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# mimeparse.rb
#
# 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
#
# ---------
#
# This is a port of Joe Gregario's mimeparse.py, which can be found at
# <http://code.google.com/p/mimeparse/>.
#
# ported from version 0.1.2
#
# Comments are mostly excerpted from the original.
module MIMEParse
module_function
# Carves up a mime-type and returns an Array of the
# [type, subtype, params] where "params" is a Hash 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" }]
def parse_mime_type(mime_type)
parts = mime_type.split(";")
params = {}
parts[1..-1].map do |param|
k,v = param.split("=").map { |s| s.strip }
params[k] = v
end
full_type = parts[0].strip
# Java URLConnection class sends an Accept header that includes a single "*"
# Turn it into a legal wildcard.
full_type = "*/*" if full_type == "*"
type, subtype = full_type.split("/")
raise "malformed mime type" unless subtype
[type.strip, subtype.strip, params]
end
# Carves up a media range and returns an Array of the
# [type, subtype, params] where "params" is a Hash 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.
def parse_media_range(range)
type, subtype, params = parse_mime_type(range)
unless params.has_key?("q") and params["q"] and params["q"].to_f and params["q"].to_f <= 1 and params["q"].to_f >= 0
params["q"] = "1"
end
[type, subtype, params]
end
# 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 fitness and 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 an Enumerable of parsed media ranges.
def fitness_and_quality_parsed(mime_type, parsed_ranges)
best_fitness = -1
best_fit_q = 0
target_type, target_subtype, target_params = parse_media_range(mime_type)
parsed_ranges.each do |type,subtype,params|
if (type == target_type or type == "*" or target_type == "*") and
(subtype == target_subtype or subtype == "*" or target_subtype == "*")
param_matches = target_params.find_all { |k,v| k != "q" and params.has_key?(k) and v == params[k] }.length
fitness = (type == target_type) ? 100 : 0
fitness += (subtype == target_subtype) ? 10 : 0
fitness += param_matches
if fitness > best_fitness
best_fitness = fitness
best_fit_q = params["q"]
end
end
end
[best_fitness, best_fit_q.to_f]
end
# 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 behaves the same as #quality except that
# "parsed_ranges" must be an Enumerable of parsed media ranges.
def quality_parsed(mime_type, parsed_ranges)
fitness_and_quality_parsed(mime_type, parsed_ranges)[1]
end
# Returns the quality "q" of a mime_type when compared against
# the media-ranges in ranges. For example:
#
# irb> 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
def quality(mime_type, ranges)
parsed_ranges = ranges.split(",").map { |r| parse_media_range(r) }
quality_parsed(mime_type, parsed_ranges)
end
# 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 an Enumerable of mime-types
#
# irb> best_match(["application/xbel+xml", "text/xml"], "text/*;q=0.5,*/*; q=0.1")
# => "text/xml"
def best_match(supported, header)
parsed_header = header.split(",").map { |r| parse_media_range(r) }
weighted_matches = supported.map do |mime_type|
[fitness_and_quality_parsed(mime_type, parsed_header), mime_type]
end
weighted_matches.sort!
weighted_matches.last[0][1].zero? ? nil : weighted_matches.last[1]
end
end
if __FILE__ == $0
require "test/unit"
class TestMimeParsing < Test::Unit::TestCase
include MIMEParse
def test_parse_media_range
assert_equal [ "application", "xml", { "q" => "1" } ],
parse_media_range("application/xml;q=1")
assert_equal [ "application", "xml", { "q" => "1" } ],
parse_media_range("application/xml")
assert_equal [ "application", "xml", { "q" => "1" } ],
parse_media_range("application/xml;q=")
assert_equal [ "application", "xml", { "q" => "1", "b" => "other" } ],
parse_media_range("application/xml ; q=1;b=other")
assert_equal [ "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 "*"
assert_equal [ "*", "*", { "q" => ".2" } ],
parse_media_range(" *; q=.2")
end
def test_rfc_2616_example
accept = "text/*;q=0.3, text/html;q=0.7, text/html;level=1, text/html;level=2;q=0.4, */*;q=0.5"
assert_equal 1, quality("text/html;level=1", accept)
assert_equal 0.7, quality("text/html", accept)
assert_equal 0.3, quality("text/plain", accept)
assert_equal 0.5, quality("image/jpeg", accept)
assert_equal 0.4, quality("text/html;level=2", accept)
assert_equal 0.7, quality("text/html;level=3", accept)
end
def test_best_match
@supported_mime_types = [ "application/xbel+xml", "application/xml" ]
# direct match
assert_best_match "application/xbel+xml", "application/xbel+xml"
# direct match with a q parameter
assert_best_match "application/xbel+xml", "application/xbel+xml; q=1"
# direct match of our second choice with a q parameter
assert_best_match "application/xml", "application/xml; q=1"
# match using a subtype wildcard
assert_best_match "application/xml", "application/*; q=1"
# match using a type wildcard
assert_best_match "application/xml", "*/*"
@supported_mime_types = [ "application/xbel+xml", "text/xml" ]
# match using a type versus a lower weighted subtype
assert_best_match "text/xml", "text/*;q=0.5,*/*;q=0.1"
# fail to match anything
assert_best_match nil, "text/html,application/atom+xml; q=0.9"
# common AJAX scenario
@supported_mime_types = [ "application/json", "text/html" ]
assert_best_match "application/json", "application/json, text/javascript, */*"
# verify fitness sorting
assert_best_match "application/json", "application/json, text/html;q=0.9"
end
def test_support_wildcards
@supported_mime_types = ['image/*', 'application/xml']
# match using a type wildcard
assert_best_match 'image/*', 'image/png'
# match using a wildcard for both requested and supported
assert_best_match 'image/*', 'image/*'
end
def assert_best_match(expected, header)
assert_equal(expected, best_match(@supported_mime_types, header))
end
end
end
#puts MIMEParse::best_match(["text/xml","text/html","application/pdf"],
# 'application/x-ms-application,image/jpeg, application/xaml+xml, image/gif, image/pjpeg, application/x-ms-xbap, */*')
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