1
2
3
4
5 """MIME-Type Parser
6
7 This module provides basic functions for handling mime-types. It can handle
8 matching mime-types against a list of media-ranges. See section 14.1 of the
9 HTTP specification [RFC 2616] for a complete explanation.
10
11 http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.1
12
13 Contents:
14 - parse_mime_type(): Parses a mime-type into its component parts.
15 - parse_media_range(): Media-ranges are mime-types with wild-cards and a 'q'
16 quality parameter.
17 - quality(): Determines the quality ('q') of a mime-type when
18 compared against a list of media-ranges.
19 - quality_parsed(): Just like quality() except the second parameter must be
20 pre-parsed.
21 - best_match(): Choose the mime-type with the highest quality ('q')
22 from a list of candidates.
23 """
24 from __future__ import absolute_import
25 from functools import reduce
26 import six
27
28 __version__ = "0.1.3"
29 __author__ = "Joe Gregorio"
30 __email__ = "joe@bitworking.org"
31 __license__ = "MIT License"
32 __credits__ = ""
33
34
36 """Parses a mime-type into its component parts.
37
38 Carves up a mime-type and returns a tuple of the (type, subtype, params)
39 where 'params' is a dictionary of all the parameters for the media range.
40 For example, the media range 'application/xhtml;q=0.5' would get parsed
41 into:
42
43 ('application', 'xhtml', {'q', '0.5'})
44 """
45 parts = mime_type.split(";")
46 params = dict(
47 [tuple([s.strip() for s in param.split("=", 1)]) for param in parts[1:]]
48 )
49 full_type = parts[0].strip()
50
51
52 if full_type == "*":
53 full_type = "*/*"
54 (type, subtype) = full_type.split("/")
55
56 return (type.strip(), subtype.strip(), params)
57
58
84
85
87 """Find the best match for a mime-type amongst parsed media-ranges.
88
89 Find the best match for a given mime-type against a list of media_ranges
90 that have already been parsed by parse_media_range(). Returns a tuple of
91 the fitness value and the value of the 'q' quality parameter of the best
92 match, or (-1, 0) if no match was found. Just as for quality_parsed(),
93 'parsed_ranges' must be a list of parsed media ranges.
94 """
95 best_fitness = -1
96 best_fit_q = 0
97 (target_type, target_subtype, target_params) = parse_media_range(mime_type)
98 for (type, subtype, params) in parsed_ranges:
99 type_match = type == target_type or type == "*" or target_type == "*"
100 subtype_match = (
101 subtype == target_subtype or subtype == "*" or target_subtype == "*"
102 )
103 if type_match and subtype_match:
104 param_matches = reduce(
105 lambda x, y: x + y,
106 [
107 1
108 for (key, value) in six.iteritems(target_params)
109 if key != "q" and key in params and value == params[key]
110 ],
111 0,
112 )
113 fitness = (type == target_type) and 100 or 0
114 fitness += (subtype == target_subtype) and 10 or 0
115 fitness += param_matches
116 if fitness > best_fitness:
117 best_fitness = fitness
118 best_fit_q = params["q"]
119
120 return best_fitness, float(best_fit_q)
121
122
124 """Find the best match for a mime-type amongst parsed media-ranges.
125
126 Find the best match for a given mime-type against a list of media_ranges
127 that have already been parsed by parse_media_range(). Returns the 'q'
128 quality parameter of the best match, 0 if no match was found. This function
129 bahaves the same as quality() except that 'parsed_ranges' must be a list of
130 parsed media ranges.
131 """
132
133 return fitness_and_quality_parsed(mime_type, parsed_ranges)[1]
134
135
137 """Return the quality ('q') of a mime-type against a list of media-ranges.
138
139 Returns the quality 'q' of a mime-type when compared against the
140 media-ranges in ranges. For example:
141
142 >>> quality('text/html','text/*;q=0.3, text/html;q=0.7,
143 text/html;level=1, text/html;level=2;q=0.4, */*;q=0.5')
144 0.7
145
146 """
147 parsed_ranges = [parse_media_range(r) for r in ranges.split(",")]
148
149 return quality_parsed(mime_type, parsed_ranges)
150
151
153 """Return mime-type with the highest quality ('q') from list of candidates.
154
155 Takes a list of supported mime-types and finds the best match for all the
156 media-ranges listed in header. The value of header must be a string that
157 conforms to the format of the HTTP Accept: header. The value of 'supported'
158 is a list of mime-types. The list of supported mime-types should be sorted
159 in order of increasing desirability, in case of a situation where there is
160 a tie.
161
162 >>> best_match(['application/xbel+xml', 'text/xml'],
163 'text/*;q=0.5,*/*; q=0.1')
164 'text/xml'
165 """
166 split_header = _filter_blank(header.split(","))
167 parsed_header = [parse_media_range(r) for r in split_header]
168 weighted_matches = []
169 pos = 0
170 for mime_type in supported:
171 weighted_matches.append(
172 (fitness_and_quality_parsed(mime_type, parsed_header), pos, mime_type)
173 )
174 pos += 1
175 weighted_matches.sort()
176
177 return weighted_matches[-1][0][1] and weighted_matches[-1][2] or ""
178
179
181 for s in i:
182 if s.strip():
183 yield s
184