internal/impl: inline small tag decoding
Inline varint decoding of small (1- and 2-byte) field tags in the
fast-path unmarshaler.
name old time/op new time/op delta
EmptyMessage/Wire/Unmarshal 40.6ns ± 1% 40.2ns ± 1% -1.02% (p=0.000 n=37+35)
EmptyMessage/Wire/Unmarshal-12 6.77ns ± 2% 7.13ns ± 5% +5.32% (p=0.000 n=37+37)
RepeatedInt32/Wire/Unmarshal 9.46µs ± 1% 6.57µs ± 1% -30.56% (p=0.000 n=38+39)
RepeatedInt32/Wire/Unmarshal-12 1.50µs ± 2% 1.05µs ± 2% -30.00% (p=0.000 n=39+37)
Required/Wire/Unmarshal 371ns ± 1% 258ns ± 1% -30.44% (p=0.000 n=38+32)
Required/Wire/Unmarshal-12 60.3ns ± 1% 44.3ns ± 2% -26.45% (p=0.000 n=38+36)
Change-Id: Ie80415dea8cb6b840eafa52f0572046a1910a9b1
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/216419
Reviewed-by: Joe Tsai <joetsai@google.com>
diff --git a/internal/encoding/wire/wire.go b/internal/encoding/wire/wire.go
index 32622b1..d7baa7f 100644
--- a/internal/encoding/wire/wire.go
+++ b/internal/encoding/wire/wire.go
@@ -176,7 +176,6 @@
// AppendVarint appends v to b as a varint-encoded uint64.
func AppendVarint(b []byte, v uint64) []byte {
- // TODO: Specialize for sizes 1 and 2 with mid-stack inlining.
switch {
case v < 1<<7:
b = append(b, byte(v))
@@ -259,7 +258,6 @@
// ConsumeVarint parses b as a varint-encoded uint64, reporting its length.
// This returns a negative length upon an error (see ParseError).
func ConsumeVarint(b []byte) (v uint64, n int) {
- // TODO: Specialize for sizes 1 and 2 with mid-stack inlining.
var y uint64
if len(b) <= 0 {
return 0, errCodeTruncated
diff --git a/internal/impl/decode.go b/internal/impl/decode.go
index fc93525..4a1d631 100644
--- a/internal/impl/decode.go
+++ b/internal/impl/decode.go
@@ -97,15 +97,27 @@
start := len(b)
for len(b) > 0 {
// Parse the tag (field number and wire type).
- // TODO: inline 1 and 2 byte variants?
- num, wtyp, n := wire.ConsumeTag(b)
- if n < 0 {
- return out, wire.ParseError(n)
+ var tag uint64
+ if b[0] < 0x80 {
+ tag = uint64(b[0])
+ b = b[1:]
+ } else if len(b) >= 2 && b[1] < 128 {
+ tag = uint64(b[0]&0x7f) + uint64(b[1])<<7
+ b = b[2:]
+ } else {
+ var n int
+ tag, n = wire.ConsumeVarint(b)
+ if n < 0 {
+ return out, wire.ParseError(n)
+ }
+ b = b[n:]
}
- if num > wire.MaxValidNumber {
+ num := wire.Number(tag >> 3)
+ wtyp := wire.Type(tag & 7)
+
+ if num < wire.MinValidNumber || num > wire.MaxValidNumber {
return out, errors.New("invalid field number")
}
- b = b[n:]
if wtyp == wire.EndGroupType {
if num != groupTag {
@@ -121,6 +133,7 @@
} else {
f = mi.coderFields[num]
}
+ var n int
err := errUnknown
switch {
case f != nil:
