internal/impl: add runtime support for *[]byte unknown representation
This CL adds runtime support for unknown fields to be represented
as *[]byte in addition to the current representation as []byte.
This CL does not change generated code to use *[]byte.
Comparison between using *[]byte and []byte:
• Every message supports unknown fields, so use of []byte
expands a message size by 24B (for 64-bit systems).
In contrast, *[]byte only expands a message by 8B.
This has significant memory implications for small messages.
• If unknown fields are encountered, *[]byte has extra overhead
allocating the 24B slice header. However, it is assumed
that messages rarely see any unknown fields at runtime,
or generally do so for a temporary period of time.
Change-Id: I81935e4ea7394166e61ff4579f76f59fa792dfc9
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/244937
Reviewed-by: Damien Neil <dneil@google.com>
diff --git a/internal/impl/message.go b/internal/impl/message.go
index c8c3859..a104e28 100644
--- a/internal/impl/message.go
+++ b/internal/impl/message.go
@@ -110,22 +110,29 @@
type (
SizeCache = int32
WeakFields = map[int32]protoreflect.ProtoMessage
- UnknownFields = []byte
+ UnknownFields = unknownFieldsA // TODO: switch to unknownFieldsB
+ unknownFieldsA = []byte
+ unknownFieldsB = *[]byte
ExtensionFields = map[int32]ExtensionField
)
var (
sizecacheType = reflect.TypeOf(SizeCache(0))
weakFieldsType = reflect.TypeOf(WeakFields(nil))
- unknownFieldsType = reflect.TypeOf(UnknownFields(nil))
+ unknownFieldsAType = reflect.TypeOf(unknownFieldsA(nil))
+ unknownFieldsBType = reflect.TypeOf(unknownFieldsB(nil))
extensionFieldsType = reflect.TypeOf(ExtensionFields(nil))
)
type structInfo struct {
sizecacheOffset offset
+ sizecacheType reflect.Type
weakOffset offset
+ weakType reflect.Type
unknownOffset offset
+ unknownType reflect.Type
extensionOffset offset
+ extensionType reflect.Type
fieldsByNumber map[pref.FieldNumber]reflect.StructField
oneofsByName map[pref.Name]reflect.StructField
@@ -152,18 +159,22 @@
case genid.SizeCache_goname, genid.SizeCacheA_goname:
if f.Type == sizecacheType {
si.sizecacheOffset = offsetOf(f, mi.Exporter)
+ si.sizecacheType = f.Type
}
case genid.WeakFields_goname, genid.WeakFieldsA_goname:
if f.Type == weakFieldsType {
si.weakOffset = offsetOf(f, mi.Exporter)
+ si.weakType = f.Type
}
case genid.UnknownFields_goname, genid.UnknownFieldsA_goname:
- if f.Type == unknownFieldsType {
+ if f.Type == unknownFieldsAType || f.Type == unknownFieldsBType {
si.unknownOffset = offsetOf(f, mi.Exporter)
+ si.unknownType = f.Type
}
case genid.ExtensionFields_goname, genid.ExtensionFieldsA_goname, genid.ExtensionFieldsB_goname:
if f.Type == extensionFieldsType {
si.extensionOffset = offsetOf(f, mi.Exporter)
+ si.extensionType = f.Type
}
default:
for _, s := range strings.Split(f.Tag.Get("protobuf"), ",") {