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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 bigEndian = false // can be smarter if we find a big-endian machine
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.
type Value struct {
// typ holds the type of the value represented by a Value.
typ *commonType
// val holds the 1-word representation of the value.
// If flag's flagIndir bit is set, then val is a pointer to the data.
// Otherwise val is a word holding the actual data.
// When the data is smaller than a word, it begins at
// the first byte (in the memory address sense) of val.
// We use unsafe.Pointer so that the garbage collector
// knows that val could be a pointer.
val unsafe.Pointer
// flag holds metadata about the value.
// The lowest bits are flag bits:
// - flagRO: obtained via unexported field, so read-only
// - flagIndir: val holds a pointer to the data
// - flagAddr: v.CanAddr is true (implies flagIndir)
// - flagMethod: v is a method value.
// The next five bits give the Kind of the value.
// This repeats typ.Kind() except for method values.
// The remaining 23+ bits give a method number for method values.
// If flag.kind() != Func, code can assume that flagMethod is unset.
// If typ.size > ptrSize, code can assume that flagIndir is set.
flag
// A method value represents a curried method invocation
// like r.Read for some receiver r. The typ+val+flag bits describe
// the receiver r, but the flag's Kind bits say Func (methods are
// functions), and the top bits of the flag give the method number
// in r's type's method table.
}
type flag uintptr
const (
flagRO flag = 1 << iota
flagIndir
flagAddr
flagMethod
flagKindShift = iota
flagKindWidth = 5 // there are 27 kinds
flagKindMask flag = 1<<flagKindWidth - 1
flagMethodShift = flagKindShift + flagKindWidth
)
func (f flag) kind() Kind {
return Kind((f >> flagKindShift) & flagKindMask)
}
// 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) Error() 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 holds the data stored
// in its leading bytes (so is not a pointer).
// Because the value sometimes holds a pointer, we use
// unsafe.Pointer to represent it, so that if iword appears
// in a struct, the garbage collector knows that might be
// a pointer.
type iword unsafe.Pointer
func (v Value) iword() iword {
if v.flag&flagIndir != 0 && v.typ.size <= ptrSize {
// Have indirect but want direct word.
return loadIword(v.val, v.typ.size)
}
return iword(v.val)
}
// loadIword loads n bytes at p from memory into an iword.
func loadIword(p unsafe.Pointer, n uintptr) iword {
// Run the copy ourselves instead of calling memmove
// to avoid moving w to the heap.
var w iword
switch n {
default:
panic("reflect: internal error: loadIword of " + strconv.Itoa(int(n)) + "-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
}
// storeIword stores n bytes from w into p.
func storeIword(p unsafe.Pointer, w iword, n uintptr) {
// Run the copy ourselves instead of calling memmove
// to avoid moving w to the heap.
switch n {
default:
panic("reflect: internal error: storeIword of " + strconv.Itoa(int(n)) + "-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 *runtimeType
word iword
}
// nonEmptyInterface is the header for a interface value with methods.
type nonEmptyInterface struct {
// see ../runtime/iface.c:/Itab
itab *struct {
ityp *runtimeType // static interface type
typ *runtimeType // dynamic concrete type
link unsafe.Pointer
bad int32
unused int32
fun [100000]unsafe.Pointer // method table
}
word iword
}
// mustBe panics if f's kind is not expected.
// Making this a method on flag instead of on Value
// (and embedding flag in Value) means that we can write
// the very clear v.mustBe(Bool) and have it compile into
// v.flag.mustBe(Bool), which will only bother to copy the
// single important word for the receiver.
func (f flag) mustBe(expected Kind) {
k := f.kind()
if k != expected {
panic(&ValueError{methodName(), k})
}
}
// mustBeExported panics if f records that the value was obtained using
// an unexported field.
func (f flag) mustBeExported() {
if f == 0 {
panic(&ValueError{methodName(), 0})
}
if f&flagRO != 0 {
panic(methodName() + " using value obtained using unexported field")
}
}
// mustBeAssignable panics if f records that the value is not assignable,
// which is to say that either it was obtained using an unexported field
// or it is not addressable.
func (f flag) mustBeAssignable() {
if f == 0 {
panic(&ValueError{methodName(), Invalid})
}
// Assignable if addressable and not read-only.
if f&flagRO != 0 {
panic(methodName() + " using value obtained using unexported field")
}
if f&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 {
if v.flag&flagAddr == 0 {
panic("reflect.Value.Addr of unaddressable value")
}
return Value{v.typ.ptrTo(), v.val, (v.flag & flagRO) | flag(Ptr)<<flagKindShift}
}
// Bool returns v's underlying value.
// It panics if v's kind is not Bool.
func (v Value) Bool() bool {
v.mustBe(Bool)
if v.flag&flagIndir != 0 {
return *(*bool)(v.val)
}
return *(*bool)(unsafe.Pointer(&v.val))
}
// Bytes returns v's underlying value.
// It panics if v's underlying value is not a slice of bytes.
func (v Value) Bytes() []byte {
v.mustBe(Slice)
if v.typ.Elem().Kind() != Uint8 {
panic("reflect.Value.Bytes of non-byte slice")
}
// Slice is always bigger than a word; assume flagIndir.
return *(*[]byte)(v.val)
}
// 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 {
return v.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 {
return v.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 {
v.mustBe(Func)
v.mustBeExported()
return v.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 {
v.mustBe(Func)
v.mustBeExported()
return v.call("CallSlice", in)
}
func (v Value) call(method string, in []Value) []Value {
// Get function pointer, type.
t := v.typ
var (
fn unsafe.Pointer
rcvr iword
)
if v.flag&flagMethod != 0 {
i := int(v.flag) >> flagMethodShift
if v.typ.Kind() == Interface {
tt := (*interfaceType)(unsafe.Pointer(v.typ))
if i < 0 || i >= len(tt.methods) {
panic("reflect: broken Value")
}
m := &tt.methods[i]
if m.pkgPath != nil {
panic(method + " of unexported method")
}
t = toCommonType(m.typ)
iface := (*nonEmptyInterface)(v.val)
if iface.itab == nil {
panic(method + " of method on nil interface value")
}
fn = iface.itab.fun[i]
rcvr = iface.word
} else {
ut := v.typ.uncommon()
if ut == nil || i < 0 || i >= len(ut.methods) {
panic("reflect: broken Value")
}
m := &ut.methods[i]
if m.pkgPath != nil {
panic(method + " of unexported method")
}
fn = m.ifn
t = toCommonType(m.mtyp)
rcvr = v.iword()
}
} else if v.flag&flagIndir != 0 {
fn = *(*unsafe.Pointer)(v.val)
} else {
fn = v.val
}
if fn == nil {
panic("reflect.Value.Call: call of nil function")
}
isSlice := method == "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: " + 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 v.flag&flagMethod != 0 {
// extra word for receiver interface word
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 v.flag&flagMethod != 0 {
// Hard-wired first argument.
*(*iword)(unsafe.Pointer(ptr)) = rcvr
off = ptrSize
}
for i, v := range in {
v.mustBeExported()
targ := t.In(i).(*commonType)
a := uintptr(targ.align)
off = (off + a - 1) &^ (a - 1)
n := targ.size
addr := unsafe.Pointer(ptr + off)
v = v.assignTo("reflect.Value.Call", targ, (*interface{})(addr))
if v.flag&flagIndir == 0 {
storeIword(addr, iword(v.val), n)
} else {
memmove(addr, v.val, n)
}
off += n
}
off = (off + ptrSize - 1) &^ (ptrSize - 1)
// Call.
call(fn, 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)
fl := flagIndir | flag(tv.Kind())<<flagKindShift
ret[i] = Value{tv.common(), unsafe.Pointer(ptr + off), fl}
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 {
k := v.kind()
switch k {
case Array:
return v.typ.Len()
case Chan:
return int(chancap(v.iword()))
case Slice:
// Slice is always bigger than a word; assume flagIndir.
return (*SliceHeader)(v.val).Cap
}
panic(&ValueError{"reflect.Value.Cap", k})
}
// Close closes the channel v.
// It panics if v's Kind is not Chan.
func (v Value) Close() {
v.mustBe(Chan)
v.mustBeExported()
chanclose(v.iword())
}
// 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 {
k := v.kind()
switch k {
case Complex64:
if v.flag&flagIndir != 0 {
return complex128(*(*complex64)(v.val))
}
return complex128(*(*complex64)(unsafe.Pointer(&v.val)))
case Complex128:
// complex128 is always bigger than a word; assume flagIndir.
return *(*complex128)(v.val)
}
panic(&ValueError{"reflect.Value.Complex", k})
}
// 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 {
k := v.kind()
switch k {
case Interface:
var (
typ *commonType
val unsafe.Pointer
)
if v.typ.NumMethod() == 0 {
eface := (*emptyInterface)(v.val)
if eface.typ == nil {
// nil interface value
return Value{}
}
typ = toCommonType(eface.typ)
val = unsafe.Pointer(eface.word)
} else {
iface := (*nonEmptyInterface)(v.val)
if iface.itab == nil {
// nil interface value
return Value{}
}
typ = toCommonType(iface.itab.typ)
val = unsafe.Pointer(iface.word)
}
fl := v.flag & flagRO
fl |= flag(typ.Kind()) << flagKindShift
if typ.size > ptrSize {
fl |= flagIndir
}
return Value{typ, val, fl}
case Ptr:
val := v.val
if v.flag&flagIndir != 0 {
val = *(*unsafe.Pointer)(val)
}
// The returned value's address is v's value.
if val == nil {
return Value{}
}
tt := (*ptrType)(unsafe.Pointer(v.typ))
typ := toCommonType(tt.elem)
fl := v.flag&flagRO | flagIndir | flagAddr
fl |= flag(typ.Kind() << flagKindShift)
return Value{typ, val, fl}
}
panic(&ValueError{"reflect.Value.Elem", k})
}
// 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 {
v.mustBe(Struct)
tt := (*structType)(unsafe.Pointer(v.typ))
if i < 0 || i >= len(tt.fields) {
panic("reflect: Field index out of range")
}
field := &tt.fields[i]
typ := toCommonType(field.typ)
// Inherit permission bits from v.
fl := v.flag & (flagRO | flagIndir | flagAddr)
// Using an unexported field forces flagRO.
if field.pkgPath != nil {
fl |= flagRO
}
fl |= flag(typ.Kind()) << flagKindShift
var val unsafe.Pointer
switch {
case fl&flagIndir != 0:
// Indirect. Just bump pointer.
val = unsafe.Pointer(uintptr(v.val) + field.offset)
case bigEndian:
// Direct. Discard leading bytes.
val = unsafe.Pointer(uintptr(v.val) << (field.offset * 8))
default:
// Direct. Discard leading bytes.
val = unsafe.Pointer(uintptr(v.val) >> (field.offset * 8))
}
return Value{typ, val, fl}
}
// 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.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 {
v.mustBe(Struct)
if f, ok := v.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.mustBe(Struct)
if f, ok := v.typ.FieldByNameFunc(match); ok {
return v.FieldByIndex(f.Index)
}
return Value{}
}
// Float returns v's underlying value, as a float64.
// It panics if v's Kind is not Float32 or Float64
func (v Value) Float() float64 {
k := v.kind()
switch k {
case Float32:
if v.flag&flagIndir != 0 {
return float64(*(*float32)(v.val))
}
return float64(*(*float32)(unsafe.Pointer(&v.val)))
case Float64:
if v.flag&flagIndir != 0 {
return *(*float64)(v.val)
}
return *(*float64)(unsafe.Pointer(&v.val))
}
panic(&ValueError{"reflect.Value.Float", k})
}
// 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 {
k := v.kind()
switch k {
case Array:
tt := (*arrayType)(unsafe.Pointer(v.typ))
if i < 0 || i > int(tt.len) {
panic("reflect: array index out of range")
}
typ := toCommonType(tt.elem)
fl := v.flag & (flagRO | flagIndir | flagAddr) // bits same as overall array
fl |= flag(typ.Kind()) << flagKindShift
offset := uintptr(i) * typ.size
var val unsafe.Pointer
switch {
case fl&flagIndir != 0:
// Indirect. Just bump pointer.
val = unsafe.Pointer(uintptr(v.val) + offset)
case bigEndian:
// Direct. Discard leading bytes.
val = unsafe.Pointer(uintptr(v.val) << (offset * 8))
default:
// Direct. Discard leading bytes.
val = unsafe.Pointer(uintptr(v.val) >> (offset * 8))
}
return Value{typ, val, fl}
case Slice:
// Element flag same as Elem of Ptr.
// Addressable, indirect, possibly read-only.
fl := flagAddr | flagIndir | v.flag&flagRO
s := (*SliceHeader)(v.val)
if i < 0 || i >= s.Len {
panic("reflect: slice index out of range")
}
tt := (*sliceType)(unsafe.Pointer(v.typ))
typ := toCommonType(tt.elem)
fl |= flag(typ.Kind()) << flagKindShift
val := unsafe.Pointer(s.Data + uintptr(i)*typ.size)
return Value{typ, val, fl}
}
panic(&ValueError{"reflect.Value.Index", k})
}
// 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 {
k := v.kind()
var p unsafe.Pointer
if v.flag&flagIndir != 0 {
p = v.val
} else {
// The escape analysis is good enough that &v.val
// does not trigger a heap allocation.
p = unsafe.Pointer(&v.val)
}
switch k {
case Int:
return int64(*(*int)(p))
case Int8:
return int64(*(*int8)(p))
case Int16:
return int64(*(*int16)(p))
case Int32:
return int64(*(*int32)(p))
case Int64:
return int64(*(*int64)(p))
}
panic(&ValueError{"reflect.Value.Int", k})
}
// CanInterface returns true if Interface can be used without panicking.
func (v Value) CanInterface() bool {
if v.flag == 0 {
panic(&ValueError{"reflect.Value.CanInterface", Invalid})
}
return v.flag&(flagMethod|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.
// It also panics if the Value was obtained by accessing
// unexported struct fields.
func (v Value) Interface() interface{} {
return valueInterface(v, true)
}
func valueInterface(v Value, safe bool) interface{} {
if v.flag == 0 {
panic(&ValueError{"reflect.Value.Interface", 0})
}
if v.flag&flagMethod != 0 {
panic("reflect.Value.Interface: cannot create interface value for method with bound receiver")
}
if safe && v.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")
}
k := v.kind()
if k == Interface {
// Special case: return the element inside the interface.
// Empty interface has one layout, all interfaces with
// methods have a second layout.
if v.NumMethod() == 0 {
return *(*interface{})(v.val)
}
return *(*interface {
M()
})(v.val)
}
// Non-interface value.
var eface emptyInterface
eface.typ = v.typ.runtimeType()
eface.word = v.iword()
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 {
v.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.
// Interface value is always bigger than a word; assume flagIndir.
return *(*[2]uintptr)(v.val)
}
// 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 {
k := v.kind()
switch k {
case Chan, Func, Map, Ptr:
if v.flag&flagMethod != 0 {
panic("reflect: IsNil of method Value")
}
ptr := v.val
if v.flag&flagIndir != 0 {
ptr = *(*unsafe.Pointer)(ptr)
}
return ptr == nil
case Interface, Slice:
// Both interface and slice are nil if first word is 0.
// Both are always bigger than a word; assume flagIndir.
return *(*unsafe.Pointer)(v.val) == nil
}
panic(&ValueError{"reflect.Value.IsNil", k})
}
// 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.flag != 0
}
// Kind returns v's Kind.
// If v is the zero Value (IsValid returns false), Kind returns Invalid.
func (v Value) Kind() Kind {
return v.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 {
k := v.kind()
switch k {
case Array:
tt := (*arrayType)(unsafe.Pointer(v.typ))
return int(tt.len)
case Chan:
return int(chanlen(v.iword()))
case Map:
return int(maplen(v.iword()))
case Slice:
// Slice is bigger than a word; assume flagIndir.
return (*SliceHeader)(v.val).Len
case String:
// String is bigger than a word; assume flagIndir.
return (*StringHeader)(v.val).Len
}
panic(&ValueError{"reflect.Value.Len", k})
}
// 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", toCommonType(tt.key), nil)
word, ok := mapaccess(v.typ.runtimeType(), v.iword(), key.iword())
if !ok {
return Value{}
}
typ := toCommonType(tt.elem)
fl := (v.flag | key.flag) & flagRO
if typ.size > ptrSize {
fl |= flagIndir
}
fl |= flag(typ.Kind()) << flagKindShift
return Value{typ, unsafe.Pointer(word), fl}
}
// 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 := toCommonType(tt.key)
fl := v.flag & flagRO
fl |= flag(keyType.Kind()) << flagKindShift
if keyType.size > ptrSize {
fl |= flagIndir
}
m := v.iword()
mlen := int32(0)
if m != nil {
mlen = maplen(m)
}
it := mapiterinit(v.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] = Value{keyType, unsafe.Pointer(keyWord), fl}
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 {
if v.typ == nil {
panic(&ValueError{"reflect.Value.Method", Invalid})
}
if v.flag&flagMethod != 0 || i < 0 || i >= v.typ.NumMethod() {
panic("reflect: Method index out of range")
}
fl := v.flag & (flagRO | flagAddr | flagIndir)
fl |= flag(Func) << flagKindShift
fl |= flag(i)<<flagMethodShift | flagMethod
return Value{v.typ, v.val, fl}
}
// NumMethod returns the number of methods in the value's method set.
func (v Value) NumMethod() int {
if v.typ == nil {
panic(&ValueError{"reflect.Value.NumMethod", Invalid})
}
if v.flag&flagMethod != 0 {
return 0
}
return v.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 {
if v.typ == nil {
panic(&ValueError{"reflect.Value.MethodByName", Invalid})
}
if v.flag&flagMethod != 0 {
return Value{}
}
m, ok := v.typ.MethodByName(name)
if !ok {
return Value{}
}
return v.Method(m.Index)
}
// 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)
}
// 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 {
k := v.kind()
switch k {
case Complex64:
return overflowFloat32(real(x)) || overflowFloat32(imag(x))
case Complex128:
return false
}
panic(&ValueError{"reflect.Value.OverflowComplex", k})
}
// 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 {
k := v.kind()
switch k {
case Float32:
return overflowFloat32(x)
case Float64:
return false
}
panic(&ValueError{"reflect.Value.OverflowFloat", k})
}
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 {
k := v.kind()
switch k {
case Int, Int8, Int16, Int32, Int64:
bitSize := v.typ.size * 8
trunc := (x << (64 - bitSize)) >> (64 - bitSize)
return x != trunc
}
panic(&ValueError{"reflect.Value.OverflowInt", k})
}
// 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 {
k := v.kind()
switch k {
case Uint, Uintptr, Uint8, Uint16, Uint32, Uint64:
bitSize := v.typ.size * 8
trunc := (x << (64 - bitSize)) >> (64 - bitSize)
return x != trunc
}
panic(&ValueError{"reflect.Value.OverflowUint", k})
}
// 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 {
k := v.kind()
switch k {
case Chan, Func, Map, Ptr, UnsafePointer:
if k == Func && v.flag&flagMethod != 0 {
panic("reflect.Value.Pointer of method Value")
}
p := v.val
if v.flag&flagIndir != 0 {
p = *(*unsafe.Pointer)(p)
}
return uintptr(p)
case Slice:
return (*SliceHeader)(v.val).Data
}
panic(&ValueError{"reflect.Value.Pointer", k})
}
// 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) {
v.mustBe(Chan)
v.mustBeExported()
return v.recv(false)
}
// internal recv, possibly non-blocking (nb).
// v is known to be a channel.
func (v Value) recv(nb bool) (val Value, ok bool) {
tt := (*chanType)(unsafe.Pointer(v.typ))
if ChanDir(tt.dir)&RecvDir == 0 {
panic("recv on send-only channel")
}
word, selected, ok := chanrecv(v.typ.runtimeType(), v.iword(), nb)
if selected {
typ := toCommonType(tt.elem)
fl := flag(typ.Kind()) << flagKindShift
if typ.size > ptrSize {
fl |= flagIndir
}
val = Value{typ, unsafe.Pointer(word), fl}
}
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) {
v.mustBe(Chan)
v.mustBeExported()
v.send(x, false)
}
// internal send, possibly non-blocking.
// v is known to be a channel.
func (v Value) send(x Value, nb bool) (selected bool) {
tt := (*chanType)(unsafe.Pointer(v.typ))
if ChanDir(tt.dir)&SendDir == 0 {
panic("send on recv-only channel")
}
x.mustBeExported()
x = x.assignTo("reflect.Value.Send", toCommonType(tt.elem), nil)
return chansend(v.typ.runtimeType(), v.iword(), x.iword(), 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) {
v.mustBeAssignable()
x.mustBeExported() // do not let unexported x leak
var target *interface{}
if v.kind() == Interface {
target = (*interface{})(v.val)
}
x = x.assignTo("reflect.Set", v.typ, target)
if x.flag&flagIndir != 0 {
memmove(v.val, x.val, v.typ.size)
} else {
storeIword(v.val, iword(x.val), v.typ.size)
}
}
// 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) {
v.mustBeAssignable()
v.mustBe(Bool)
*(*bool)(v.val) = x
}
// SetBytes sets v's underlying value.
// It panics if v's underlying value is not a slice of bytes.
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")
}
*(*[]byte)(v.val) = 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) {
v.mustBeAssignable()
switch k := v.kind(); k {
default:
panic(&ValueError{"reflect.Value.SetComplex", k})
case Complex64:
*(*complex64)(v.val) = complex64(x)
case Complex128:
*(*complex128)(v.val) = 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) {
v.mustBeAssignable()
switch k := v.kind(); k {
default:
panic(&ValueError{"reflect.Value.SetFloat", k})
case Float32:
*(*float32)(v.val) = float32(x)
case Float64:
*(*float64)(v.val) = 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) {
v.mustBeAssignable()
switch k := v.kind(); k {
default:
panic(&ValueError{"reflect.Value.SetInt", k})
case Int:
*(*int)(v.val) = int(x)
case Int8:
*(*int8)(v.val) = int8(x)
case Int16:
*(*int16)(v.val) = int16(x)
case Int32:
*(*int32)(v.val) = int32(x)
case Int64:
*(*int64)(v.val) = x
}
}
// SetLen sets v's length to n.
// It panics if v's Kind is not Slice or if n is negative or
// greater than the capacity of the slice.
func (v Value) SetLen(n int) {
v.mustBeAssignable()
v.mustBe(Slice)
s := (*SliceHeader)(v.val)
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) {
v.mustBe(Map)
v.mustBeExported()
key.mustBeExported()
tt := (*mapType)(unsafe.Pointer(v.typ))
key = key.assignTo("reflect.Value.SetMapIndex", toCommonType(tt.key), nil)
if val.typ != nil {
val.mustBeExported()
val = val.assignTo("reflect.Value.SetMapIndex", toCommonType(tt.elem), nil)
}
mapassign(v.typ.runtimeType(), v.iword(), key.iword(), val.iword(), val.typ != nil)
}
// 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) {
v.mustBeAssignable()
switch k := v.kind(); k {
default:
panic(&ValueError{"reflect.Value.SetUint", k})
case Uint:
*(*uint)(v.val) = uint(x)
case Uint8:
*(*uint8)(v.val) = uint8(x)
case Uint16:
*(*uint16)(v.val) = uint16(x)
case Uint32:
*(*uint32)(v.val) = uint32(x)
case Uint64:
*(*uint64)(v.val) = x
case Uintptr:
*(*uintptr)(v.val) = 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) {
v.mustBeAssignable()
v.mustBe(UnsafePointer)
*(*unsafe.Pointer)(v.val) = 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) {
v.mustBeAssignable()
v.mustBe(String)
*(*string)(v.val) = 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 {
var (
cap int
typ *sliceType
base unsafe.Pointer
)
switch k := v.kind(); k {
default:
panic(&ValueError{"reflect.Value.Slice", k})
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 = (*sliceType)(unsafe.Pointer(toCommonType(tt.slice)))
base = v.val
case Slice:
typ = (*sliceType)(unsafe.Pointer(v.typ))
s := (*SliceHeader)(v.val)
base = unsafe.Pointer(s.Data)
cap = s.Cap
}
if beg < 0 || end < beg || end > cap {
panic("reflect.Value.Slice: slice index out of bounds")
}
// Declare slice so that gc can see the base pointer in it.
var x []byte
// Reinterpret as *SliceHeader to edit.
s := (*SliceHeader)(unsafe.Pointer(&x))
s.Data = uintptr(base) + uintptr(beg)*toCommonType(typ.elem).Size()
s.Len = end - beg
s.Cap = cap - beg
fl := v.flag&flagRO | flagIndir | flag(Slice)<<flagKindShift
return Value{typ.common(), unsafe.Pointer(&x), fl}
}
// 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 {
switch k := v.kind(); k {
case Invalid:
return "<invalid Value>"
case String:
return *(*string)(v.val)
}
// If you call String on a reflect.Value of other type, it's better to
// print something than to panic. Useful in debugging.
return "<" + v.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) {
v.mustBe(Chan)
v.mustBeExported()
return v.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 {
v.mustBe(Chan)
v.mustBeExported()
return v.send(x, true)
}
// Type returns v's type.
func (v Value) Type() Type {
f := v.flag
if f == 0 {
panic(&ValueError{"reflect.Value.Type", Invalid})
}
if f&flagMethod == 0 {
// Easy case
return v.typ
}
// Method value.
// v.typ describes the receiver, not the method type.
i := int(v.flag) >> flagMethodShift
if v.typ.Kind() == Interface {
// Method on interface.
tt := (*interfaceType)(unsafe.Pointer(v.typ))
if i < 0 || i >= len(tt.methods) {
panic("reflect: broken Value")
}
m := &tt.methods[i]
return toCommonType(m.typ)
}
// Method on concrete type.
ut := v.typ.uncommon()
if ut == nil || i < 0 || i >= len(ut.methods) {
panic("reflect: broken Value")
}
m := &ut.methods[i]
return toCommonType(m.mtyp)
}
// 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 {
k := v.kind()
var p unsafe.Pointer
if v.flag&flagIndir != 0 {
p = v.val
} else {
// The escape analysis is good enough that &v.val
// does not trigger a heap allocation.
p = unsafe.Pointer(&v.val)
}
switch k {
case Uint:
return uint64(*(*uint)(p))
case Uint8:
return uint64(*(*uint8)(p))
case Uint16:
return uint64(*(*uint16)(p))
case Uint32:
return uint64(*(*uint32)(p))
case Uint64:
return uint64(*(*uint64)(p))
case Uintptr:
return uint64(*(*uintptr)(p))
}
panic(&ValueError{"reflect.Value.Uint", k})
}
// 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 {
if v.typ == nil {
panic(&ValueError{"reflect.Value.UnsafeAddr", Invalid})
}
if v.flag&flagAddr == 0 {
panic("reflect.Value.UnsafeAddr of unaddressable value")
}
return uintptr(v.val)
}
// 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(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.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.mustBe(Slice)
t.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 {
dk := dst.kind()
if dk != Array && dk != Slice {
panic(&ValueError{"reflect.Copy", dk})
}
if dk == Array {
dst.mustBeAssignable()
}
dst.mustBeExported()
sk := src.kind()
if sk != Array && sk != Slice {
panic(&ValueError{"reflect.Copy", sk})
}
src.mustBeExported()
de := dst.typ.Elem()
se := src.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 src.flag&flagIndir == 0 {
for i := 0; i < n; i++ {
dst.Index(i).Set(src.Index(i))
}
return n
}
// Copy via memmove.
var da, sa unsafe.Pointer
if dk == Array {
da = dst.val
} else {
da = unsafe.Pointer((*SliceHeader)(dst.val).Data)
}
if sk == Array {
sa = src.val
} else {
sa = unsafe.Pointer((*SliceHeader)(src.val).Data)
}
memmove(da, sa, uintptr(n)*de.Size())
return n
}
/*
* constructors
*/
// implemented in package runtime
func unsafe_New(Type) unsafe.Pointer
func unsafe_NewArray(Type, int) unsafe.Pointer
// 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")
}
// Declare slice so that gc can see the base pointer in it.
var x []byte
// Reinterpret as *SliceHeader to edit.
s := (*SliceHeader)(unsafe.Pointer(&x))
s.Data = uintptr(unsafe_NewArray(typ.Elem(), cap))
s.Len = len
s.Cap = cap
return Value{typ.common(), unsafe.Pointer(&x), flagIndir | flag(Slice)<<flagKindShift}
}
// 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("reflect.MakeChan: negative buffer size")
}
if typ.ChanDir() != BothDir {
panic("reflect.MakeChan: unidirectional channel type")
}
ch := makechan(typ.runtimeType(), uint32(buffer))
return Value{typ.common(), unsafe.Pointer(ch), flag(Chan) << flagKindShift}
}
// 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 Value{typ.common(), unsafe.Pointer(m), flag(Map) << flagKindShift}
}
// Indirect returns the value that v points to.
// If v is a nil pointer, Indirect returns a zero 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{}
}
// TODO(rsc): Eliminate this terrible hack.
// In the call to packValue, eface.typ doesn't escape,
// and eface.word is an integer. So it looks like
// i (= eface) doesn't escape. But really it does,
// because eface.word is actually a pointer.
escapes(i)
// For an interface value with the noAddr bit set,
// the representation is identical to an empty interface.
eface := *(*emptyInterface)(unsafe.Pointer(&i))
typ := toCommonType(eface.typ)
fl := flag(typ.Kind()) << flagKindShift
if typ.size > ptrSize {
fl |= flagIndir
}
return Value{typ, unsafe.Pointer(eface.word), fl}
}
// 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)")
}
t := typ.common()
fl := flag(t.Kind()) << flagKindShift
if t.size <= ptrSize {
return Value{t, nil, fl}
}
return Value{t, unsafe_New(typ), fl | flagIndir}
}
// 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)
fl := flag(Ptr) << flagKindShift
return Value{typ.common().ptrTo(), ptr, fl}
}
// NewAt returns a Value representing a pointer to a value of the
// specified type, using p as that pointer.
func NewAt(typ Type, p unsafe.Pointer) Value {
fl := flag(Ptr) << flagKindShift
return Value{typ.common().ptrTo(), p, fl}
}
// assignTo returns a value v that can be assigned directly to typ.
// It panics if v is not assignable to typ.
// For a conversion to an interface type, target is a suggested scratch space to use.
func (v Value) assignTo(context string, dst *commonType, target *interface{}) Value {
if v.flag&flagMethod != 0 {
panic(context + ": cannot assign method value to type " + dst.String())
}
switch {
case directlyAssignable(dst, v.typ):
// Overwrite type so that they match.
// Same memory layout, so no harm done.
v.typ = dst
fl := v.flag & (flagRO | flagAddr | flagIndir)
fl |= flag(dst.Kind()) << flagKindShift
return Value{dst, v.val, fl}
case implements(dst, v.typ):
if target == nil {
target = new(interface{})
}
x := valueInterface(v, false)
if dst.NumMethod() == 0 {
*target = x
} else {
ifaceE2I(dst.runtimeType(), x, unsafe.Pointer(target))
}
return Value{dst, unsafe.Pointer(target), flagIndir | flag(Interface)<<flagKindShift}
}
// Failed.
panic(context + ": value of type " + v.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 *runtimeType, ch iword, nb bool) (val iword, selected, received bool)
func chansend(t *runtimeType, ch iword, val iword, nb bool) bool
func makechan(typ *runtimeType, size uint32) (ch iword)
func makemap(t *runtimeType) (m iword)
func mapaccess(t *runtimeType, m iword, key iword) (val iword, ok bool)
func mapassign(t *runtimeType, m iword, key, val iword, ok bool)
func mapiterinit(t *runtimeType, 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 *runtimeType, src interface{}, dst unsafe.Pointer)
// Dummy annotation marking that the value x escapes,
// for use in cases where the reflect code is so clever that
// the compiler cannot follow.
func escapes(x interface{}) {
if dummy.b {
dummy.x = x
}
}
var dummy struct {
b bool
x interface{}
}