1 files changed, 297 insertions, 0 deletions
diff --git a/Lib/persist.py b/Lib/persist.py
new file mode 100755
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--- /dev/null
+++ b/Lib/persist.py
@@ -0,0 +1,297 @@
+# persist.py
+#
+# Implement limited persistence.
+#
+# Simple interface:
+#	persist.save()		save __main__ module on file (overwrite)
+#	persist.load()		load __main__ module from file (merge)
+#
+# These use the filename persist.defaultfile, initialized to 'wsrestore.py'.
+#
+# A raw interface also exists:
+#	persist.writedict(dict, fp)	save dictionary to open file
+#	persist.readdict(dict, fp)	read (merge) dictionary from open file
+#
+# Internally, the function dump() and a whole bunch of support of functions
+# traverse a graph of objects and print them in a restorable form
+# (which happens to be a Python module).
+#
+# XXX Limitations:
+# - Volatile objects are dumped as strings:
+#   - open files, windows etc.
+# - Other 'obscure' objects are dumped as strings:
+#   - classes, instances and methods
+#   - compiled regular expressions
+#   - anything else reasonably obscure (e.g., capabilities)
+#   - type objects for obscure objects
+# - It's slow when there are many of lists or dictionaries
+#   (This could be fixed if there were a quick way to compute a hash
+#   function of any object, even if recursive)
+
+defaultfile = 'wsrestore.py'
+
+def save():
+	import __main__
+	import posix
+	# XXX On SYSV, if len(defaultfile) >= 14, this is wrong!
+	backup = defaultfile + '~'
+	try:
+		posix.unlink(backup)
+	except posix.error:
+		pass
+	try:
+		posix.rename(defaultfile, backup)
+	except posix.error:
+		pass
+	fp = open(defaultfile, 'w')
+	writedict(__main__.__dict__, fp)
+	fp.close()
+
+def load():
+	import __main__
+	fp = open(defaultfile, 'r')
+	readdict(__main__.__dict__, fp)
+
+def writedict(dict, fp):
+	import sys
+	savestdout = sys.stdout
+	try:
+		sys.stdout = fp
+		dump(dict)	# Writes to sys.stdout
+	finally:
+		sys.stdout = savestdout
+
+def readdict(dict, fp):
+	contents = fp.read()		# Or: util.readopenfile(fp)
+	globals = {}
+	exec(contents, globals)
+	top = globals['top']
+	for key in top.keys():
+		if dict.has_key(key):
+			print 'warning:', key, 'not overwritten'
+		else:
+			dict[key] = top[key]
+
+
+# Function dump(x) prints (on sys.stdout!) a sequence of Python statements
+# that, when executed in an empty environment, will reconstruct the
+# contents of an arbitrary dictionary.
+
+import sys
+
+# Name used for objects dict on output.
+#
+FUNNYNAME = FN = 'A'
+
+# Top-level function.  Call with the object you want to dump.
+#
+def dump(x):
+	types = {}
+	stack = []			# Used by test for recursive objects
+	print FN, '= {}'
+	topuid = dumpobject(x, types, stack)
+	print 'top =', FN, '[', `topuid`, ']'
+
+# Generic function to dump any object.
+#
+dumpswitch = {}
+#
+def dumpobject(x, types, stack):
+	typerepr = `type(x)`
+	if not types.has_key(typerepr):
+		types[typerepr] = {}
+	typedict = types[typerepr]
+	if dumpswitch.has_key(typerepr):
+		return dumpswitch[typerepr](x, typedict, types, stack)
+	else:
+		return dumpbadvalue(x, typedict, types, stack)
+
+# Generic function to dump unknown values.
+# This assumes that the Python interpreter prints such values as
+# <foo object at xxxxxxxx>.
+# The object will be read back as a string: '<foo object at xxxxxxxx>'.
+# In some cases it may be possible to fix the dump manually;
+# to ease the editing, these cases are labeled with an XXX comment.
+#
+def dumpbadvalue(x, typedict, types, stack):
+	xrepr = `x`
+	if typedict.has_key(xrepr):
+		return typedict[xrepr]
+	uid = genuid()
+	typedict[xrepr] = uid
+	print FN, '[', `uid`, '] =', `xrepr`, '# XXX'
+	return uid
+
+# Generic function to dump pure, simple values, except strings
+#
+def dumpvalue(x, typedict, types, stack):
+	xrepr = `x`
+	if typedict.has_key(xrepr):
+		return typedict[xrepr]
+	uid = genuid()
+	typedict[xrepr] = uid
+	print FN, '[', `uid`, '] =', `x`
+	return uid
+
+# Functions to dump string objects
+#
+def dumpstring(x, typedict, types, stack):
+	# XXX This can break if strings have embedded '\0' bytes
+	# XXX because of a bug in the dictionary module
+	if typedict.has_key(x):
+		return typedict[x]
+	uid = genuid()
+	typedict[x] = uid
+	print FN, '[', `uid`, '] =', `x`
+	return uid
+
+# Function to dump type objects
+#
+typeswitch = {}
+class some_class():
+	def method(self): pass
+some_instance = some_class()
+#
+def dumptype(x, typedict, types, stack):
+	xrepr = `x`
+	if typedict.has_key(xrepr):
+		return typedict[xrepr]
+	uid = genuid()
+	typedict[xrepr] = uid
+	if typeswitch.has_key(xrepr):
+		print FN, '[', `uid`, '] =', typeswitch[xrepr]
+	elif x = type(sys):
+		print 'import sys'
+		print FN, '[', `uid`, '] = type(sys)'
+	elif x = type(sys.stderr):
+		print 'import sys'
+		print FN, '[', `uid`, '] = type(sys.stderr)'
+	elif x = type(dumptype):
+		print 'def some_function(): pass'
+		print FN, '[', `uid`, '] = type(some_function)'
+	elif x = type(some_class):
+		print 'class some_class(): pass'
+		print FN, '[', `uid`, '] = type(some_class)'
+	elif x = type(some_instance):
+		print 'class another_class(): pass'
+		print 'some_instance = another_class()'
+		print FN, '[', `uid`, '] = type(some_instance)'
+	elif x = type(some_instance.method):
+		print 'class yet_another_class():'
+		print '    def method(): pass'
+		print 'another_instance = yet_another_class()'
+		print FN, '[', `uid`, '] = type(another_instance.method)'
+	else:
+		# Unknown type
+		print FN, '[', `uid`, '] =', `xrepr`, '# XXX'
+	return uid
+
+# Initialize the typeswitch
+#
+for x in None, 0, 0.0, '', (), [], {}:
+	typeswitch[`type(x)`] = 'type(' + `x` + ')'
+for s in 'type(0)', 'abs', '[].append':
+	typeswitch[`type(eval(s))`] = 'type(' + s + ')'
+
+# Dump a tuple object
+#
+def dumptuple(x, typedict, types, stack):
+	item_uids = []
+	xrepr = ''
+	for item in x:
+		item_uid = dumpobject(item, types, stack)
+		item_uids.append(item_uid)
+		xrepr = xrepr + ' ' + item_uid
+	del stack[-1:]
+	if typedict.has_key(xrepr):
+		return typedict[xrepr]
+	uid = genuid()
+	typedict[xrepr] = uid
+	print FN, '[', `uid`, '] = (',
+	for item_uid in item_uids:
+		print FN, '[', `item_uid`, '],',
+	print ')'
+	return uid
+
+# Dump a list object
+#
+def dumplist(x, typedict, types, stack):
+	# Check for recursion
+	for x1, uid1 in stack:
+		if x is x1: return uid1
+	# Check for occurrence elsewhere in the typedict
+	for uid1 in typedict.keys():
+		if x is typedict[uid1]: return uid1
+	# This uses typedict differently!
+	uid = genuid()
+	typedict[uid] = x
+	print FN, '[', `uid`, '] = []'
+	stack.append(x, uid)
+	item_uids = []
+	for item in x:
+		item_uid = dumpobject(item, types, stack)
+		item_uids.append(item_uid)
+	del stack[-1:]
+	for item_uid in item_uids:
+		print FN, '[', `uid`, '].append(', FN, '[', `item_uid`, '])'
+	return uid
+
+# Dump a dictionary object
+#
+def dumpdict(x, typedict, types, stack):
+	# Check for recursion
+	for x1, uid1 in stack:
+		if x is x1: return uid1
+	# Check for occurrence elsewhere in the typedict
+	for uid1 in typedict.keys():
+		if x is typedict[uid1]: return uid1
+	# This uses typedict differently!
+	uid = genuid()
+	typedict[uid] = x
+	print FN, '[', `uid`, '] = {}'
+	stack.append(x, uid)
+	item_uids = []
+	for key in x.keys():
+		val_uid = dumpobject(x[key], types, stack)
+		item_uids.append(key, val_uid)
+	del stack[-1:]
+	for key, val_uid in item_uids:
+		print FN, '[', `uid`, '][', `key`, '] =',
+		print FN, '[', `val_uid`, ']'
+	return uid
+
+# Dump a module object
+#
+def dumpmodule(x, typedict, types, stack):
+	xrepr = `x`
+	if typedict.has_key(xrepr):
+		return typedict[xrepr]
+	from string import split
+	# `x` has the form <module 'foo'>
+	name = xrepr[9:-2]
+	uid = genuid()
+	typedict[xrepr] = uid
+	print 'import', name
+	print FN, '[', `uid`, '] =', name
+	return uid
+
+
+# Initialize dumpswitch, a table of functions to dump various objects,
+# indexed by `type(x)`.
+#
+for x in None, 0, 0.0:
+	dumpswitch[`type(x)`] = dumpvalue
+for x, f in ('', dumpstring), (type(0), dumptype), ((), dumptuple), \
+		([], dumplist), ({}, dumpdict), (sys, dumpmodule):
+	dumpswitch[`type(x)`] = f
+
+
+# Generate the next unique id; a string consisting of digits.
+# The seed is stored as seed[0].
+#
+seed = [0]
+#
+def genuid():
+	x = seed[0]
+	seed[0] = seed[0] + 1
+	return `x`