all: replace reflect.SliceHeader with unsafe.Slice

Closes #2420

.github/workflows/govetblock.txt

@@ -1,2 +1,4 @@
+github.com/hajimehoshi/ebiten/v2/internal/cocoa
 github.com/hajimehoshi/ebiten/v2/internal/glfwwin
 github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver/directx
+github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver/metal/mtl

internal/cocoa/api_cocoa_darwin.go

@@ -15,7 +15,6 @@
 package cocoa
 
 import (
-	"reflect"
 	"unsafe"
 
 	"github.com/ebitengine/purego/objc"
@@ -277,15 +276,13 @@ func (s NSString) InitWithUTF8String(utf8 string) NSString {
 }
 
 func (s NSString) String() string {
-	// this will be nicer with unsafe.Slice once ebitengine requires 1.17
-	// reflect.SliceHeader is used because it will force Go to copy the string
-	// into Go memory when casted to a string
-	var b []byte
-	header := (*reflect.SliceHeader)(unsafe.Pointer(&b))
-	header.Data = uintptr(s.Send(sel_UTF8String))
-	header.Len = int(s.Send(sel_length))
-	header.Cap = header.Len
-	return string(b)
+	// The lifetime of the underlying C string is shorter than s [1].
+	// Copy the bytes to ensure that the returned string's lifetime is unrelated to s.
+	// [1] https://developer.apple.com/documentation/foundation/nsstring/1411189-utf8string?language=objc
+	src := unsafe.Slice((*byte)(unsafe.Pointer(s.Send(sel_UTF8String))), s.Send(sel_length))
+	dst := make([]byte, len(src))
+	copy(dst, src)
+	return string(dst)
 }
 
 type NSNotification struct {

internal/glfwwin/win32window_windows.go

@@ -9,7 +9,6 @@ import (
 	"errors"
 	"fmt"
 	"math"
-	"reflect"
 	"runtime"
 	"unsafe"
 
@@ -100,11 +99,7 @@ func createIcon(image *Image, xhot, yhot int, icon bool) (_HICON, error) {
 	}()
 
 	source := image.Pixels
-	var target []byte
-	h := (*reflect.SliceHeader)(unsafe.Pointer(&target))
-	h.Data = uintptr(unsafe.Pointer(targetPtr))
-	h.Len = len(source)
-	h.Cap = len(source)
+	target := unsafe.Slice((*byte)(unsafe.Pointer(targetPtr)), len(source))
 	for i := 0; i < len(source)/4; i++ {
 		target[4*i] = source[4*i+2]
 		target[4*i+1] = source[4*i+1]

internal/graphicsdriver/directx/graphics_windows.go

@@ -18,7 +18,6 @@ import (
 	"errors"
 	"fmt"
 	"os"
-	"reflect"
 	"strings"
 	"time"
 	"unsafe"
@@ -1013,14 +1012,14 @@ func (g *Graphics) SetVertices(vertices []float32, indices []uint16) (ferr error
 	if err != nil {
 		return err
 	}
-	copyFloat32s(m, vertices)
+	copy(unsafe.Slice((*float32)(unsafe.Pointer(m)), len(vertices)), vertices)
 	g.vertices[g.frameIndex][vidx].Unmap(0, nil)
 
 	m, err = g.indices[g.frameIndex][iidx].Map(0, &_D3D12_RANGE{0, 0})
 	if err != nil {
 		return err
 	}
-	copyUint16s(m, indices)
+	copy(unsafe.Slice((*uint16)(unsafe.Pointer(m)), len(indices)), indices)
 	g.indices[g.frameIndex][iidx].Unmap(0, nil)
 
 	return nil
@@ -1471,12 +1470,7 @@ func (i *Image) ReadPixels(buf []byte, x, y, width, height int) error {
 		return err
 	}
 
-	var dstBytes []byte
-	h := (*reflect.SliceHeader)(unsafe.Pointer(&dstBytes))
-	h.Data = uintptr(m)
-	h.Len = int(i.totalBytes)
-	h.Cap = int(i.totalBytes)
-
+	dstBytes := unsafe.Slice((*byte)(unsafe.Pointer(m)), i.totalBytes)
 	for j := 0; j < height; j++ {
 		copy(buf[j*width*4:(j+1)*width*4], dstBytes[j*int(i.layouts.Footprint.RowPitch):])
 	}
@@ -1510,11 +1504,7 @@ func (i *Image) WritePixels(args []*graphicsdriver.WritePixelsArgs) error {
 
 	i.graphics.needFlushCopyCommandList = true
 
-	var srcBytes []byte
-	h := (*reflect.SliceHeader)(unsafe.Pointer(&srcBytes))
-	h.Data = uintptr(m)
-	h.Len = int(i.totalBytes)
-	h.Cap = int(i.totalBytes)
+	srcBytes := unsafe.Slice((*byte)(unsafe.Pointer(m)), i.totalBytes)
 	for _, a := range args {
 		for j := 0; j < a.Height; j++ {
 			copy(srcBytes[(a.Y+j)*int(i.layouts.Footprint.RowPitch)+a.X*4:], a.Pixels[j*a.Width*4:(j+1)*a.Width*4])
@@ -1725,24 +1715,6 @@ func (i *Image) ensureDepthStencilView(device *_ID3D12Device) error {
 	return nil
 }
 
-func copyFloat32s(dst uintptr, src []float32) {
-	var dsts []float32
-	h := (*reflect.SliceHeader)(unsafe.Pointer(&dsts))
-	h.Data = dst
-	h.Len = len(src)
-	h.Cap = len(src)
-	copy(dsts, src)
-}
-
-func copyUint16s(dst uintptr, src []uint16) {
-	var dsts []uint16
-	h := (*reflect.SliceHeader)(unsafe.Pointer(&dsts))
-	h.Data = dst
-	h.Len = len(src)
-	h.Cap = len(src)
-	copy(dsts, src)
-}
-
 type stencilMode int
 
 const (

internal/graphicsdriver/directx/pipeline_windows.go

@@ -228,7 +228,7 @@ func (p *pipelineStates) useGraphicsPipelineState(device *_ID3D12Device, command
 	}
 
 	// Update the constant buffer.
-	copyFloat32s(m, uniforms)
+	copy(unsafe.Slice((*float32)(unsafe.Pointer(m)), len(uniforms)), uniforms)
 
 	commandList.SetPipelineState(pipelineState)
 

internal/graphicsdriver/metal/mtl/mtl_darwin.go

@@ -25,7 +25,6 @@ package mtl
 import (
 	"errors"
 	"fmt"
-	"reflect"
 	"runtime"
 	"unsafe"
 
@@ -1086,18 +1085,7 @@ func (b Buffer) Length() uintptr {
 
 func (b Buffer) CopyToContents(data unsafe.Pointer, lengthInBytes uintptr) {
 	contents := b.buffer.Send(sel_contents)
-	// use unsafe.Slice when ebitengine reaches 1.17
-	var contentSlice []byte
-	contentHeader := (*reflect.SliceHeader)(unsafe.Pointer(&contentSlice))
-	contentHeader.Data = uintptr(contents)
-	contentHeader.Len = int(lengthInBytes)
-	contentHeader.Cap = int(lengthInBytes)
-	var dataSlice []byte
-	dataHeader := (*reflect.SliceHeader)(unsafe.Pointer(&dataSlice))
-	dataHeader.Data = uintptr(data)
-	dataHeader.Len = int(lengthInBytes)
-	dataHeader.Cap = int(lengthInBytes)
-	copy(contentSlice, dataSlice)
+	copy(unsafe.Slice((*byte)(unsafe.Pointer(contents)), lengthInBytes), unsafe.Slice((*byte)(data), lengthInBytes))
 	if runtime.GOOS != "ios" {
 		b.buffer.Send(sel_didModifyRange, 0, lengthInBytes)
 	}

internal/graphicsdriver/opengl/bytes.go

@@ -1,42 +0,0 @@
-// Copyright 2018 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 opengl
-
-import (
-	"reflect"
-	"unsafe"
-)
-
-func float32sToBytes(v []float32) []byte {
-	f32h := (*reflect.SliceHeader)(unsafe.Pointer(&v))
-
-	var b []byte
-	bh := (*reflect.SliceHeader)(unsafe.Pointer(&b))
-	bh.Data = f32h.Data
-	bh.Len = len(v) * 4
-	bh.Cap = len(v) * 4
-	return b
-}
-
-func uint16sToBytes(v []uint16) []byte {
-	u16h := (*reflect.SliceHeader)(unsafe.Pointer(&v))
-
-	var b []byte
-	bh := (*reflect.SliceHeader)(unsafe.Pointer(&b))
-	bh.Data = u16h.Data
-	bh.Len = len(v) * 2
-	bh.Cap = len(v) * 2
-	return b
-}

internal/graphicsdriver/opengl/context_gles.go

@@ -21,6 +21,7 @@ package opengl
 import (
 	"errors"
 	"fmt"
+	"unsafe"
 
 	"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver"
 	"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver/opengl/glconst"
@@ -421,11 +422,13 @@ func (c *context) bindElementArrayBuffer(b buffer) {
 }
 
 func (c *context) arrayBufferSubData(data []float32) {
-	c.ctx.BufferSubData(glconst.ARRAY_BUFFER, 0, float32sToBytes(data))
+	s := unsafe.Slice((*byte)(unsafe.Pointer(&data[0])), len(data)*4)
+	c.ctx.BufferSubData(glconst.ARRAY_BUFFER, 0, s)
 }
 
 func (c *context) elementArrayBufferSubData(data []uint16) {
-	c.ctx.BufferSubData(glconst.ELEMENT_ARRAY_BUFFER, 0, uint16sToBytes(data))
+	s := unsafe.Slice((*byte)(unsafe.Pointer(&data[0])), len(data)*2)
+	c.ctx.BufferSubData(glconst.ELEMENT_ARRAY_BUFFER, 0, s)
 }
 
 func (c *context) deleteBuffer(b buffer) {

internal/jsutil/slice_js.go

@@ -15,7 +15,6 @@
 package jsutil
 
 import (
-	"reflect"
 	"runtime"
 	"syscall/js"
 	"unsafe"
@@ -32,22 +31,14 @@ func copyUint16SliceToTemporaryArrayBuffer(src []uint16) {
 	if len(src) == 0 {
 		return
 	}
-	h := (*reflect.SliceHeader)(unsafe.Pointer(&src))
-	h.Len *= 2
-	h.Cap *= 2
-	bs := *(*[]byte)(unsafe.Pointer(h))
+	js.CopyBytesToJS(temporaryUint8Array, unsafe.Slice((*byte)(unsafe.Pointer(&src[0])), len(src)*2))
 	runtime.KeepAlive(src)
-	js.CopyBytesToJS(temporaryUint8Array, bs)
 }
 
 func copyFloat32SliceToTemporaryArrayBuffer(src []float32) {
 	if len(src) == 0 {
 		return
 	}
-	h := (*reflect.SliceHeader)(unsafe.Pointer(&src))
-	h.Len *= 4
-	h.Cap *= 4
-	bs := *(*[]byte)(unsafe.Pointer(h))
+	js.CopyBytesToJS(temporaryUint8Array, unsafe.Slice((*byte)(unsafe.Pointer(&src[0])), len(src)*4))
 	runtime.KeepAlive(src)
-	js.CopyBytesToJS(temporaryUint8Array, bs)
 }