From d2ab2602554dbae2d8dede0f33685b4fc9270336 Mon Sep 17 00:00:00 2001
From: Philippe Pittoli <karchnu@karchnu.fr>
Date: Wed, 1 Feb 2023 11:08:05 +0100
Subject: [PATCH] Crystal bindings: (typed|untyped) message serialization.

---
 .../crystal/some-crystal-app/src/message.cr   | 68 +++++++++++++++----
 1 file changed, 56 insertions(+), 12 deletions(-)

diff --git a/zig-impl/crystal/some-crystal-app/src/message.cr b/zig-impl/crystal/some-crystal-app/src/message.cr
index 7b48fc5..37f0fed 100644
--- a/zig-impl/crystal/some-crystal-app/src/message.cr
+++ b/zig-impl/crystal/some-crystal-app/src/message.cr
@@ -1,25 +1,69 @@
-# TODO:
+# TODO: tests.
+
+# Serialization (and deserialization) doesn't refer to IPC format.
+# IPC serialization format: 'length + value'
+# IPCMessage serialization: 'value'
+# 'Value' is:
+# - simply the message payload for UntypedMessage
+# - type (u8) + payload for TypedMessage
 module IPCMessage
 	class UntypedMessage
-		@fd      : Int32
-		@payload : Bytes
-		def initialize(@fd, string : String)
+		property payload : Bytes
+		def initialize(string : String)
 			@payload = Bytes.new string.to_unsafe, string.size
 		end
-		def initialize(@fd, @payload)
+		def initialize(@payload)
+		end
+
+		def self.deserialize(payload) : UntypedMessage
+			IPCMessage::UntypedMessage.new payload
+		end
+
+		def serialize
+			@payload
 		end
 	end
 
+	# WARNING: you can only have up to 256 types.
 	class TypedMessage < UntypedMessage
-		@type    : UInt8? = nil
-		def initialize(fd, @type, string : String)
-			super fd, string
+		property type    : UInt8? = nil
+		def initialize(@type, string : String)
+			super string
 		end
-		def initialize(fd, @type, payload)
-			super fd, payload
+		def initialize(@type, payload)
+			super payload
 		end
-		def initialize(fd, payload)
-			super fd, payload
+		def initialize(payload)
+			super payload
+		end
+
+		def self.deserialize(bytes : Bytes) : TypedMessage?
+			if bytes.size == 0
+				nil
+			else
+				type = bytes[0]
+				IPCMessage::TypedMessage.new type, bytes[1..]
+			end
+		end
+
+		def serialize
+			bytes = Bytes.new (1 + @payload.size)
+			type = @type
+			bytes[0] = type.nil? ? 0 : type
+			bytes[1..].copy_from @payload
+			bytes
 		end
 	end
 end
+
+# Send both typed and untyped messages.
+class IPC
+	def schedule(fd : Int32, m : (IPCMessage::TypedMessage | IPCMessage::UntypedMessage))
+		payload = m.serialize
+		schedule fd, payload, payload.size
+	end
+	def write(fd : Int32, m : (IPCMessage::TypedMessage | IPCMessage::UntypedMessage))
+		payload = m.serialize
+		write fd, payload, payload.size
+	end
+end