initial commit

gluon/storage.py

@@ -0,0 +1,226 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+"""
+This file is part of the web2py Web Framework
+Copyrighted by Massimo Di Pierro <mdipierro@cs.depaul.edu>
+License: LGPLv3 (http://www.gnu.org/licenses/lgpl.html)
+
+Provides:
+
+- List; like list but returns None instead of IndexOutOfBounds
+- Storage; like dictionary allowing also for `obj.foo` for `obj['foo']`
+"""
+
+import cPickle
+import portalocker
+
+__all__ = ['List', 'Storage', 'Settings', 'Messages',
+           'StorageList', 'load_storage', 'save_storage']
+
+
+class List(list):
+    """
+    Like a regular python list but a[i] if i is out of bounds return None
+    instead of IndexOutOfBounds
+    """
+
+    def __call__(self, i, default=None):
+        if 0<=i<len(self):
+            return self[i]
+        else:
+            return default
+
+class Storage(dict):
+
+    """
+    A Storage object is like a dictionary except `obj.foo` can be used
+    in addition to `obj['foo']`, and setting obj.foo = None deletes item foo.
+
+        >>> o = Storage(a=1)
+        >>> print o.a
+        1
+
+        >>> o['a']
+        1
+
+        >>> o.a = 2
+        >>> print o['a']
+        2
+
+        >>> del o.a
+        >>> print o.a
+        None
+
+    """
+
+    def __getattr__(self, key):
+        return dict.get(self, key, None)
+
+    def __setattr__(self, key, value):
+        if value is None:
+            if key in self:
+                del self[key]
+        else:
+            self[key] = value
+
+    def __delattr__(self, key):
+        if key in self:
+            del self[key]
+        else:
+            raise AttributeError, "missing key=%s" % key
+
+    def __getitem__(self, key):
+        return dict.get(self, key, None)
+
+    def __repr__(self):
+        return '<Storage ' + dict.__repr__(self) + '>'
+
+    def __getstate__(self):
+        return dict(self)
+
+    def __setstate__(self, value):
+        for (k, v) in value.items():
+            self[k] = v
+
+    def getlist(self, key):
+        """Return a Storage value as a list.
+
+        If the value is a list it will be returned as-is.
+        If object is None, an empty list will be returned.
+        Otherwise, [value] will be returned.
+
+        Example output for a query string of ?x=abc&y=abc&y=def
+        >>> request = Storage()
+        >>> request.vars = Storage()
+        >>> request.vars.x = 'abc'
+        >>> request.vars.y = ['abc', 'def']
+        >>> request.vars.getlist('x')
+        ['abc']
+        >>> request.vars.getlist('y')
+        ['abc', 'def']
+        >>> request.vars.getlist('z')
+        []
+
+        """
+        value = self.get(key, None)
+        if isinstance(value, (list, tuple)):
+            return value
+        elif value is None:
+            return []
+        return [value]
+
+    def getfirst(self, key):
+        """Return the first or only value when given a request.vars-style key.
+
+        If the value is a list, its first item will be returned;
+        otherwise, the value will be returned as-is.
+
+        Example output for a query string of ?x=abc&y=abc&y=def
+        >>> request = Storage()
+        >>> request.vars = Storage()
+        >>> request.vars.x = 'abc'
+        >>> request.vars.y = ['abc', 'def']
+        >>> request.vars.getfirst('x')
+        'abc'
+        >>> request.vars.getfirst('y')
+        'abc'
+        >>> request.vars.getfirst('z')
+
+        """
+        value = self.getlist(key)
+        if len(value):
+            return value[0]
+        return None
+
+    def getlast(self, key):
+        """Returns the last or only single value when given a request.vars-style key.
+
+        If the value is a list, the last item will be returned;
+        otherwise, the value will be returned as-is.
+
+        Simulated output with a query string of ?x=abc&y=abc&y=def
+        >>> request = Storage()
+        >>> request.vars = Storage()
+        >>> request.vars.x = 'abc'
+        >>> request.vars.y = ['abc', 'def']
+        >>> request.vars.getlast('x')
+        'abc'
+        >>> request.vars.getlast('y')
+        'def'
+        >>> request.vars.getlast('z')
+
+        """
+        value = self.getlist(key)
+        if len(value):
+            return value[-1]
+        return None
+
+class StorageList(Storage):
+    """
+    like Storage but missing elements default to [] instead of None
+    """
+    def __getattr__(self, key):
+        if key in self:
+            return self[key]
+        else:
+            self[key] = []
+            return self[key]
+
+def load_storage(filename):
+    fp = open(filename, 'rb')
+    try:
+        portalocker.lock(fp, portalocker.LOCK_EX)
+        storage = cPickle.load(fp)
+        portalocker.unlock(fp)
+    finally:
+        fp.close()
+    return Storage(storage)
+
+
+def save_storage(storage, filename):
+    fp = open(filename, 'wb')
+    try:
+        portalocker.lock(fp, portalocker.LOCK_EX)
+        cPickle.dump(dict(storage), fp)
+        portalocker.unlock(fp)
+    finally:
+        fp.close()
+
+
+class Settings(Storage):
+
+    def __setattr__(self, key, value):
+        if key != 'lock_keys' and self.get('lock_keys', None)\
+             and not key in self:
+            raise SyntaxError, 'setting key \'%s\' does not exist' % key
+        if key != 'lock_values' and self.get('lock_values', None):
+            raise SyntaxError, 'setting value cannot be changed: %s' % key
+        self[key] = value
+
+
+class Messages(Storage):
+
+    def __init__(self, T):
+        self['T'] = T
+
+    def __setattr__(self, key, value):
+        if key != 'lock_keys' and self.get('lock_keys', None)\
+             and not key in self:
+            raise SyntaxError, 'setting key \'%s\' does not exist' % key
+        if key != 'lock_values' and self.get('lock_values', None):
+            raise SyntaxError, 'setting value cannot be changed: %s' % key
+        self[key] = value
+
+    def __getattr__(self, key):
+        value = self[key]
+        if isinstance(value, str):
+            return str(self['T'](value))
+        return value
+
+if __name__ == '__main__':
+    import doctest
+    doctest.testmod()
+
+
+