internal/pipewire: specify opcode and file count with message

This adds checking of FileCount while writing a message. Message encoding is relocated to an exported method to be used externally, probably for test stubbing.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pipewire/core.go

@@ -133,6 +133,12 @@ type CoreInfo struct {
 	Properties *SPADict `json:"props"`
 }
 
+// Opcode satisfies [Message] with a constant value.
+func (c *CoreInfo) Opcode() byte { return PW_CORE_EVENT_INFO }
+
+// FileCount satisfies [Message] with a constant value.
+func (c *CoreInfo) FileCount() Int { return 0 }
+
 // Size satisfies [KnownSize] with a value computed at runtime.
 func (c *CoreInfo) Size() Word {
 	return SizePrefix +
@@ -160,6 +166,12 @@ type CoreDone struct {
 	Sequence Int `json:"seq"`
 }
 
+// Opcode satisfies [Message] with a constant value.
+func (c *CoreDone) Opcode() byte { return PW_CORE_EVENT_DONE }
+
+// FileCount satisfies [Message] with a constant value.
+func (c *CoreDone) FileCount() Int { return 0 }
+
 // Size satisfies [KnownSize] with a constant value.
 func (c *CoreDone) Size() Word { return SizePrefix + Size(SizeInt) + Size(SizeInt) }
 
@@ -179,6 +191,12 @@ type CorePing struct {
 	Sequence Int `json:"seq"`
 }
 
+// Opcode satisfies [Message] with a constant value.
+func (c *CorePing) Opcode() byte { return PW_CORE_EVENT_PING }
+
+// FileCount satisfies [Message] with a constant value.
+func (c *CorePing) FileCount() Int { return 0 }
+
 // Size satisfies [KnownSize] with a constant value.
 func (c *CorePing) Size() Word { return SizePrefix + Size(SizeInt) + Size(SizeInt) }
 
@@ -209,6 +227,9 @@ type CoreError struct {
 	Message String `json:"message"`
 }
 
+// FileCount satisfies [Message] with a constant value.
+func (c *CoreError) FileCount() Int { return 0 }
+
 func (c *CoreError) Error() string {
 	return "received Core::Error on" +
 		" id " + strconv.Itoa(int(c.ID)) +
@@ -232,6 +253,18 @@ func (c *CoreError) MarshalBinary() ([]byte, error) { return Marshal(c) }
 // UnmarshalBinary satisfies [encoding.BinaryUnmarshaler] via [Unmarshal].
 func (c *CoreError) UnmarshalBinary(data []byte) error { return Unmarshal(data, c) }
 
+// CoreErrorMethod is [CoreError] as a method [Message].
+type CoreErrorMethod struct{ CoreError }
+
+// Opcode satisfies [Message] with a constant value.
+func (c *CoreErrorMethod) Opcode() byte { return PW_CORE_METHOD_ERROR }
+
+// CoreErrorEvent is [CoreError] as an event [Message].
+type CoreErrorEvent struct{ CoreError }
+
+// Opcode satisfies [Message] with a constant value.
+func (c *CoreErrorEvent) Opcode() byte { return PW_CORE_EVENT_ERROR }
+
 // The CoreBoundProps event is emitted when a local object ID is bound to a global ID.
 // It is emitted before the global becomes visible in the registry.
 type CoreBoundProps struct {
@@ -243,6 +276,12 @@ type CoreBoundProps struct {
 	Properties *SPADict `json:"props"`
 }
 
+// Opcode satisfies [Message] with a constant value.
+func (c *CoreBoundProps) Opcode() byte { return PW_CORE_EVENT_BOUND_PROPS }
+
+// FileCount satisfies [Message] with a constant value.
+func (c *CoreBoundProps) FileCount() Int { return 0 }
+
 // Size satisfies [KnownSize] with a value computed at runtime.
 func (c *CoreBoundProps) Size() Word {
 	return SizePrefix +
@@ -294,6 +333,12 @@ type CoreHello struct {
 	Version Int `json:"version"`
 }
 
+// Opcode satisfies [Message] with a constant value.
+func (c *CoreHello) Opcode() byte { return PW_CORE_METHOD_HELLO }
+
+// FileCount satisfies [Message] with a constant value.
+func (c *CoreHello) FileCount() Int { return 0 }
+
 // Size satisfies [KnownSize] with a constant value.
 func (c *CoreHello) Size() Word { return SizePrefix + Size(SizeInt) }
 
@@ -308,7 +353,6 @@ func (c *CoreHello) UnmarshalBinary(data []byte) error { return Unmarshal(data,
 func (ctx *Context) coreHello() error {
 	return ctx.writeMessage(
 		PW_ID_CORE,
-		PW_CORE_METHOD_HELLO,
 		&CoreHello{PW_VERSION_CORE},
 	)
 }
@@ -328,6 +372,12 @@ type CoreSync struct {
 	Sequence Int `json:"seq"`
 }
 
+// Opcode satisfies [Message] with a constant value.
+func (c *CoreSync) Opcode() byte { return PW_CORE_METHOD_SYNC }
+
+// FileCount satisfies [Message] with a constant value.
+func (c *CoreSync) FileCount() Int { return 0 }
+
 // Size satisfies [KnownSize] with a constant value.
 func (c *CoreSync) Size() Word { return SizePrefix + Size(SizeInt) + Size(SizeInt) }
 
@@ -342,7 +392,6 @@ func (c *CoreSync) UnmarshalBinary(data []byte) error { return Unmarshal(data, c
 func (ctx *Context) coreSync(id Int) error {
 	return ctx.writeMessage(
 		PW_ID_CORE,
-		PW_CORE_METHOD_SYNC,
 		&CoreSync{id, CoreSyncSequenceOffset + Int(ctx.sequence)},
 	)
 }
@@ -390,6 +439,12 @@ type CorePong struct {
 	Sequence Int `json:"seq"`
 }
 
+// Opcode satisfies [Message] with a constant value.
+func (c *CorePong) Opcode() byte { return PW_CORE_METHOD_PONG }
+
+// FileCount satisfies [Message] with a constant value.
+func (c *CorePong) FileCount() Int { return 0 }
+
 // Size satisfies [KnownSize] with a constant value.
 func (c *CorePong) Size() Word { return SizePrefix + Size(SizeInt) + Size(SizeInt) }
 
@@ -414,6 +469,12 @@ type CoreGetRegistry struct {
 	NewID Int `json:"new_id"`
 }
 
+// Opcode satisfies [Message] with a constant value.
+func (c *CoreGetRegistry) Opcode() byte { return PW_CORE_METHOD_GET_REGISTRY }
+
+// FileCount satisfies [Message] with a constant value.
+func (c *CoreGetRegistry) FileCount() Int { return 0 }
+
 // Size satisfies [KnownSize] with a constant value.
 func (c *CoreGetRegistry) Size() Word { return SizePrefix + Size(SizeInt) + Size(SizeInt) }
 
@@ -431,7 +492,6 @@ func (ctx *Context) GetRegistry() (*Registry, error) {
 	registry.ID = newId
 	return &registry, ctx.writeMessage(
 		PW_ID_CORE,
-		PW_CORE_METHOD_GET_REGISTRY,
 		&CoreGetRegistry{PW_VERSION_REGISTRY, newId},
 	)
 }
@@ -450,6 +510,12 @@ type RegistryGlobal struct {
 	Properties *SPADict `json:"props"`
 }
 
+// Opcode satisfies [Message] with a constant value.
+func (c *RegistryGlobal) Opcode() byte { return PW_REGISTRY_EVENT_GLOBAL }
+
+// FileCount satisfies [Message] with a constant value.
+func (c *RegistryGlobal) FileCount() Int { return 0 }
+
 // Size satisfies [KnownSize] with a value computed at runtime.
 func (c *RegistryGlobal) Size() Word {
 	return SizePrefix +
@@ -481,6 +547,12 @@ type RegistryBind struct {
 	NewID Int `json:"new_id"`
 }
 
+// Opcode satisfies [Message] with a constant value.
+func (c *RegistryBind) Opcode() byte { return PW_REGISTRY_METHOD_BIND }
+
+// FileCount satisfies [Message] with a constant value.
+func (c *RegistryBind) FileCount() Int { return 0 }
+
 // Size satisfies [KnownSize] with a value computed at runtime.
 func (c *RegistryBind) Size() Word {
 	return SizePrefix +
@@ -507,7 +579,6 @@ func (registry *Registry) bind(proxy eventProxy, id, version Int) (Int, error) {
 	}
 	return bind.NewID, registry.ctx.writeMessage(
 		registry.ID,
-		PW_REGISTRY_METHOD_BIND,
 		&bind,
 	)
 }