encoding/binary: simplify Read and Write

There's no need to manually manage the backing slice for bs. Removing it simplifies the code, removes some allocations, and speeds it up slightly. Fixes #27403 name old time/op new time/op delta ReadSlice1000Int32s-8 6.39µs ± 1% 6.31µs ± 1% -1.37% (p=0.000 n=27+27) ReadStruct-8 1.25µs ± 2% 1.23µs ± 2% -1.06% (p=0.003 n=30+29) ReadInts-8 301ns ± 0% 297ns ± 1% -1.21% (p=0.000 n=27+30) WriteInts-8 325ns ± 1% 320ns ± 1% -1.59% (p=0.000 n=26+29) WriteSlice1000Int32s-8 6.60µs ± 0% 6.52µs ± 0% -1.23% (p=0.000 n=28+27) PutUint16-8 0.72ns ± 2% 0.71ns ± 2% ~ (p=0.286 n=30+30) PutUint32-8 0.71ns ± 1% 0.71ns ± 0% -0.42% (p=0.003 n=30+25) PutUint64-8 0.78ns ± 2% 0.78ns ± 0% -0.55% (p=0.001 n=30+27) LittleEndianPutUint16-8 0.57ns ± 0% 0.57ns ± 0% ~ (all equal) LittleEndianPutUint32-8 0.57ns ± 0% 0.57ns ± 0% ~ (all equal) LittleEndianPutUint64-8 0.57ns ± 0% 0.57ns ± 0% ~ (all equal) PutUvarint32-8 23.1ns ± 1% 23.1ns ± 1% ~ (p=0.925 n=26+29) PutUvarint64-8 57.5ns ± 2% 57.3ns ± 1% ~ (p=0.338 n=30+26) [Geo mean] 23.0ns 22.9ns -0.61% name old speed new speed delta ReadSlice1000Int32s-8 626MB/s ± 1% 634MB/s ± 1% +1.38% (p=0.000 n=27+27) ReadStruct-8 60.2MB/s ± 2% 60.8MB/s ± 2% +1.08% (p=0.002 n=30+29) ReadInts-8 100MB/s ± 1% 101MB/s ± 1% +1.24% (p=0.000 n=27+30) WriteInts-8 92.2MB/s ± 1% 93.6MB/s ± 1% +1.56% (p=0.000 n=26+29) WriteSlice1000Int32s-8 606MB/s ± 0% 614MB/s ± 0% +1.24% (p=0.000 n=28+27) PutUint16-8 2.80GB/s ± 1% 2.80GB/s ± 1% ~ (p=0.095 n=28+29) PutUint32-8 5.61GB/s ± 1% 5.62GB/s ± 1% ~ (p=0.069 n=27+28) PutUint64-8 10.2GB/s ± 1% 10.2GB/s ± 0% +0.15% (p=0.039 n=27+27) LittleEndianPutUint16-8 3.50GB/s ± 1% 3.50GB/s ± 1% ~ (p=0.552 n=30+29) LittleEndianPutUint32-8 7.01GB/s ± 1% 7.02GB/s ± 1% ~ (p=0.160 n=29+27) LittleEndianPutUint64-8 14.0GB/s ± 1% 14.0GB/s ± 1% ~ (p=0.413 n=29+29) PutUvarint32-8 174MB/s ± 1% 173MB/s ± 1% ~ (p=0.648 n=25+30) PutUvarint64-8 139MB/s ± 2% 140MB/s ± 1% ~ (p=0.271 n=30+26) [Geo mean] 906MB/s 911MB/s +0.55% name old alloc/op new alloc/op delta ReadSlice1000Int32s-8 4.14kB ± 0% 4.13kB ± 0% -0.19% (p=0.000 n=30+30) ReadStruct-8 200B ± 0% 200B ± 0% ~ (all equal) ReadInts-8 64.0B ± 0% 32.0B ± 0% -50.00% (p=0.000 n=30+30) WriteInts-8 112B ± 0% 64B ± 0% -42.86% (p=0.000 n=30+30) WriteSlice1000Int32s-8 4.14kB ± 0% 4.13kB ± 0% -0.19% (p=0.000 n=30+30) PutUint16-8 0.00B 0.00B ~ (all equal) PutUint32-8 0.00B 0.00B ~ (all equal) PutUint64-8 0.00B 0.00B ~ (all equal) LittleEndianPutUint16-8 0.00B 0.00B ~ (all equal) LittleEndianPutUint32-8 0.00B 0.00B ~ (all equal) LittleEndianPutUint64-8 0.00B 0.00B ~ (all equal) PutUvarint32-8 0.00B 0.00B ~ (all equal) PutUvarint64-8 0.00B 0.00B ~ (all equal) [Geo mean] 476B 370B -22.22% name old allocs/op new allocs/op delta ReadSlice1000Int32s-8 3.00 ± 0% 2.00 ± 0% -33.33% (p=0.000 n=30+30) ReadStruct-8 16.0 ± 0% 16.0 ± 0% ~ (all equal) ReadInts-8 8.00 ± 0% 8.00 ± 0% ~ (all equal) WriteInts-8 14.0 ± 0% 14.0 ± 0% ~ (all equal) WriteSlice1000Int32s-8 3.00 ± 0% 2.00 ± 0% -33.33% (p=0.000 n=30+30) PutUint16-8 0.00 0.00 ~ (all equal) PutUint32-8 0.00 0.00 ~ (all equal) PutUint64-8 0.00 0.00 ~ (all equal) LittleEndianPutUint16-8 0.00 0.00 ~ (all equal) LittleEndianPutUint32-8 0.00 0.00 ~ (all equal) LittleEndianPutUint64-8 0.00 0.00 ~ (all equal) PutUvarint32-8 0.00 0.00 ~ (all equal) PutUvarint64-8 0.00 0.00 ~ (all equal) [Geo mean] 6.94 5.90 -14.97% Change-Id: I3790b93e4190d98621d5f2c47e42929a18f56c2e Reviewed-on: https://go-review.googlesource.com/133135 Run-TryBot: Josh Bleecher Snyder <[email protected]> TryBot-Result: Gobot Gobot <[email protected]> Reviewed-by: Brad Fitzpatrick <[email protected]>
golang · Sep 4, 2018 · 2179e49 · 2179e49
1 parent e2e44a5
commit 2179e49
Showing 1 changed file with 14 additions and 26 deletions.
diff --git a/src/encoding/binary/binary.go b/src/encoding/binary/binary.go
@@ -161,23 +161,17 @@ func (bigEndian) GoString() string { return "binary.BigEndian" }
 func Read(r io.Reader, order ByteOrder, data interface{}) error {
 	// Fast path for basic types and slices.
 	if n := intDataSize(data); n != 0 {
-		var b [8]byte
-		var bs []byte
-		if n > len(b) {
-			bs = make([]byte, n)
-		} else {
-			bs = b[:n]
-		}
+		bs := make([]byte, n)
 		if _, err := io.ReadFull(r, bs); err != nil {
 			return err
 		}
 		switch data := data.(type) {
 		case *bool:
-			*data = b[0] != 0
+			*data = bs[0] != 0
 		case *int8:
-			*data = int8(b[0])
+			*data = int8(bs[0])
 		case *uint8:
-			*data = b[0]
+			*data = bs[0]
 		case *int16:
 			*data = int16(order.Uint16(bs))
 		case *uint16:
@@ -260,25 +254,19 @@ func Read(r io.Reader, order ByteOrder, data interface{}) error {
 func Write(w io.Writer, order ByteOrder, data interface{}) error {
 	// Fast path for basic types and slices.
 	if n := intDataSize(data); n != 0 {
-		var b [8]byte
-		var bs []byte
-		if n > len(b) {
-			bs = make([]byte, n)
-		} else {
-			bs = b[:n]
-		}
+		bs := make([]byte, n)
 		switch v := data.(type) {
 		case *bool:
 			if *v {
-				b[0] = 1
+				bs[0] = 1
 			} else {
-				b[0] = 0
+				bs[0] = 0
 			}
 		case bool:
 			if v {
-				b[0] = 1
+				bs[0] = 1
 			} else {
-				b[0] = 0
+				bs[0] = 0
 			}
 		case []bool:
 			for i, x := range v {
@@ -289,19 +277,19 @@ func Write(w io.Writer, order ByteOrder, data interface{}) error {
 				}
 			}
 		case *int8:
-			b[0] = byte(*v)
+			bs[0] = byte(*v)
 		case int8:
-			b[0] = byte(v)
+			bs[0] = byte(v)
 		case []int8:
 			for i, x := range v {
 				bs[i] = byte(x)
 			}
 		case *uint8:
-			b[0] = *v
+			bs[0] = *v
 		case uint8:
-			b[0] = v
+			bs[0] = v
 		case []uint8:
-			bs = v
+			bs = v // TODO(josharian): avoid allocating bs in this case?
 		case *int16:
 			order.PutUint16(bs, uint16(*v))
 		case int16: