KeyError
+    def __setitem__(self, key, value):
+        self.conn.execute('insert or replace into dict (key, value) values (?, ?)', (key, value))
+    def __delitem__(self, key):
+        self.conn.execute('delete from dict where key = ?', (key,))
+    def __contains__(self, key):
+        return bool(self.conn.execute('select count(*) from dict where key = ?', (key,)).fetchone()[0])
-- 
2.44.0