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
|
# frozen_string_literal: true
require 'zlib'
module Aws
module EventStream
# This class provides #encode method for encoding
# Aws::EventStream::Message into binary.
#
# * {#encode} - encode Aws::EventStream::Message into binary
# when output IO-like object is provided, binary string
# would be written to IO. If not, the encoded binary string
# would be returned directly
#
# ## Examples
#
# message = Aws::EventStream::Message.new(
# headers: {
# "foo" => Aws::EventStream::HeaderValue.new(
# value: "bar", type: "string"
# )
# },
# payload: "payload"
# )
# encoder = Aws::EventsStream::Encoder.new
# file = Tempfile.new
#
# # encode into IO ouput
# encoder.encode(message, file)
#
# # get encoded binary string
# encoded_message = encoder.encode(message)
#
# file.read == encoded_message
# # => true
#
class Encoder
# bytes of total overhead in a message, including prelude
# and 4 bytes total message crc checksum
OVERHEAD_LENGTH = 16
# Maximum header length allowed (after encode) 128kb
MAX_HEADERS_LENGTH = 131072
# Maximum payload length allowed (after encode) 16mb
MAX_PAYLOAD_LENGTH = 16777216
# Encodes Aws::EventStream::Message to output IO when
# provided, else return the encoded binary string
#
# @param [Aws::EventStream::Message] message
#
# @param [IO#write, nil] io An IO-like object that
# responds to `#write`, encoded message will be
# written to this IO when provided
#
# @return [nil, String] when output IO is provided,
# encoded message will be written to that IO, nil
# will be returned. Else, encoded binary string is
# returned.
def encode(message, io = nil)
encoded = encode_message(message)
if io
io.write(encoded)
io.close
else
encoded
end
end
# Encodes an Aws::EventStream::Message
# into String
#
# @param [Aws::EventStream::Message] message
#
# @return [String]
def encode_message(message)
# create context buffer with encode headers
encoded_header = encode_headers(message)
header_length = encoded_header.bytesize
# encode payload
if message.payload.length > MAX_PAYLOAD_LENGTH
raise Aws::EventStream::Errors::EventPayloadLengthExceedError.new
end
encoded_payload = message.payload.read
total_length = header_length + encoded_payload.bytesize + OVERHEAD_LENGTH
# create message buffer with prelude section
encoded_prelude = encode_prelude(total_length, header_length)
# append message context (headers, payload)
encoded_content = [
encoded_prelude,
encoded_header,
encoded_payload,
].pack('a*a*a*')
# append message checksum
message_checksum = Zlib.crc32(encoded_content)
[encoded_content, message_checksum].pack('a*N')
end
# Encodes headers part of an Aws::EventStream::Message
# into String
#
# @param [Aws::EventStream::Message] message
#
# @return [String]
def encode_headers(message)
header_entries = message.headers.map do |key, value|
encoded_key = [key.bytesize, key].pack('Ca*')
# header value
pattern, value_length, type_index = Types.pattern[value.type]
encoded_value = [type_index].pack('C')
# boolean types doesn't need to specify value
next [encoded_key, encoded_value].pack('a*a*') if !!pattern == pattern
encoded_value = [encoded_value, value.value.bytesize].pack('a*S>') unless value_length
[
encoded_key,
encoded_value,
pattern ? [value.value].pack(pattern) : value.value,
].pack('a*a*a*')
end
header_entries.join.tap do |encoded_header|
break encoded_header if encoded_header.bytesize <= MAX_HEADERS_LENGTH
raise Aws::EventStream::Errors::EventHeadersLengthExceedError.new
end
end
private
def encode_prelude(total_length, headers_length)
prelude_body = [total_length, headers_length].pack('NN')
checksum = Zlib.crc32(prelude_body)
[prelude_body, checksum].pack('a*N')
end
end
end
end
|
