encoding/binary: add float support to fast path

This adds float type support to the main switch blocks in Read and
Write, instead of falling back to reflection. This gives a considerable
speedup for the float types:

ReadFloats-8                 129ns ± 9%       70ns ± 8%   -46.02%  (p=0.001 n=7+7)
WriteFloats-8                131ns ± 6%       86ns ±11%   -34.59%  (p=0.001 n=7+7)
ReadSlice1000Float32s-8     14.6µs ±14%      4.8µs ±12%   -67.29%  (p=0.001 n=7+7)
WriteSlice1000Float32s-8    16.4µs ±20%      4.7µs ± 8%   -71.01%  (p=0.001 n=7+7)

Change-Id: I0be99d068b07d10dd6eb1137b45eff6f7c216b87
GitHub-Last-Rev: 4ff326e99ca35977d819f0ba29c10d9efc7e811c
GitHub-Pull-Request: golang/go#31803
Reviewed-on: https://go-review.googlesource.com/c/go/+/174959
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

1 files changed, 36 insertions, 0 deletions

diff --git a/src/encoding/binary/binary.go b/src/encoding/binary/binary.go
index 33066fc77a..a99ca01994 100644
--- a/src/encoding/binary/binary.go
+++ b/src/encoding/binary/binary.go
@@ -185,6 +185,10 @@ func Read(r io.Reader, order ByteOrder, data interface{}) error {
 			*data = int64(order.Uint64(bs))
 		case *uint64:
 			*data = order.Uint64(bs)
+		case *float32:
+			*data = math.Float32frombits(order.Uint32(bs))
+		case *float64:
+			*data = math.Float64frombits(order.Uint64(bs))
 		case []bool:
 			for i, x := range bs { // Easier to loop over the input for 8-bit values.
 				data[i] = x != 0
@@ -219,6 +223,14 @@ func Read(r io.Reader, order ByteOrder, data interface{}) error {
 			for i := range data {
 				data[i] = order.Uint64(bs[8*i:])
 			}
+		case []float32:
+			for i := range data {
+				data[i] = math.Float32frombits(order.Uint32(bs[4*i:]))
+			}
+		case []float64:
+			for i := range data {
+				data[i] = math.Float64frombits(order.Uint64(bs[8*i:]))
+			}
 		default:
 			n = 0 // fast path doesn't apply
 		}
@@ -343,6 +355,22 @@ func Write(w io.Writer, order ByteOrder, data interface{}) error {
 			for i, x := range v {
 				order.PutUint64(bs[8*i:], x)
 			}
+		case *float32:
+			order.PutUint32(bs, math.Float32bits(*v))
+		case float32:
+			order.PutUint32(bs, math.Float32bits(v))
+		case []float32:
+			for i, x := range v {
+				order.PutUint32(bs[4*i:], math.Float32bits(x))
+			}
+		case *float64:
+			order.PutUint64(bs, math.Float64bits(*v))
+		case float64:
+			order.PutUint64(bs, math.Float64bits(v))
+		case []float64:
+			for i, x := range v {
+				order.PutUint64(bs[8*i:], math.Float64bits(x))
+			}
 		}
 		_, err := w.Write(bs)
 		return err
@@ -696,6 +724,14 @@ func intDataSize(data interface{}) int {
 		return 8 * len(data)
 	case []uint64:
 		return 8 * len(data)
+	case float32, *float32:
+		return 4
+	case float64, *float64:
+		return 8
+	case []float32:
+		return 4 * len(data)
+	case []float64:
+		return 8 * len(data)
 	}
 	return 0
 }