4a5e5b1a54
This replaces the routing logic with a new, faster strategy based on on-the-fly generation of Python code. As part of replacing the logic, the architecture has been refactored to decouple routing from falcon.API, thereby making it possible for users to easily replace the default router with their own. Closes #114 Co-Authored-By: Kurt Griffiths <mail@kgriffs.com>
229 lines
8.5 KiB
Python
229 lines
8.5 KiB
Python
# Copyright 2013 by Richard Olsson
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import re
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class CompiledRouter(object):
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"""Fast URI router which compiles its routing logic to Python code.
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This class is a Falcon router, which handles the routing from URI paths
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to resource class instance methods. It implements the necessary router
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methods add_route() and find(). Generally you do not need to use this
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router class directly, as an instance is created by default when the
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falcon.API class is initialized.
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The router treats URI paths as a tree of URI segments and searches by
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checking the URI one segment at a time. Instead of interpreting the route
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tree for each look-up, it generates inlined, bespoke Python code to
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perform the search, then compiles that code. This makes the route
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provessing blazingly fast.
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The generated code for the test() method looks something like this:
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def test(path, return_values, expressions, params):
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path_len = len(path)
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if path_len > 0 and path[0] == "books":
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if path_len > 1:
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params["book_id"] = path[1]
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return return_values[1]
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return return_values[0]
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if path_len > 0 and path[0] == "authors"
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if path_len > 1:
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params["author_id"] = path[1]
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if path_len > 2:
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match = expressions[0].search(path[2])
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if match is not None:
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params.update(match.groupdict())
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return return_values[4]
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return return_values[3]
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return return_values[2]
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"""
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def __init__(self):
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self._roots = []
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self._find = self._compile()
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self._code_lines = None
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self._expressions = None
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self._return_values = None
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self._compile()
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def add_route(self, uri_template, method_map, resource):
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"""Adds a route between URI path template and resource."""
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# Can't start with a number, since these eventually get passed as
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# args to on_* responders
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if re.search('{\d', uri_template):
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raise ValueError('Field names may not start with a digit.')
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if re.search('\s', uri_template):
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raise ValueError('URI templates may not include whitespace.')
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path = uri_template.strip('/').split('/')
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def insert(nodes, path_index=0):
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for node in nodes:
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if node.matches(path[path_index]):
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path_index += 1
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if path_index == len(path):
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node.method_map = method_map
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node.resource = resource
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else:
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insert(node.children, path_index)
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return
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# NOTE(richardolsson): If we got this far, the node doesn't already
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# exist and needs to be created. This builds a new branch of the
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# routing tree recursively until it reaches the new node leaf.
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new_node = CompiledRouterNode(path[path_index])
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nodes.append(new_node)
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if path_index == len(path) - 1:
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new_node.method_map = method_map
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new_node.resource = resource
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else:
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insert(new_node.children, path_index + 1)
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insert(self._roots)
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self._find = self._compile()
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def find(self, uri):
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"""Finds resource and method map for a URI, or returns None."""
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path = uri.lstrip('/').split('/')
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params = {}
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node = self._find(path, self._return_values, self._expressions, params)
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if node is not None:
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return node.resource, node.method_map, params
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else:
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return None, None, None
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def _compile_node(self, node=None, pad=' ', level=0):
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"""Generates Python code for a router node (and it's children)."""
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def line(pad, lstr):
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self._code_lines.append(pad + lstr)
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if node.is_var:
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line(pad, 'if path_len > %d:' % level)
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if node.is_complex:
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# NOTE(richardolsson): Complex nodes are nodes which contain
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# anything more than a single literal or variable, and they
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# need to be checked using a pre-compiled regular expression.
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expression_idx = len(self._expressions)
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self._expressions.append(node.var_regex)
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line(pad, ' match = expressions[%d].match(path[%d]) # %s' % (
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expression_idx, level, node.var_regex.pattern))
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line(pad, ' if match is not None:')
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line(pad, ' params.update(match.groupdict())')
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pad += ' '
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else:
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line(pad, ' params["%s"] = path[%d]' % (node.var_name, level))
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else:
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line(pad, 'if path_len > %d and path[%d] == "%s":' % (
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level, level, node.raw_segment))
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if node.resource is not None:
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resource_idx = len(self._return_values)
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self._return_values.append(node)
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if len(node.children):
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for child in node.children:
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self._compile_node(child, pad + ' ', level + 1)
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if node.resource is not None:
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line(pad, ' return return_values[%d]' % resource_idx)
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def _compile(self):
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"""Generates Python code for entire routing tree.
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The generated code is compiled and the resulting Python method is
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returned.
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"""
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self._return_values = []
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self._expressions = []
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self._code_lines = [
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'def find(path, return_values, expressions, params):',
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' path_len = len(path)',
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]
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for root in self._roots:
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self._compile_node(root)
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src = '\n'.join(self._code_lines)
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scope = {}
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exec(compile(src, '<string>', 'exec'), scope)
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return scope['find']
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class CompiledRouterNode(object):
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"""Represents a single URI segment in a URI."""
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def __init__(self, raw_segment, method_map=None, resource=None):
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self.children = []
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self.raw_segment = raw_segment
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self.method_map = method_map
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self.resource = resource
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seg = raw_segment.replace('.', '\\.')
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matches = list(re.finditer('{([-_a-zA-Z0-9]+)}', seg))
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if matches:
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self.is_var = True
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# NOTE(richardolsson): if there is a single variable and it spans
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# the entire segment, the segment is uncomplex and the variable
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# name is simply the string contained within curly braces.
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if len(matches) == 1 and matches[0].span() == (0, len(seg)):
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self.is_complex = False
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self.var_name = raw_segment[1:-1]
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else:
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# NOTE(richardolsson): Complex segments need to be converted
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# into regular expressions will be used to match and extract
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# variable values. The regular expressions contain both
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# literal spans and named group expressions for the variables.
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self.is_complex = True
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seg_fields = []
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prev_end_idx = 0
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for match in matches:
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var_start_idx, var_end_idx = match.span()
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seg_fields.append(seg[prev_end_idx:var_start_idx])
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var_name = match.groups()[0].replace('-', '_')
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seg_fields.append('(?P<%s>[^/]+)' % var_name)
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prev_end_idx = var_end_idx
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seg_fields.append(seg[prev_end_idx:])
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seg_pattern = ''.join(seg_fields)
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self.var_regex = re.compile(seg_pattern)
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else:
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self.is_var = False
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def matches(self, segment):
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"""Returns True if this node matches the supplied URI segment."""
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if self.is_var:
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if self.is_complex:
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match = self.var_regex.search(segment)
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if match:
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return True
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else:
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return False
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else:
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return True
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elif segment == self.raw_segment:
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return True
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else:
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return False
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