Fix confusion between slice capacity and length

gogo · Sep 9, 2019 · d0d6954 · d0d6954
1 parent f6b4f34
commit d0d6954
Show file tree

Hide file tree

Showing 3 changed files with 5 additions and 4 deletions.
diff --git a/proto/table_marshal.go b/proto/table_marshal.go
@@ -2936,7 +2936,7 @@ func Size(pb Message) int {
 func Marshal(pb Message) ([]byte, error) {
 	if m, ok := pb.(newMarshaler); ok {
 		siz := m.XXX_Size()
-		b := make([]byte, 0, siz)
+		b := make([]byte, siz)
 		return m.XXX_Marshal(b, false)
 	}
 	if m, ok := pb.(Marshaler); ok {
@@ -2969,6 +2969,7 @@ func (p *Buffer) Marshal(pb Message) error {
 	if m, ok := pb.(newMarshaler); ok {
 		siz := m.XXX_Size()
 		p.grow(siz) // make sure buf has enough capacity
+		p.buf = p.buf[:siz]
 		p.buf, err = m.XXX_Marshal(p.buf, p.deterministic)
 		return err
 	}

diff --git a/protoc-gen-gogo/generator/generator.go b/protoc-gen-gogo/generator/generator.go
@@ -2717,7 +2717,7 @@ func (g *Generator) generateCommonMethods(mc *msgCtx) {
 	if gogoproto.IsMarshaler(g.file.FileDescriptorProto, mc.message.DescriptorProto) ||
 		gogoproto.IsUnsafeMarshaler(g.file.FileDescriptorProto, mc.message.DescriptorProto) {
 		if gogoproto.IsStableMarshaler(g.file.FileDescriptorProto, mc.message.DescriptorProto) {
-			g.P("b = b[:cap(b)]")
+			g.P("b = b[:len(b)]")
 			g.P("n, err := m.MarshalToSizedBuffer(b)")
 			g.P("if err != nil {")
 			g.In()
@@ -2731,7 +2731,7 @@ func (g *Generator) generateCommonMethods(mc *msgCtx) {
 			g.P("return xxx_messageInfo_", mc.goName, ".Marshal(b, m, deterministic)")
 			g.P("} else {")
 			g.In()
-			g.P("b = b[:cap(b)]")
+			g.P("b = b[:len(b)]")
 			g.P("n, err := m.MarshalToSizedBuffer(b)")
 			g.P("if err != nil {")
 			g.In()

diff --git a/test/protobuffer/protobuffer.pb.go b/test/protobuffer/protobuffer.pb.go