1 files changed, 49 insertions, 0 deletions
diff --git a/lib/plum/frame/settings.rb b/lib/plum/frame/settings.rb
new file mode 100644
index 0000000..71a92eb
--- /dev/null
+++ b/lib/plum/frame/settings.rb
@@ -0,0 +1,49 @@
+# frozen-string-literal: true
+
+using Plum::BinaryString
+module Plum
+  class Frame::Settings < Frame
+    register_subclass 0x04
+
+    SETTINGS_TYPE = {
+      header_table_size:      0x01,
+      enable_push:            0x02,
+      max_concurrent_streams: 0x03,
+      initial_window_size:    0x04,
+      max_frame_size:         0x05,
+      max_header_list_size:   0x06
+    }.freeze
+
+    # Creates a SETTINGS frame.
+    # @param args [Hash<Symbol, Integer>] The settings values to send.
+    def initialize(**args)
+      payload = "".b
+      args.each { |key, value|
+        id = SETTINGS_TYPE[key] or raise ArgumentError.new("invalid settings type: #{key}")
+        payload.push_uint16(id)
+        payload.push_uint32(value)
+      }
+      initialize_base(type: :settings, stream_id: 0, payload: payload)
+    end
+
+    # Creates a SETTINGS frame with ACK flag.
+    def self.ack
+      frame = allocate
+      frame.send(:initialize_base, type: :settings, stream_id: 0, flags_value: 0x01)
+      frame
+    end
+
+    # Parses SETTINGS frame payload. Ignores unknown settings type (see RFC7540 6.5.2).
+    # @return [Hash<Symbol, Integer>] The parsed strings.
+    def parse_settings
+      settings = {}
+      payload.each_byteslice(6) do |param|
+        id = param.uint16
+        name = SETTINGS_TYPE.key(id)
+        # ignore unknown settings type
+        settings[name] = param.uint32(2) if name
+      end
+      settings
+    end
+  end
+end