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| # cython: auto_pickle=False | |
| 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'] | |
| """ | |
| from __future__ import absolute_import #, unicode_literals | |
| try: | |
| # Prefer cStringIO since io.StringIO() does not support writing 'str' in Py2. | |
| from cStringIO import StringIO | |
| except ImportError: | |
| from io 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 | |