1 files changed, 594 insertions, 0 deletions
diff --git a/src/syscall/js/js.go b/src/syscall/js/js.go
new file mode 100644
index 0000000..a48bbd4
--- /dev/null
+++ b/src/syscall/js/js.go
@@ -0,0 +1,594 @@
+// 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.
+
+// +build js,wasm
+
+// Package js gives access to the WebAssembly host environment when using the js/wasm architecture.
+// Its API is based on JavaScript semantics.
+//
+// This package is EXPERIMENTAL. Its current scope is only to allow tests to run, but not yet to provide a
+// comprehensive API for users. It is exempt from the Go compatibility promise.
+package js
+
+import (
+	"runtime"
+	"unsafe"
+)
+
+// ref is used to identify a JavaScript value, since the value itself can not be passed to WebAssembly.
+//
+// The JavaScript value "undefined" is represented by the value 0.
+// A JavaScript number (64-bit float, except 0 and NaN) is represented by its IEEE 754 binary representation.
+// All other values are represented as an IEEE 754 binary representation of NaN with bits 0-31 used as
+// an ID and bits 32-34 used to differentiate between string, symbol, function and object.
+type ref uint64
+
+// nanHead are the upper 32 bits of a ref which are set if the value is not encoded as an IEEE 754 number (see above).
+const nanHead = 0x7FF80000
+
+// Wrapper is implemented by types that are backed by a JavaScript value.
+type Wrapper interface {
+	// JSValue returns a JavaScript value associated with an object.
+	JSValue() Value
+}
+
+// Value represents a JavaScript value. The zero value is the JavaScript value "undefined".
+// Values can be checked for equality with the Equal method.
+type Value struct {
+	_     [0]func() // uncomparable; to make == not compile
+	ref   ref       // identifies a JavaScript value, see ref type
+	gcPtr *ref      // used to trigger the finalizer when the Value is not referenced any more
+}
+
+const (
+	// the type flags need to be in sync with wasm_exec.js
+	typeFlagNone = iota
+	typeFlagObject
+	typeFlagString
+	typeFlagSymbol
+	typeFlagFunction
+)
+
+// JSValue implements Wrapper interface.
+func (v Value) JSValue() Value {
+	return v
+}
+
+func makeValue(r ref) Value {
+	var gcPtr *ref
+	typeFlag := (r >> 32) & 7
+	if (r>>32)&nanHead == nanHead && typeFlag != typeFlagNone {
+		gcPtr = new(ref)
+		*gcPtr = r
+		runtime.SetFinalizer(gcPtr, func(p *ref) {
+			finalizeRef(*p)
+		})
+	}
+
+	return Value{ref: r, gcPtr: gcPtr}
+}
+
+func finalizeRef(r ref)
+
+func predefValue(id uint32, typeFlag byte) Value {
+	return Value{ref: (nanHead|ref(typeFlag))<<32 | ref(id)}
+}
+
+func floatValue(f float64) Value {
+	if f == 0 {
+		return valueZero
+	}
+	if f != f {
+		return valueNaN
+	}
+	return Value{ref: *(*ref)(unsafe.Pointer(&f))}
+}
+
+// Error wraps a JavaScript error.
+type Error struct {
+	// Value is the underlying JavaScript error value.
+	Value
+}
+
+// Error implements the error interface.
+func (e Error) Error() string {
+	return "JavaScript error: " + e.Get("message").String()
+}
+
+var (
+	valueUndefined = Value{ref: 0}
+	valueNaN       = predefValue(0, typeFlagNone)
+	valueZero      = predefValue(1, typeFlagNone)
+	valueNull      = predefValue(2, typeFlagNone)
+	valueTrue      = predefValue(3, typeFlagNone)
+	valueFalse     = predefValue(4, typeFlagNone)
+	valueGlobal    = predefValue(5, typeFlagObject)
+	jsGo           = predefValue(6, typeFlagObject) // instance of the Go class in JavaScript
+
+	objectConstructor = valueGlobal.Get("Object")
+	arrayConstructor  = valueGlobal.Get("Array")
+)
+
+// Equal reports whether v and w are equal according to JavaScript's === operator.
+func (v Value) Equal(w Value) bool {
+	return v.ref == w.ref && v.ref != valueNaN.ref
+}
+
+// Undefined returns the JavaScript value "undefined".
+func Undefined() Value {
+	return valueUndefined
+}
+
+// IsUndefined reports whether v is the JavaScript value "undefined".
+func (v Value) IsUndefined() bool {
+	return v.ref == valueUndefined.ref
+}
+
+// Null returns the JavaScript value "null".
+func Null() Value {
+	return valueNull
+}
+
+// IsNull reports whether v is the JavaScript value "null".
+func (v Value) IsNull() bool {
+	return v.ref == valueNull.ref
+}
+
+// IsNaN reports whether v is the JavaScript value "NaN".
+func (v Value) IsNaN() bool {
+	return v.ref == valueNaN.ref
+}
+
+// Global returns the JavaScript global object, usually "window" or "global".
+func Global() Value {
+	return valueGlobal
+}
+
+// ValueOf returns x as a JavaScript value:
+//
+//  | Go                     | JavaScript             |
+//  | ---------------------- | ---------------------- |
+//  | js.Value               | [its value]            |
+//  | js.Func                | function               |
+//  | nil                    | null                   |
+//  | bool                   | boolean                |
+//  | integers and floats    | number                 |
+//  | string                 | string                 |
+//  | []interface{}          | new array              |
+//  | map[string]interface{} | new object             |
+//
+// Panics if x is not one of the expected types.
+func ValueOf(x interface{}) Value {
+	switch x := x.(type) {
+	case Value: // should precede Wrapper to avoid a loop
+		return x
+	case Wrapper:
+		return x.JSValue()
+	case nil:
+		return valueNull
+	case bool:
+		if x {
+			return valueTrue
+		} else {
+			return valueFalse
+		}
+	case int:
+		return floatValue(float64(x))
+	case int8:
+		return floatValue(float64(x))
+	case int16:
+		return floatValue(float64(x))
+	case int32:
+		return floatValue(float64(x))
+	case int64:
+		return floatValue(float64(x))
+	case uint:
+		return floatValue(float64(x))
+	case uint8:
+		return floatValue(float64(x))
+	case uint16:
+		return floatValue(float64(x))
+	case uint32:
+		return floatValue(float64(x))
+	case uint64:
+		return floatValue(float64(x))
+	case uintptr:
+		return floatValue(float64(x))
+	case unsafe.Pointer:
+		return floatValue(float64(uintptr(x)))
+	case float32:
+		return floatValue(float64(x))
+	case float64:
+		return floatValue(x)
+	case string:
+		return makeValue(stringVal(x))
+	case []interface{}:
+		a := arrayConstructor.New(len(x))
+		for i, s := range x {
+			a.SetIndex(i, s)
+		}
+		return a
+	case map[string]interface{}:
+		o := objectConstructor.New()
+		for k, v := range x {
+			o.Set(k, v)
+		}
+		return o
+	default:
+		panic("ValueOf: invalid value")
+	}
+}
+
+func stringVal(x string) ref
+
+// Type represents the JavaScript type of a Value.
+type Type int
+
+const (
+	TypeUndefined Type = iota
+	TypeNull
+	TypeBoolean
+	TypeNumber
+	TypeString
+	TypeSymbol
+	TypeObject
+	TypeFunction
+)
+
+func (t Type) String() string {
+	switch t {
+	case TypeUndefined:
+		return "undefined"
+	case TypeNull:
+		return "null"
+	case TypeBoolean:
+		return "boolean"
+	case TypeNumber:
+		return "number"
+	case TypeString:
+		return "string"
+	case TypeSymbol:
+		return "symbol"
+	case TypeObject:
+		return "object"
+	case TypeFunction:
+		return "function"
+	default:
+		panic("bad type")
+	}
+}
+
+func (t Type) isObject() bool {
+	return t == TypeObject || t == TypeFunction
+}
+
+// Type returns the JavaScript type of the value v. It is similar to JavaScript's typeof operator,
+// except that it returns TypeNull instead of TypeObject for null.
+func (v Value) Type() Type {
+	switch v.ref {
+	case valueUndefined.ref:
+		return TypeUndefined
+	case valueNull.ref:
+		return TypeNull
+	case valueTrue.ref, valueFalse.ref:
+		return TypeBoolean
+	}
+	if v.isNumber() {
+		return TypeNumber
+	}
+	typeFlag := (v.ref >> 32) & 7
+	switch typeFlag {
+	case typeFlagObject:
+		return TypeObject
+	case typeFlagString:
+		return TypeString
+	case typeFlagSymbol:
+		return TypeSymbol
+	case typeFlagFunction:
+		return TypeFunction
+	default:
+		panic("bad type flag")
+	}
+}
+
+// Get returns the JavaScript property p of value v.
+// It panics if v is not a JavaScript object.
+func (v Value) Get(p string) Value {
+	if vType := v.Type(); !vType.isObject() {
+		panic(&ValueError{"Value.Get", vType})
+	}
+	r := makeValue(valueGet(v.ref, p))
+	runtime.KeepAlive(v)
+	return r
+}
+
+func valueGet(v ref, p string) ref
+
+// Set sets the JavaScript property p of value v to ValueOf(x).
+// It panics if v is not a JavaScript object.
+func (v Value) Set(p string, x interface{}) {
+	if vType := v.Type(); !vType.isObject() {
+		panic(&ValueError{"Value.Set", vType})
+	}
+	xv := ValueOf(x)
+	valueSet(v.ref, p, xv.ref)
+	runtime.KeepAlive(v)
+	runtime.KeepAlive(xv)
+}
+
+func valueSet(v ref, p string, x ref)
+
+// Delete deletes the JavaScript property p of value v.
+// It panics if v is not a JavaScript object.
+func (v Value) Delete(p string) {
+	if vType := v.Type(); !vType.isObject() {
+		panic(&ValueError{"Value.Delete", vType})
+	}
+	valueDelete(v.ref, p)
+	runtime.KeepAlive(v)
+}
+
+func valueDelete(v ref, p string)
+
+// Index returns JavaScript index i of value v.
+// It panics if v is not a JavaScript object.
+func (v Value) Index(i int) Value {
+	if vType := v.Type(); !vType.isObject() {
+		panic(&ValueError{"Value.Index", vType})
+	}
+	r := makeValue(valueIndex(v.ref, i))
+	runtime.KeepAlive(v)
+	return r
+}
+
+func valueIndex(v ref, i int) ref
+
+// SetIndex sets the JavaScript index i of value v to ValueOf(x).
+// It panics if v is not a JavaScript object.
+func (v Value) SetIndex(i int, x interface{}) {
+	if vType := v.Type(); !vType.isObject() {
+		panic(&ValueError{"Value.SetIndex", vType})
+	}
+	xv := ValueOf(x)
+	valueSetIndex(v.ref, i, xv.ref)
+	runtime.KeepAlive(v)
+	runtime.KeepAlive(xv)
+}
+
+func valueSetIndex(v ref, i int, x ref)
+
+func makeArgs(args []interface{}) ([]Value, []ref) {
+	argVals := make([]Value, len(args))
+	argRefs := make([]ref, len(args))
+	for i, arg := range args {
+		v := ValueOf(arg)
+		argVals[i] = v
+		argRefs[i] = v.ref
+	}
+	return argVals, argRefs
+}
+
+// Length returns the JavaScript property "length" of v.
+// It panics if v is not a JavaScript object.
+func (v Value) Length() int {
+	if vType := v.Type(); !vType.isObject() {
+		panic(&ValueError{"Value.SetIndex", vType})
+	}
+	r := valueLength(v.ref)
+	runtime.KeepAlive(v)
+	return r
+}
+
+func valueLength(v ref) int
+
+// Call does a JavaScript call to the method m of value v with the given arguments.
+// It panics if v has no method m.
+// The arguments get mapped to JavaScript values according to the ValueOf function.
+func (v Value) Call(m string, args ...interface{}) Value {
+	argVals, argRefs := makeArgs(args)
+	res, ok := valueCall(v.ref, m, argRefs)
+	runtime.KeepAlive(v)
+	runtime.KeepAlive(argVals)
+	if !ok {
+		if vType := v.Type(); !vType.isObject() { // check here to avoid overhead in success case
+			panic(&ValueError{"Value.Call", vType})
+		}
+		if propType := v.Get(m).Type(); propType != TypeFunction {
+			panic("syscall/js: Value.Call: property " + m + " is not a function, got " + propType.String())
+		}
+		panic(Error{makeValue(res)})
+	}
+	return makeValue(res)
+}
+
+func valueCall(v ref, m string, args []ref) (ref, bool)
+
+// Invoke does a JavaScript call of the value v with the given arguments.
+// It panics if v is not a JavaScript function.
+// The arguments get mapped to JavaScript values according to the ValueOf function.
+func (v Value) Invoke(args ...interface{}) Value {
+	argVals, argRefs := makeArgs(args)
+	res, ok := valueInvoke(v.ref, argRefs)
+	runtime.KeepAlive(v)
+	runtime.KeepAlive(argVals)
+	if !ok {
+		if vType := v.Type(); vType != TypeFunction { // check here to avoid overhead in success case
+			panic(&ValueError{"Value.Invoke", vType})
+		}
+		panic(Error{makeValue(res)})
+	}
+	return makeValue(res)
+}
+
+func valueInvoke(v ref, args []ref) (ref, bool)
+
+// New uses JavaScript's "new" operator with value v as constructor and the given arguments.
+// It panics if v is not a JavaScript function.
+// The arguments get mapped to JavaScript values according to the ValueOf function.
+func (v Value) New(args ...interface{}) Value {
+	argVals, argRefs := makeArgs(args)
+	res, ok := valueNew(v.ref, argRefs)
+	runtime.KeepAlive(v)
+	runtime.KeepAlive(argVals)
+	if !ok {
+		if vType := v.Type(); vType != TypeFunction { // check here to avoid overhead in success case
+			panic(&ValueError{"Value.Invoke", vType})
+		}
+		panic(Error{makeValue(res)})
+	}
+	return makeValue(res)
+}
+
+func valueNew(v ref, args []ref) (ref, bool)
+
+func (v Value) isNumber() bool {
+	return v.ref == valueZero.ref ||
+		v.ref == valueNaN.ref ||
+		(v.ref != valueUndefined.ref && (v.ref>>32)&nanHead != nanHead)
+}
+
+func (v Value) float(method string) float64 {
+	if !v.isNumber() {
+		panic(&ValueError{method, v.Type()})
+	}
+	if v.ref == valueZero.ref {
+		return 0
+	}
+	return *(*float64)(unsafe.Pointer(&v.ref))
+}
+
+// Float returns the value v as a float64.
+// It panics if v is not a JavaScript number.
+func (v Value) Float() float64 {
+	return v.float("Value.Float")
+}
+
+// Int returns the value v truncated to an int.
+// It panics if v is not a JavaScript number.
+func (v Value) Int() int {
+	return int(v.float("Value.Int"))
+}
+
+// Bool returns the value v as a bool.
+// It panics if v is not a JavaScript boolean.
+func (v Value) Bool() bool {
+	switch v.ref {
+	case valueTrue.ref:
+		return true
+	case valueFalse.ref:
+		return false
+	default:
+		panic(&ValueError{"Value.Bool", v.Type()})
+	}
+}
+
+// Truthy returns the JavaScript "truthiness" of the value v. In JavaScript,
+// false, 0, "", null, undefined, and NaN are "falsy", and everything else is
+// "truthy". See https://developer.mozilla.org/en-US/docs/Glossary/Truthy.
+func (v Value) Truthy() bool {
+	switch v.Type() {
+	case TypeUndefined, TypeNull:
+		return false
+	case TypeBoolean:
+		return v.Bool()
+	case TypeNumber:
+		return v.ref != valueNaN.ref && v.ref != valueZero.ref
+	case TypeString:
+		return v.String() != ""
+	case TypeSymbol, TypeFunction, TypeObject:
+		return true
+	default:
+		panic("bad type")
+	}
+}
+
+// String returns the value v as a string.
+// String is a special case because of Go's String method convention. Unlike the other getters,
+// it does not panic if v's Type is not TypeString. Instead, it returns a string of the form "<T>"
+// or "<T: V>" where T is v's type and V is a string representation of v's value.
+func (v Value) String() string {
+	switch v.Type() {
+	case TypeString:
+		return jsString(v)
+	case TypeUndefined:
+		return "<undefined>"
+	case TypeNull:
+		return "<null>"
+	case TypeBoolean:
+		return "<boolean: " + jsString(v) + ">"
+	case TypeNumber:
+		return "<number: " + jsString(v) + ">"
+	case TypeSymbol:
+		return "<symbol>"
+	case TypeObject:
+		return "<object>"
+	case TypeFunction:
+		return "<function>"
+	default:
+		panic("bad type")
+	}
+}
+
+func jsString(v Value) string {
+	str, length := valuePrepareString(v.ref)
+	runtime.KeepAlive(v)
+	b := make([]byte, length)
+	valueLoadString(str, b)
+	finalizeRef(str)
+	return string(b)
+}
+
+func valuePrepareString(v ref) (ref, int)
+
+func valueLoadString(v ref, b []byte)
+
+// InstanceOf reports whether v is an instance of type t according to JavaScript's instanceof operator.
+func (v Value) InstanceOf(t Value) bool {
+	r := valueInstanceOf(v.ref, t.ref)
+	runtime.KeepAlive(v)
+	runtime.KeepAlive(t)
+	return r
+}
+
+func valueInstanceOf(v ref, t ref) bool
+
+// A ValueError occurs when a Value method is invoked on
+// a Value that does not support it. Such cases are documented
+// in the description of each method.
+type ValueError struct {
+	Method string
+	Type   Type
+}
+
+func (e *ValueError) Error() string {
+	return "syscall/js: call of " + e.Method + " on " + e.Type.String()
+}
+
+// CopyBytesToGo copies bytes from src to dst.
+// It panics if src is not an Uint8Array or Uint8ClampedArray.
+// It returns the number of bytes copied, which will be the minimum of the lengths of src and dst.
+func CopyBytesToGo(dst []byte, src Value) int {
+	n, ok := copyBytesToGo(dst, src.ref)
+	runtime.KeepAlive(src)
+	if !ok {
+		panic("syscall/js: CopyBytesToGo: expected src to be an Uint8Array or Uint8ClampedArray")
+	}
+	return n
+}
+
+func copyBytesToGo(dst []byte, src ref) (int, bool)
+
+// CopyBytesToJS copies bytes from src to dst.
+// It panics if dst is not an Uint8Array or Uint8ClampedArray.
+// It returns the number of bytes copied, which will be the minimum of the lengths of src and dst.
+func CopyBytesToJS(dst Value, src []byte) int {
+	n, ok := copyBytesToJS(dst.ref, src)
+	runtime.KeepAlive(dst)
+	if !ok {
+		panic("syscall/js: CopyBytesToJS: expected dst to be an Uint8Array or Uint8ClampedArray")
+	}
+	return n
+}
+
+func copyBytesToJS(dst ref, src []byte) (int, bool)