proto, internal/impl: avoid string->[]byte conversions
We trust the compiler to optimize away the string->[]byte conversion in
code like:
b = wire.AppendBytes(b, []byte(s))
In testing (go 1.12.5 linux/amd64), this optimization is not happening.
Perhaps newer versions of the compiler will optimize this, but we
shouldn't rely on it; avoid unnecessary conversions.
Benchmark differences vs https://golang.org/cl/171462:
name old time/op new time/op delta
Wire/Marshal/google_message1_proto2-6 310ns ± 2% 189ns ± 3% -39.20% (p=0.000 n=8+8)
Wire/Marshal/google_message1_proto3-6 389ns ± 8% 261ns ± 2% -33.03% (p=0.000 n=8+8)
Wire/Marshal/google_message2-6 103µs ±11% 59µs ± 4% -42.17% (p=0.000 n=8+8)
name old alloc/op new alloc/op delta
Wire/Marshal/google_message1_proto2-6 592B ± 0% 240B ± 0% -59.46% (p=0.000 n=8+8)
Wire/Marshal/google_message1_proto3-6 576B ± 0% 224B ± 0% -61.11% (p=0.000 n=8+8)
Wire/Marshal/google_message2-6 196kB ± 0% 90kB ± 0% -54.05% (p=0.000 n=8+8)
name old allocs/op new allocs/op delta
Wire/Marshal/google_message1_proto2-6 5.00 ± 0% 1.00 ± 0% -80.00% (p=0.000 n=8+8)
Wire/Marshal/google_message1_proto3-6 5.00 ± 0% 1.00 ± 0% -80.00% (p=0.000 n=8+8)
Wire/Marshal/google_message2-6 1.66k ± 0% 0.00k ± 0% -99.94% (p=0.000 n=8+8)
Change-Id: Idab7634b8c86604dffa46895ba2e61be38c9bd9c
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/183380
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
diff --git a/internal/encoding/wire/wire.go b/internal/encoding/wire/wire.go
index 456fc54..ba0abf6 100644
--- a/internal/encoding/wire/wire.go
+++ b/internal/encoding/wire/wire.go
@@ -425,6 +425,11 @@
return append(AppendVarint(b, uint64(len(v))), v...)
}
+// AppendString appends v to b as a lenght-prefixed bytes value.
+func AppendString(b []byte, v string) []byte {
+ return append(AppendVarint(b, uint64(len(v))), v...)
+}
+
// ConsumeBytes parses b as a length-prefixed bytes value, reporting its length.
// This returns a negative length upon an error (see ParseError).
func ConsumeBytes(b []byte) (v []byte, n int) {