Warning

This document is for an in-development version of Galaxy. You can alternatively view this page in the latest release if it exists or view the top of the latest release's documentation.

Source code for mimeparse

"""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 explanation.

   http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.1

Contents:
    - parse_mime_type():   Parses a mime-type into its 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.
"""
from functools import reduce

__version__ = "0.1.2"
__author__ = 'Joe Gregorio'
__email__ = "joe@bitworking.org"
__credits__ = ""


[docs]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:]]) full_type = parts[0].strip() # Java URLConnection class sends an Accept header that includes a single "*" # Turn it into a legal wildcard. if full_type == '*': full_type = '*/*' (type, subtype) = full_type.split("/") return (type.strip(), subtype.strip(), params)
[docs]def parse_media_range(range): r""" 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: .. raw:: text ('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 'q' not in params 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)
[docs]def fitness_and_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 a tuple of the fitness value and the value of the 'q' quality parameter of the best match, or (-1, 0) if no match was found. Just as for quality_parsed(), 'parsed_ranges' must be a list of parsed media ranges. """ best_fitness = -1 best_fit_q = 0 (target_type, target_subtype, target_params) =\ parse_media_range(mime_type) for (type, subtype, params) in parsed_ranges: if (type == target_type or type == '*' or target_type == '*') and \ (subtype == target_subtype or subtype == '*' or target_subtype == '*'): param_matches = reduce(lambda x, y: x + y, [1 for (key, value) in target_params.items() if key != 'q' and key in params and value == params[key]], 0) 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 best_fitness, float(best_fit_q)
[docs]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. """ return fitness_and_quality_parsed(mime_type, parsed_ranges)[1]
[docs]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)
[docs]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 = [(fitness_and_quality_parsed(mime_type, parsed_header), mime_type) for mime_type in supported] weighted_matches.sort() return weighted_matches[-1][0][1] 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')) # Java URLConnection class sends an Accept header that includes a single * self.assertEqual(('*', '*', {'q': '.2'}), parse_media_range(" *; q=.2")) 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'), '') # common AJAX scenario mime_types_supported = ['application/json', 'text/html'] self.assertEqual(best_match(mime_types_supported, 'application/json, text/javascript, */*'), 'application/json') # verify fitness ordering self.assertEqual(best_match(mime_types_supported, 'application/json, text/html;q=0.9'), 'application/json') 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()