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/encode.go b/internal/impl/encode.go
index 8c8a794..845c67d 100644
--- a/internal/impl/encode.go
+++ b/internal/impl/encode.go
@@ -79,8 +79,9 @@
size += f.funcs.size(fptr, f, opts)
}
if mi.unknownOffset.IsValid() {
- u := *p.Apply(mi.unknownOffset).Bytes()
- size += len(u)
+ if u := mi.getUnknownBytes(p); u != nil {
+ size += len(*u)
+ }
}
if mi.sizecacheOffset.IsValid() {
if size > math.MaxInt32 {
@@ -141,8 +142,9 @@
}
}
if mi.unknownOffset.IsValid() && !mi.isMessageSet {
- u := *p.Apply(mi.unknownOffset).Bytes()
- b = append(b, u...)
+ if u := mi.getUnknownBytes(p); u != nil {
+ b = append(b, (*u)...)
+ }
}
return b, nil
}