From 4258e041a395dc7f7976b619cd5727cca0a187ff Mon Sep 17 00:00:00 2001 From: Joe Gregorio Date: Sat, 30 Jun 2007 15:44:21 -0700 Subject: Initial checkin --- mimeparse.py | 162 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 162 insertions(+) create mode 100644 mimeparse.py diff --git a/mimeparse.py b/mimeparse.py new file mode 100644 index 0000000..701ef31 --- /dev/null +++ b/mimeparse.py @@ -0,0 +1,162 @@ +"""MIME-Type Parser + +This module provides basic functions for handling mime-types. It can handle +matching mime-types against a list of media-ranges. See section 14.1 of +the HTTP specification [RFC 2616] for a complete explaination. + + http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.1 + +Contents: + - parse_mime_type(): Parses a mime-type into it's component parts. + - parse_media_range(): Media-ranges are mime-types with wild-cards and a 'q' quality parameter. + - quality(): Determines the quality ('q') of a mime-type when compared against a list of media-ranges. + - quality_parsed(): Just like quality() except the second parameter must be pre-parsed. + - best_match(): Choose the mime-type with the highest quality ('q') from a list of candidates. +""" + +__version__ = "0.1.1" +__author__ = 'Joe Gregorio' +__email__ = "joe@bitworking.org" +__credits__ = "" + +def parse_mime_type(mime_type): + """Carves up a mime_type and returns a tuple of the + (type, subtype, params) where 'params' is a dictionary + of all the parameters for the media range. + For example, the media range 'application/xhtml;q=0.5' would + get parsed into: + + ('application', 'xhtml', {'q', '0.5'}) + """ + parts = mime_type.split(";") + params = dict([tuple([s.strip() for s in param.split("=")])\ + for param in parts[1:] ]) + (type, subtype) = parts[0].split("/") + return (type.strip(), subtype.strip(), params) + +def parse_media_range(range): + """Carves up a media range and returns a tuple of the + (type, subtype, params) where 'params' is a dictionary + of all the parameters for the media range. + For example, the media range 'application/*;q=0.5' would + get parsed into: + + ('application', '*', {'q', '0.5'}) + + In addition this function also guarantees that there + is a value for 'q' in the params dictionary, filling it + in with a proper default if necessary. + """ + (type, subtype, params) = parse_mime_type(range) + if not params.has_key('q') or not params['q'] or \ + not float(params['q']) or float(params['q']) > 1\ + or float(params['q']) < 0: + params['q'] = '1' + return (type, subtype, params) + +def quality_parsed(mime_type, parsed_ranges): + """Find the best match for a given mime_type against + a list of media_ranges that have already been + parsed by parse_media_range(). Returns the + 'q' quality parameter of the best match, 0 if no + match was found. This function bahaves the same as quality() + except that 'parsed_ranges' must be a list of + parsed media ranges. """ + best_fitness = -1 + best_match = "" + best_fit_q = 0 + (target_type, target_subtype, target_params) =\ + parse_media_range(mime_type) + for (type, subtype, params) in parsed_ranges: + param_matches = reduce(lambda x, y: x+y, [1 for (key, value) in \ + target_params.iteritems() if key != 'q' and \ + params.has_key(key) and value == params[key]], 0) + if (type == target_type or type == '*' or target_type == '*') and \ + (subtype == target_subtype or subtype == '*' or target_subtype == '*'): + fitness = (type == target_type) and 100 or 0 + fitness += (subtype == target_subtype) and 10 or 0 + fitness += param_matches + if fitness > best_fitness: + best_fitness = fitness + best_fit_q = params['q'] + + return float(best_fit_q) + +def quality(mime_type, ranges): + """Returns the quality 'q' of a mime_type when compared + against the media-ranges in ranges. For example: + + >>> quality('text/html','text/*;q=0.3, text/html;q=0.7, text/html;level=1, text/html;level=2;q=0.4, */*;q=0.5') + 0.7 + + """ + parsed_ranges = [parse_media_range(r) for r in ranges.split(",")] + return quality_parsed(mime_type, parsed_ranges) + +def best_match(supported, header): + """Takes a list of supported mime-types and finds the best + match for all the media-ranges listed in header. The value of + header must be a string that conforms to the format of the + HTTP Accept: header. The value of 'supported' is a list of + mime-types. + + >>> best_match(['application/xbel+xml', 'text/xml'], 'text/*;q=0.5,*/*; q=0.1') + 'text/xml' + """ + parsed_header = [parse_media_range(r) for r in header.split(",")] + weighted_matches = [(quality_parsed(mime_type, parsed_header), mime_type)\ + for mime_type in supported] + weighted_matches.sort() + return weighted_matches[-1][0] and weighted_matches[-1][1] or '' + +if __name__ == "__main__": + import unittest + + class TestMimeParsing(unittest.TestCase): + + def test_parse_media_range(self): + self.assert_(('application', 'xml', {'q': '1'}) == parse_media_range('application/xml;q=1')) + self.assertEqual(('application', 'xml', {'q': '1'}), parse_media_range('application/xml')) + self.assertEqual(('application', 'xml', {'q': '1'}), parse_media_range('application/xml;q=')) + self.assertEqual(('application', 'xml', {'q': '1'}), parse_media_range('application/xml ; q=')) + self.assertEqual(('application', 'xml', {'q': '1', 'b': 'other'}), parse_media_range('application/xml ; q=1;b=other')) + self.assertEqual(('application', 'xml', {'q': '1', 'b': 'other'}), parse_media_range('application/xml ; q=2;b=other')) + + def test_rfc_2616_example(self): + accept = "text/*;q=0.3, text/html;q=0.7, text/html;level=1, text/html;level=2;q=0.4, */*;q=0.5" + self.assertEqual(1, quality("text/html;level=1", accept)) + self.assertEqual(0.7, quality("text/html", accept)) + self.assertEqual(0.3, quality("text/plain", accept)) + self.assertEqual(0.5, quality("image/jpeg", accept)) + self.assertEqual(0.4, quality("text/html;level=2", accept)) + self.assertEqual(0.7, quality("text/html;level=3", accept)) + + def test_best_match(self): + mime_types_supported = ['application/xbel+xml', 'application/xml'] + # direct match + self.assertEqual(best_match(mime_types_supported, 'application/xbel+xml'), 'application/xbel+xml') + # direct match with a q parameter + self.assertEqual(best_match(mime_types_supported, 'application/xbel+xml; q=1'), 'application/xbel+xml') + # direct match of our second choice with a q parameter + self.assertEqual(best_match(mime_types_supported, 'application/xml; q=1'), 'application/xml') + # match using a subtype wildcard + self.assertEqual(best_match(mime_types_supported, 'application/*; q=1'), 'application/xml') + # match using a type wildcard + self.assertEqual(best_match(mime_types_supported, '*/*'), 'application/xml') + + mime_types_supported = ['application/xbel+xml', 'text/xml'] + # match using a type versus a lower weighted subtype + self.assertEqual(best_match(mime_types_supported, 'text/*;q=0.5,*/*; q=0.1'), 'text/xml') + # fail to match anything + self.assertEqual(best_match(mime_types_supported, 'text/html,application/atom+xml; q=0.9'), '') + + def test_support_wildcards(self): + mime_types_supported = ['image/*', 'application/xml'] + # match using a type wildcard + self.assertEqual(best_match(mime_types_supported, 'image/png'), 'image/*') + # match using a wildcard for both requested and supported + self.assertEqual(best_match(mime_types_supported, 'image/*'), 'image/*') + + unittest.main() + + -- cgit v1.2.1