github.com/goplusjs/gopherjs@v1.2.6-0.20211206034512-f187917453b8/compiler/natives/src/internal/reflectlite/value.go

// +build js

package reflectlite

import (
	"unsafe"

	"github.com/gopherjs/gopherjs/js"
)

func (v Value) object() *js.Object {
	if v.typ.Kind() == Array || v.typ.Kind() == Struct {
		return js.InternalObject(v.ptr)
	}
	if v.flag&flagIndir != 0 {
		val := js.InternalObject(v.ptr).Call("$get")
		if val != js.Global.Get("$ifaceNil") && val.Get("constructor") != jsType(v.typ) {
			switch v.typ.Kind() {
			case Uint64, Int64:
				val = jsType(v.typ).New(val.Get("$high"), val.Get("$low"))
			case Complex64, Complex128:
				val = jsType(v.typ).New(val.Get("$real"), val.Get("$imag"))
			case Slice:
				if val == val.Get("constructor").Get("nil") {
					val = jsType(v.typ).Get("nil")
					break
				}
				newVal := jsType(v.typ).New(val.Get("$array"))
				newVal.Set("$offset", val.Get("$offset"))
				newVal.Set("$length", val.Get("$length"))
				newVal.Set("$capacity", val.Get("$capacity"))
				val = newVal
			}
		}
		return js.InternalObject(val.Unsafe())
	}
	return js.InternalObject(v.ptr)
}

func (v Value) assignTo(context string, dst *rtype, target unsafe.Pointer) Value {
	if v.flag&flagMethod != 0 {
		v = makeMethodValue(context, v)
	}
	switch {
	case directlyAssignable(dst, v.typ):
		// Overwrite type so that they match.
		// Same memory layout, so no harm done.
		fl := v.flag&(flagAddr|flagIndir) | v.flag.ro()
		fl |= flag(dst.Kind())
		return Value{dst, v.ptr, fl}

	case implements(dst, v.typ):
		if target == nil {
			target = unsafe_New(dst)
		}
		// GopherJS: Skip the v.Kind() == Interface && v.IsNil() if statement
		//           from upstream. ifaceE2I below does not panic, and it needs
		//           to run, given its custom implementation.
		x := valueInterface(v)
		if dst.NumMethod() == 0 {
			*(*interface{})(target) = x
		} else {
			ifaceE2I(dst, x, target)
		}
		return Value{dst, target, flagIndir | flag(Interface)}
	}

	// Failed.
	panic(context + ": value of type " + v.typ.String() + " is not assignable to type " + dst.String())
}

var callHelper = js.Global.Get("$call").Interface().(func(...interface{}) *js.Object)

func (v Value) call(op string, in []Value) []Value {
	var (
		t    *funcType
		fn   unsafe.Pointer
		rcvr *js.Object
	)
	if v.flag&flagMethod != 0 {
		_, t, fn = methodReceiver(op, v, int(v.flag)>>flagMethodShift)
		rcvr = v.object()
		if isWrapped(v.typ) {
			rcvr = jsType(v.typ).New(rcvr)
		}
	} else {
		t = (*funcType)(unsafe.Pointer(v.typ))
		fn = unsafe.Pointer(v.object().Unsafe())
		rcvr = js.Undefined
	}

	if fn == nil {
		panic("reflect.Value.Call: call of nil function")
	}

	isSlice := op == "CallSlice"
	n := t.NumIn()
	if isSlice {
		if !t.IsVariadic() {
			panic("reflect: CallSlice of non-variadic function")
		}
		if len(in) < n {
			panic("reflect: CallSlice with too few input arguments")
		}
		if len(in) > n {
			panic("reflect: CallSlice with too many input arguments")
		}
	} else {
		if t.IsVariadic() {
			n--
		}
		if len(in) < n {
			panic("reflect: Call with too few input arguments")
		}
		if !t.IsVariadic() && len(in) > n {
			panic("reflect: Call with too many input arguments")
		}
	}
	for _, x := range in {
		if x.Kind() == Invalid {
			panic("reflect: " + op + " using zero Value argument")
		}
	}
	for i := 0; i < n; i++ {
		if xt, targ := in[i].Type(), t.In(i); !xt.AssignableTo(targ) {
			panic("reflect: " + op + " using " + xt.String() + " as type " + targ.String())
		}
	}
	if !isSlice && t.IsVariadic() {
		// prepare slice for remaining values
		m := len(in) - n
		slice := MakeSlice(t.In(n), m, m)
		elem := t.In(n).Elem()
		for i := 0; i < m; i++ {
			x := in[n+i]
			if xt := x.Type(); !xt.AssignableTo(elem) {
				panic("reflect: cannot use " + xt.String() + " as type " + elem.String() + " in " + op)
			}
			slice.Index(i).Set(x)
		}
		origIn := in
		in = make([]Value, n+1)
		copy(in[:n], origIn)
		in[n] = slice
	}

	nin := len(in)
	if nin != t.NumIn() {
		panic("reflect.Value.Call: wrong argument count")
	}
	nout := t.NumOut()

	argsArray := js.Global.Get("Array").New(t.NumIn())
	for i, arg := range in {
		argsArray.SetIndex(i, unwrapJsObject(t.In(i), arg.assignTo("reflect.Value.Call", t.In(i).common(), nil).object()))
	}
	results := callHelper(js.InternalObject(fn), rcvr, argsArray)

	switch nout {
	case 0:
		return nil
	case 1:
		return []Value{makeValue(t.Out(0), wrapJsObject(t.Out(0), results), 0)}
	default:
		ret := make([]Value, nout)
		for i := range ret {
			ret[i] = makeValue(t.Out(i), wrapJsObject(t.Out(i), results.Index(i)), 0)
		}
		return ret
	}
}

func (v Value) Cap() int {
	k := v.kind()
	switch k {
	case Array:
		return v.typ.Len()
	case Chan, Slice:
		return v.object().Get("$capacity").Int()
	}
	panic(&ValueError{"reflect.Value.Cap", k})
}

func (v Value) Index(i int) Value {
	switch k := v.kind(); k {
	case Array:
		tt := (*arrayType)(unsafe.Pointer(v.typ))
		if i < 0 || i > int(tt.len) {
			panic("reflect: array index out of range")
		}
		typ := tt.elem
		fl := v.flag&(flagIndir|flagAddr) | v.flag.ro() | flag(typ.Kind())

		a := js.InternalObject(v.ptr)
		if fl&flagIndir != 0 && typ.Kind() != Array && typ.Kind() != Struct {
			return Value{typ, unsafe.Pointer(jsType(PtrTo(typ)).New(
				js.InternalObject(func() *js.Object { return wrapJsObject(typ, a.Index(i)) }),
				js.InternalObject(func(x *js.Object) { a.SetIndex(i, unwrapJsObject(typ, x)) }),
			).Unsafe()), fl}
		}
		return makeValue(typ, wrapJsObject(typ, a.Index(i)), fl)

	case Slice:
		s := v.object()
		if i < 0 || i >= s.Get("$length").Int() {
			panic("reflect: slice index out of range")
		}
		tt := (*sliceType)(unsafe.Pointer(v.typ))
		typ := tt.elem
		fl := flagAddr | flagIndir | v.flag.ro() | flag(typ.Kind())

		i += s.Get("$offset").Int()
		a := s.Get("$array")
		if fl&flagIndir != 0 && typ.Kind() != Array && typ.Kind() != Struct {
			return Value{typ, unsafe.Pointer(jsType(PtrTo(typ)).New(
				js.InternalObject(func() *js.Object { return wrapJsObject(typ, a.Index(i)) }),
				js.InternalObject(func(x *js.Object) { a.SetIndex(i, unwrapJsObject(typ, x)) }),
			).Unsafe()), fl}
		}
		return makeValue(typ, wrapJsObject(typ, a.Index(i)), fl)

	case String:
		str := *(*string)(v.ptr)
		if i < 0 || i >= len(str) {
			panic("reflect: string index out of range")
		}
		fl := v.flag.ro() | flag(Uint8) | flagIndir
		c := str[i]
		return Value{uint8Type, unsafe.Pointer(&c), fl}

	default:
		panic(&ValueError{"reflect.Value.Index", k})
	}
}

func (v Value) InterfaceData() [2]uintptr {
	panic("InterfaceData is not supported by GopherJS")
}

func (v Value) IsNil() bool {
	switch k := v.kind(); k {
	case Ptr, Slice:
		return v.object() == jsType(v.typ).Get("nil")
	case Chan:
		return v.object() == js.Global.Get("$chanNil")
	case Func:
		return v.object() == js.Global.Get("$throwNilPointerError")
	case Map:
		return v.object() == js.InternalObject(false)
	case Interface:
		return v.object() == js.Global.Get("$ifaceNil")
	case UnsafePointer:
		return v.object().Unsafe() == 0
	default:
		panic(&ValueError{"reflect.Value.IsNil", k})
	}
}

func (v Value) Len() int {
	switch k := v.kind(); k {
	case Array, String:
		return v.object().Length()
	case Slice:
		return v.object().Get("$length").Int()
	case Chan:
		return v.object().Get("$buffer").Get("length").Int()
	case Map:
		return js.Global.Call("$keys", v.object()).Length()
	default:
		panic(&ValueError{"reflect.Value.Len", k})
	}
}

func (v Value) Pointer() uintptr {
	switch k := v.kind(); k {
	case Chan, Map, Ptr, UnsafePointer:
		if v.IsNil() {
			return 0
		}
		return v.object().Unsafe()
	case Func:
		if v.IsNil() {
			return 0
		}
		return 1
	case Slice:
		if v.IsNil() {
			return 0
		}
		return v.object().Get("$array").Unsafe()
	default:
		panic(&ValueError{"reflect.Value.Pointer", k})
	}
}

func (v Value) Set(x Value) {
	v.mustBeAssignable()
	x.mustBeExported()
	x = x.assignTo("reflect.Set", v.typ, nil)
	if v.flag&flagIndir != 0 {
		switch v.typ.Kind() {
		case Array:
			jsType(v.typ).Call("copy", js.InternalObject(v.ptr), js.InternalObject(x.ptr))
		case Interface:
			js.InternalObject(v.ptr).Call("$set", js.InternalObject(valueInterface(x)))
		case Struct:
			copyStruct(js.InternalObject(v.ptr), js.InternalObject(x.ptr), v.typ)
		default:
			js.InternalObject(v.ptr).Call("$set", x.object())
		}
		return
	}
	v.ptr = x.ptr
}

func (v Value) SetBytes(x []byte) {
	v.mustBeAssignable()
	v.mustBe(Slice)
	if v.typ.Elem().Kind() != Uint8 {
		panic("reflect.Value.SetBytes of non-byte slice")
	}
	slice := js.InternalObject(x)
	if v.typ.Name() != "" || v.typ.Elem().Name() != "" {
		typedSlice := jsType(v.typ).New(slice.Get("$array"))
		typedSlice.Set("$offset", slice.Get("$offset"))
		typedSlice.Set("$length", slice.Get("$length"))
		typedSlice.Set("$capacity", slice.Get("$capacity"))
		slice = typedSlice
	}
	js.InternalObject(v.ptr).Call("$set", slice)
}

func (v Value) SetCap(n int) {
	v.mustBeAssignable()
	v.mustBe(Slice)
	s := js.InternalObject(v.ptr).Call("$get")
	if n < s.Get("$length").Int() || n > s.Get("$capacity").Int() {
		panic("reflect: slice capacity out of range in SetCap")
	}
	newSlice := jsType(v.typ).New(s.Get("$array"))
	newSlice.Set("$offset", s.Get("$offset"))
	newSlice.Set("$length", s.Get("$length"))
	newSlice.Set("$capacity", n)
	js.InternalObject(v.ptr).Call("$set", newSlice)
}

func (v Value) SetLen(n int) {
	v.mustBeAssignable()
	v.mustBe(Slice)
	s := js.InternalObject(v.ptr).Call("$get")
	if n < 0 || n > s.Get("$capacity").Int() {
		panic("reflect: slice length out of range in SetLen")
	}
	newSlice := jsType(v.typ).New(s.Get("$array"))
	newSlice.Set("$offset", s.Get("$offset"))
	newSlice.Set("$length", n)
	newSlice.Set("$capacity", s.Get("$capacity"))
	js.InternalObject(v.ptr).Call("$set", newSlice)
}

func (v Value) Slice(i, j int) Value {
	var (
		cap int
		typ Type
		s   *js.Object
	)
	switch kind := v.kind(); kind {
	case Array:
		if v.flag&flagAddr == 0 {
			panic("reflect.Value.Slice: slice of unaddressable array")
		}
		tt := (*arrayType)(unsafe.Pointer(v.typ))
		cap = int(tt.len)
		typ = SliceOf(tt.elem)
		s = jsType(typ).New(v.object())

	case Slice:
		typ = v.typ
		s = v.object()
		cap = s.Get("$capacity").Int()

	case String:
		str := *(*string)(v.ptr)
		if i < 0 || j < i || j > len(str) {
			panic("reflect.Value.Slice: string slice index out of bounds")
		}
		return ValueOf(str[i:j])

	default:
		panic(&ValueError{"reflect.Value.Slice", kind})
	}

	if i < 0 || j < i || j > cap {
		panic("reflect.Value.Slice: slice index out of bounds")
	}

	return makeValue(typ, js.Global.Call("$subslice", s, i, j), v.flag.ro())
}

func (v Value) Slice3(i, j, k int) Value {
	var (
		cap int
		typ Type
		s   *js.Object
	)
	switch kind := v.kind(); kind {
	case Array:
		if v.flag&flagAddr == 0 {
			panic("reflect.Value.Slice: slice of unaddressable array")
		}
		tt := (*arrayType)(unsafe.Pointer(v.typ))
		cap = int(tt.len)
		typ = SliceOf(tt.elem)
		s = jsType(typ).New(v.object())

	case Slice:
		typ = v.typ
		s = v.object()
		cap = s.Get("$capacity").Int()

	default:
		panic(&ValueError{"reflect.Value.Slice3", kind})
	}

	if i < 0 || j < i || k < j || k > cap {
		panic("reflect.Value.Slice3: slice index out of bounds")
	}

	return makeValue(typ, js.Global.Call("$subslice", s, i, j, k), v.flag.ro())
}

func (v Value) Close() {
	v.mustBe(Chan)
	v.mustBeExported()
	js.Global.Call("$close", v.object())
}

func (v Value) Elem() Value {
	switch k := v.kind(); k {
	case Interface:
		val := v.object()
		if val == js.Global.Get("$ifaceNil") {
			return Value{}
		}
		typ := reflectType(val.Get("constructor"))
		return makeValue(typ, val.Get("$val"), v.flag.ro())

	case Ptr:
		if v.IsNil() {
			return Value{}
		}
		val := v.object()
		tt := (*ptrType)(unsafe.Pointer(v.typ))
		fl := v.flag&flagRO | flagIndir | flagAddr
		fl |= flag(tt.elem.Kind())
		return Value{tt.elem, unsafe.Pointer(wrapJsObject(tt.elem, val).Unsafe()), fl}

	default:
		panic(&ValueError{"reflect.Value.Elem", k})
	}
}

// NumField returns the number of fields in the struct v.
// It panics if v's Kind is not Struct.
func (v Value) NumField() int {
	v.mustBe(Struct)
	tt := (*structType)(unsafe.Pointer(v.typ))
	return len(tt.fields)
}

// MapKeys returns a slice containing all the keys present in the map,
// in unspecified order.
// It panics if v's Kind is not Map.
// It returns an empty slice if v represents a nil map.
func (v Value) MapKeys() []Value {
	v.mustBe(Map)
	tt := (*mapType)(unsafe.Pointer(v.typ))
	keyType := tt.key

	fl := v.flag.ro() | flag(keyType.Kind())

	m := v.pointer()
	mlen := int(0)
	if m != nil {
		mlen = maplen(m)
	}
	it := mapiterinit(v.typ, m)
	a := make([]Value, mlen)
	var i int
	for i = 0; i < len(a); i++ {
		key := mapiterkey(it)
		if key == nil {
			// Someone deleted an entry from the map since we
			// called maplen above. It's a data race, but nothing
			// we can do about it.
			break
		}
		a[i] = copyVal(keyType, fl, key)
		mapiternext(it)
	}
	return a[:i]
}

// MapIndex returns the value associated with key in the map v.
// It panics if v's Kind is not Map.
// It returns the zero Value if key is not found in the map or if v represents a nil map.
// As in Go, the key's value must be assignable to the map's key type.
func (v Value) MapIndex(key Value) Value {
	v.mustBe(Map)
	tt := (*mapType)(unsafe.Pointer(v.typ))

	// Do not require key to be exported, so that DeepEqual
	// and other programs can use all the keys returned by
	// MapKeys as arguments to MapIndex. If either the map
	// or the key is unexported, though, the result will be
	// considered unexported. This is consistent with the
	// behavior for structs, which allow read but not write
	// of unexported fields.
	key = key.assignTo("reflect.Value.MapIndex", tt.key, nil)

	var k unsafe.Pointer
	if key.flag&flagIndir != 0 {
		k = key.ptr
	} else {
		k = unsafe.Pointer(&key.ptr)
	}
	e := mapaccess(v.typ, v.pointer(), k)
	if e == nil {
		return Value{}
	}
	typ := tt.elem
	fl := (v.flag | key.flag).ro()
	fl |= flag(typ.Kind())
	return copyVal(typ, fl, e)
}

func (v Value) Field(i int) Value {
	if v.kind() != Struct {
		panic(&ValueError{"reflect.Value.Field", v.kind()})
	}
	tt := (*structType)(unsafe.Pointer(v.typ))
	if uint(i) >= uint(len(tt.fields)) {
		panic("reflect: Field index out of range")
	}

	prop := jsType(v.typ).Get("fields").Index(i).Get("prop").String()
	field := &tt.fields[i]
	typ := field.typ

	fl := v.flag&(flagStickyRO|flagIndir|flagAddr) | flag(typ.Kind())
	if !field.name.isExported() {
		if field.embedded() {
			fl |= flagEmbedRO
		} else {
			fl |= flagStickyRO
		}
	}

	if tag := tt.fields[i].name.tag(); tag != "" && i != 0 {
		if jsTag := getJsTag(tag); jsTag != "" {
			for {
				v = v.Field(0)
				if v.typ == jsObjectPtr {
					o := v.object().Get("object")
					return Value{typ, unsafe.Pointer(jsType(PtrTo(typ)).New(
						js.InternalObject(func() *js.Object { return js.Global.Call("$internalize", o.Get(jsTag), jsType(typ)) }),
						js.InternalObject(func(x *js.Object) { o.Set(jsTag, js.Global.Call("$externalize", x, jsType(typ))) }),
					).Unsafe()), fl}
				}
				if v.typ.Kind() == Ptr {
					v = v.Elem()
				}
			}
		}
	}

	s := js.InternalObject(v.ptr)
	if fl&flagIndir != 0 && typ.Kind() != Array && typ.Kind() != Struct {
		return Value{typ, unsafe.Pointer(jsType(PtrTo(typ)).New(
			js.InternalObject(func() *js.Object { return wrapJsObject(typ, s.Get(prop)) }),
			js.InternalObject(func(x *js.Object) { s.Set(prop, unwrapJsObject(typ, x)) }),
		).Unsafe()), fl}
	}
	return makeValue(typ, wrapJsObject(typ, s.Get(prop)), fl)
}