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