// 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" "unsafe" ) const ptrSize = 4 << (^uintptr(0) >> 63) // unsafe.Sizeof(uintptr(0)) but an ideal const // 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 "", and all other methods panic. // Most functions and methods never return an invalid value. // If one does, its documentation states the conditions explicitly. // // A Value can be used concurrently by multiple goroutines provided that // the underlying Go value can be used concurrently for the equivalent // direct operations. // // Using == on two Values does not compare the underlying values // they represent, but rather the contents of the Value structs. // To compare two Values, compare the results of the Interface method. type Value struct { // typ holds the type of the value represented by a Value. typ *rtype // Pointer-valued data or, if flagIndir is set, pointer to data. // Valid when either flagIndir is set or typ.pointers() is true. ptr unsafe.Pointer // flag holds metadata about the value. // The lowest bits are flag bits: // - flagStickyRO: obtained via unexported not embedded field, so read-only // - flagEmbedRO: obtained via unexported embedded 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 ifaceIndir(typ), 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 ( flagKindWidth = 5 // there are 27 kinds flagKindMask flag = 1<>flagMethodShift) } else if v.flag&flagIndir != 0 { fn = *(*unsafe.Pointer)(v.ptr) } else { fn = v.ptr } if fn == nil { panic("reflect.Value.Call: call of nil function") } isSlice := op == "CallSlice" n := t.NumIn() if isSlice { if !t.IsVariadic() { panic("reflect: CallSlice of non-variadic function") } if len(in) < n { panic("reflect: CallSlice with too few input arguments") } if len(in) > n { panic("reflect: CallSlice with too many input arguments") } } else { if t.IsVariadic() { n-- } if len(in) < n { panic("reflect: Call with too few input arguments") } if !t.IsVariadic() && len(in) > n { panic("reflect: Call with too many input arguments") } } for _, x := range in { if x.Kind() == Invalid { panic("reflect: " + op + " using zero Value argument") } } for i := 0; i < n; i++ { if xt, targ := in[i].Type(), t.In(i); !xt.AssignableTo(targ) { panic("reflect: " + op + " using " + xt.String() + " as type " + targ.String()) } } if !isSlice && t.IsVariadic() { // prepare slice for remaining values m := len(in) - n slice := MakeSlice(t.In(n), m, m) elem := t.In(n).Elem() for i := 0; i < m; i++ { x := in[n+i] if xt := x.Type(); !xt.AssignableTo(elem) { panic("reflect: cannot use " + xt.String() + " as type " + elem.String() + " in " + op) } slice.Index(i).Set(x) } origIn := in in = make([]Value, n+1) copy(in[:n], origIn) in[n] = slice } nin := len(in) if nin != t.NumIn() { panic("reflect.Value.Call: wrong argument count") } nout := t.NumOut() // Compute frame type. frametype, _, retOffset, _, framePool := funcLayout(t, rcvrtype) // Allocate a chunk of memory for frame. var args unsafe.Pointer if nout == 0 { args = framePool.Get().(unsafe.Pointer) } else { // Can't use pool if the function has return values. // We will leak pointer to args in ret, so its lifetime is not scoped. args = unsafe_New(frametype) } off := uintptr(0) // Copy inputs into args. if rcvrtype != nil { storeRcvr(rcvr, args) off = ptrSize } for i, v := range in { v.mustBeExported() targ := t.In(i).(*rtype) a := uintptr(targ.align) off = (off + a - 1) &^ (a - 1) n := targ.size addr := unsafe.Pointer(uintptr(args) + off) v = v.assignTo("reflect.Value.Call", targ, addr) if v.flag&flagIndir != 0 { typedmemmove(targ, addr, v.ptr) } else { *(*unsafe.Pointer)(addr) = v.ptr } off += n } // Call. call(frametype, fn, args, uint32(frametype.size), uint32(retOffset)) // For testing; see TestCallMethodJump. if callGC { runtime.GC() } var ret []Value if nout == 0 { // This is untyped because the frame is really a // stack, even though it's a heap object. memclrNoHeapPointers(args, frametype.size) framePool.Put(args) } else { // Zero the now unused input area of args, // because the Values returned by this function contain pointers to the args object, // and will thus keep the args object alive indefinitely. memclrNoHeapPointers(args, retOffset) // Wrap Values around return values in args. ret = make([]Value, nout) off = retOffset 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()) ret[i] = Value{tv.common(), unsafe.Pointer(uintptr(args) + off), fl} off += tv.Size() } } return ret } // callReflect is the call implementation used by a function // returned by MakeFunc. In many ways it is the opposite of the // method Value.call above. The method above converts a call using Values // into a call of a function with a concrete argument frame, while // callReflect converts a call of a function with a concrete argument // frame into a call using Values. // It is in this file so that it can be next to the call method above. // The remainder of the MakeFunc implementation is in makefunc.go. // // NOTE: This function must be marked as a "wrapper" in the generated code, // so that the linker can make it work correctly for panic and recover. // The gc compilers know to do that for the name "reflect.callReflect". func callReflect(ctxt *makeFuncImpl, frame unsafe.Pointer) { ftyp := ctxt.typ f := ctxt.fn // Copy argument frame into Values. ptr := frame off := uintptr(0) in := make([]Value, 0, int(ftyp.inCount)) for _, typ := range ftyp.in() { off += -off & uintptr(typ.align-1) addr := unsafe.Pointer(uintptr(ptr) + off) v := Value{typ, nil, flag(typ.Kind())} if ifaceIndir(typ) { // value cannot be inlined in interface data. // Must make a copy, because f might keep a reference to it, // and we cannot let f keep a reference to the stack frame // after this function returns, not even a read-only reference. v.ptr = unsafe_New(typ) typedmemmove(typ, v.ptr, addr) v.flag |= flagIndir } else { v.ptr = *(*unsafe.Pointer)(addr) } in = append(in, v) off += typ.size } // Call underlying function. out := f(in) numOut := ftyp.NumOut() if len(out) != numOut { panic("reflect: wrong return count from function created by MakeFunc") } // Copy results back into argument frame. if numOut > 0 { off += -off & (ptrSize - 1) if runtime.GOARCH == "amd64p32" { off = align(off, 8) } for i, typ := range ftyp.out() { v := out[i] if v.typ != typ { panic("reflect: function created by MakeFunc using " + funcName(f) + " returned wrong type: have " + out[i].typ.String() + " for " + typ.String()) } if v.flag&flagRO != 0 { panic("reflect: function created by MakeFunc using " + funcName(f) + " returned value obtained from unexported field") } off += -off & uintptr(typ.align-1) addr := unsafe.Pointer(uintptr(ptr) + off) if v.flag&flagIndir != 0 { typedmemmove(typ, addr, v.ptr) } else { *(*unsafe.Pointer)(addr) = v.ptr } off += typ.size } } // runtime.getArgInfo expects to be able to find ctxt on the // stack when it finds our caller, makeFuncStub. Make sure it // doesn't get garbage collected. runtime.KeepAlive(ctxt) } // methodReceiver returns information about the receiver // described by v. The Value v may or may not have the // flagMethod bit set, so the kind cached in v.flag should // not be used. // The return value rcvrtype gives the method's actual receiver type. // The return value t gives the method type signature (without the receiver). // The return value fn is a pointer to the method code. func methodReceiver(op string, v Value, methodIndex int) (rcvrtype, t *rtype, fn unsafe.Pointer) { i := methodIndex if v.typ.Kind() == Interface { tt := (*interfaceType)(unsafe.Pointer(v.typ)) if uint(i) >= uint(len(tt.methods)) { panic("reflect: internal error: invalid method index") } m := &tt.methods[i] if !tt.nameOff(m.name).isExported() { panic("reflect: " + op + " of unexported method") } iface := (*nonEmptyInterface)(v.ptr) if iface.itab == nil { panic("reflect: " + op + " of method on nil interface value") } rcvrtype = iface.itab.typ fn = unsafe.Pointer(&iface.itab.fun[i]) t = tt.typeOff(m.typ) } else { rcvrtype = v.typ ut := v.typ.uncommon() if ut == nil || uint(i) >= uint(ut.mcount) { panic("reflect: internal error: invalid method index") } m := ut.methods()[i] if !v.typ.nameOff(m.name).isExported() { panic("reflect: " + op + " of unexported method") } ifn := v.typ.textOff(m.ifn) fn = unsafe.Pointer(&ifn) t = v.typ.typeOff(m.mtyp) } return } // v is a method receiver. Store at p the word which is used to // encode that receiver at the start of the argument list. // Reflect uses the "interface" calling convention for // methods, which always uses one word to record the receiver. func storeRcvr(v Value, p unsafe.Pointer) { t := v.typ if t.Kind() == Interface { // the interface data word becomes the receiver word iface := (*nonEmptyInterface)(v.ptr) *(*unsafe.Pointer)(p) = iface.word } else if v.flag&flagIndir != 0 && !ifaceIndir(t) { *(*unsafe.Pointer)(p) = *(*unsafe.Pointer)(v.ptr) } else { *(*unsafe.Pointer)(p) = v.ptr } } // align returns the result of rounding x up to a multiple of n. // n must be a power of two. func align(x, n uintptr) uintptr { return (x + n - 1) &^ (n - 1) } // callMethod is the call implementation used by a function returned // by makeMethodValue (used by v.Method(i).Interface()). // It is a streamlined version of the usual reflect call: the caller has // already laid out the argument frame for us, so we don't have // to deal with individual Values for each argument. // It is in this file so that it can be next to the two similar functions above. // The remainder of the makeMethodValue implementation is in makefunc.go. // // NOTE: This function must be marked as a "wrapper" in the generated code, // so that the linker can make it work correctly for panic and recover. // The gc compilers know to do that for the name "reflect.callMethod". func callMethod(ctxt *methodValue, frame unsafe.Pointer) { rcvr := ctxt.rcvr rcvrtype, t, fn := methodReceiver("call", rcvr, ctxt.method) frametype, argSize, retOffset, _, framePool := funcLayout(t, rcvrtype) // Make a new frame that is one word bigger so we can store the receiver. args := framePool.Get().(unsafe.Pointer) // Copy in receiver and rest of args. // Avoid constructing out-of-bounds pointers if there are no args. storeRcvr(rcvr, args) if argSize-ptrSize > 0 { typedmemmovepartial(frametype, unsafe.Pointer(uintptr(args)+ptrSize), frame, ptrSize, argSize-ptrSize) } // Call. call(frametype, fn, args, uint32(frametype.size), uint32(retOffset)) // Copy return values. On amd64p32, the beginning of return values // is 64-bit aligned, so the caller's frame layout (which doesn't have // a receiver) is different from the layout of the fn call, which has // a receiver. // Ignore any changes to args and just copy return values. // Avoid constructing out-of-bounds pointers if there are no return values. if frametype.size-retOffset > 0 { callerRetOffset := retOffset - ptrSize if runtime.GOARCH == "amd64p32" { callerRetOffset = align(argSize-ptrSize, 8) } typedmemmovepartial(frametype, unsafe.Pointer(uintptr(frame)+callerRetOffset), unsafe.Pointer(uintptr(args)+retOffset), retOffset, frametype.size-retOffset) } // This is untyped because the frame is really a stack, even // though it's a heap object. memclrNoHeapPointers(args, frametype.size) framePool.Put(args) // See the comment in callReflect. runtime.KeepAlive(ctxt) } // funcName returns the name of f, for use in error messages. func funcName(f func([]Value) []Value) string { pc := *(*uintptr)(unsafe.Pointer(&f)) rf := runtime.FuncForPC(pc) if rf != nil { return rf.Name() } return "closure" } // 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 chancap(v.pointer()) case Slice: // Slice is always bigger than a word; assume flagIndir. return (*sliceHeader)(v.ptr).Cap } panic(&ValueError{"reflect.Value.Cap", v.kind()}) } // 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.pointer()) } // 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: return complex128(*(*complex64)(v.ptr)) case Complex128: return *(*complex128)(v.ptr) } panic(&ValueError{"reflect.Value.Complex", v.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 { k := v.kind() switch k { case Interface: var eface interface{} if v.typ.NumMethod() == 0 { eface = *(*interface{})(v.ptr) } else { eface = (interface{})(*(*interface { M() })(v.ptr)) } x := unpackEface(eface) if x.flag != 0 { x.flag |= v.flag & flagRO } return x case Ptr: ptr := v.ptr if v.flag&flagIndir != 0 { ptr = *(*unsafe.Pointer)(ptr) } // The returned value's address is v's value. if ptr == nil { return Value{} } tt := (*ptrType)(unsafe.Pointer(v.typ)) typ := tt.elem fl := v.flag&flagRO | flagIndir | flagAddr fl |= flag(typ.Kind()) return Value{typ, ptr, fl} } panic(&ValueError{"reflect.Value.Elem", v.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 { if v.kind() != Struct { panic(&ValueError{"reflect.Value.Field", v.kind()}) } tt := (*structType)(unsafe.Pointer(v.typ)) if uint(i) >= uint(len(tt.fields)) { panic("reflect: Field index out of range") } field := &tt.fields[i] typ := field.typ // Inherit permission bits from v, but clear flagEmbedRO. fl := v.flag&(flagStickyRO|flagIndir|flagAddr) | flag(typ.Kind()) // Using an unexported field forces flagRO. if !field.name.isExported() { if field.name.name() == "" { fl |= flagEmbedRO } else { fl |= flagStickyRO } } // Either flagIndir is set and v.ptr points at struct, // or flagIndir is not set and v.ptr is the actual struct data. // In the former case, we want v.ptr + offset. // In the latter case, we must have field.offset = 0, // so v.ptr + field.offset is still okay. ptr := unsafe.Pointer(uintptr(v.ptr) + field.offset) return Value{typ, ptr, 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 { if len(index) == 1 { return v.Field(index[0]) } v.mustBe(Struct) for i, x := range index { if i > 0 { if v.Kind() == Ptr && v.typ.Elem().Kind() == Struct { if v.IsNil() { panic("reflect: indirection through nil pointer to embedded 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 { 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: return float64(*(*float32)(v.ptr)) case Float64: return *(*float64)(v.ptr) } panic(&ValueError{"reflect.Value.Float", v.kind()}) } var uint8Type = TypeOf(uint8(0)).(*rtype) // Index returns v's i'th element. // It panics if v's Kind is not Array, Slice, or String or i is out of range. func (v Value) Index(i int) Value { switch v.kind() { case Array: tt := (*arrayType)(unsafe.Pointer(v.typ)) if uint(i) >= uint(tt.len) { panic("reflect: array index out of range") } typ := tt.elem offset := uintptr(i) * typ.size // Either flagIndir is set and v.ptr points at array, // or flagIndir is not set and v.ptr is the actual array data. // In the former case, we want v.ptr + offset. // In the latter case, we must be doing Index(0), so offset = 0, // so v.ptr + offset is still okay. val := unsafe.Pointer(uintptr(v.ptr) + offset) fl := v.flag&(flagRO|flagIndir|flagAddr) | flag(typ.Kind()) // bits same as overall array return Value{typ, val, fl} case Slice: // Element flag same as Elem of Ptr. // Addressable, indirect, possibly read-only. s := (*sliceHeader)(v.ptr) if uint(i) >= uint(s.Len) { panic("reflect: slice index out of range") } tt := (*sliceType)(unsafe.Pointer(v.typ)) typ := tt.elem val := arrayAt(s.Data, i, typ.size) fl := flagAddr | flagIndir | v.flag&flagRO | flag(typ.Kind()) return Value{typ, val, fl} case String: s := (*stringHeader)(v.ptr) if uint(i) >= uint(s.Len) { panic("reflect: string index out of range") } p := arrayAt(s.Data, i, 1) fl := v.flag&flagRO | flag(Uint8) | flagIndir return Value{uint8Type, p, fl} } panic(&ValueError{"reflect.Value.Index", v.kind()}) } // 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() p := v.ptr 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)(p) } panic(&ValueError{"reflect.Value.Int", v.kind()}) } // CanInterface reports whether Interface can be used without panicking. func (v Value) CanInterface() bool { if v.flag == 0 { panic(&ValueError{"reflect.Value.CanInterface", Invalid}) } return v.flag&flagRO == 0 } // Interface returns v's current value as an interface{}. // It is equivalent to: // var i interface{} = (v's underlying value) // It panics if the Value was obtained by accessing // unexported struct fields. func (v Value) Interface() (i interface{}) { return valueInterface(v, true) } func valueInterface(v Value, safe bool) interface{} { if v.flag == 0 { panic(&ValueError{"reflect.Value.Interface", 0}) } 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") } if v.flag&flagMethod != 0 { v = makeMethodValue("Interface", v) } if v.kind() == 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.ptr) } return *(*interface { M() })(v.ptr) } // TODO: pass safe to packEface so we don't need to copy if safe==true? return packEface(v) } // 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 { // TODO: deprecate this 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.ptr) } // IsNil reports whether its argument v is nil. The argument must be // a chan, func, interface, map, pointer, or slice value; if it is // not, IsNil panics. Note that IsNil is not always equivalent to a // regular comparison with nil in Go. For example, if v was created // by calling ValueOf with an uninitialized interface variable i, // i==nil will be true but v.IsNil will panic as v will be the zero // Value. func (v Value) IsNil() bool { k := v.kind() switch k { case Chan, Func, Map, Ptr: if v.flag&flagMethod != 0 { return false } ptr := v.ptr 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.ptr) == nil } panic(&ValueError{"reflect.Value.IsNil", v.kind()}) } // IsValid reports whether 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 chanlen(v.pointer()) case Map: return maplen(v.pointer()) case Slice: // Slice is bigger than a word; assume flagIndir. return (*sliceHeader)(v.ptr).Len case String: // String is bigger than a word; assume flagIndir. return (*stringHeader)(v.ptr).Len } panic(&ValueError{"reflect.Value.Len", v.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 { v.mustBe(Map) tt := (*mapType)(unsafe.Pointer(v.typ)) // Do not require key to be exported, so that DeepEqual // and other programs can use all the keys returned by // MapKeys as arguments to MapIndex. If either the map // or the key is unexported, though, the result will be // considered unexported. This is consistent with the // behavior for structs, which allow read but not write // of unexported fields. key = key.assignTo("reflect.Value.MapIndex", tt.key, nil) var k unsafe.Pointer if key.flag&flagIndir != 0 { k = key.ptr } else { k = unsafe.Pointer(&key.ptr) } e := mapaccess(v.typ, v.pointer(), k) if e == nil { return Value{} } typ := tt.elem fl := (v.flag | key.flag) & flagRO fl |= flag(typ.Kind()) if ifaceIndir(typ) { // Copy result so future changes to the map // won't change the underlying value. c := unsafe_New(typ) typedmemmove(typ, c, e) return Value{typ, c, fl | flagIndir} } else { return Value{typ, *(*unsafe.Pointer)(e), 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 := tt.key fl := v.flag&flagRO | flag(keyType.Kind()) m := v.pointer() mlen := int(0) if m != nil { mlen = maplen(m) } it := mapiterinit(v.typ, m) a := make([]Value, mlen) var i int for i = 0; i < len(a); i++ { key := mapiterkey(it) if key == nil { // Someone deleted an entry from the map since we // called maplen above. It's a data race, but nothing // we can do about it. break } if ifaceIndir(keyType) { // Copy result so future changes to the map // won't change the underlying value. c := unsafe_New(keyType) typedmemmove(keyType, c, key) a[i] = Value{keyType, c, fl | flagIndir} } else { a[i] = Value{keyType, *(*unsafe.Pointer)(key), 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 or if v is a nil interface value. func (v Value) Method(i int) Value { if v.typ == nil { panic(&ValueError{"reflect.Value.Method", Invalid}) } if v.flag&flagMethod != 0 || uint(i) >= uint(v.typ.NumMethod()) { panic("reflect: Method index out of range") } if v.typ.Kind() == Interface && v.IsNil() { panic("reflect: Method on nil interface value") } fl := v.flag & (flagStickyRO | flagIndir) // Clear flagEmbedRO fl |= flag(Func) fl |= flag(i)<> (64 - bitSize) return x != trunc } panic(&ValueError{"reflect.Value.OverflowInt", v.kind()}) } // OverflowUint reports whether 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", v.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. // // If v's Kind is Func, the returned pointer is an underlying // code pointer, but not necessarily enough to identify a // single function uniquely. The only guarantee is that the // result is zero if and only if v is a nil func Value. // // If v's Kind is Slice, the returned pointer is to the first // element of the slice. If the slice is nil the returned value // is 0. If the slice is empty but non-nil the return value is non-zero. func (v Value) Pointer() uintptr { // TODO: deprecate k := v.kind() switch k { case Chan, Map, Ptr, UnsafePointer: return uintptr(v.pointer()) case Func: if v.flag&flagMethod != 0 { // As the doc comment says, the returned pointer is an // underlying code pointer but not necessarily enough to // identify a single function uniquely. All method expressions // created via reflect have the same underlying code pointer, // so their Pointers are equal. The function used here must // match the one used in makeMethodValue. f := methodValueCall return **(**uintptr)(unsafe.Pointer(&f)) } p := v.pointer() // Non-nil func value points at data block. // First word of data block is actual code. if p != nil { p = *(*unsafe.Pointer)(p) } return uintptr(p) case Slice: return (*SliceHeader)(v.ptr).Data } panic(&ValueError{"reflect.Value.Pointer", v.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) { 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("reflect: recv on send-only channel") } t := tt.elem val = Value{t, nil, flag(t.Kind())} var p unsafe.Pointer if ifaceIndir(t) { p = unsafe_New(t) val.ptr = p val.flag |= flagIndir } else { p = unsafe.Pointer(&val.ptr) } selected, ok := chanrecv(v.typ, v.pointer(), nb, p) if !selected { val = Value{} } 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("reflect: send on recv-only channel") } x.mustBeExported() x = x.assignTo("reflect.Value.Send", tt.elem, nil) var p unsafe.Pointer if x.flag&flagIndir != 0 { p = x.ptr } else { p = unsafe.Pointer(&x.ptr) } return chansend(v.typ, v.pointer(), p, 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 unsafe.Pointer if v.kind() == Interface { target = v.ptr } x = x.assignTo("reflect.Set", v.typ, target) if x.flag&flagIndir != 0 { typedmemmove(v.typ, v.ptr, x.ptr) } else { *(*unsafe.Pointer)(v.ptr) = x.ptr } } // 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.ptr) = 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.ptr) = x } // setRunes sets v's underlying value. // It panics if v's underlying value is not a slice of runes (int32s). func (v Value) setRunes(x []rune) { v.mustBeAssignable() v.mustBe(Slice) if v.typ.Elem().Kind() != Int32 { panic("reflect.Value.setRunes of non-rune slice") } *(*[]rune)(v.ptr) = 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", v.kind()}) case Complex64: *(*complex64)(v.ptr) = complex64(x) case Complex128: *(*complex128)(v.ptr) = 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", v.kind()}) case Float32: *(*float32)(v.ptr) = float32(x) case Float64: *(*float64)(v.ptr) = 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", v.kind()}) case Int: *(*int)(v.ptr) = int(x) case Int8: *(*int8)(v.ptr) = int8(x) case Int16: *(*int16)(v.ptr) = int16(x) case Int32: *(*int32)(v.ptr) = int32(x) case Int64: *(*int64)(v.ptr) = 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.ptr) if uint(n) > uint(s.Cap) { panic("reflect: slice length out of range in SetLen") } s.Len = n } // SetCap sets v's capacity to n. // It panics if v's Kind is not Slice or if n is smaller than the length or // greater than the capacity of the slice. func (v Value) SetCap(n int) { v.mustBeAssignable() v.mustBe(Slice) s := (*sliceHeader)(v.ptr) if n < s.Len || n > s.Cap { panic("reflect: slice capacity out of range in SetCap") } s.Cap = 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. // Otherwise if v holds a nil map, SetMapIndex will panic. // 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", tt.key, nil) var k unsafe.Pointer if key.flag&flagIndir != 0 { k = key.ptr } else { k = unsafe.Pointer(&key.ptr) } if val.typ == nil { mapdelete(v.typ, v.pointer(), k) return } val.mustBeExported() val = val.assignTo("reflect.Value.SetMapIndex", tt.elem, nil) var e unsafe.Pointer if val.flag&flagIndir != 0 { e = val.ptr } else { e = unsafe.Pointer(&val.ptr) } mapassign(v.typ, v.pointer(), k, e) } // 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", v.kind()}) case Uint: *(*uint)(v.ptr) = uint(x) case Uint8: *(*uint8)(v.ptr) = uint8(x) case Uint16: *(*uint16)(v.ptr) = uint16(x) case Uint32: *(*uint32)(v.ptr) = uint32(x) case Uint64: *(*uint64)(v.ptr) = x case Uintptr: *(*uintptr)(v.ptr) = 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.ptr) = 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.ptr) = x } // Slice returns v[i:j]. // It panics if v's Kind is not Array, Slice or String, or if v is an unaddressable array, // or if the indexes are out of bounds. func (v Value) Slice(i, j int) Value { var ( cap int typ *sliceType base unsafe.Pointer ) switch kind := v.kind(); kind { default: panic(&ValueError{"reflect.Value.Slice", v.kind()}) case Array: if v.flag&flagAddr == 0 { panic("reflect.Value.Slice: slice of unaddressable array") } tt := (*arrayType)(unsafe.Pointer(v.typ)) cap = int(tt.len) typ = (*sliceType)(unsafe.Pointer(tt.slice)) base = v.ptr case Slice: typ = (*sliceType)(unsafe.Pointer(v.typ)) s := (*sliceHeader)(v.ptr) base = s.Data cap = s.Cap case String: s := (*stringHeader)(v.ptr) if i < 0 || j < i || j > s.Len { panic("reflect.Value.Slice: string slice index out of bounds") } t := stringHeader{arrayAt(s.Data, i, 1), j - i} return Value{v.typ, unsafe.Pointer(&t), v.flag} } if i < 0 || j < i || j > cap { panic("reflect.Value.Slice: slice index out of bounds") } // Declare slice so that gc can see the base pointer in it. var x []unsafe.Pointer // Reinterpret as *sliceHeader to edit. s := (*sliceHeader)(unsafe.Pointer(&x)) s.Len = j - i s.Cap = cap - i if cap-i > 0 { s.Data = arrayAt(base, i, typ.elem.Size()) } else { // do not advance pointer, to avoid pointing beyond end of slice s.Data = base } fl := v.flag&flagRO | flagIndir | flag(Slice) return Value{typ.common(), unsafe.Pointer(&x), fl} } // Slice3 is the 3-index form of the slice operation: it returns v[i:j:k]. // It panics if v's Kind is not Array or Slice, or if v is an unaddressable array, // or if the indexes are out of bounds. func (v Value) Slice3(i, j, k int) Value { var ( cap int typ *sliceType base unsafe.Pointer ) switch kind := v.kind(); kind { default: panic(&ValueError{"reflect.Value.Slice3", v.kind()}) case Array: if v.flag&flagAddr == 0 { panic("reflect.Value.Slice3: slice of unaddressable array") } tt := (*arrayType)(unsafe.Pointer(v.typ)) cap = int(tt.len) typ = (*sliceType)(unsafe.Pointer(tt.slice)) base = v.ptr case Slice: typ = (*sliceType)(unsafe.Pointer(v.typ)) s := (*sliceHeader)(v.ptr) base = s.Data cap = s.Cap } if i < 0 || j < i || k < j || k > cap { panic("reflect.Value.Slice3: slice index out of bounds") } // Declare slice so that the garbage collector // can see the base pointer in it. var x []unsafe.Pointer // Reinterpret as *sliceHeader to edit. s := (*sliceHeader)(unsafe.Pointer(&x)) s.Len = j - i s.Cap = k - i if k-i > 0 { s.Data = arrayAt(base, i, typ.elem.Size()) } else { // do not advance pointer, to avoid pointing beyond end of slice s.Data = base } fl := v.flag&flagRO | flagIndir | flag(Slice) 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 "" where T is v's type. // The fmt package treats Values specially. It does not call their String // method implicitly but instead prints the concrete values they hold. func (v Value) String() string { switch k := v.kind(); k { case Invalid: return "" case String: return *(*string)(v.ptr) } // 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.Type().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 delivers a value, x is the transferred value and ok is true. // If the receive cannot finish without blocking, x is the zero Value and ok is false. // If the channel is closed, x is the zero value for the channel's element type and ok is false. 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 reports whether the value was sent. // 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 uint(i) >= uint(len(tt.methods)) { panic("reflect: internal error: invalid method index") } m := &tt.methods[i] return v.typ.typeOff(m.typ) } // Method on concrete type. ut := v.typ.uncommon() if ut == nil || uint(i) >= uint(ut.mcount) { panic("reflect: internal error: invalid method index") } m := ut.methods()[i] return v.typ.typeOff(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() p := v.ptr 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)(p) case Uintptr: return uint64(*(*uintptr)(p)) } panic(&ValueError{"reflect.Value.Uint", v.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 { // TODO: deprecate 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.ptr) } // StringHeader is the runtime representation of a string. // It cannot be used safely or portably and its representation may // change in a later release. // Moreover, the Data field is not sufficient to guarantee the data // it references will not be garbage collected, so programs must keep // a separate, correctly typed pointer to the underlying data. type StringHeader struct { Data uintptr Len int } // stringHeader is a safe version of StringHeader used within this package. type stringHeader struct { Data unsafe.Pointer Len int } // SliceHeader is the runtime representation of a slice. // It cannot be used safely or portably and its representation may // change in a later release. // Moreover, the Data field is not sufficient to guarantee the data // it references will not be garbage collected, so programs must keep // a separate, correctly typed pointer to the underlying data. type SliceHeader struct { Data uintptr Len int Cap int } // sliceHeader is a safe version of SliceHeader used within this package. type sliceHeader struct { Data unsafe.Pointer Len int Cap int } func typesMustMatch(what string, t1, t2 Type) { if t1 != t2 { panic(what + ": " + t1.String() + " != " + t2.String()) } } // arrayAt returns the i-th element of p, a C-array whose elements are // eltSize wide (in bytes). func arrayAt(p unsafe.Pointer, i int, eltSize uintptr) unsafe.Pointer { return unsafe.Pointer(uintptr(p) + uintptr(i)*eltSize) } // 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) var ds, ss sliceHeader if dk == Array { ds.Data = dst.ptr ds.Len = dst.Len() ds.Cap = ds.Len } else { ds = *(*sliceHeader)(dst.ptr) } if sk == Array { ss.Data = src.ptr ss.Len = src.Len() ss.Cap = ss.Len } else { ss = *(*sliceHeader)(src.ptr) } return typedslicecopy(de.common(), ds, ss) } // A runtimeSelect is a single case passed to rselect. // This must match ../runtime/select.go:/runtimeSelect type runtimeSelect struct { dir SelectDir // SelectSend, SelectRecv or SelectDefault typ *rtype // channel type ch unsafe.Pointer // channel val unsafe.Pointer // ptr to data (SendDir) or ptr to receive buffer (RecvDir) } // rselect runs a select. It returns the index of the chosen case. // If the case was a receive, val is filled in with the received value. // The conventional OK bool indicates whether the receive corresponds // to a sent value. //go:noescape func rselect([]runtimeSelect) (chosen int, recvOK bool) // A SelectDir describes the communication direction of a select case. type SelectDir int // NOTE: These values must match ../runtime/select.go:/selectDir. const ( _ SelectDir = iota SelectSend // case Chan <- Send SelectRecv // case <-Chan: SelectDefault // default ) // A SelectCase describes a single case in a select operation. // The kind of case depends on Dir, the communication direction. // // If Dir is SelectDefault, the case represents a default case. // Chan and Send must be zero Values. // // If Dir is SelectSend, the case represents a send operation. // Normally Chan's underlying value must be a channel, and Send's underlying value must be // assignable to the channel's element type. As a special case, if Chan is a zero Value, // then the case is ignored, and the field Send will also be ignored and may be either zero // or non-zero. // // If Dir is SelectRecv, the case represents a receive operation. // Normally Chan's underlying value must be a channel and Send must be a zero Value. // If Chan is a zero Value, then the case is ignored, but Send must still be a zero Value. // When a receive operation is selected, the received Value is returned by Select. // type SelectCase struct { Dir SelectDir // direction of case Chan Value // channel to use (for send or receive) Send Value // value to send (for send) } // Select executes a select operation described by the list of cases. // Like the Go select statement, it blocks until at least one of the cases // can proceed, makes a uniform pseudo-random choice, // and then executes that case. It returns the index of the chosen case // and, if that case was a receive operation, the value received and a // boolean indicating whether the value corresponds to a send on the channel // (as opposed to a zero value received because the channel is closed). func Select(cases []SelectCase) (chosen int, recv Value, recvOK bool) { // NOTE: Do not trust that caller is not modifying cases data underfoot. // The range is safe because the caller cannot modify our copy of the len // and each iteration makes its own copy of the value c. runcases := make([]runtimeSelect, len(cases)) haveDefault := false for i, c := range cases { rc := &runcases[i] rc.dir = c.Dir switch c.Dir { default: panic("reflect.Select: invalid Dir") case SelectDefault: // default if haveDefault { panic("reflect.Select: multiple default cases") } haveDefault = true if c.Chan.IsValid() { panic("reflect.Select: default case has Chan value") } if c.Send.IsValid() { panic("reflect.Select: default case has Send value") } case SelectSend: ch := c.Chan if !ch.IsValid() { break } ch.mustBe(Chan) ch.mustBeExported() tt := (*chanType)(unsafe.Pointer(ch.typ)) if ChanDir(tt.dir)&SendDir == 0 { panic("reflect.Select: SendDir case using recv-only channel") } rc.ch = ch.pointer() rc.typ = &tt.rtype v := c.Send if !v.IsValid() { panic("reflect.Select: SendDir case missing Send value") } v.mustBeExported() v = v.assignTo("reflect.Select", tt.elem, nil) if v.flag&flagIndir != 0 { rc.val = v.ptr } else { rc.val = unsafe.Pointer(&v.ptr) } case SelectRecv: if c.Send.IsValid() { panic("reflect.Select: RecvDir case has Send value") } ch := c.Chan if !ch.IsValid() { break } ch.mustBe(Chan) ch.mustBeExported() tt := (*chanType)(unsafe.Pointer(ch.typ)) if ChanDir(tt.dir)&RecvDir == 0 { panic("reflect.Select: RecvDir case using send-only channel") } rc.ch = ch.pointer() rc.typ = &tt.rtype rc.val = unsafe_New(tt.elem) } } chosen, recvOK = rselect(runcases) if runcases[chosen].dir == SelectRecv { tt := (*chanType)(unsafe.Pointer(runcases[chosen].typ)) t := tt.elem p := runcases[chosen].val fl := flag(t.Kind()) if ifaceIndir(t) { recv = Value{t, p, fl | flagIndir} } else { recv = Value{t, *(*unsafe.Pointer)(p), fl} } } return chosen, recv, recvOK } /* * constructors */ // implemented in package runtime func unsafe_New(*rtype) unsafe.Pointer func unsafe_NewArray(*rtype, 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") } if len < 0 { panic("reflect.MakeSlice: negative len") } if cap < 0 { panic("reflect.MakeSlice: negative cap") } if len > cap { panic("reflect.MakeSlice: len > cap") } s := sliceHeader{unsafe_NewArray(typ.Elem().(*rtype), cap), len, cap} return Value{typ.common(), unsafe.Pointer(&s), flagIndir | flag(Slice)} } // 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.(*rtype), uint64(buffer)) return Value{typ.common(), ch, flag(Chan)} } // 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.(*rtype)) return Value{typ.common(), m, flag(Map)} } // 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: Maybe allow contents of a Value to live on the stack. // For now we make the contents always escape to the heap. It // makes life easier in a few places (see chanrecv/mapassign // comment below). escapes(i) return unpackEface(i) } // Zero returns a Value representing the 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. // The returned value is neither addressable nor settable. func Zero(typ Type) Value { if typ == nil { panic("reflect: Zero(nil)") } t := typ.common() fl := flag(t.Kind()) if ifaceIndir(t) { return Value{t, unsafe_New(typ.(*rtype)), fl | flagIndir} } return Value{t, nil, fl} } // 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(typ). func New(typ Type) Value { if typ == nil { panic("reflect: New(nil)") } ptr := unsafe_New(typ.(*rtype)) fl := flag(Ptr) 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) 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 *rtype, target unsafe.Pointer) Value { if v.flag&flagMethod != 0 { v = makeMethodValue(context, v) } switch { case directlyAssignable(dst, v.typ): // Overwrite type so that they match. // Same memory layout, so no harm done. v.typ = dst fl := v.flag & (flagRO | flagAddr | flagIndir) fl |= flag(dst.Kind()) return Value{dst, v.ptr, fl} case implements(dst, v.typ): if target == nil { target = unsafe_New(dst) } x := valueInterface(v, false) if dst.NumMethod() == 0 { *(*interface{})(target) = x } else { ifaceE2I(dst, x, target) } return Value{dst, target, flagIndir | flag(Interface)} } // Failed. panic(context + ": value of type " + v.typ.String() + " is not assignable to type " + dst.String()) } // Convert returns the value v converted to type t. // If the usual Go conversion rules do not allow conversion // of the value v to type t, Convert panics. func (v Value) Convert(t Type) Value { if v.flag&flagMethod != 0 { v = makeMethodValue("Convert", v) } op := convertOp(t.common(), v.typ) if op == nil { panic("reflect.Value.Convert: value of type " + v.typ.String() + " cannot be converted to type " + t.String()) } return op(v, t) } // convertOp returns the function to convert a value of type src // to a value of type dst. If the conversion is illegal, convertOp returns nil. func convertOp(dst, src *rtype) func(Value, Type) Value { switch src.Kind() { case Int, Int8, Int16, Int32, Int64: switch dst.Kind() { case Int, Int8, Int16, Int32, Int64, Uint, Uint8, Uint16, Uint32, Uint64, Uintptr: return cvtInt case Float32, Float64: return cvtIntFloat case String: return cvtIntString } case Uint, Uint8, Uint16, Uint32, Uint64, Uintptr: switch dst.Kind() { case Int, Int8, Int16, Int32, Int64, Uint, Uint8, Uint16, Uint32, Uint64, Uintptr: return cvtUint case Float32, Float64: return cvtUintFloat case String: return cvtUintString } case Float32, Float64: switch dst.Kind() { case Int, Int8, Int16, Int32, Int64: return cvtFloatInt case Uint, Uint8, Uint16, Uint32, Uint64, Uintptr: return cvtFloatUint case Float32, Float64: return cvtFloat } case Complex64, Complex128: switch dst.Kind() { case Complex64, Complex128: return cvtComplex } case String: if dst.Kind() == Slice && dst.Elem().PkgPath() == "" { switch dst.Elem().Kind() { case Uint8: return cvtStringBytes case Int32: return cvtStringRunes } } case Slice: if dst.Kind() == String && src.Elem().PkgPath() == "" { switch src.Elem().Kind() { case Uint8: return cvtBytesString case Int32: return cvtRunesString } } } // dst and src have same underlying type. if haveIdenticalUnderlyingType(dst, src, false) { return cvtDirect } // dst and src are unnamed pointer types with same underlying base type. if dst.Kind() == Ptr && dst.Name() == "" && src.Kind() == Ptr && src.Name() == "" && haveIdenticalUnderlyingType(dst.Elem().common(), src.Elem().common(), false) { return cvtDirect } if implements(dst, src) { if src.Kind() == Interface { return cvtI2I } return cvtT2I } return nil } // makeInt returns a Value of type t equal to bits (possibly truncated), // where t is a signed or unsigned int type. func makeInt(f flag, bits uint64, t Type) Value { typ := t.common() ptr := unsafe_New(typ) switch typ.size { case 1: *(*uint8)(ptr) = uint8(bits) case 2: *(*uint16)(ptr) = uint16(bits) case 4: *(*uint32)(ptr) = uint32(bits) case 8: *(*uint64)(ptr) = bits } return Value{typ, ptr, f | flagIndir | flag(typ.Kind())} } // makeFloat returns a Value of type t equal to v (possibly truncated to float32), // where t is a float32 or float64 type. func makeFloat(f flag, v float64, t Type) Value { typ := t.common() ptr := unsafe_New(typ) switch typ.size { case 4: *(*float32)(ptr) = float32(v) case 8: *(*float64)(ptr) = v } return Value{typ, ptr, f | flagIndir | flag(typ.Kind())} } // makeComplex returns a Value of type t equal to v (possibly truncated to complex64), // where t is a complex64 or complex128 type. func makeComplex(f flag, v complex128, t Type) Value { typ := t.common() ptr := unsafe_New(typ) switch typ.size { case 8: *(*complex64)(ptr) = complex64(v) case 16: *(*complex128)(ptr) = v } return Value{typ, ptr, f | flagIndir | flag(typ.Kind())} } func makeString(f flag, v string, t Type) Value { ret := New(t).Elem() ret.SetString(v) ret.flag = ret.flag&^flagAddr | f return ret } func makeBytes(f flag, v []byte, t Type) Value { ret := New(t).Elem() ret.SetBytes(v) ret.flag = ret.flag&^flagAddr | f return ret } func makeRunes(f flag, v []rune, t Type) Value { ret := New(t).Elem() ret.setRunes(v) ret.flag = ret.flag&^flagAddr | f return ret } // These conversion functions are returned by convertOp // for classes of conversions. For example, the first function, cvtInt, // takes any value v of signed int type and returns the value converted // to type t, where t is any signed or unsigned int type. // convertOp: intXX -> [u]intXX func cvtInt(v Value, t Type) Value { return makeInt(v.flag&flagRO, uint64(v.Int()), t) } // convertOp: uintXX -> [u]intXX func cvtUint(v Value, t Type) Value { return makeInt(v.flag&flagRO, v.Uint(), t) } // convertOp: floatXX -> intXX func cvtFloatInt(v Value, t Type) Value { return makeInt(v.flag&flagRO, uint64(int64(v.Float())), t) } // convertOp: floatXX -> uintXX func cvtFloatUint(v Value, t Type) Value { return makeInt(v.flag&flagRO, uint64(v.Float()), t) } // convertOp: intXX -> floatXX func cvtIntFloat(v Value, t Type) Value { return makeFloat(v.flag&flagRO, float64(v.Int()), t) } // convertOp: uintXX -> floatXX func cvtUintFloat(v Value, t Type) Value { return makeFloat(v.flag&flagRO, float64(v.Uint()), t) } // convertOp: floatXX -> floatXX func cvtFloat(v Value, t Type) Value { return makeFloat(v.flag&flagRO, v.Float(), t) } // convertOp: complexXX -> complexXX func cvtComplex(v Value, t Type) Value { return makeComplex(v.flag&flagRO, v.Complex(), t) } // convertOp: intXX -> string func cvtIntString(v Value, t Type) Value { return makeString(v.flag&flagRO, string(v.Int()), t) } // convertOp: uintXX -> string func cvtUintString(v Value, t Type) Value { return makeString(v.flag&flagRO, string(v.Uint()), t) } // convertOp: []byte -> string func cvtBytesString(v Value, t Type) Value { return makeString(v.flag&flagRO, string(v.Bytes()), t) } // convertOp: string -> []byte func cvtStringBytes(v Value, t Type) Value { return makeBytes(v.flag&flagRO, []byte(v.String()), t) } // convertOp: []rune -> string func cvtRunesString(v Value, t Type) Value { return makeString(v.flag&flagRO, string(v.runes()), t) } // convertOp: string -> []rune func cvtStringRunes(v Value, t Type) Value { return makeRunes(v.flag&flagRO, []rune(v.String()), t) } // convertOp: direct copy func cvtDirect(v Value, typ Type) Value { f := v.flag t := typ.common() ptr := v.ptr if f&flagAddr != 0 { // indirect, mutable word - make a copy c := unsafe_New(t) typedmemmove(t, c, ptr) ptr = c f &^= flagAddr } return Value{t, ptr, v.flag&flagRO | f} // v.flag&flagRO|f == f? } // convertOp: concrete -> interface func cvtT2I(v Value, typ Type) Value { target := unsafe_New(typ.common()) x := valueInterface(v, false) if typ.NumMethod() == 0 { *(*interface{})(target) = x } else { ifaceE2I(typ.(*rtype), x, target) } return Value{typ.common(), target, v.flag&flagRO | flagIndir | flag(Interface)} } // convertOp: interface -> interface func cvtI2I(v Value, typ Type) Value { if v.IsNil() { ret := Zero(typ) ret.flag |= v.flag & flagRO return ret } return cvtT2I(v.Elem(), typ) } // implemented in ../runtime func chancap(ch unsafe.Pointer) int func chanclose(ch unsafe.Pointer) func chanlen(ch unsafe.Pointer) int // Note: some of the noescape annotations below are technically a lie, // but safe in the context of this package. Functions like chansend // and mapassign don't escape the referent, but may escape anything // the referent points to (they do shallow copies of the referent). // It is safe in this package because the referent may only point // to something a Value may point to, and that is always in the heap // (due to the escapes() call in ValueOf). //go:noescape func chanrecv(t *rtype, ch unsafe.Pointer, nb bool, val unsafe.Pointer) (selected, received bool) //go:noescape func chansend(t *rtype, ch unsafe.Pointer, val unsafe.Pointer, nb bool) bool func makechan(typ *rtype, size uint64) (ch unsafe.Pointer) func makemap(t *rtype) (m unsafe.Pointer) //go:noescape func mapaccess(t *rtype, m unsafe.Pointer, key unsafe.Pointer) (val unsafe.Pointer) //go:noescape func mapassign(t *rtype, m unsafe.Pointer, key, val unsafe.Pointer) //go:noescape func mapdelete(t *rtype, m unsafe.Pointer, key unsafe.Pointer) // m escapes into the return value, but the caller of mapiterinit // doesn't let the return value escape. //go:noescape func mapiterinit(t *rtype, m unsafe.Pointer) unsafe.Pointer //go:noescape func mapiterkey(it unsafe.Pointer) (key unsafe.Pointer) //go:noescape func mapiternext(it unsafe.Pointer) //go:noescape func maplen(m unsafe.Pointer) int // call calls fn with a copy of the n argument bytes pointed at by arg. // After fn returns, reflectcall copies n-retoffset result bytes // back into arg+retoffset before returning. If copying result bytes back, // the caller must pass the argument frame type as argtype, so that // call can execute appropriate write barriers during the copy. func call(argtype *rtype, fn, arg unsafe.Pointer, n uint32, retoffset uint32) func ifaceE2I(t *rtype, src interface{}, dst unsafe.Pointer) // typedmemmove copies a value of type t to dst from src. //go:noescape func typedmemmove(t *rtype, dst, src unsafe.Pointer) // typedmemmovepartial is like typedmemmove but assumes that // dst and src point off bytes into the value and only copies size bytes. //go:noescape func typedmemmovepartial(t *rtype, dst, src unsafe.Pointer, off, size uintptr) // typedslicecopy copies a slice of elemType values from src to dst, // returning the number of elements copied. //go:noescape func typedslicecopy(elemType *rtype, dst, src sliceHeader) int //go:noescape func memclrNoHeapPointers(ptr unsafe.Pointer, n uintptr) // 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{} }