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from cStringIO import StringIO
class StringIOTree(object):
"""
See module docs.
"""
def __init__(self, stream=None):
self.prepended_children = []
if stream is None:
stream = StringIO()
self.stream = stream
self.write = stream.write
self.markers = []
def getvalue(self):
content = [x.getvalue() for x in self.prepended_children]
content.append(self.stream.getvalue())
return "".join(content)
def copyto(self, target):
"""Potentially cheaper than getvalue as no string concatenation
needs to happen."""
for child in self.prepended_children:
child.copyto(target)
stream_content = self.stream.getvalue()
if stream_content:
target.write(stream_content)
def commit(self):
# Save what we have written until now so that the buffer
# itself is empty -- this makes it ready for insertion
if self.stream.tell():
self.prepended_children.append(StringIOTree(self.stream))
self.prepended_children[-1].markers = self.markers
self.markers = []
self.stream = StringIO()
self.write = self.stream.write
def insert(self, iotree):
"""
Insert a StringIOTree (and all of its contents) at this location.
Further writing to self appears after what is inserted.
"""
self.commit()
self.prepended_children.append(iotree)
def insertion_point(self):
"""
Returns a new StringIOTree, which is left behind at the current position
(it what is written to the result will appear right before whatever is
next written to self).
Calling getvalue() or copyto() on the result will only return the
contents written to it.
"""
# Save what we have written until now
# This is so that getvalue on the result doesn't include it.
self.commit()
# Construct the new forked object to return
other = StringIOTree()
self.prepended_children.append(other)
return other
def allmarkers(self):
children = self.prepended_children
return [m for c in children for m in c.allmarkers()] + self.markers
__doc__ = r"""
Implements a buffer with insertion points. When you know you need to
"get back" to a place and write more later, simply call insertion_point()
at that spot and get a new StringIOTree object that is "left behind".
EXAMPLE:
>>> a = StringIOTree()
>>> a.write('first\n')
>>> b = a.insertion_point()
>>> a.write('third\n')
>>> b.write('second\n')
>>> a.getvalue().split()
['first', 'second', 'third']
>>> c = b.insertion_point()
>>> d = c.insertion_point()
>>> d.write('alpha\n')
>>> b.write('gamma\n')
>>> c.write('beta\n')
>>> b.getvalue().split()
['second', 'alpha', 'beta', 'gamma']
>>> i = StringIOTree()
>>> d.insert(i)
>>> i.write('inserted\n')
>>> out = StringIO()
>>> a.copyto(out)
>>> out.getvalue().split()
['first', 'second', 'alpha', 'inserted', 'beta', 'gamma', 'third']
"""
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