tree 11c3f04d2a418e428728329da19c1ab86ce9ba44
parent 4194195e12daf3d3bf61191c5d92da72de18dc28
author Joe Tsai <joetsai@digital-static.net> 1595828267 -0700
committer Joe Tsai <joetsai@digital-static.net> 1595954199 +0000

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>