jsutil: Avoid creating Uint8Array when copying bytes from Go to JS

Updates #1435

internal/graphicsdriver/opengl/context_js.go

@@ -202,7 +202,7 @@ func (c *context) framebufferPixels(f *framebuffer, width, height int) []byte {
 	c.bindFramebuffer(f.native)
 
 	l := 4 * width * height
-	p := jsutil.TemporaryUint8Array(l)
+	p := jsutil.TemporaryUint8Array(l, nil)
 	gl.Call("readPixels", 0, 0, width, height, gles.RGBA, gles.UNSIGNED_BYTE, p)
 
 	return jsutil.Uint8ArrayToSlice(p, l)
@@ -387,8 +387,7 @@ func (c *context) uniformFloats(p program, location string, v []float32, typ sha
 		base = typ.Sub[0].Main
 	}
 
-	arr := jsutil.TemporaryFloat32Array(len(v))
+	arr := jsutil.TemporaryFloat32Array(len(v), v)
-	jsutil.CopySliceToJS(arr, v)
 
 	switch base {
 	case shaderir.Float:
@@ -484,8 +483,7 @@ func (c *context) bindElementArrayBuffer(b buffer) {
 func (c *context) arrayBufferSubData(data []float32) {
 	gl := c.gl
 	l := len(data) * 4
-	arr := jsutil.TemporaryUint8Array(l)
+	arr := jsutil.TemporaryUint8Array(l, data)
-	jsutil.CopySliceToJS(arr, data)
 	if isWebGL2Available {
 		gl.Call("bufferSubData", gles.ARRAY_BUFFER, 0, arr, 0, l)
 	} else {
@@ -496,8 +494,7 @@ func (c *context) arrayBufferSubData(data []float32) {
 func (c *context) elementArrayBufferSubData(data []uint16) {
 	gl := c.gl
 	l := len(data) * 2
-	arr := jsutil.TemporaryUint8Array(l)
+	arr := jsutil.TemporaryUint8Array(l, data)
-	jsutil.CopySliceToJS(arr, data)
 	if isWebGL2Available {
 		gl.Call("bufferSubData", gles.ELEMENT_ARRAY_BUFFER, 0, arr, 0, l)
 	} else {
@@ -542,8 +539,7 @@ func (c *context) texSubImage2D(t textureNative, width, height int, args []*driv
 	c.bindTexture(t)
 	gl := c.gl
 	for _, a := range args {
-		arr := jsutil.TemporaryUint8Array(len(a.Pixels))
+		arr := jsutil.TemporaryUint8Array(len(a.Pixels), a.Pixels)
-		jsutil.CopySliceToJS(arr, a.Pixels)
 		if isWebGL2Available {
 			// void texSubImage2D(GLenum target, GLint level, GLint xoffset, GLint yoffset,
 			//                    GLsizei width, GLsizei height,
@@ -578,8 +574,7 @@ func (c *context) replacePixelsWithPBO(buffer buffer, t textureNative, width, he
 
 	stride := 4 * width
 	for _, a := range args {
-		arr := jsutil.TemporaryUint8Array(len(a.Pixels))
+		arr := jsutil.TemporaryUint8Array(len(a.Pixels), a.Pixels)
-		jsutil.CopySliceToJS(arr, a.Pixels)
 		offset := 4 * (a.Y*width + a.X)
 		for j := 0; j < a.Height; j++ {
 			gl.Call("bufferSubData", gles.PIXEL_UNPACK_BUFFER, offset+stride*j, arr, 4*a.Width*j, 4*a.Width)
@@ -597,7 +592,7 @@ func (c *context) getBufferSubData(buffer buffer, width, height int) []byte {
 	gl := c.gl
 	gl.Call("bindBuffer", gles.PIXEL_UNPACK_BUFFER, buffer)
 	l := 4 * width * height
-	arr := jsutil.TemporaryUint8Array(l)
+	arr := jsutil.TemporaryUint8Array(l, nil)
 	if isWebGL2Available {
 		gl.Call("getBufferSubData", gles.PIXEL_UNPACK_BUFFER, 0, arr, 0, l)
 	} else {

internal/jsutil/buf_js.go

@@ -18,11 +18,6 @@ import (
 	"syscall/js"
 )
 
-// isTypedArrayWritable represents whether TypedArray is writable or not.
-// TypedArray's properties are not writable in the Web standard, but are writable with go2cpp.
-// This enables to avoid unnecessary allocations of js.Value.
-var isTypedArrayWritable = js.Global().Get("go2cpp").Truthy()
-
 var (
 	// temporaryArrayBuffer is a temporary buffer used at gl.readPixels or gl.texSubImage2D.
 	// The read data is converted to Go's byte slice as soon as possible.
@@ -43,40 +38,32 @@ func ensureTemporaryArrayBufferSize(byteLength int) {
 		}
 		temporaryArrayBuffer = js.Global().Get("ArrayBuffer").New(bufl)
 	}
+	if temporaryUint8Array.Get("byteLength").Int() < temporaryArrayBuffer.Get("byteLength").Int() {
+		temporaryUint8Array = js.Global().Get("Uint8Array").New(temporaryArrayBuffer)
+	}
+	if temporaryFloat32Array.Get("byteLength").Int() < temporaryArrayBuffer.Get("byteLength").Int() {
+		temporaryFloat32Array = js.Global().Get("Float32Array").New(temporaryArrayBuffer)
+	}
 }
 
 // TemporaryUint8Array returns a Uint8Array whose length is at least minLength.
 // Be careful that the length can exceed the given minLength.
-func TemporaryUint8Array(minLength int) js.Value {
+// data must be a slice of a numeric type for initialization, or nil if you don't need initialization.
+func TemporaryUint8Array(minLength int, data interface{}) js.Value {
 	ensureTemporaryArrayBufferSize(minLength)
-	if temporaryUint8Array.Get("byteLength").Int() < temporaryArrayBuffer.Get("byteLength").Int() {
+	if data != nil {
-		temporaryUint8Array = js.Global().Get("Uint8Array").New(temporaryArrayBuffer)
+		copySliceToTemporaryArrayBuffer(data)
 	}
 	return temporaryUint8Array
 }
 
 // TemporaryFloat32Array returns a Float32Array whose length is at least minLength.
 // Be careful that the length can exceed the given minLength.
-func TemporaryFloat32Array(minLength int) js.Value {
+// data must be a slice of a numeric type for initialization, or nil if you don't need initialization.
+func TemporaryFloat32Array(minLength int, data interface{}) js.Value {
 	ensureTemporaryArrayBufferSize(minLength * 4)
-	if temporaryFloat32Array.Get("byteLength").Int() < temporaryArrayBuffer.Get("byteLength").Int() {
+	if data != nil {
-		temporaryFloat32Array = js.Global().Get("Float32Array").New(temporaryArrayBuffer)
+		copySliceToTemporaryArrayBuffer(data)
 	}
 	return temporaryFloat32Array
 }
-
-var uint8ArrayObj js.Value
-
-// TODO: Remove this
-func uint8Array(buffer js.Value, byteOffset, byteLength int) js.Value {
-	if isTypedArrayWritable {
-		if Equal(uint8ArrayObj, js.Undefined()) {
-			uint8ArrayObj = js.Global().Get("Uint8Array").New()
-		}
-		uint8ArrayObj.Set("buffer", buffer)
-		uint8ArrayObj.Set("byteOffset", byteOffset)
-		uint8ArrayObj.Set("byteLength", byteLength)
-		return uint8ArrayObj
-	}
-	return js.Global().Get("Uint8Array").New(buffer, byteOffset, byteLength)
-}

internal/jsutil/jsutil_js_test.go

@@ -1,77 +0,0 @@
-// Copyright 2019 The Ebiten Authors
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package jsutil_test
-
-import (
-	"syscall/js"
-	"testing"
-
-	. "github.com/hajimehoshi/ebiten/v2/internal/jsutil"
-)
-
-func TestCopySliceToJS(t *testing.T) {
-	tests := []struct {
-		in  interface{}
-		out js.Value
-	}{
-		{
-			in:  []int8{1, 2, 3},
-			out: js.Global().Get("Int8Array").Call("of", 1, 2, 3),
-		},
-		{
-			in:  []int16{1, 2, 3},
-			out: js.Global().Get("Int16Array").Call("of", 1, 2, 3),
-		},
-		{
-			in:  []int32{1, 2, 3},
-			out: js.Global().Get("Int32Array").Call("of", 1, 2, 3),
-		},
-		{
-			in:  []uint8{1, 2, 3},
-			out: js.Global().Get("Uint8Array").Call("of", 1, 2, 3),
-		},
-		{
-			in:  []uint16{1, 2, 3},
-			out: js.Global().Get("Uint16Array").Call("of", 1, 2, 3),
-		},
-		{
-			in:  []uint32{1, 2, 3},
-			out: js.Global().Get("Uint32Array").Call("of", 1, 2, 3),
-		},
-		{
-			in:  []float32{1, 2, 3},
-			out: js.Global().Get("Float32Array").Call("of", 1, 2, 3),
-		},
-		{
-			in:  []float64{1, 2, 3},
-			out: js.Global().Get("Float64Array").Call("of", 1, 2, 3),
-		},
-	}
-	for _, test := range tests {
-		got := test.out.Get("constructor").New(test.out.Get("length"))
-		CopySliceToJS(got, test.in)
-		want := test.out
-		if got.Length() != want.Length() {
-			t.Errorf("length: got: %d, want: %d", got.Length(), want.Length())
-		}
-		for i := 0; i < got.Length(); i++ {
-			gotv := got.Index(i).Float()
-			wantv := want.Index(i).Float()
-			if gotv != wantv {
-				t.Errorf("[%d]: got: %v, want: %v", i, gotv, wantv)
-			}
-		}
-	}
-}

internal/jsutil/slice_js.go

@@ -93,13 +93,12 @@ func sliceToByteSlice(s interface{}) (bs []byte) {
 	return
 }
 
-func CopySliceToJS(dst js.Value, src interface{}) {
+func copySliceToTemporaryArrayBuffer(src interface{}) {
 	switch s := src.(type) {
 	case []uint8:
-		js.CopyBytesToJS(dst, s)
+		js.CopyBytesToJS(temporaryUint8Array, s)
 	case []int8, []int16, []int32, []uint16, []uint32, []float32, []float64:
-		a := uint8Array(dst.Get("buffer"), dst.Get("byteOffset").Int(), dst.Get("byteLength").Int())
+		js.CopyBytesToJS(temporaryUint8Array, sliceToByteSlice(s))
-		js.CopyBytesToJS(a, sliceToByteSlice(s))
 	default:
 		panic(fmt.Sprintf("jsutil: unexpected value at CopySliceToJS: %T", s))
 	}