Remove bytes read/written from marshal.Marshallable API.

Users of the API only care about whether the copy in/out succeeds in
their entirety, which is already signalled by the returned error.

PiperOrigin-RevId: 296297843

3 files changed, 14 insertions, 13 deletions

diff --git a/tools/go_marshal/gomarshal/generator_interfaces.go b/tools/go_marshal/gomarshal/generator_interfaces.go
index 3aa299ccd..834c58cee 100644
--- a/tools/go_marshal/gomarshal/generator_interfaces.go
+++ b/tools/go_marshal/gomarshal/generator_interfaces.go
@@ -507,13 +507,14 @@ func (g *interfaceGenerator) emitMarshallable() {
 	g.emit("// CopyOut implements marshal.Marshallable.CopyOut.\n")
 	g.recordUsedImport("marshal")
 	g.recordUsedImport("usermem")
-	g.emit("func (%s *%s) CopyOut(task marshal.Task, addr usermem.Addr) (int, error) {\n", g.r, g.typeName())
+	g.emit("func (%s *%s) CopyOut(task marshal.Task, addr usermem.Addr) error {\n", g.r, g.typeName())
 	g.inIndent(func() {
 		fallback := func() {
 			g.emit("// Type %s doesn't have a packed layout in memory, fall back to MarshalBytes.\n", g.typeName())
 			g.emit("buf := task.CopyScratchBuffer(%s.SizeBytes())\n", g.r)
 			g.emit("%s.MarshalBytes(buf)\n", g.r)
-			g.emit("return task.CopyOutBytes(addr, buf)\n")
+			g.emit("_, err := task.CopyOutBytes(addr, buf)\n")
+			g.emit("return err\n")
 		}
 		if thisPacked {
 			g.recordUsedImport("reflect")
@@ -539,11 +540,11 @@ func (g *interfaceGenerator) emitMarshallable() {
 			g.emit("hdr.Len = %s.SizeBytes()\n", g.r)
 			g.emit("hdr.Cap = %s.SizeBytes()\n\n", g.r)
 
-			g.emit("len, err := task.CopyOutBytes(addr, buf)\n")
+			g.emit("_, err := task.CopyOutBytes(addr, buf)\n")
 			g.emit("// Since we bypassed the compiler's escape analysis, indicate that %s\n", g.r)
 			g.emit("// must live until after the CopyOutBytes.\n")
 			g.emit("runtime.KeepAlive(%s)\n", g.r)
-			g.emit("return len, err\n")
+			g.emit("return err\n")
 		} else {
 			fallback()
 		}
@@ -553,20 +554,20 @@ func (g *interfaceGenerator) emitMarshallable() {
 	g.emit("// CopyIn implements marshal.Marshallable.CopyIn.\n")
 	g.recordUsedImport("marshal")
 	g.recordUsedImport("usermem")
-	g.emit("func (%s *%s) CopyIn(task marshal.Task, addr usermem.Addr) (int, error) {\n", g.r, g.typeName())
+	g.emit("func (%s *%s) CopyIn(task marshal.Task, addr usermem.Addr) error {\n", g.r, g.typeName())
 	g.inIndent(func() {
 		fallback := func() {
 			g.emit("// Type %s doesn't have a packed layout in memory, fall back to UnmarshalBytes.\n", g.typeName())
 			g.emit("buf := task.CopyScratchBuffer(%s.SizeBytes())\n", g.r)
-			g.emit("n, err := task.CopyInBytes(addr, buf)\n")
+			g.emit("_, err := task.CopyInBytes(addr, buf)\n")
 			g.emit("if err != nil {\n")
 			g.inIndent(func() {
-				g.emit("return n, err\n")
+				g.emit("return err\n")
 			})
 			g.emit("}\n")
 
 			g.emit("%s.UnmarshalBytes(buf)\n", g.r)
-			g.emit("return n, nil\n")
+			g.emit("return nil\n")
 		}
 		if thisPacked {
 			g.recordUsedImport("reflect")
@@ -592,11 +593,11 @@ func (g *interfaceGenerator) emitMarshallable() {
 			g.emit("hdr.Len = %s.SizeBytes()\n", g.r)
 			g.emit("hdr.Cap = %s.SizeBytes()\n\n", g.r)
 
-			g.emit("len, err := task.CopyInBytes(addr, buf)\n")
+			g.emit("_, err := task.CopyInBytes(addr, buf)\n")
 			g.emit("// Since we bypassed the compiler's escape analysis, indicate that %s\n", g.r)
 			g.emit("// must live until after the CopyInBytes.\n")
 			g.emit("runtime.KeepAlive(%s)\n", g.r)
-			g.emit("return len, err\n")
+			g.emit("return err\n")
 		} else {
 			fallback()
 		}
diff --git a/tools/go_marshal/gomarshal/generator_tests.go b/tools/go_marshal/gomarshal/generator_tests.go
index 8c28b00d0..2326e7a07 100644
--- a/tools/go_marshal/gomarshal/generator_tests.go
+++ b/tools/go_marshal/gomarshal/generator_tests.go
@@ -92,7 +92,7 @@ func (g *testGenerator) emitTestNonZeroSize() {
 		g.emit("x := &%s{}\n", g.typeName())
 		g.emit("if x.SizeBytes() == 0 {\n")
 		g.inIndent(func() {
-			g.emit("t.Fatal(\"Marshallable.Size() should not return zero\")\n")
+			g.emit("t.Fatal(\"Marshallable.SizeBytes() should not return zero\")\n")
 		})
 		g.emit("}\n")
 	})
diff --git a/tools/go_marshal/marshal/marshal.go b/tools/go_marshal/marshal/marshal.go
index 20353850d..f129788e0 100644
--- a/tools/go_marshal/marshal/marshal.go
+++ b/tools/go_marshal/marshal/marshal.go
@@ -91,12 +91,12 @@ type Marshallable interface {
 	// marshalled does not escape. The implementation should avoid creating
 	// extra copies in memory by directly deserializing to the object's
 	// underlying memory.
-	CopyIn(task Task, addr usermem.Addr) (int, error)
+	CopyIn(task Task, addr usermem.Addr) error
 
 	// CopyOut serializes a Marshallable type to a task's memory. This may only
 	// be called from a task goroutine. This is more efficient than calling
 	// MarshalUnsafe on Marshallable.Packed types, as the type being serialized
 	// does not escape. The implementation should avoid creating extra copies in
 	// memory by directly serializing from the object's underlying memory.
-	CopyOut(task Task, addr usermem.Addr) (int, error)
+	CopyOut(task Task, addr usermem.Addr) error
 }