1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
|
# frozen_string_literal: true
module HTTP2
# To decompress header blocks, a decoder only needs to maintain a
# dynamic table as a decoding context.
# No other state information is needed.
module Header
class EncodingContext
include Error
UPPER = /[[:upper:]]/.freeze
# @private
# Static table
# - http://tools.ietf.org/html/draft-ietf-httpbis-header-compression-10#appendix-A
STATIC_TABLE = [
[":authority", ""],
[":method", "GET"],
[":method", "POST"],
[":path", "/"],
[":path", "/index.html"],
[":scheme", "http"],
[":scheme", "https"],
[":status", "200"],
[":status", "204"],
[":status", "206"],
[":status", "304"],
[":status", "400"],
[":status", "404"],
[":status", "500"],
["accept-charset", ""],
["accept-encoding", "gzip, deflate"],
["accept-language", ""],
["accept-ranges", ""],
["accept", ""],
["access-control-allow-origin", ""],
["age", ""],
["allow", ""],
["authorization", ""],
["cache-control", ""],
["content-disposition", ""],
["content-encoding", ""],
["content-language", ""],
["content-length", ""],
["content-location", ""],
["content-range", ""],
["content-type", ""],
["cookie", ""],
["date", ""],
["etag", ""],
["expect", ""],
["expires", ""],
["from", ""],
["host", ""],
["if-match", ""],
["if-modified-since", ""],
["if-none-match", ""],
["if-range", ""],
["if-unmodified-since", ""],
["last-modified", ""],
["link", ""],
["location", ""],
["max-forwards", ""],
["proxy-authenticate", ""],
["proxy-authorization", ""],
["range", ""],
["referer", ""],
["refresh", ""],
["retry-after", ""],
["server", ""],
["set-cookie", ""],
["strict-transport-security", ""],
["transfer-encoding", ""],
["user-agent", ""],
["vary", ""],
["via", ""],
["www-authenticate", ""]
].each(&:freeze).freeze
STATIC_TABLE_BY_FIELD =
STATIC_TABLE
.each_with_object({})
.with_index { |((field, value), hs), idx| (hs[field] ||= []) << [idx, value].freeze }
.each_value(&:freeze)
.freeze
STATIC_TABLE_SIZE = STATIC_TABLE.size
DEFAULT_OPTIONS = {
huffman: :shorter,
index: :all,
table_size: 4096
}.freeze
STATIC_ALL = %i[all static].freeze
STATIC_NEVER = %i[never static].freeze
# Current table of header key-value pairs.
attr_reader :table
# Current encoding options
#
# :table_size Integer maximum dynamic table size in bytes
# :huffman Symbol :always, :never, :shorter
# :index Symbol :all, :static, :never
attr_reader :options
# Current table size in octets
attr_reader :current_table_size
# Initializes compression context with appropriate client/server
# defaults and maximum size of the dynamic table.
#
# @param options [Hash] encoding options
# :table_size Integer maximum dynamic table size in bytes
# :huffman Symbol :always, :never, :shorter
# :index Symbol :all, :static, :never
def initialize(options = {})
@table = []
@options = DEFAULT_OPTIONS.merge(options)
@limit = @options[:table_size]
@_table_updated = false
@current_table_size = 0
end
# Duplicates current compression context
# @return [EncodingContext]
def dup
other = EncodingContext.new(@options)
t = @table
l = @limit
other.instance_eval do
@table = t.dup # shallow copy
@limit = l
end
other
end
# Finds an entry in current dynamic table by index.
# Note that index is zero-based in this module.
#
# If the index is greater than the last index in the static table,
# an entry in the dynamic table is dereferenced.
#
# If the index is greater than the last header index, an error is raised.
#
# @param index [Integer] zero-based index in the dynamic table.
# @return [Array] +[key, value]+
def dereference(index)
# NOTE: index is zero-based in this module.
return STATIC_TABLE[index] if index < STATIC_TABLE_SIZE
idx = index - STATIC_TABLE_SIZE
raise CompressionError, "Index too large" if idx >= @table.size
@table[index - STATIC_TABLE_SIZE]
end
# Header Block Processing
# - http://tools.ietf.org/html/draft-ietf-httpbis-header-compression-10#section-4.1
#
# @param cmd [Hash] { type:, name:, value:, index: }
# @return [Array, nil] +[name, value]+ header field that is added to the decoded header list,
# or nil if +cmd[:type]+ is +:changetablesize+
def process(cmd)
type = cmd[:type]
name = cmd[:name]
value = cmd[:value]
case type
when :changetablesize
raise CompressionError, "tried to change table size after adding elements to table" if @_table_updated
# we can receive multiple table size change commands inside a header frame. However,
# we should blow up if we receive another frame where the new table size is bigger.
table_size_updated = @limit != @options[:table_size]
raise CompressionError, "dynamic table size update exceed limit" if !table_size_updated && value > @limit
self.table_size = value
nil
when :indexed
# Indexed Representation
# An _indexed representation_ entails the following actions:
# o The header field corresponding to the referenced entry in either
# the static table or dynamic table is added to the decoded header
# list.
dereference(name)
when :incremental, :noindex, :neverindexed
# A _literal representation_ that is _not added_ to the dynamic table
# entails the following action:
# o The header field is added to the decoded header list.
# A _literal representation_ that is _added_ to the dynamic table
# entails the following actions:
# o The header field is added to the decoded header list.
# o The header field is inserted at the beginning of the dynamic table.
case name
when Integer
name, v = dereference(name)
value ||= v
when UPPER
raise ProtocolError, "Invalid uppercase key: #{name}"
end
emit = [name, value]
# add to table
if type == :incremental && size_check(name.bytesize + value.bytesize + 32)
@table.unshift(emit)
@current_table_size += name.bytesize + value.bytesize + 32
@_table_updated = true
end
emit
else
raise CompressionError, "Invalid type: #{type}"
end
end
# Plan header compression according to +@options [:index]+
# :never Do not use dynamic table or static table reference at all.
# :static Use static table only.
# :all Use all of them.
#
# @param headers [Array] +[[name, value], ...]+
# @return [Array] array of commands
def encode(headers)
# Literals commands are marked with :noindex when index is not used
noindex = STATIC_NEVER.include?(@options[:index])
headers.each do |field, value|
# Literal header names MUST be translated to lowercase before
# encoding and transmission.
field = field.downcase if UPPER.match?(field)
value = "/" if field == ":path" && value.empty?
cmd = addcmd(field, value)
cmd[:type] = :noindex if noindex && cmd[:type] == :incremental
process(cmd)
yield cmd
end
end
# Emits command for a header.
# Prefer static table over dynamic table.
# Prefer exact match over name-only match.
#
# +@options [:index]+ controls whether to use the dynamic table,
# static table, or both.
# :never Do not use dynamic table or static table reference at all.
# :static Use static table only.
# :all Use all of them.
#
# @param field [String] the header field
# @param value [String] the header value
# @return [Hash] command
def addcmd(field, value)
# @type var exact: Integer?
exact = nil
# @type var name_only: Integer?
name_only = nil
index_type = @options[:index]
if STATIC_ALL.include?(index_type) &&
STATIC_TABLE_BY_FIELD.key?(field)
STATIC_TABLE_BY_FIELD[field].each do |i, svalue|
name_only ||= i
if value == svalue
exact = i
break
end
end
end
if index_type == :all && !exact
@table.each_with_index do |(hfield, hvalue), i|
next unless field == hfield
if value == hvalue
exact = i + STATIC_TABLE_SIZE
break
else
name_only ||= i + STATIC_TABLE_SIZE
end
end
end
if exact
{ name: exact, type: :indexed }
else
{ name: name_only || field, value: value, type: :incremental }
end
end
# Alter dynamic table size.
# When the size is reduced, some headers might be evicted.
def table_size=(size)
@limit = size
size_check(0)
end
def listen_on_table
yield
ensure
@_table_updated = false
end
private
# To keep the dynamic table size lower than or equal to @limit,
# remove one or more entries at the end of the dynamic table.
#
# @param cmdsize [Integer]
# @return [Boolean] whether +cmd+ fits in the dynamic table.
def size_check(cmdsize)
unless @table.empty?
while @current_table_size + cmdsize > @limit
name, value = @table.pop
@current_table_size -= name.bytesize + value.bytesize + 32
break if @table.empty?
end
end
cmdsize <= @limit
end
end
end
end
|
