generate: Emit Send/Receive functions

generate/generate.go

@@ -35,6 +35,15 @@ type Message interface {
 	Method() uint16
 }
 
+// Send encodes a message and sends it along a transaction.
+func Send(trans hopp.Trans, message Message) (n int, err error) {
+	writer, err := trans.SendWriter(message.Method())
+	if err != nil { return n, err }
+	defer writer.Close()
+	encoder := tape.NewEncoder(writer)
+	return message.Encode(encoder)
+}
+
 // canAssign determines if data from the given source tag can be assigned to
 // a Go type represented by destination. It is designed to receive destination
 // values from [generate.Generator.generateCanAssign]. The eventual Go type and
@@ -121,6 +130,10 @@ func (this *Generator) Generate(protocol *Protocol) (n int, err error) {
 		n += nn; if err != nil { return n, err }
 	}
 
+	// receive
+	nn, err = this.generateReceive()
+	n += nn; if err != nil { return n, err }
+
 	return n, nil
 }
 
@@ -1184,6 +1197,51 @@ func (this *Generator) generateCanAssign(typ Type, tagSource string) (n int, err
 	return n, nil
 }
 
+// generateReceive generates a function Receive(hopp.Trans) (Message, int, error)
+func (this *Generator) generateReceive() (n int, err error) {
+	nn, err := this.iprintf(
+		"\n// Receive decodes a message from a transaction and returns it as a value.\n" +
+		"// Use a type switch to determine what type of message it is.\n")
+	n += nn; if err != nil { return n, err }
+	nn, err = this.iprintf(
+		"func Receive(trans hopp.Trans) (message any, n int, err error) {\n")
+	n += nn; if err != nil { return n, err }
+	this.push()
+		nn, err = this.iprintf("method, reader, err := trans.ReceiveReader()\n")
+		n += nn; if err != nil { return n, err }
+		nn, err = this.iprintf("decoder := tape.NewDecoder(reader)\n")
+		n += nn; if err != nil { return n, err }
+		nn, err = this.iprintf("if err != nil { return nil, n, err }\n")
+		n += nn; if err != nil { return n, err }
+		nn, err = this.iprintf("switch method {\n")
+		n += nn; if err != nil { return n, err }
+		for method, message := range this.protocol.Messages {
+			nn, err = this.iprintf("case %04X:\n", method)
+			n += nn; if err != nil { return n, err }
+			this.push()
+				nn, err = this.iprintf(
+					"var message %s\n",
+					this.resolveMessageName(message.Name))
+				n += nn; if err != nil { return n, err }
+				nn, err := this.iprintf(
+					"nn, err := message.Decode(decoder)\n")
+				n += nn; if err != nil { return n, err }
+				nn, err = this.iprintf("n += nn; if err != nil { return nil, n, err }\n")
+				n += nn; if err != nil { return n, err }
+				nn, err = this.iprintf("return message, n, nil\n")
+				n += nn; if err != nil { return n, err }
+			this.pop()
+		}
+		nn, err = this.iprint("}\n")
+		n += nn; if err != nil { return n, err }
+		nn, err = this.iprintf("return nil, n, hopp.ErrUnknownMethod\n")
+		n += nn; if err != nil { return n, err }
+	this.pop()
+	nn, err = this.iprint("}\n")
+	n += nn; if err != nil { return n, err }
+	return n, nil
+}
+
 func (this *Generator) validateIntBitSize(size int) error {
 	switch size {
 	case 5, 8, 16, 32, 64: return nil