SF.net SVN: fclient: [372] trunk/sandbox/fcp2/fcp_lib/pmstruct.py

[<jU...@us...>]

Revision: 372
          http://fclient.svn.sourceforge.net/fclient/?rev=372&view=rev
Author:   jUrner
Date:     2008-04-08 03:07:36 -0700 (Tue, 08 Apr 2008)

Log Message:
-----------
poor mans struct to handle persistent data

Added Paths:
-----------
    trunk/sandbox/fcp2/fcp_lib/pmstruct.py

Added: trunk/sandbox/fcp2/fcp_lib/pmstruct.py
===================================================================
--- trunk/sandbox/fcp2/fcp_lib/pmstruct.py	                        (rev 0)
+++ trunk/sandbox/fcp2/fcp_lib/pmstruct.py	2008-04-08 10:07:36 UTC (rev 372)
@@ -0,0 +1,140 @@
+"""Poor mans structure
+
+
+
+"""
+
+import base64
+#****************************************************************************
+#
+#****************************************************************************
+Str = (base64.b64decode, base64.b64encode, (str, unicode))
+Int = (int, str, int)
+Float = (float, float)
+
+
+
+class PoorMansStruct(object):
+	"""Poor mans structure
+	
+	Converts a maping to a string and vice versa	
+	
+	
+	Subclasses must define a _fields_ attribute wich is a mapping from field name 
+	to conversion 	methods (fieldName, (getter, setter, fieldType)). getter() should convert
+	the fields value to the desired python type, setter should convert the python
+	type to string. Both will be called with one argument: the value to convert
+	and should rasise if the value can not be converted. fieldType is the data type 
+	expected on mappping conversion.
+		
+	For convenience the module defines some standard types like Int, Float
+	and String.
+	
+	>>> class S(PoorMansStruct):
+	...    _fields_ = [
+	...        ('Foo', (int, str, int)),
+	...        ('Bar', Str),
+	...        ]
+	
+	To convert a mapping to a string, call toString() with the mapping to convert
+	>>> p = S.toString({'Foo': 123456, 'Bar': 'abcdefg'})
+	>>> p
+	'123456\\x01YWJjZGVmZw=='
+	
+	To convert a string to a mapping call fromString() with the string to convert
+	>>> d = S.fromString(p)
+	>>> sorted(d.items())
+	[('Bar', 'abcdefg'), ('Foo', 123456)]
+	
+	
+	Field names must corrospond to mapping names
+	>>> p = S.toString({'IAmInvalid': 123456, 'Bar': 'abcdefg'})
+	Traceback (most recent call last):
+		...
+	KeyError: 'Foo'
+	
+	
+	All field names must be present in the mapping passed
+	>>> p = S.toString({'Bar': 'abcdefg'})
+	Traceback (most recent call last):
+		...
+	KeyError: 'Foo'
+	
+	types of the mapping have to corrospond to field types
+	>>> p = S.toString({'Foo': 'invalid-int', 'Bar': 'abcdefg'})
+	Traceback (most recent call last):
+		...
+	ValueError: Invalid type for field "Foo, expected: <type 'int'>"
+	
+	invalid field types are detected on converting the string back to a mapping
+	>>> p = 'invalid-int\\x01YWJjZGVmZw=='
+	>>> S.fromString(p)
+	Traceback (most recent call last):
+		...
+	ValueError: Invalid field #0: (invalid literal for int() with base 10: 'invalid-int')
+		
+	too few fields in the input strig will be recognized
+	>>> p = 'YWJjZGVmZw=='
+	>>> S.fromString(p)
+	Traceback (most recent call last):
+		...
+	ValueError: Too few fields in input string
+	
+	...aswell as too many
+	>>> p = '999\x01123456\x01YWJjZGVmZw=='
+	>>> S.fromString(p)
+	Traceback (most recent call last):
+		...
+	ValueError: Too many fields in input string
+	"""
+		
+	_sep_ = '\x01'
+	_fields_ = []
+	
+	
+	@classmethod
+	def fromString(klass, string):
+		params = string.split(klass._sep_)
+		if len(params) > len(klass._fields_):
+			raise ValueError('Too many fields in input string')
+		if len(params) < len(klass._fields_):
+			raise ValueError('Too few fields in input string')
+		out = {}
+		for n, (fieldName, (getter, setter, fieldType)) in enumerate(klass._fields_):
+			try:
+				out[fieldName] = getter(params[n])
+			except Exception, details:
+				raise ValueError('Invalid field #%s: (%s)' % (n, details))
+		return out
+		
+	@classmethod
+	def toString(klass, mapping):
+		out = []
+		for n, (fieldName, (getter, setter, fieldType)) in enumerate(klass._fields_):
+			value = mapping[fieldName]
+			if not isinstance(value, fieldType):
+				raise ValueError('Invalid type for field "%s, expected: %s"' % (fieldName, fieldType))
+			try:
+				value = setter(value)
+				assert isinstance(value, str)
+				out.append(value)
+			except Exception, details:
+				raise ValueError('Invalid field "%s": (%s)' % (fieldName, details))
+		return klass._sep_.join(out)	
+			
+
+"""
+class PersistentParams(PoorMansStruct):
+	_fields_ = [
+			('Flags', PoorMansStruct.Int),
+			('InitTime', PoorMansStruct.Float),
+			('PerisitstentUserData', PoorMansStruct.Str),
+			]
+"""			
+#****************************************************************************
+#
+#****************************************************************************
+if __name__ == '__main__':
+	import doctest
+	print 'doctests failed: %s/%s' % doctest.testmod()
+


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