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([tuple([s.strip() for s in param.split('=', 1)])\
47 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
80
81
83 """Find the best match for a mime-type amongst parsed media-ranges.
84
85 Find the best match for a given mime-type against a list of media_ranges
86 that have already been parsed by parse_media_range(). Returns a tuple of
87 the fitness value and the value of the 'q' quality parameter of the best
88 match, or (-1, 0) if no match was found. Just as for quality_parsed(),
89 'parsed_ranges' must be a list of parsed media ranges.
90 """
91 best_fitness = -1
92 best_fit_q = 0
93 (target_type, target_subtype, target_params) =\
94 parse_media_range(mime_type)
95 for (type, subtype, params) in parsed_ranges:
96 type_match = (type == target_type or\
97 type == '*' or\
98 target_type == '*')
99 subtype_match = (subtype == target_subtype or\
100 subtype == '*' or\
101 target_subtype == '*')
102 if type_match and subtype_match:
103 param_matches = reduce(lambda x, y: x + y, [1 for (key, value) in \
104 six.iteritems(target_params) if key != 'q' and \
105 key in params and value == params[key]], 0)
106 fitness = (type == target_type) and 100 or 0
107 fitness += (subtype == target_subtype) and 10 or 0
108 fitness += param_matches
109 if fitness > best_fitness:
110 best_fitness = fitness
111 best_fit_q = params['q']
112
113 return best_fitness, float(best_fit_q)
114
115
117 """Find the best match for a mime-type amongst parsed media-ranges.
118
119 Find the best match for a given mime-type against a list of media_ranges
120 that have already been parsed by parse_media_range(). Returns the 'q'
121 quality parameter of the best match, 0 if no match was found. This function
122 bahaves the same as quality() except that 'parsed_ranges' must be a list of
123 parsed media ranges.
124 """
125
126 return fitness_and_quality_parsed(mime_type, parsed_ranges)[1]
127
128
130 """Return the quality ('q') of a mime-type against a list of media-ranges.
131
132 Returns the quality 'q' of a mime-type when compared against the
133 media-ranges in ranges. For example:
134
135 >>> quality('text/html','text/*;q=0.3, text/html;q=0.7,
136 text/html;level=1, text/html;level=2;q=0.4, */*;q=0.5')
137 0.7
138
139 """
140 parsed_ranges = [parse_media_range(r) for r in ranges.split(',')]
141
142 return quality_parsed(mime_type, parsed_ranges)
143
144
146 """Return mime-type with the highest quality ('q') from list of candidates.
147
148 Takes a list of supported mime-types and finds the best match for all the
149 media-ranges listed in header. The value of header must be a string that
150 conforms to the format of the HTTP Accept: header. The value of 'supported'
151 is a list of mime-types. The list of supported mime-types should be sorted
152 in order of increasing desirability, in case of a situation where there is
153 a tie.
154
155 >>> best_match(['application/xbel+xml', 'text/xml'],
156 'text/*;q=0.5,*/*; q=0.1')
157 'text/xml'
158 """
159 split_header = _filter_blank(header.split(','))
160 parsed_header = [parse_media_range(r) for r in split_header]
161 weighted_matches = []
162 pos = 0
163 for mime_type in supported:
164 weighted_matches.append((fitness_and_quality_parsed(mime_type,
165 parsed_header), pos, mime_type))
166 pos += 1
167 weighted_matches.sort()
168
169 return weighted_matches[-1][0][1] and weighted_matches[-1][2] or ''
170
171
173 for s in i:
174 if s.strip():
175 yield s
176