root/galaxy-central/eggs/Paste-1.6-py2.6.egg/paste/util/mimeparse.py

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1"""MIME-Type Parser
2
3This module provides basic functions for handling mime-types. It can handle
4matching mime-types against a list of media-ranges. See section 14.1 of
5the HTTP specification [RFC 2616] for a complete explaination.
6
7   http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.1
8
9Contents:
10    - parse_mime_type():   Parses a mime-type into it's component parts.
11    - parse_media_range(): Media-ranges are mime-types with wild-cards and a 'q' quality parameter.
12    - quality():           Determines the quality ('q') of a mime-type when compared against a list of media-ranges.
13    - quality_parsed():    Just like quality() except the second parameter must be pre-parsed.
14    - best_match():        Choose the mime-type with the highest quality ('q') from a list of candidates.
15    - desired_matches():   Provide a list in order of server-desired priorities from a list of candidates.
16"""
17
18__version__ = "0.1.1"
19__author__ = 'Joe Gregorio'
20__email__ = "joe@bitworking.org"
21__credits__ = ""
22
23def parse_mime_type(mime_type):
24    """Carves up a mime_type and returns a tuple of the
25       (type, subtype, params) where 'params' is a dictionary
26       of all the parameters for the media range.
27       For example, the media range 'application/xhtml;q=0.5' would
28       get parsed into:
29
30       ('application', 'xhtml', {'q', '0.5'})
31       """
32    parts = mime_type.split(";")
33    params = dict([tuple([s.strip() for s in param.split("=")])\
34            for param in parts[1:] ])
35    (type, subtype) = parts[0].split("/")
36    return (type.strip(), subtype.strip(), params)
37
38def parse_media_range(range):
39    """Carves up a media range and returns a tuple of the
40       (type, subtype, params) where 'params' is a dictionary
41       of all the parameters for the media range.
42       
43       For example, the media range ``application/*;q=0.5`` would
44       get parsed into::
45
46         ('application', '*', {'q', '0.5'})
47
48       In addition this function also guarantees that there
49       is a value for 'q' in the params dictionary, filling it
50       in with a proper default if necessary.
51       """
52    (type, subtype, params) = parse_mime_type(range)
53    if not params.has_key('q') or not params['q'] or \
54            not float(params['q']) or float(params['q']) > 1\
55            or float(params['q']) < 0:
56        params['q'] = '1'
57    return (type, subtype, params)
58
59def quality_parsed(mime_type, parsed_ranges):
60    """Find the best match for a given mime_type against
61       a list of media_ranges that have already been
62       parsed by parse_media_range(). Returns the
63       'q' quality parameter of the best match, 0 if no
64       match was found. This function bahaves the same as quality()
65       except that 'parsed_ranges' must be a list of
66       parsed media ranges. """
67    best_fitness = -1
68    best_match = ""
69    best_fit_q = 0
70    (target_type, target_subtype, target_params) =\
71            parse_media_range(mime_type)
72    for (type, subtype, params) in parsed_ranges:
73        param_matches = sum([1 for (key, value) in \
74                target_params.iteritems() if key != 'q' and \
75                params.has_key(key) and value == params[key]])
76        if (type == target_type or type == '*') and \
77                (subtype == target_subtype or subtype == "*"):
78            fitness = (type == target_type) and 100 or 0
79            fitness += (subtype == target_subtype) and 10 or 0
80            fitness += param_matches
81            if fitness > best_fitness:
82                best_fitness = fitness
83                best_fit_q = params['q']
84           
85    return float(best_fit_q)
86   
87def quality(mime_type, ranges):
88    """Returns the quality 'q' of a mime_type when compared
89    against the media-ranges in ranges. For example:
90
91    >>> 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')
92    0.7
93   
94    """
95    parsed_ranges = [parse_media_range(r) for r in ranges.split(",")]
96    return quality_parsed(mime_type, parsed_ranges)
97
98def best_match(supported, header):
99    """Takes a list of supported mime-types and finds the best
100    match for all the media-ranges listed in header. The value of
101    header must be a string that conforms to the format of the
102    HTTP Accept: header. The value of 'supported' is a list of
103    mime-types.
104   
105    >>> best_match(['application/xbel+xml', 'text/xml'], 'text/*;q=0.5,*/*; q=0.1')
106    'text/xml'
107    """
108    parsed_header = [parse_media_range(r) for r in header.split(",")]
109    weighted_matches = [(quality_parsed(mime_type, parsed_header), mime_type)\
110            for mime_type in supported]
111    weighted_matches.sort()
112    return weighted_matches[-1][0] and weighted_matches[-1][1] or ''
113
114def desired_matches(desired, header):
115    """Takes a list of desired mime-types in the order the server prefers to
116    send them regardless of the browsers preference.
117   
118    Browsers (such as Firefox) technically want XML over HTML depending on how
119    one reads the specification. This function is provided for a server to
120    declare a set of desired mime-types it supports, and returns a subset of
121    the desired list in the same order should each one be Accepted by the
122    browser.
123   
124    >>> sorted_match(['text/html', 'application/xml'], \
125    ...     'text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png')
126    ['text/html', 'application/xml']
127    >>> sorted_match(['text/html', 'application/xml'], 'application/xml,application/json')
128    ['application/xml']
129    """
130    matches = []
131    parsed_ranges = [parse_media_range(r) for r in header.split(",")]
132    for mimetype in desired:
133        if quality_parsed(mimetype, parsed_ranges):
134            matches.append(mimetype)
135    return matches
136
137if __name__ == "__main__":
138    import unittest
139
140    class TestMimeParsing(unittest.TestCase):
141
142        def test_parse_media_range(self):
143            self.assert_(('application', 'xml', {'q': '1'}) == parse_media_range('application/xml;q=1'))
144            self.assertEqual(('application', 'xml', {'q': '1'}), parse_media_range('application/xml'))
145            self.assertEqual(('application', 'xml', {'q': '1'}), parse_media_range('application/xml;q='))
146            self.assertEqual(('application', 'xml', {'q': '1'}), parse_media_range('application/xml ; q='))
147            self.assertEqual(('application', 'xml', {'q': '1', 'b': 'other'}), parse_media_range('application/xml ; q=1;b=other'))
148            self.assertEqual(('application', 'xml', {'q': '1', 'b': 'other'}), parse_media_range('application/xml ; q=2;b=other'))
149
150        def test_rfc_2616_example(self):
151            accept = "text/*;q=0.3, text/html;q=0.7, text/html;level=1, text/html;level=2;q=0.4, */*;q=0.5"
152            self.assertEqual(1, quality("text/html;level=1", accept))
153            self.assertEqual(0.7, quality("text/html", accept))
154            self.assertEqual(0.3, quality("text/plain", accept))
155            self.assertEqual(0.5, quality("image/jpeg", accept))
156            self.assertEqual(0.4, quality("text/html;level=2", accept))
157            self.assertEqual(0.7, quality("text/html;level=3", accept))
158
159        def test_best_match(self):
160            mime_types_supported = ['application/xbel+xml', 'application/xml']
161            # direct match
162            self.assertEqual(best_match(mime_types_supported, 'application/xbel+xml'), 'application/xbel+xml')
163            # direct match with a q parameter
164            self.assertEqual(best_match(mime_types_supported, 'application/xbel+xml; q=1'), 'application/xbel+xml')
165            # direct match of our second choice with a q parameter
166            self.assertEqual(best_match(mime_types_supported, 'application/xml; q=1'), 'application/xml')
167            # match using a subtype wildcard
168            self.assertEqual(best_match(mime_types_supported, 'application/*; q=1'), 'application/xml')
169            # match using a type wildcard
170            self.assertEqual(best_match(mime_types_supported, '*/*'), 'application/xml')
171
172            mime_types_supported = ['application/xbel+xml', 'text/xml']
173            # match using a type versus a lower weighted subtype
174            self.assertEqual(best_match(mime_types_supported, 'text/*;q=0.5,*/*; q=0.1'), 'text/xml')
175            # fail to match anything
176            self.assertEqual(best_match(mime_types_supported, 'text/html,application/atom+xml; q=0.9'), '')
177
178    unittest.main()
Note: リポジトリブラウザについてのヘルプは TracBrowser を参照してください。