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jsutil: Avoid allocating ArrayBuffer unnecessarily

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This commit is contained in:
Hajime Hoshi 2019-09-26 23:59:00 +09:00
parent 9a42b264fd
commit 59333ba1ad
1 changed files with 20 additions and 8 deletions
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28
internal/jsutil/go113_js.go
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@ -96,44 +96,56 @@ func sliceToByteSlice(s interface{}) (bs []byte) {
return
}
var temporaryBuffer = js.Global().Get("ArrayBuffer").New(16)
func getTemporaryUint8Array(size int) js.Value {
if l := temporaryBuffer.Get("byteLength").Int(); l < size {
for l < size {
l *= 2
}
temporaryBuffer = js.Global().Get("ArrayBuffer").New(l)
}
return js.Global().Get("Uint8Array").New(temporaryBuffer, 0, size)
}
func SliceToTypedArray(s interface{}) (js.Value, func()) {
switch s := s.(type) {
case []int8:
a := js.Global().Get("Uint8Array").New(len(s))
a := getTemporaryUint8Array(len(s))
js.CopyBytesToJS(a, sliceToByteSlice(s))
buf := a.Get("buffer")
return js.Global().Get("Int8Array").New(buf, a.Get("byteOffset"), a.Get("byteLength")), func() {}
case []int16:
a := js.Global().Get("Uint8Array").New(len(s) * 2)
a := getTemporaryUint8Array(len(s) * 2)
js.CopyBytesToJS(a, sliceToByteSlice(s))
buf := a.Get("buffer")
return js.Global().Get("Int16Array").New(buf, a.Get("byteOffset"), a.Get("byteLength").Int()/2), func() {}
case []int32:
a := js.Global().Get("Uint8Array").New(len(s) * 4)
a := getTemporaryUint8Array(len(s) * 4)
js.CopyBytesToJS(a, sliceToByteSlice(s))
buf := a.Get("buffer")
return js.Global().Get("Int32Array").New(buf, a.Get("byteOffset"), a.Get("byteLength").Int()/4), func() {}
case []uint8:
a := js.Global().Get("Uint8Array").New(len(s))
a := getTemporaryUint8Array(len(s))
js.CopyBytesToJS(a, s)
return a, func() {}
case []uint16:
a := js.Global().Get("Uint8Array").New(len(s) * 2)
a := getTemporaryUint8Array(len(s) * 2)
js.CopyBytesToJS(a, sliceToByteSlice(s))
buf := a.Get("buffer")
return js.Global().Get("Uint16Array").New(buf, a.Get("byteOffset"), a.Get("byteLength").Int()/2), func() {}
case []uint32:
a := js.Global().Get("Uint8Array").New(len(s) * 4)
a := getTemporaryUint8Array(len(s) * 4)
js.CopyBytesToJS(a, sliceToByteSlice(s))
buf := a.Get("buffer")
return js.Global().Get("Uint32Array").New(buf, a.Get("byteOffset"), a.Get("byteLength").Int()/4), func() {}
case []float32:
a := js.Global().Get("Uint8Array").New(len(s) * 4)
a := getTemporaryUint8Array(len(s) * 4)
js.CopyBytesToJS(a, sliceToByteSlice(s))
buf := a.Get("buffer")
return js.Global().Get("Float32Array").New(buf, a.Get("byteOffset"), a.Get("byteLength").Int()/4), func() {}
case []float64:
a := js.Global().Get("Uint8Array").New(len(s) * 8)
a := getTemporaryUint8Array(len(s) * 8)
js.CopyBytesToJS(a, sliceToByteSlice(s))
buf := a.Get("buffer")
return js.Global().Get("Float64Array").New(buf, a.Get("byteOffset"), a.Get("byteLength").Int()/8), func() {}