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// Copyright 2009 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.
package reflect
import (
"math"
"runtime"
"strconv"
"unsafe"
)
const ptrSize = unsafe.Sizeof((*byte)(nil))
const cannotSet = "cannot set value obtained from unexported struct field"
// TODO: This will have to go away when
// the new gc goes in.
func memmove(adst, asrc unsafe.Pointer, n uintptr) {
dst := uintptr(adst)
src := uintptr(asrc)
switch {
case src < dst && src+n > dst:
// byte copy backward
// careful: i is unsigned
for i := n; i > 0; {
i--
*(*byte)(unsafe.Pointer(dst + i)) = *(*byte)(unsafe.Pointer(src + i))
}
case (n|src|dst)&(ptrSize-1) != 0:
// byte copy forward
for i := uintptr(0); i < n; i++ {
*(*byte)(unsafe.Pointer(dst + i)) = *(*byte)(unsafe.Pointer(src + i))
}
default:
// word copy forward
for i := uintptr(0); i < n; i += ptrSize {
*(*uintptr)(unsafe.Pointer(dst + i)) = *(*uintptr)(unsafe.Pointer(src + i))
}
}
}
// Value is the reflection interface to a Go value.
//
// Not all methods apply to all kinds of values. Restrictions,
// if any, are noted in the documentation for each method.
// Use the Kind method to find out the kind of value before
// calling kind-specific methods. Calling a method
// inappropriate to the kind of type causes a run time panic.
//
// The zero Value represents no value.
// Its IsValid method returns false, its Kind method returns Invalid,
// its String method returns "<invalid Value>", and all other methods panic.
// Most functions and methods never return an invalid value.
// If one does, its documentation states the conditions explicitly.
//
// The fields of Value are exported so that clients can copy and
// pass Values around, but they should not be edited or inspected
// directly. A future language change may make it possible not to
// export these fields while still keeping Values usable as values.
type Value struct {
Internal interface{}
InternalMethod int
}
// 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
Kind Kind
}
func (e *ValueError) String() string {
if e.Kind == 0 {
return "reflect: call of " + e.Method + " on zero Value"
}
return "reflect: call of " + e.Method + " on " + e.Kind.String() + " Value"
}
// methodName returns the name of the calling method,
// assumed to be two stack frames above.
func methodName() string {
pc, _, _, _ := runtime.Caller(2)
f := runtime.FuncForPC(pc)
if f == nil {
return "unknown method"
}
return f.Name()
}
// An iword is the word that would be stored in an
// interface to represent a given value v. Specifically, if v is
// bigger than a pointer, its word is a pointer to v's data.
// Otherwise, its word is a zero uintptr with the data stored
// in the leading bytes.
type iword uintptr
func loadIword(p unsafe.Pointer, size uintptr) iword {
// Run the copy ourselves instead of calling memmove
// to avoid moving v to the heap.
w := iword(0)
switch size {
default:
panic("reflect: internal error: loadIword of " + strconv.Itoa(int(size)) + "-byte value")
case 0:
case 1:
*(*uint8)(unsafe.Pointer(&w)) = *(*uint8)(p)
case 2:
*(*uint16)(unsafe.Pointer(&w)) = *(*uint16)(p)
case 3:
*(*[3]byte)(unsafe.Pointer(&w)) = *(*[3]byte)(p)
case 4:
*(*uint32)(unsafe.Pointer(&w)) = *(*uint32)(p)
case 5:
*(*[5]byte)(unsafe.Pointer(&w)) = *(*[5]byte)(p)
case 6:
*(*[6]byte)(unsafe.Pointer(&w)) = *(*[6]byte)(p)
case 7:
*(*[7]byte)(unsafe.Pointer(&w)) = *(*[7]byte)(p)
case 8:
*(*uint64)(unsafe.Pointer(&w)) = *(*uint64)(p)
}
return w
}
func storeIword(p unsafe.Pointer, w iword, size uintptr) {
// Run the copy ourselves instead of calling memmove
// to avoid moving v to the heap.
switch size {
default:
panic("reflect: internal error: storeIword of " + strconv.Itoa(int(size)) + "-byte value")
case 0:
case 1:
*(*uint8)(p) = *(*uint8)(unsafe.Pointer(&w))
case 2:
*(*uint16)(p) = *(*uint16)(unsafe.Pointer(&w))
case 3:
*(*[3]byte)(p) = *(*[3]byte)(unsafe.Pointer(&w))
case 4:
*(*uint32)(p) = *(*uint32)(unsafe.Pointer(&w))
case 5:
*(*[5]byte)(p) = *(*[5]byte)(unsafe.Pointer(&w))
case 6:
*(*[6]byte)(p) = *(*[6]byte)(unsafe.Pointer(&w))
case 7:
*(*[7]byte)(p) = *(*[7]byte)(unsafe.Pointer(&w))
case 8:
*(*uint64)(p) = *(*uint64)(unsafe.Pointer(&w))
}
}
// emptyInterface is the header for an interface{} value.
type emptyInterface struct {
typ *runtime.Type
word iword
}
// nonEmptyInterface is the header for a interface value with methods.
type nonEmptyInterface struct {
// see ../runtime/iface.c:/Itab
itab *struct {
ityp *runtime.Type // static interface type
typ *runtime.Type // dynamic concrete type
link unsafe.Pointer
bad int32
unused int32
fun [100000]unsafe.Pointer // method table
}
word iword
}
// Regarding the implementation of Value:
//
// The Internal interface is a true interface value in the Go sense,
// but it also serves as a (type, address) pair in which one cannot
// be changed separately from the other. That is, it serves as a way
// to prevent unsafe mutations of the Internal state even though
// we cannot (yet?) hide the field while preserving the ability for
// clients to make copies of Values.
//
// The internal method converts a Value into the expanded internalValue struct.
// If we could avoid exporting fields we'd probably make internalValue the
// definition of Value.
//
// If a Value is addressable (CanAddr returns true), then the Internal
// interface value holds a pointer to the actual field data, and Set stores
// through that pointer. If a Value is not addressable (CanAddr returns false),
// then the Internal interface value holds the actual value.
//
// In addition to whether a value is addressable, we track whether it was
// obtained by using an unexported struct field. Such values are allowed
// to be read, mainly to make fmt.Print more useful, but they are not
// allowed to be written. We call such values read-only.
//
// A Value can be set (via the Set, SetUint, etc. methods) only if it is both
// addressable and not read-only.
//
// The two permission bits - addressable and read-only - are stored in
// the bottom two bits of the type pointer in the interface value.
//
// ordinary value: Internal = value
// addressable value: Internal = value, Internal.typ |= flagAddr
// read-only value: Internal = value, Internal.typ |= flagRO
// addressable, read-only value: Internal = value, Internal.typ |= flagAddr | flagRO
//
// It is important that the read-only values have the extra bit set
// (as opposed to using the bit to mean writable), because client code
// can grab the interface field and try to use it. Having the extra bit
// set makes the type pointer compare not equal to any real type,
// so that a client cannot, say, write through v.Internal.(*int).
// The runtime routines that access interface types reject types with
// low bits set.
//
// If a Value fv = v.Method(i), then fv = v with the InternalMethod
// field set to i+1. Methods are never addressable.
//
// All in all, this is a lot of effort just to avoid making this new API
// depend on a language change we'll probably do anyway, but
// it's helpful to keep the two separate, and much of the logic is
// necessary to implement the Interface method anyway.
const (
flagAddr uint32 = 1 << iota // holds address of value
flagRO // read-only
reflectFlags = 3
)
// An internalValue is the unpacked form of a Value.
// The zero Value unpacks to a zero internalValue
type internalValue struct {
typ *commonType // type of value
kind Kind // kind of value
flag uint32
word iword
addr unsafe.Pointer
rcvr iword
method bool
nilmethod bool
}
func (v Value) internal() internalValue {
var iv internalValue
eface := *(*emptyInterface)(unsafe.Pointer(&v.Internal))
p := uintptr(unsafe.Pointer(eface.typ))
iv.typ = toCommonType((*runtime.Type)(unsafe.Pointer(p &^ reflectFlags)))
if iv.typ == nil {
return iv
}
iv.flag = uint32(p & reflectFlags)
iv.word = eface.word
if iv.flag&flagAddr != 0 {
iv.addr = unsafe.Pointer(iv.word)
iv.typ = iv.typ.Elem().common()
if iv.typ.size <= ptrSize {
iv.word = loadIword(iv.addr, iv.typ.size)
}
} else {
if iv.typ.size > ptrSize {
iv.addr = unsafe.Pointer(iv.word)
}
}
iv.kind = iv.typ.Kind()
// Is this a method? If so, iv describes the receiver.
// Rewrite to describe the method function.
if v.InternalMethod != 0 {
// If this Value is a method value (x.Method(i) for some Value x)
// then we will invoke it using the interface form of the method,
// which always passes the receiver as a single word.
// Record that information.
i := v.InternalMethod - 1
if iv.kind == Interface {
it := (*interfaceType)(unsafe.Pointer(iv.typ))
if i < 0 || i >= len(it.methods) {
panic("reflect: broken Value")
}
m := &it.methods[i]
if m.pkgPath != nil {
iv.flag |= flagRO
}
iv.typ = toCommonType(m.typ)
iface := (*nonEmptyInterface)(iv.addr)
if iface.itab == nil {
iv.word = 0
iv.nilmethod = true
} else {
iv.word = iword(iface.itab.fun[i])
}
iv.rcvr = iface.word
} else {
ut := iv.typ.uncommon()
if ut == nil || i < 0 || i >= len(ut.methods) {
panic("reflect: broken Value")
}
m := &ut.methods[i]
if m.pkgPath != nil {
iv.flag |= flagRO
}
iv.typ = toCommonType(m.mtyp)
iv.rcvr = iv.word
iv.word = iword(m.ifn)
}
iv.kind = Func
iv.method = true
iv.flag &^= flagAddr
iv.addr = nil
}
return iv
}
// packValue returns a Value with the given flag bits, type, and interface word.
func packValue(flag uint32, typ *runtime.Type, word iword) Value {
if typ == nil {
panic("packValue")
}
t := uintptr(unsafe.Pointer(typ))
t |= uintptr(flag)
eface := emptyInterface{(*runtime.Type)(unsafe.Pointer(t)), word}
return Value{Internal: *(*interface{})(unsafe.Pointer(&eface))}
}
// valueFromAddr returns a Value using the given type and address.
func valueFromAddr(flag uint32, typ Type, addr unsafe.Pointer) Value {
if flag&flagAddr != 0 {
// Addressable, so the internal value is
// an interface containing a pointer to the real value.
return packValue(flag, PtrTo(typ).runtimeType(), iword(addr))
}
var w iword
if n := typ.Size(); n <= ptrSize {
// In line, so the interface word is the actual value.
w = loadIword(addr, n)
} else {
// Not in line: the interface word is the address.
w = iword(addr)
}
return packValue(flag, typ.runtimeType(), w)
}
// valueFromIword returns a Value using the given type and interface word.
func valueFromIword(flag uint32, typ Type, w iword) Value {
if flag&flagAddr != 0 {
panic("reflect: internal error: valueFromIword addressable")
}
return packValue(flag, typ.runtimeType(), w)
}
func (iv internalValue) mustBe(want Kind) {
if iv.kind != want {
panic(&ValueError{methodName(), iv.kind})
}
}
func (iv internalValue) mustBeExported() {
if iv.kind == 0 {
panic(&ValueError{methodName(), iv.kind})
}
if iv.flag&flagRO != 0 {
panic(methodName() + " using value obtained using unexported field")
}
}
func (iv internalValue) mustBeAssignable() {
if iv.kind == 0 {
panic(&ValueError{methodName(), iv.kind})
}
// Assignable if addressable and not read-only.
if iv.flag&flagRO != 0 {
panic(methodName() + " using value obtained using unexported field")
}
if iv.flag&flagAddr == 0 {
panic(methodName() + " using unaddressable value")
}
}
// Addr returns a pointer value representing the address of v.
// It panics if CanAddr() returns false.
// Addr is typically used to obtain a pointer to a struct field
// or slice element in order to call a method that requires a
// pointer receiver.
func (v Value) Addr() Value {
iv := v.internal()
if iv.flag&flagAddr == 0 {
panic("reflect.Value.Addr of unaddressable value")
}
return valueFromIword(iv.flag&flagRO, PtrTo(iv.typ.toType()), iword(iv.addr))
}
// Bool returns v's underlying value.
// It panics if v's kind is not Bool.
func (v Value) Bool() bool {
iv := v.internal()
iv.mustBe(Bool)
return *(*bool)(unsafe.Pointer(&iv.word))
}
// CanAddr returns true if the value's address can be obtained with Addr.
// Such values are called addressable. A value is addressable if it is
// an element of a slice, an element of an addressable array,
// a field of an addressable struct, or the result of dereferencing a pointer.
// If CanAddr returns false, calling Addr will panic.
func (v Value) CanAddr() bool {
iv := v.internal()
return iv.flag&flagAddr != 0
}
// CanSet returns true if the value of v can be changed.
// A Value can be changed only if it is addressable and was not
// obtained by the use of unexported struct fields.
// If CanSet returns false, calling Set or any type-specific
// setter (e.g., SetBool, SetInt64) will panic.
func (v Value) CanSet() bool {
iv := v.internal()
return iv.flag&(flagAddr|flagRO) == flagAddr
}
// Call calls the function v with the input arguments in.
// For example, if len(in) == 3, v.Call(in) represents the Go call v(in[0], in[1], in[2]).
// Call panics if v's Kind is not Func.
// It returns the output results as Values.
// As in Go, each input argument must be assignable to the
// type of the function's corresponding input parameter.
// If v is a variadic function, Call creates the variadic slice parameter
// itself, copying in the corresponding values.
func (v Value) Call(in []Value) []Value {
iv := v.internal()
iv.mustBe(Func)
iv.mustBeExported()
return iv.call("Call", in)
}
// CallSlice calls the variadic function v with the input arguments in,
// assigning the slice in[len(in)-1] to v's final variadic argument.
// For example, if len(in) == 3, v.Call(in) represents the Go call v(in[0], in[1], in[2]...).
// Call panics if v's Kind is not Func or if v is not variadic.
// It returns the output results as Values.
// As in Go, each input argument must be assignable to the
// type of the function's corresponding input parameter.
func (v Value) CallSlice(in []Value) []Value {
iv := v.internal()
iv.mustBe(Func)
iv.mustBeExported()
return iv.call("CallSlice", in)
}
func (iv internalValue) call(method string, in []Value) []Value {
if iv.word == 0 {
if iv.nilmethod {
panic("reflect.Value.Call: call of method on nil interface value")
}
panic("reflect.Value.Call: call of nil function")
}
isSlice := method == "CallSlice"
t := iv.typ
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: " + method + " using zero Value argument")
}
}
for i := 0; i < n; i++ {
if xt, targ := in[i].Type(), t.In(i); !xt.AssignableTo(targ) {
panic("reflect: " + method + " 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 " + method)
}
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()
// Compute arg size & allocate.
// This computation is 5g/6g/8g-dependent
// and probably wrong for gccgo, but so
// is most of this function.
size := uintptr(0)
if iv.method {
// extra word for interface value
size += ptrSize
}
for i := 0; i < nin; i++ {
tv := t.In(i)
a := uintptr(tv.Align())
size = (size + a - 1) &^ (a - 1)
size += tv.Size()
}
size = (size + ptrSize - 1) &^ (ptrSize - 1)
for i := 0; i < nout; i++ {
tv := t.Out(i)
a := uintptr(tv.Align())
size = (size + a - 1) &^ (a - 1)
size += tv.Size()
}
// size must be > 0 in order for &args[0] to be valid.
// the argument copying is going to round it up to
// a multiple of ptrSize anyway, so make it ptrSize to begin with.
if size < ptrSize {
size = ptrSize
}
// round to pointer size
size = (size + ptrSize - 1) &^ (ptrSize - 1)
// Copy into args.
//
// TODO(rsc): revisit when reference counting happens.
// The values are holding up the in references for us,
// but something must be done for the out references.
// For now make everything look like a pointer by pretending
// to allocate a []*int.
args := make([]*int, size/ptrSize)
ptr := uintptr(unsafe.Pointer(&args[0]))
off := uintptr(0)
if iv.method {
// Hard-wired first argument.
*(*iword)(unsafe.Pointer(ptr)) = iv.rcvr
off = ptrSize
}
for i, v := range in {
iv := v.internal()
iv.mustBeExported()
targ := t.In(i).(*commonType)
a := uintptr(targ.align)
off = (off + a - 1) &^ (a - 1)
n := targ.size
addr := unsafe.Pointer(ptr + off)
iv = convertForAssignment("reflect.Value.Call", addr, targ, iv)
if iv.addr == nil {
storeIword(addr, iv.word, n)
} else {
memmove(addr, iv.addr, n)
}
off += n
}
off = (off + ptrSize - 1) &^ (ptrSize - 1)
// Call.
call(unsafe.Pointer(iv.word), unsafe.Pointer(ptr), uint32(size))
// Copy return values out of args.
//
// TODO(rsc): revisit like above.
ret := make([]Value, nout)
for i := 0; i < nout; i++ {
tv := t.Out(i)
a := uintptr(tv.Align())
off = (off + a - 1) &^ (a - 1)
ret[i] = valueFromAddr(0, tv, unsafe.Pointer(ptr+off))
off += tv.Size()
}
return ret
}
// Cap returns v's capacity.
// It panics if v's Kind is not Array, Chan, or Slice.
func (v Value) Cap() int {
iv := v.internal()
switch iv.kind {
case Array:
return iv.typ.Len()
case Chan:
return int(chancap(iv.word))
case Slice:
return (*SliceHeader)(iv.addr).Cap
}
panic(&ValueError{"reflect.Value.Cap", iv.kind})
}
// Close closes the channel v.
// It panics if v's Kind is not Chan.
func (v Value) Close() {
iv := v.internal()
iv.mustBe(Chan)
iv.mustBeExported()
ch := iv.word
chanclose(ch)
}
// Complex returns v's underlying value, as a complex128.
// It panics if v's Kind is not Complex64 or Complex128
func (v Value) Complex() complex128 {
iv := v.internal()
switch iv.kind {
case Complex64:
if iv.addr == nil {
return complex128(*(*complex64)(unsafe.Pointer(&iv.word)))
}
return complex128(*(*complex64)(iv.addr))
case Complex128:
return *(*complex128)(iv.addr)
}
panic(&ValueError{"reflect.Value.Complex", iv.kind})
}
// Elem returns the value that the interface v contains
// or that the pointer v points to.
// It panics if v's Kind is not Interface or Ptr.
// It returns the zero Value if v is nil.
func (v Value) Elem() Value {
iv := v.internal()
return iv.Elem()
}
func (iv internalValue) Elem() Value {
switch iv.kind {
case Interface:
// Empty interface and non-empty interface have different layouts.
// Convert to empty interface.
var eface emptyInterface
if iv.typ.NumMethod() == 0 {
eface = *(*emptyInterface)(iv.addr)
} else {
iface := (*nonEmptyInterface)(iv.addr)
if iface.itab != nil {
eface.typ = iface.itab.typ
}
eface.word = iface.word
}
if eface.typ == nil {
return Value{}
}
return valueFromIword(iv.flag&flagRO, toType(eface.typ), eface.word)
case Ptr:
// The returned value's address is v's value.
if iv.word == 0 {
return Value{}
}
return valueFromAddr(iv.flag&flagRO|flagAddr, iv.typ.Elem(), unsafe.Pointer(iv.word))
}
panic(&ValueError{"reflect.Value.Elem", iv.kind})
}
// Field returns the i'th field of the struct v.
// It panics if v's Kind is not Struct or i is out of range.
func (v Value) Field(i int) Value {
iv := v.internal()
iv.mustBe(Struct)
t := iv.typ.toType()
if i < 0 || i >= t.NumField() {
panic("reflect: Field index out of range")
}
f := t.Field(i)
// Inherit permission bits from v.
flag := iv.flag
// Using an unexported field forces flagRO.
if f.PkgPath != "" {
flag |= flagRO
}
return valueFromValueOffset(flag, f.Type, iv, f.Offset)
}
// valueFromValueOffset returns a sub-value of outer
// (outer is an array or a struct) with the given flag and type
// starting at the given byte offset into outer.
func valueFromValueOffset(flag uint32, typ Type, outer internalValue, offset uintptr) Value {
if outer.addr != nil {
return valueFromAddr(flag, typ, unsafe.Pointer(uintptr(outer.addr)+offset))
}
// outer is so tiny it is in line.
// We have to use outer.word and derive
// the new word (it cannot possibly be bigger).
// In line, so not addressable.
if flag&flagAddr != 0 {
panic("reflect: internal error: misuse of valueFromValueOffset")
}
b := *(*[ptrSize]byte)(unsafe.Pointer(&outer.word))
for i := uintptr(0); i < typ.Size(); i++ {
b[i] = b[offset+i]
}
for i := typ.Size(); i < ptrSize; i++ {
b[i] = 0
}
w := *(*iword)(unsafe.Pointer(&b))
return valueFromIword(flag, typ, w)
}
// FieldByIndex returns the nested field corresponding to index.
// It panics if v's Kind is not struct.
func (v Value) FieldByIndex(index []int) Value {
v.internal().mustBe(Struct)
for i, x := range index {
if i > 0 {
if v.Kind() == Ptr && v.Elem().Kind() == Struct {
v = v.Elem()
}
}
v = v.Field(x)
}
return v
}
// FieldByName returns the struct field with the given name.
// It returns the zero Value if no field was found.
// It panics if v's Kind is not struct.
func (v Value) FieldByName(name string) Value {
iv := v.internal()
iv.mustBe(Struct)
if f, ok := iv.typ.FieldByName(name); ok {
return v.FieldByIndex(f.Index)
}
return Value{}
}
// FieldByNameFunc returns the struct field with a name
// that satisfies the match function.
// It panics if v's Kind is not struct.
// It returns the zero Value if no field was found.
func (v Value) FieldByNameFunc(match func(string) bool) Value {
v.internal().mustBe(Struct)
if f, ok := v.Type().FieldByNameFunc(match); ok {
return v.FieldByIndex(f.Index)
}
return Value{}
}
// Float returns v's underlying value, as an float64.
// It panics if v's Kind is not Float32 or Float64
func (v Value) Float() float64 {
iv := v.internal()
switch iv.kind {
case Float32:
return float64(*(*float32)(unsafe.Pointer(&iv.word)))
case Float64:
// If the pointer width can fit an entire float64,
// the value is in line when stored in an interface.
if iv.addr == nil {
return *(*float64)(unsafe.Pointer(&iv.word))
}
// Otherwise we have a pointer.
return *(*float64)(iv.addr)
}
panic(&ValueError{"reflect.Value.Float", iv.kind})
}
// Index returns v's i'th element.
// It panics if v's Kind is not Array or Slice or i is out of range.
func (v Value) Index(i int) Value {
iv := v.internal()
switch iv.kind {
default:
panic(&ValueError{"reflect.Value.Index", iv.kind})
case Array:
flag := iv.flag // element flag same as overall array
t := iv.typ.toType()
if i < 0 || i > t.Len() {
panic("reflect: array index out of range")
}
typ := t.Elem()
return valueFromValueOffset(flag, typ, iv, uintptr(i)*typ.Size())
case Slice:
// Element flag same as Elem of Ptr.
// Addressable, possibly read-only.
flag := iv.flag&flagRO | flagAddr
s := (*SliceHeader)(iv.addr)
if i < 0 || i >= s.Len {
panic("reflect: slice index out of range")
}
typ := iv.typ.Elem()
addr := unsafe.Pointer(s.Data + uintptr(i)*typ.Size())
return valueFromAddr(flag, typ, addr)
}
panic("not reached")
}
// Int returns v's underlying value, as an int64.
// It panics if v's Kind is not Int, Int8, Int16, Int32, or Int64.
func (v Value) Int() int64 {
iv := v.internal()
switch iv.kind {
case Int:
return int64(*(*int)(unsafe.Pointer(&iv.word)))
case Int8:
return int64(*(*int8)(unsafe.Pointer(&iv.word)))
case Int16:
return int64(*(*int16)(unsafe.Pointer(&iv.word)))
case Int32:
return int64(*(*int32)(unsafe.Pointer(&iv.word)))
case Int64:
if iv.addr == nil {
return *(*int64)(unsafe.Pointer(&iv.word))
}
return *(*int64)(iv.addr)
}
panic(&ValueError{"reflect.Value.Int", iv.kind})
}
// CanInterface returns true if Interface can be used without panicking.
func (v Value) CanInterface() bool {
iv := v.internal()
if iv.kind == Invalid {
panic(&ValueError{"reflect.Value.CanInterface", iv.kind})
}
return v.InternalMethod == 0 && iv.flag&flagRO == 0
}
// Interface returns v's value as an interface{}.
// If v is a method obtained by invoking Value.Method
// (as opposed to Type.Method), Interface cannot return an
// interface value, so it panics.
func (v Value) Interface() interface{} {
return valueInterface(v, true)
}
func valueInterface(v Value, safe bool) interface{} {
iv := v.internal()
return iv.valueInterface(safe)
}
func (iv internalValue) valueInterface(safe bool) interface{} {
if iv.kind == 0 {
panic(&ValueError{"reflect.Value.Interface", iv.kind})
}
if iv.method {
panic("reflect.Value.Interface: cannot create interface value for method with bound receiver")
}
if safe && iv.flag&flagRO != 0 {
// Do not allow access to unexported values via Interface,
// because they might be pointers that should not be
// writable or methods or function that should not be callable.
panic("reflect.Value.Interface: cannot return value obtained from unexported field or method")
}
if iv.kind == Interface {
// Special case: return the element inside the interface.
// Won't recurse further because an interface cannot contain an interface.
if iv.IsNil() {
return nil
}
return iv.Elem().Interface()
}
// Non-interface value.
var eface emptyInterface
eface.typ = iv.typ.runtimeType()
eface.word = iv.word
return *(*interface{})(unsafe.Pointer(&eface))
}
// InterfaceData returns the interface v's value as a uintptr pair.
// It panics if v's Kind is not Interface.
func (v Value) InterfaceData() [2]uintptr {
iv := v.internal()
iv.mustBe(Interface)
// We treat this as a read operation, so we allow
// it even for unexported data, because the caller
// has to import "unsafe" to turn it into something
// that can be abused.
return *(*[2]uintptr)(iv.addr)
}
// IsNil returns true if v is a nil value.
// It panics if v's Kind is not Chan, Func, Interface, Map, Ptr, or Slice.
func (v Value) IsNil() bool {
return v.internal().IsNil()
}
func (iv internalValue) IsNil() bool {
switch iv.kind {
case Chan, Func, Map, Ptr:
if iv.method {
panic("reflect: IsNil of method Value")
}
return iv.word == 0
case Interface, Slice:
// Both interface and slice are nil if first word is 0.
return *(*uintptr)(iv.addr) == 0
}
panic(&ValueError{"reflect.Value.IsNil", iv.kind})
}
// IsValid returns true if v represents a value.
// It returns false if v is the zero Value.
// If IsValid returns false, all other methods except String panic.
// Most functions and methods never return an invalid value.
// If one does, its documentation states the conditions explicitly.
func (v Value) IsValid() bool {
return v.Internal != nil
}
// Kind returns v's Kind.
// If v is the zero Value (IsValid returns false), Kind returns Invalid.
func (v Value) Kind() Kind {
return v.internal().kind
}
// Len returns v's length.
// It panics if v's Kind is not Array, Chan, Map, Slice, or String.
func (v Value) Len() int {
iv := v.internal()
switch iv.kind {
case Array:
return iv.typ.Len()
case Chan:
return int(chanlen(iv.word))
case Map:
return int(maplen(iv.word))
case Slice:
return (*SliceHeader)(iv.addr).Len
case String:
return (*StringHeader)(iv.addr).Len
}
panic(&ValueError{"reflect.Value.Len", iv.kind})
}
// 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 {
iv := v.internal()
iv.mustBe(Map)
typ := iv.typ.toType()
// Do not require ikey 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.
ikey := key.internal()
ikey = convertForAssignment("reflect.Value.MapIndex", nil, typ.Key(), ikey)
if iv.word == 0 {
return Value{}
}
flag := (iv.flag | ikey.flag) & flagRO
elemType := typ.Elem()
elemWord, ok := mapaccess(typ.runtimeType(), iv.word, ikey.word)
if !ok {
return Value{}
}
return valueFromIword(flag, elemType, elemWord)
}
// 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 {
iv := v.internal()
iv.mustBe(Map)
keyType := iv.typ.Key()
flag := iv.flag & flagRO
m := iv.word
mlen := int32(0)
if m != 0 {
mlen = maplen(m)
}
it := mapiterinit(iv.typ.runtimeType(), m)
a := make([]Value, mlen)
var i int
for i = 0; i < len(a); i++ {
keyWord, ok := mapiterkey(it)
if !ok {
break
}
a[i] = valueFromIword(flag, keyType, keyWord)
mapiternext(it)
}
return a[:i]
}
// Method returns a function value corresponding to v's i'th method.
// The arguments to a Call on the returned function should not include
// a receiver; the returned function will always use v as the receiver.
// Method panics if i is out of range.
func (v Value) Method(i int) Value {
iv := v.internal()
if iv.kind == Invalid {
panic(&ValueError{"reflect.Value.Method", Invalid})
}
if i < 0 || i >= iv.typ.NumMethod() {
panic("reflect: Method index out of range")
}
return Value{v.Internal, i + 1}
}
// NumMethod returns the number of methods in the value's method set.
func (v Value) NumMethod() int {
iv := v.internal()
if iv.kind == Invalid {
panic(&ValueError{"reflect.Value.NumMethod", Invalid})
}
return iv.typ.NumMethod()
}
// MethodByName returns a function value corresponding to the method
// of v with the given name.
// The arguments to a Call on the returned function should not include
// a receiver; the returned function will always use v as the receiver.
// It returns the zero Value if no method was found.
func (v Value) MethodByName(name string) Value {
iv := v.internal()
if iv.kind == Invalid {
panic(&ValueError{"reflect.Value.MethodByName", Invalid})
}
m, ok := iv.typ.MethodByName(name)
if ok {
return Value{v.Internal, m.Index + 1}
}
return Value{}
}
// NumField returns the number of fields in the struct v.
// It panics if v's Kind is not Struct.
func (v Value) NumField() int {
iv := v.internal()
iv.mustBe(Struct)
return iv.typ.NumField()
}
// OverflowComplex returns true if the complex128 x cannot be represented by v's type.
// It panics if v's Kind is not Complex64 or Complex128.
func (v Value) OverflowComplex(x complex128) bool {
iv := v.internal()
switch iv.kind {
case Complex64:
return overflowFloat32(real(x)) || overflowFloat32(imag(x))
case Complex128:
return false
}
panic(&ValueError{"reflect.Value.OverflowComplex", iv.kind})
}
// OverflowFloat returns true if the float64 x cannot be represented by v's type.
// It panics if v's Kind is not Float32 or Float64.
func (v Value) OverflowFloat(x float64) bool {
iv := v.internal()
switch iv.kind {
case Float32:
return overflowFloat32(x)
case Float64:
return false
}
panic(&ValueError{"reflect.Value.OverflowFloat", iv.kind})
}
func overflowFloat32(x float64) bool {
if x < 0 {
x = -x
}
return math.MaxFloat32 <= x && x <= math.MaxFloat64
}
// OverflowInt returns true if the int64 x cannot be represented by v's type.
// It panics if v's Kind is not Int, Int8, int16, Int32, or Int64.
func (v Value) OverflowInt(x int64) bool {
iv := v.internal()
switch iv.kind {
case Int, Int8, Int16, Int32, Int64:
bitSize := iv.typ.size * 8
trunc := (x << (64 - bitSize)) >> (64 - bitSize)
return x != trunc
}
panic(&ValueError{"reflect.Value.OverflowInt", iv.kind})
}
// OverflowUint returns true if the uint64 x cannot be represented by v's type.
// It panics if v's Kind is not Uint, Uintptr, Uint8, Uint16, Uint32, or Uint64.
func (v Value) OverflowUint(x uint64) bool {
iv := v.internal()
switch iv.kind {
case Uint, Uintptr, Uint8, Uint16, Uint32, Uint64:
bitSize := iv.typ.size * 8
trunc := (x << (64 - bitSize)) >> (64 - bitSize)
return x != trunc
}
panic(&ValueError{"reflect.Value.OverflowUint", iv.kind})
}
// Pointer returns v's value as a uintptr.
// It returns uintptr instead of unsafe.Pointer so that
// code using reflect cannot obtain unsafe.Pointers
// without importing the unsafe package explicitly.
// It panics if v's Kind is not Chan, Func, Map, Ptr, Slice, or UnsafePointer.
func (v Value) Pointer() uintptr {
iv := v.internal()
switch iv.kind {
case Chan, Func, Map, Ptr, UnsafePointer:
if iv.kind == Func && v.InternalMethod != 0 {
panic("reflect.Value.Pointer of method Value")
}
return uintptr(iv.word)
case Slice:
return (*SliceHeader)(iv.addr).Data
}
panic(&ValueError{"reflect.Value.Pointer", iv.kind})
}
// Recv receives and returns a value from the channel v.
// It panics if v's Kind is not Chan.
// The receive blocks until a value is ready.
// The boolean value ok is true if the value x corresponds to a send
// on the channel, false if it is a zero value received because the channel is closed.
func (v Value) Recv() (x Value, ok bool) {
iv := v.internal()
iv.mustBe(Chan)
iv.mustBeExported()
return iv.recv(false)
}
// internal recv, possibly non-blocking (nb)
func (iv internalValue) recv(nb bool) (val Value, ok bool) {
t := iv.typ.toType()
if t.ChanDir()&RecvDir == 0 {
panic("recv on send-only channel")
}
ch := iv.word
if ch == 0 {
panic("recv on nil channel")
}
valWord, selected, ok := chanrecv(iv.typ.runtimeType(), ch, nb)
if selected {
val = valueFromIword(0, t.Elem(), valWord)
}
return
}
// Send sends x on the channel v.
// It panics if v's kind is not Chan or if x's type is not the same type as v's element type.
// As in Go, x's value must be assignable to the channel's element type.
func (v Value) Send(x Value) {
iv := v.internal()
iv.mustBe(Chan)
iv.mustBeExported()
iv.send(x, false)
}
// internal send, possibly non-blocking
func (iv internalValue) send(x Value, nb bool) (selected bool) {
t := iv.typ.toType()
if t.ChanDir()&SendDir == 0 {
panic("send on recv-only channel")
}
ix := x.internal()
ix.mustBeExported() // do not let unexported x leak
ix = convertForAssignment("reflect.Value.Send", nil, t.Elem(), ix)
ch := iv.word
if ch == 0 {
panic("send on nil channel")
}
return chansend(iv.typ.runtimeType(), ch, ix.word, nb)
}
// Set assigns x to the value v.
// It panics if CanSet returns false.
// As in Go, x's value must be assignable to v's type.
func (v Value) Set(x Value) {
iv := v.internal()
ix := x.internal()
iv.mustBeAssignable()
ix.mustBeExported() // do not let unexported x leak
ix = convertForAssignment("reflect.Set", iv.addr, iv.typ, ix)
n := ix.typ.size
if n <= ptrSize {
storeIword(iv.addr, ix.word, n)
} else {
memmove(iv.addr, ix.addr, n)
}
}
// SetBool sets v's underlying value.
// It panics if v's Kind is not Bool or if CanSet() is false.
func (v Value) SetBool(x bool) {
iv := v.internal()
iv.mustBeAssignable()
iv.mustBe(Bool)
*(*bool)(iv.addr) = x
}
// SetComplex sets v's underlying value to x.
// It panics if v's Kind is not Complex64 or Complex128, or if CanSet() is false.
func (v Value) SetComplex(x complex128) {
iv := v.internal()
iv.mustBeAssignable()
switch iv.kind {
default:
panic(&ValueError{"reflect.Value.SetComplex", iv.kind})
case Complex64:
*(*complex64)(iv.addr) = complex64(x)
case Complex128:
*(*complex128)(iv.addr) = x
}
}
// SetFloat sets v's underlying value to x.
// It panics if v's Kind is not Float32 or Float64, or if CanSet() is false.
func (v Value) SetFloat(x float64) {
iv := v.internal()
iv.mustBeAssignable()
switch iv.kind {
default:
panic(&ValueError{"reflect.Value.SetFloat", iv.kind})
case Float32:
*(*float32)(iv.addr) = float32(x)
case Float64:
*(*float64)(iv.addr) = x
}
}
// SetInt sets v's underlying value to x.
// It panics if v's Kind is not Int, Int8, Int16, Int32, or Int64, or if CanSet() is false.
func (v Value) SetInt(x int64) {
iv := v.internal()
iv.mustBeAssignable()
switch iv.kind {
default:
panic(&ValueError{"reflect.Value.SetInt", iv.kind})
case Int:
*(*int)(iv.addr) = int(x)
case Int8:
*(*int8)(iv.addr) = int8(x)
case Int16:
*(*int16)(iv.addr) = int16(x)
case Int32:
*(*int32)(iv.addr) = int32(x)
case Int64:
*(*int64)(iv.addr) = x
}
}
// SetLen sets v's length to n.
// It panics if v's Kind is not Slice.
func (v Value) SetLen(n int) {
iv := v.internal()
iv.mustBeAssignable()
iv.mustBe(Slice)
s := (*SliceHeader)(iv.addr)
if n < 0 || n > int(s.Cap) {
panic("reflect: slice length out of range in SetLen")
}
s.Len = n
}
// SetMapIndex sets the value associated with key in the map v to val.
// It panics if v's Kind is not Map.
// If val is the zero Value, SetMapIndex deletes the key from the map.
// As in Go, key's value must be assignable to the map's key type,
// and val's value must be assignable to the map's value type.
func (v Value) SetMapIndex(key, val Value) {
iv := v.internal()
ikey := key.internal()
ival := val.internal()
iv.mustBe(Map)
iv.mustBeExported()
ikey.mustBeExported()
ikey = convertForAssignment("reflect.Value.SetMapIndex", nil, iv.typ.Key(), ikey)
if ival.kind != Invalid {
ival.mustBeExported()
ival = convertForAssignment("reflect.Value.SetMapIndex", nil, iv.typ.Elem(), ival)
}
mapassign(iv.typ.runtimeType(), iv.word, ikey.word, ival.word, ival.kind != Invalid)
}
// SetUint sets v's underlying value to x.
// It panics if v's Kind is not Uint, Uintptr, Uint8, Uint16, Uint32, or Uint64, or if CanSet() is false.
func (v Value) SetUint(x uint64) {
iv := v.internal()
iv.mustBeAssignable()
switch iv.kind {
default:
panic(&ValueError{"reflect.Value.SetUint", iv.kind})
case Uint:
*(*uint)(iv.addr) = uint(x)
case Uint8:
*(*uint8)(iv.addr) = uint8(x)
case Uint16:
*(*uint16)(iv.addr) = uint16(x)
case Uint32:
*(*uint32)(iv.addr) = uint32(x)
case Uint64:
*(*uint64)(iv.addr) = x
case Uintptr:
*(*uintptr)(iv.addr) = uintptr(x)
}
}
// SetPointer sets the unsafe.Pointer value v to x.
// It panics if v's Kind is not UnsafePointer.
func (v Value) SetPointer(x unsafe.Pointer) {
iv := v.internal()
iv.mustBeAssignable()
iv.mustBe(UnsafePointer)
*(*unsafe.Pointer)(iv.addr) = x
}
// SetString sets v's underlying value to x.
// It panics if v's Kind is not String or if CanSet() is false.
func (v Value) SetString(x string) {
iv := v.internal()
iv.mustBeAssignable()
iv.mustBe(String)
*(*string)(iv.addr) = x
}
// Slice returns a slice of v.
// It panics if v's Kind is not Array or Slice.
func (v Value) Slice(beg, end int) Value {
iv := v.internal()
if iv.kind != Array && iv.kind != Slice {
panic(&ValueError{"reflect.Value.Slice", iv.kind})
}
cap := v.Cap()
if beg < 0 || end < beg || end > cap {
panic("reflect.Value.Slice: slice index out of bounds")
}
var typ Type
var base uintptr
switch iv.kind {
case Array:
if iv.flag&flagAddr == 0 {
panic("reflect.Value.Slice: slice of unaddressable array")
}
typ = toType((*arrayType)(unsafe.Pointer(iv.typ)).slice)
base = uintptr(iv.addr)
case Slice:
typ = iv.typ.toType()
base = (*SliceHeader)(iv.addr).Data
}
s := new(SliceHeader)
s.Data = base + uintptr(beg)*typ.Elem().Size()
s.Len = end - beg
s.Cap = cap - beg
return valueFromAddr(iv.flag&flagRO, typ, unsafe.Pointer(s))
}
// String returns the string v's underlying value, 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 Kind is not String.
// Instead, it returns a string of the form "<T value>" where T is v's type.
func (v Value) String() string {
iv := v.internal()
switch iv.kind {
case Invalid:
return "<invalid Value>"
case String:
return *(*string)(iv.addr)
}
return "<" + iv.typ.String() + " Value>"
}
// TryRecv attempts to receive a value from the channel v but will not block.
// It panics if v's Kind is not Chan.
// If the receive cannot finish without blocking, x is the zero Value.
// The boolean ok is true if the value x corresponds to a send
// on the channel, false if it is a zero value received because the channel is closed.
func (v Value) TryRecv() (x Value, ok bool) {
iv := v.internal()
iv.mustBe(Chan)
iv.mustBeExported()
return iv.recv(true)
}
// TrySend attempts to send x on the channel v but will not block.
// It panics if v's Kind is not Chan.
// It returns true if the value was sent, false otherwise.
// As in Go, x's value must be assignable to the channel's element type.
func (v Value) TrySend(x Value) bool {
iv := v.internal()
iv.mustBe(Chan)
iv.mustBeExported()
return iv.send(x, true)
}
// Type returns v's type.
func (v Value) Type() Type {
t := v.internal().typ
if t == nil {
panic(&ValueError{"reflect.Value.Type", Invalid})
}
return t.toType()
}
// Uint returns v's underlying value, as a uint64.
// It panics if v's Kind is not Uint, Uintptr, Uint8, Uint16, Uint32, or Uint64.
func (v Value) Uint() uint64 {
iv := v.internal()
switch iv.kind {
case Uint:
return uint64(*(*uint)(unsafe.Pointer(&iv.word)))
case Uint8:
return uint64(*(*uint8)(unsafe.Pointer(&iv.word)))
case Uint16:
return uint64(*(*uint16)(unsafe.Pointer(&iv.word)))
case Uint32:
return uint64(*(*uint32)(unsafe.Pointer(&iv.word)))
case Uintptr:
return uint64(*(*uintptr)(unsafe.Pointer(&iv.word)))
case Uint64:
if iv.addr == nil {
return *(*uint64)(unsafe.Pointer(&iv.word))
}
return *(*uint64)(iv.addr)
}
panic(&ValueError{"reflect.Value.Uint", iv.kind})
}
// UnsafeAddr returns a pointer to v's data.
// It is for advanced clients that also import the "unsafe" package.
// It panics if v is not addressable.
func (v Value) UnsafeAddr() uintptr {
iv := v.internal()
if iv.kind == Invalid {
panic(&ValueError{"reflect.Value.UnsafeAddr", iv.kind})
}
if iv.flag&flagAddr == 0 {
panic("reflect.Value.UnsafeAddr of unaddressable value")
}
return uintptr(iv.addr)
}
// StringHeader is the runtime representation of a string.
// It cannot be used safely or portably.
type StringHeader struct {
Data uintptr
Len int
}
// SliceHeader is the runtime representation of a slice.
// It cannot be used safely or portably.
type SliceHeader struct {
Data uintptr
Len int
Cap int
}
func typesMustMatch(what string, t1, t2 Type) {
if t1 != t2 {
panic("reflect: " + what + ": " + t1.String() + " != " + t2.String())
}
}
// grow grows the slice s so that it can hold extra more values, allocating
// more capacity if needed. It also returns the old and new slice lengths.
func grow(s Value, extra int) (Value, int, int) {
i0 := s.Len()
i1 := i0 + extra
if i1 < i0 {
panic("reflect.Append: slice overflow")
}
m := s.Cap()
if i1 <= m {
return s.Slice(0, i1), i0, i1
}
if m == 0 {
m = extra
} else {
for m < i1 {
if i0 < 1024 {
m += m
} else {
m += m / 4
}
}
}
t := MakeSlice(s.Type(), i1, m)
Copy(t, s)
return t, i0, i1
}
// Append appends the values x to a slice s and returns the resulting slice.
// As in Go, each x's value must be assignable to the slice's element type.
func Append(s Value, x ...Value) Value {
s.internal().mustBe(Slice)
s, i0, i1 := grow(s, len(x))
for i, j := i0, 0; i < i1; i, j = i+1, j+1 {
s.Index(i).Set(x[j])
}
return s
}
// AppendSlice appends a slice t to a slice s and returns the resulting slice.
// The slices s and t must have the same element type.
func AppendSlice(s, t Value) Value {
s.internal().mustBe(Slice)
t.internal().mustBe(Slice)
typesMustMatch("reflect.AppendSlice", s.Type().Elem(), t.Type().Elem())
s, i0, i1 := grow(s, t.Len())
Copy(s.Slice(i0, i1), t)
return s
}
// Copy copies the contents of src into dst until either
// dst has been filled or src has been exhausted.
// It returns the number of elements copied.
// Dst and src each must have kind Slice or Array, and
// dst and src must have the same element type.
func Copy(dst, src Value) int {
idst := dst.internal()
isrc := src.internal()
if idst.kind != Array && idst.kind != Slice {
panic(&ValueError{"reflect.Copy", idst.kind})
}
if idst.kind == Array {
idst.mustBeAssignable()
}
idst.mustBeExported()
if isrc.kind != Array && isrc.kind != Slice {
panic(&ValueError{"reflect.Copy", isrc.kind})
}
isrc.mustBeExported()
de := idst.typ.Elem()
se := isrc.typ.Elem()
typesMustMatch("reflect.Copy", de, se)
n := dst.Len()
if sn := src.Len(); n > sn {
n = sn
}
// If sk is an in-line array, cannot take its address.
// Instead, copy element by element.
if isrc.addr == nil {
for i := 0; i < n; i++ {
dst.Index(i).Set(src.Index(i))
}
return n
}
// Copy via memmove.
var da, sa unsafe.Pointer
if idst.kind == Array {
da = idst.addr
} else {
da = unsafe.Pointer((*SliceHeader)(idst.addr).Data)
}
if isrc.kind == Array {
sa = isrc.addr
} else {
sa = unsafe.Pointer((*SliceHeader)(isrc.addr).Data)
}
memmove(da, sa, uintptr(n)*de.Size())
return n
}
/*
* constructors
*/
// MakeSlice creates a new zero-initialized slice value
// for the specified slice type, length, and capacity.
func MakeSlice(typ Type, len, cap int) Value {
if typ.Kind() != Slice {
panic("reflect: MakeSlice of non-slice type")
}
s := &SliceHeader{
Data: uintptr(unsafe.NewArray(typ.Elem(), cap)),
Len: len,
Cap: cap,
}
return valueFromAddr(0, typ, unsafe.Pointer(s))
}
// MakeChan creates a new channel with the specified type and buffer size.
func MakeChan(typ Type, buffer int) Value {
if typ.Kind() != Chan {
panic("reflect: MakeChan of non-chan type")
}
if buffer < 0 {
panic("MakeChan: negative buffer size")
}
if typ.ChanDir() != BothDir {
panic("MakeChan: unidirectional channel type")
}
ch := makechan(typ.runtimeType(), uint32(buffer))
return valueFromIword(0, typ, ch)
}
// MakeMap creates a new map of the specified type.
func MakeMap(typ Type) Value {
if typ.Kind() != Map {
panic("reflect: MakeMap of non-map type")
}
m := makemap(typ.runtimeType())
return valueFromIword(0, typ, m)
}
// Indirect returns the value that v points to.
// If v is a nil pointer, Indirect returns a nil Value.
// If v is not a pointer, Indirect returns v.
func Indirect(v Value) Value {
if v.Kind() != Ptr {
return v
}
return v.Elem()
}
// ValueOf returns a new Value initialized to the concrete value
// stored in the interface i. ValueOf(nil) returns the zero Value.
func ValueOf(i interface{}) Value {
if i == nil {
return Value{}
}
// For an interface value with the noAddr bit set,
// the representation is identical to an empty interface.
eface := *(*emptyInterface)(unsafe.Pointer(&i))
return packValue(0, eface.typ, eface.word)
}
// Zero returns a Value representing a zero value for the specified type.
// The result is different from the zero value of the Value struct,
// which represents no value at all.
// For example, Zero(TypeOf(42)) returns a Value with Kind Int and value 0.
func Zero(typ Type) Value {
if typ == nil {
panic("reflect: Zero(nil)")
}
if typ.Size() <= ptrSize {
return valueFromIword(0, typ, 0)
}
return valueFromAddr(0, typ, unsafe.New(typ))
}
// New returns a Value representing a pointer to a new zero value
// for the specified type. That is, the returned Value's Type is PtrTo(t).
func New(typ Type) Value {
if typ == nil {
panic("reflect: New(nil)")
}
ptr := unsafe.New(typ)
return valueFromIword(0, PtrTo(typ), iword(ptr))
}
// convertForAssignment
func convertForAssignment(what string, addr unsafe.Pointer, dst Type, iv internalValue) internalValue {
if iv.method {
panic(what + ": cannot assign method value to type " + dst.String())
}
dst1 := dst.(*commonType)
if directlyAssignable(dst1, iv.typ) {
// Overwrite type so that they match.
// Same memory layout, so no harm done.
iv.typ = dst1
return iv
}
if implements(dst1, iv.typ) {
if addr == nil {
addr = unsafe.Pointer(new(interface{}))
}
x := iv.valueInterface(false)
if dst.NumMethod() == 0 {
*(*interface{})(addr) = x
} else {
ifaceE2I(dst1.runtimeType(), x, addr)
}
iv.addr = addr
iv.word = iword(addr)
iv.typ = dst1
return iv
}
// Failed.
panic(what + ": value of type " + iv.typ.String() + " is not assignable to type " + dst.String())
}
// implemented in ../pkg/runtime
func chancap(ch iword) int32
func chanclose(ch iword)
func chanlen(ch iword) int32
func chanrecv(t *runtime.Type, ch iword, nb bool) (val iword, selected, received bool)
func chansend(t *runtime.Type, ch iword, val iword, nb bool) bool
func makechan(typ *runtime.Type, size uint32) (ch iword)
func makemap(t *runtime.Type) iword
func mapaccess(t *runtime.Type, m iword, key iword) (val iword, ok bool)
func mapassign(t *runtime.Type, m iword, key, val iword, ok bool)
func mapiterinit(t *runtime.Type, m iword) *byte
func mapiterkey(it *byte) (key iword, ok bool)
func mapiternext(it *byte)
func maplen(m iword) int32
func call(fn, arg unsafe.Pointer, n uint32)
func ifaceE2I(t *runtime.Type, src interface{}, dst unsafe.Pointer)