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// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build js && wasm
package rand
import "syscall/js"
// The maximum buffer size for crypto.getRandomValues is 65536 bytes.
// https://developer.mozilla.org/en-US/docs/Web/API/Crypto/getRandomValues#exceptions
const maxGetRandomRead = 64 << 10
var batchedGetRandom func([]byte) error
func init() {
Reader = &reader{}
batchedGetRandom = batched(getRandom, maxGetRandomRead)
}
var jsCrypto = js.Global().Get("crypto")
var uint8Array = js.Global().Get("Uint8Array")
// reader implements a pseudorandom generator
// using JavaScript crypto.getRandomValues method.
// See https://developer.mozilla.org/en-US/docs/Web/API/Crypto/getRandomValues.
type reader struct{}
func (r *reader) Read(b []byte) (int, error) {
if err := batchedGetRandom(b); err != nil {
return 0, err
}
return len(b), nil
}
func getRandom(b []byte) error {
a := uint8Array.New(len(b))
jsCrypto.Call("getRandomValues", a)
js.CopyBytesToGo(b, a)
return nil
}
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