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Diffstat (limited to 'src/pkg/reflect/value.go')
| -rw-r--r-- | src/pkg/reflect/value.go | 1736 |
1 files changed, 1736 insertions, 0 deletions
diff --git a/src/pkg/reflect/value.go b/src/pkg/reflect/value.go new file mode 100644 index 000000000..d3c510ac2 --- /dev/null +++ b/src/pkg/reflect/value.go @@ -0,0 +1,1736 @@ +// Copyright 2009 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package reflect + +import ( + "math" + "runtime" + "strconv" + "unsafe" +) + +const ptrSize = unsafe.Sizeof((*byte)(nil)) +const cannotSet = "cannot set value obtained from unexported struct field" + +// TODO: This will have to go away when +// the new gc goes in. +func memmove(adst, asrc unsafe.Pointer, n uintptr) { + dst := uintptr(adst) + src := uintptr(asrc) + switch { + case src < dst && src+n > dst: + // byte copy backward + // careful: i is unsigned + for i := n; i > 0; { + i-- + *(*byte)(unsafe.Pointer(dst + i)) = *(*byte)(unsafe.Pointer(src + i)) + } + case (n|src|dst)&(ptrSize-1) != 0: + // byte copy forward + for i := uintptr(0); i < n; i++ { + *(*byte)(unsafe.Pointer(dst + i)) = *(*byte)(unsafe.Pointer(src + i)) + } + default: + // word copy forward + for i := uintptr(0); i < n; i += ptrSize { + *(*uintptr)(unsafe.Pointer(dst + i)) = *(*uintptr)(unsafe.Pointer(src + i)) + } + } +} + +// Value is the reflection interface to a Go value. +// +// Not all methods apply to all kinds of values. Restrictions, +// if any, are noted in the documentation for each method. +// Use the Kind method to find out the kind of value before +// calling kind-specific methods. Calling a method +// inappropriate to the kind of type causes a run time panic. +// +// The zero Value represents no value. +// Its IsValid method returns false, its Kind method returns Invalid, +// its String method returns "<invalid Value>", and all other methods panic. +// Most functions and methods never return an invalid value. +// If one does, its documentation states the conditions explicitly. +// +// The fields of Value are exported so that clients can copy and +// pass Values around, but they should not be edited or inspected +// directly. A future language change may make it possible not to +// export these fields while still keeping Values usable as values. +type Value struct { + Internal interface{} + InternalMethod int +} + +// A ValueError occurs when a Value method is invoked on +// a Value that does not support it. Such cases are documented +// in the description of each method. +type ValueError struct { + Method string + Kind Kind +} + +func (e *ValueError) String() string { + if e.Kind == 0 { + return "reflect: call of " + e.Method + " on zero Value" + } + return "reflect: call of " + e.Method + " on " + e.Kind.String() + " Value" +} + +// methodName returns the name of the calling method, +// assumed to be two stack frames above. +func methodName() string { + pc, _, _, _ := runtime.Caller(2) + f := runtime.FuncForPC(pc) + if f == nil { + return "unknown method" + } + return f.Name() +} + +// An iword is the word that would be stored in an +// interface to represent a given value v. Specifically, if v is +// bigger than a pointer, its word is a pointer to v's data. +// Otherwise, its word is a zero uintptr with the data stored +// in the leading bytes. +type iword uintptr + +func loadIword(p unsafe.Pointer, size uintptr) iword { + // Run the copy ourselves instead of calling memmove + // to avoid moving v to the heap. + w := iword(0) + switch size { + default: + panic("reflect: internal error: loadIword of " + strconv.Itoa(int(size)) + "-byte value") + case 0: + case 1: + *(*uint8)(unsafe.Pointer(&w)) = *(*uint8)(p) + case 2: + *(*uint16)(unsafe.Pointer(&w)) = *(*uint16)(p) + case 3: + *(*[3]byte)(unsafe.Pointer(&w)) = *(*[3]byte)(p) + case 4: + *(*uint32)(unsafe.Pointer(&w)) = *(*uint32)(p) + case 5: + *(*[5]byte)(unsafe.Pointer(&w)) = *(*[5]byte)(p) + case 6: + *(*[6]byte)(unsafe.Pointer(&w)) = *(*[6]byte)(p) + case 7: + *(*[7]byte)(unsafe.Pointer(&w)) = *(*[7]byte)(p) + case 8: + *(*uint64)(unsafe.Pointer(&w)) = *(*uint64)(p) + } + return w +} + +func storeIword(p unsafe.Pointer, w iword, size uintptr) { + // Run the copy ourselves instead of calling memmove + // to avoid moving v to the heap. + switch size { + default: + panic("reflect: internal error: storeIword of " + strconv.Itoa(int(size)) + "-byte value") + case 0: + case 1: + *(*uint8)(p) = *(*uint8)(unsafe.Pointer(&w)) + case 2: + *(*uint16)(p) = *(*uint16)(unsafe.Pointer(&w)) + case 3: + *(*[3]byte)(p) = *(*[3]byte)(unsafe.Pointer(&w)) + case 4: + *(*uint32)(p) = *(*uint32)(unsafe.Pointer(&w)) + case 5: + *(*[5]byte)(p) = *(*[5]byte)(unsafe.Pointer(&w)) + case 6: + *(*[6]byte)(p) = *(*[6]byte)(unsafe.Pointer(&w)) + case 7: + *(*[7]byte)(p) = *(*[7]byte)(unsafe.Pointer(&w)) + case 8: + *(*uint64)(p) = *(*uint64)(unsafe.Pointer(&w)) + } +} + +// emptyInterface is the header for an interface{} value. +type emptyInterface struct { + typ *runtime.Type + word iword +} + +// nonEmptyInterface is the header for a interface value with methods. +type nonEmptyInterface struct { + // see ../runtime/iface.c:/Itab + itab *struct { + ityp *runtime.Type // static interface type + typ *runtime.Type // dynamic concrete type + link unsafe.Pointer + bad int32 + unused int32 + fun [100000]unsafe.Pointer // method table + } + word iword +} + +// Regarding the implementation of Value: +// +// The Internal interface is a true interface value in the Go sense, +// but it also serves as a (type, address) pair in which one cannot +// be changed separately from the other. That is, it serves as a way +// to prevent unsafe mutations of the Internal state even though +// we cannot (yet?) hide the field while preserving the ability for +// clients to make copies of Values. +// +// The internal method converts a Value into the expanded internalValue struct. +// If we could avoid exporting fields we'd probably make internalValue the +// definition of Value. +// +// If a Value is addressable (CanAddr returns true), then the Internal +// interface value holds a pointer to the actual field data, and Set stores +// through that pointer. If a Value is not addressable (CanAddr returns false), +// then the Internal interface value holds the actual value. +// +// In addition to whether a value is addressable, we track whether it was +// obtained by using an unexported struct field. Such values are allowed +// to be read, mainly to make fmt.Print more useful, but they are not +// allowed to be written. We call such values read-only. +// +// A Value can be set (via the Set, SetUint, etc. methods) only if it is both +// addressable and not read-only. +// +// The two permission bits - addressable and read-only - are stored in +// the bottom two bits of the type pointer in the interface value. +// +// ordinary value: Internal = value +// addressable value: Internal = value, Internal.typ |= flagAddr +// read-only value: Internal = value, Internal.typ |= flagRO +// addressable, read-only value: Internal = value, Internal.typ |= flagAddr | flagRO +// +// It is important that the read-only values have the extra bit set +// (as opposed to using the bit to mean writable), because client code +// can grab the interface field and try to use it. Having the extra bit +// set makes the type pointer compare not equal to any real type, +// so that a client cannot, say, write through v.Internal.(*int). +// The runtime routines that access interface types reject types with +// low bits set. +// +// If a Value fv = v.Method(i), then fv = v with the InternalMethod +// field set to i+1. Methods are never addressable. +// +// All in all, this is a lot of effort just to avoid making this new API +// depend on a language change we'll probably do anyway, but +// it's helpful to keep the two separate, and much of the logic is +// necessary to implement the Interface method anyway. + +const ( + flagAddr uint32 = 1 << iota // holds address of value + flagRO // read-only + + reflectFlags = 3 +) + +// An internalValue is the unpacked form of a Value. +// The zero Value unpacks to a zero internalValue +type internalValue struct { + typ *commonType // type of value + kind Kind // kind of value + flag uint32 + word iword + addr unsafe.Pointer + rcvr iword + method bool + nilmethod bool +} + +func (v Value) internal() internalValue { + var iv internalValue + eface := *(*emptyInterface)(unsafe.Pointer(&v.Internal)) + p := uintptr(unsafe.Pointer(eface.typ)) + iv.typ = toCommonType((*runtime.Type)(unsafe.Pointer(p &^ reflectFlags))) + if iv.typ == nil { + return iv + } + iv.flag = uint32(p & reflectFlags) + iv.word = eface.word + if iv.flag&flagAddr != 0 { + iv.addr = unsafe.Pointer(iv.word) + iv.typ = iv.typ.Elem().common() + if iv.typ.size <= ptrSize { + iv.word = loadIword(iv.addr, iv.typ.size) + } + } else { + if iv.typ.size > ptrSize { + iv.addr = unsafe.Pointer(iv.word) + } + } + iv.kind = iv.typ.Kind() + + // Is this a method? If so, iv describes the receiver. + // Rewrite to describe the method function. + if v.InternalMethod != 0 { + // If this Value is a method value (x.Method(i) for some Value x) + // then we will invoke it using the interface form of the method, + // which always passes the receiver as a single word. + // Record that information. + i := v.InternalMethod - 1 + if iv.kind == Interface { + it := (*interfaceType)(unsafe.Pointer(iv.typ)) + if i < 0 || i >= len(it.methods) { + panic("reflect: broken Value") + } + m := &it.methods[i] + if m.pkgPath != nil { + iv.flag |= flagRO + } + iv.typ = toCommonType(m.typ) + iface := (*nonEmptyInterface)(iv.addr) + if iface.itab == nil { + iv.word = 0 + iv.nilmethod = true + } else { + iv.word = iword(iface.itab.fun[i]) + } + iv.rcvr = iface.word + } else { + ut := iv.typ.uncommon() + if ut == nil || i < 0 || i >= len(ut.methods) { + panic("reflect: broken Value") + } + m := &ut.methods[i] + if m.pkgPath != nil { + iv.flag |= flagRO + } + iv.typ = toCommonType(m.mtyp) + iv.rcvr = iv.word + iv.word = iword(m.ifn) + } + iv.kind = Func + iv.method = true + iv.flag &^= flagAddr + iv.addr = nil + } + + return iv +} + +// packValue returns a Value with the given flag bits, type, and interface word. +func packValue(flag uint32, typ *runtime.Type, word iword) Value { + if typ == nil { + panic("packValue") + } + t := uintptr(unsafe.Pointer(typ)) + t |= uintptr(flag) + eface := emptyInterface{(*runtime.Type)(unsafe.Pointer(t)), word} + return Value{Internal: *(*interface{})(unsafe.Pointer(&eface))} +} + +// valueFromAddr returns a Value using the given type and address. +func valueFromAddr(flag uint32, typ Type, addr unsafe.Pointer) Value { + if flag&flagAddr != 0 { + // Addressable, so the internal value is + // an interface containing a pointer to the real value. + return packValue(flag, PtrTo(typ).runtimeType(), iword(addr)) + } + + var w iword + if n := typ.Size(); n <= ptrSize { + // In line, so the interface word is the actual value. + w = loadIword(addr, n) + } else { + // Not in line: the interface word is the address. + w = iword(addr) + } + return packValue(flag, typ.runtimeType(), w) +} + +// valueFromIword returns a Value using the given type and interface word. +func valueFromIword(flag uint32, typ Type, w iword) Value { + if flag&flagAddr != 0 { + panic("reflect: internal error: valueFromIword addressable") + } + return packValue(flag, typ.runtimeType(), w) +} + +func (iv internalValue) mustBe(want Kind) { + if iv.kind != want { + panic(&ValueError{methodName(), iv.kind}) + } +} + +func (iv internalValue) mustBeExported() { + if iv.kind == 0 { + panic(&ValueError{methodName(), iv.kind}) + } + if iv.flag&flagRO != 0 { + panic(methodName() + " using value obtained using unexported field") + } +} + +func (iv internalValue) mustBeAssignable() { + if iv.kind == 0 { + panic(&ValueError{methodName(), iv.kind}) + } + // Assignable if addressable and not read-only. + if iv.flag&flagRO != 0 { + panic(methodName() + " using value obtained using unexported field") + } + if iv.flag&flagAddr == 0 { + panic(methodName() + " using unaddressable value") + } +} + +// Addr returns a pointer value representing the address of v. +// It panics if CanAddr() returns false. +// Addr is typically used to obtain a pointer to a struct field +// or slice element in order to call a method that requires a +// pointer receiver. +func (v Value) Addr() Value { + iv := v.internal() + if iv.flag&flagAddr == 0 { + panic("reflect.Value.Addr of unaddressable value") + } + return valueFromIword(iv.flag&flagRO, PtrTo(iv.typ.toType()), iword(iv.addr)) +} + +// Bool returns v's underlying value. +// It panics if v's kind is not Bool. +func (v Value) Bool() bool { + iv := v.internal() + iv.mustBe(Bool) + return *(*bool)(unsafe.Pointer(&iv.word)) +} + +// CanAddr returns true if the value's address can be obtained with Addr. +// Such values are called addressable. A value is addressable if it is +// an element of a slice, an element of an addressable array, +// a field of an addressable struct, or the result of dereferencing a pointer. +// If CanAddr returns false, calling Addr will panic. +func (v Value) CanAddr() bool { + iv := v.internal() + return iv.flag&flagAddr != 0 +} + +// CanSet returns true if the value of v can be changed. +// A Value can be changed only if it is addressable and was not +// obtained by the use of unexported struct fields. +// If CanSet returns false, calling Set or any type-specific +// setter (e.g., SetBool, SetInt64) will panic. +func (v Value) CanSet() bool { + iv := v.internal() + return iv.flag&(flagAddr|flagRO) == flagAddr +} + +// Call calls the function v with the input arguments in. +// For example, if len(in) == 3, v.Call(in) represents the Go call v(in[0], in[1], in[2]). +// Call panics if v's Kind is not Func. +// It returns the output results as Values. +// As in Go, each input argument must be assignable to the +// type of the function's corresponding input parameter. +// If v is a variadic function, Call creates the variadic slice parameter +// itself, copying in the corresponding values. +func (v Value) Call(in []Value) []Value { + iv := v.internal() + iv.mustBe(Func) + iv.mustBeExported() + return iv.call("Call", in) +} + +// CallSlice calls the variadic function v with the input arguments in, +// assigning the slice in[len(in)-1] to v's final variadic argument. +// For example, if len(in) == 3, v.Call(in) represents the Go call v(in[0], in[1], in[2]...). +// Call panics if v's Kind is not Func or if v is not variadic. +// It returns the output results as Values. +// As in Go, each input argument must be assignable to the +// type of the function's corresponding input parameter. +func (v Value) CallSlice(in []Value) []Value { + iv := v.internal() + iv.mustBe(Func) + iv.mustBeExported() + return iv.call("CallSlice", in) +} + +func (iv internalValue) call(method string, in []Value) []Value { + if iv.word == 0 { + if iv.nilmethod { + panic("reflect.Value.Call: call of method on nil interface value") + } + panic("reflect.Value.Call: call of nil function") + } + + isSlice := method == "CallSlice" + t := iv.typ + n := t.NumIn() + if isSlice { + if !t.IsVariadic() { + panic("reflect: CallSlice of non-variadic function") + } + if len(in) < n { + panic("reflect: CallSlice with too few input arguments") + } + if len(in) > n { + panic("reflect: CallSlice with too many input arguments") + } + } else { + if t.IsVariadic() { + n-- + } + if len(in) < n { + panic("reflect: Call with too few input arguments") + } + if !t.IsVariadic() && len(in) > n { + panic("reflect: Call with too many input arguments") + } + } + for _, x := range in { + if x.Kind() == Invalid { + panic("reflect: " + method + " using zero Value argument") + } + } + for i := 0; i < n; i++ { + if xt, targ := in[i].Type(), t.In(i); !xt.AssignableTo(targ) { + panic("reflect: " + method + " using " + xt.String() + " as type " + targ.String()) + } + } + if !isSlice && t.IsVariadic() { + // prepare slice for remaining values + m := len(in) - n + slice := MakeSlice(t.In(n), m, m) + elem := t.In(n).Elem() + for i := 0; i < m; i++ { + x := in[n+i] + if xt := x.Type(); !xt.AssignableTo(elem) { + panic("reflect: cannot use " + xt.String() + " as type " + elem.String() + " in " + method) + } + slice.Index(i).Set(x) + } + origIn := in + in = make([]Value, n+1) + copy(in[:n], origIn) + in[n] = slice + } + + nin := len(in) + if nin != t.NumIn() { + panic("reflect.Value.Call: wrong argument count") + } + nout := t.NumOut() + + // Compute arg size & allocate. + // This computation is 5g/6g/8g-dependent + // and probably wrong for gccgo, but so + // is most of this function. + size := uintptr(0) + if iv.method { + // extra word for interface value + size += ptrSize + } + for i := 0; i < nin; i++ { + tv := t.In(i) + a := uintptr(tv.Align()) + size = (size + a - 1) &^ (a - 1) + size += tv.Size() + } + size = (size + ptrSize - 1) &^ (ptrSize - 1) + for i := 0; i < nout; i++ { + tv := t.Out(i) + a := uintptr(tv.Align()) + size = (size + a - 1) &^ (a - 1) + size += tv.Size() + } + + // size must be > 0 in order for &args[0] to be valid. + // the argument copying is going to round it up to + // a multiple of ptrSize anyway, so make it ptrSize to begin with. + if size < ptrSize { + size = ptrSize + } + + // round to pointer size + size = (size + ptrSize - 1) &^ (ptrSize - 1) + + // Copy into args. + // + // TODO(rsc): revisit when reference counting happens. + // The values are holding up the in references for us, + // but something must be done for the out references. + // For now make everything look like a pointer by pretending + // to allocate a []*int. + args := make([]*int, size/ptrSize) + ptr := uintptr(unsafe.Pointer(&args[0])) + off := uintptr(0) + if iv.method { + // Hard-wired first argument. + *(*iword)(unsafe.Pointer(ptr)) = iv.rcvr + off = ptrSize + } + for i, v := range in { + iv := v.internal() + iv.mustBeExported() + targ := t.In(i).(*commonType) + a := uintptr(targ.align) + off = (off + a - 1) &^ (a - 1) + n := targ.size + addr := unsafe.Pointer(ptr + off) + iv = convertForAssignment("reflect.Value.Call", addr, targ, iv) + if iv.addr == nil { + storeIword(addr, iv.word, n) + } else { + memmove(addr, iv.addr, n) + } + off += n + } + off = (off + ptrSize - 1) &^ (ptrSize - 1) + + // Call. + call(unsafe.Pointer(iv.word), unsafe.Pointer(ptr), uint32(size)) + + // Copy return values out of args. + // + // TODO(rsc): revisit like above. + ret := make([]Value, nout) + for i := 0; i < nout; i++ { + tv := t.Out(i) + a := uintptr(tv.Align()) + off = (off + a - 1) &^ (a - 1) + ret[i] = valueFromAddr(0, tv, unsafe.Pointer(ptr+off)) + off += tv.Size() + } + + return ret +} + +// Cap returns v's capacity. +// It panics if v's Kind is not Array, Chan, or Slice. +func (v Value) Cap() int { + iv := v.internal() + switch iv.kind { + case Array: + return iv.typ.Len() + case Chan: + return int(chancap(iv.word)) + case Slice: + return (*SliceHeader)(iv.addr).Cap + } + panic(&ValueError{"reflect.Value.Cap", iv.kind}) +} + +// Close closes the channel v. +// It panics if v's Kind is not Chan. +func (v Value) Close() { + iv := v.internal() + iv.mustBe(Chan) + iv.mustBeExported() + ch := iv.word + chanclose(ch) +} + +// Complex returns v's underlying value, as a complex128. +// It panics if v's Kind is not Complex64 or Complex128 +func (v Value) Complex() complex128 { + iv := v.internal() + switch iv.kind { + case Complex64: + if iv.addr == nil { + return complex128(*(*complex64)(unsafe.Pointer(&iv.word))) + } + return complex128(*(*complex64)(iv.addr)) + case Complex128: + return *(*complex128)(iv.addr) + } + panic(&ValueError{"reflect.Value.Complex", iv.kind}) +} + +// Elem returns the value that the interface v contains +// or that the pointer v points to. +// It panics if v's Kind is not Interface or Ptr. +// It returns the zero Value if v is nil. +func (v Value) Elem() Value { + iv := v.internal() + return iv.Elem() +} + +func (iv internalValue) Elem() Value { + switch iv.kind { + case Interface: + // Empty interface and non-empty interface have different layouts. + // Convert to empty interface. + var eface emptyInterface + if iv.typ.NumMethod() == 0 { + eface = *(*emptyInterface)(iv.addr) + } else { + iface := (*nonEmptyInterface)(iv.addr) + if iface.itab != nil { + eface.typ = iface.itab.typ + } + eface.word = iface.word + } + if eface.typ == nil { + return Value{} + } + return valueFromIword(iv.flag&flagRO, toType(eface.typ), eface.word) + + case Ptr: + // The returned value's address is v's value. + if iv.word == 0 { + return Value{} + } + return valueFromAddr(iv.flag&flagRO|flagAddr, iv.typ.Elem(), unsafe.Pointer(iv.word)) + } + panic(&ValueError{"reflect.Value.Elem", iv.kind}) +} + +// Field returns the i'th field of the struct v. +// It panics if v's Kind is not Struct or i is out of range. +func (v Value) Field(i int) Value { + iv := v.internal() + iv.mustBe(Struct) + t := iv.typ.toType() + if i < 0 || i >= t.NumField() { + panic("reflect: Field index out of range") + } + f := t.Field(i) + + // Inherit permission bits from v. + flag := iv.flag + // Using an unexported field forces flagRO. + if f.PkgPath != "" { + flag |= flagRO + } + return valueFromValueOffset(flag, f.Type, iv, f.Offset) +} + +// valueFromValueOffset returns a sub-value of outer +// (outer is an array or a struct) with the given flag and type +// starting at the given byte offset into outer. +func valueFromValueOffset(flag uint32, typ Type, outer internalValue, offset uintptr) Value { + if outer.addr != nil { + return valueFromAddr(flag, typ, unsafe.Pointer(uintptr(outer.addr)+offset)) + } + + // outer is so tiny it is in line. + // We have to use outer.word and derive + // the new word (it cannot possibly be bigger). + // In line, so not addressable. + if flag&flagAddr != 0 { + panic("reflect: internal error: misuse of valueFromValueOffset") + } + b := *(*[ptrSize]byte)(unsafe.Pointer(&outer.word)) + for i := uintptr(0); i < typ.Size(); i++ { + b[i] = b[offset+i] + } + for i := typ.Size(); i < ptrSize; i++ { + b[i] = 0 + } + w := *(*iword)(unsafe.Pointer(&b)) + return valueFromIword(flag, typ, w) +} + +// FieldByIndex returns the nested field corresponding to index. +// It panics if v's Kind is not struct. +func (v Value) FieldByIndex(index []int) Value { + v.internal().mustBe(Struct) + for i, x := range index { + if i > 0 { + if v.Kind() == Ptr && v.Elem().Kind() == Struct { + v = v.Elem() + } + } + v = v.Field(x) + } + return v +} + +// FieldByName returns the struct field with the given name. +// It returns the zero Value if no field was found. +// It panics if v's Kind is not struct. +func (v Value) FieldByName(name string) Value { + iv := v.internal() + iv.mustBe(Struct) + if f, ok := iv.typ.FieldByName(name); ok { + return v.FieldByIndex(f.Index) + } + return Value{} +} + +// FieldByNameFunc returns the struct field with a name +// that satisfies the match function. +// It panics if v's Kind is not struct. +// It returns the zero Value if no field was found. +func (v Value) FieldByNameFunc(match func(string) bool) Value { + v.internal().mustBe(Struct) + if f, ok := v.Type().FieldByNameFunc(match); ok { + return v.FieldByIndex(f.Index) + } + return Value{} +} + +// Float returns v's underlying value, as an float64. +// It panics if v's Kind is not Float32 or Float64 +func (v Value) Float() float64 { + iv := v.internal() + switch iv.kind { + case Float32: + return float64(*(*float32)(unsafe.Pointer(&iv.word))) + case Float64: + // If the pointer width can fit an entire float64, + // the value is in line when stored in an interface. + if iv.addr == nil { + return *(*float64)(unsafe.Pointer(&iv.word)) + } + // Otherwise we have a pointer. + return *(*float64)(iv.addr) + } + panic(&ValueError{"reflect.Value.Float", iv.kind}) +} + +// Index returns v's i'th element. +// It panics if v's Kind is not Array or Slice or i is out of range. +func (v Value) Index(i int) Value { + iv := v.internal() + switch iv.kind { + default: + panic(&ValueError{"reflect.Value.Index", iv.kind}) + case Array: + flag := iv.flag // element flag same as overall array + t := iv.typ.toType() + if i < 0 || i > t.Len() { + panic("reflect: array index out of range") + } + typ := t.Elem() + return valueFromValueOffset(flag, typ, iv, uintptr(i)*typ.Size()) + + case Slice: + // Element flag same as Elem of Ptr. + // Addressable, possibly read-only. + flag := iv.flag&flagRO | flagAddr + s := (*SliceHeader)(iv.addr) + if i < 0 || i >= s.Len { + panic("reflect: slice index out of range") + } + typ := iv.typ.Elem() + addr := unsafe.Pointer(s.Data + uintptr(i)*typ.Size()) + return valueFromAddr(flag, typ, addr) + } + + panic("not reached") +} + +// Int returns v's underlying value, as an int64. +// It panics if v's Kind is not Int, Int8, Int16, Int32, or Int64. +func (v Value) Int() int64 { + iv := v.internal() + switch iv.kind { + case Int: + return int64(*(*int)(unsafe.Pointer(&iv.word))) + case Int8: + return int64(*(*int8)(unsafe.Pointer(&iv.word))) + case Int16: + return int64(*(*int16)(unsafe.Pointer(&iv.word))) + case Int32: + return int64(*(*int32)(unsafe.Pointer(&iv.word))) + case Int64: + if iv.addr == nil { + return *(*int64)(unsafe.Pointer(&iv.word)) + } + return *(*int64)(iv.addr) + } + panic(&ValueError{"reflect.Value.Int", iv.kind}) +} + +// CanInterface returns true if Interface can be used without panicking. +func (v Value) CanInterface() bool { + iv := v.internal() + if iv.kind == Invalid { + panic(&ValueError{"reflect.Value.CanInterface", iv.kind}) + } + // TODO(rsc): Check flagRO too. Decide what to do about asking for + // interface for a value obtained via an unexported field. + // If the field were of a known type, say chan int or *sync.Mutex, + // the caller could interfere with the data after getting the + // interface. But fmt.Print depends on being able to look. + // Now that reflect is more efficient the special cases in fmt + // might be less important. + return v.InternalMethod == 0 +} + +// Interface returns v's value as an interface{}. +// If v is a method obtained by invoking Value.Method +// (as opposed to Type.Method), Interface cannot return an +// interface value, so it panics. +func (v Value) Interface() interface{} { + return v.internal().Interface() +} + +func (iv internalValue) Interface() interface{} { + if iv.kind == 0 { + panic(&ValueError{"reflect.Value.Interface", iv.kind}) + } + if iv.method { + panic("reflect.Value.Interface: cannot create interface value for method with bound receiver") + } + /* + if v.flag()&noExport != 0 { + panic("reflect.Value.Interface: cannot return value obtained from unexported struct field") + } + */ + + if iv.kind == Interface { + // Special case: return the element inside the interface. + // Won't recurse further because an interface cannot contain an interface. + if iv.IsNil() { + return nil + } + return iv.Elem().Interface() + } + + // Non-interface value. + var eface emptyInterface + eface.typ = iv.typ.runtimeType() + eface.word = iv.word + return *(*interface{})(unsafe.Pointer(&eface)) +} + +// InterfaceData returns the interface v's value as a uintptr pair. +// It panics if v's Kind is not Interface. +func (v Value) InterfaceData() [2]uintptr { + iv := v.internal() + iv.mustBe(Interface) + // We treat this as a read operation, so we allow + // it even for unexported data, because the caller + // has to import "unsafe" to turn it into something + // that can be abused. + return *(*[2]uintptr)(iv.addr) +} + +// IsNil returns true if v is a nil value. +// It panics if v's Kind is not Chan, Func, Interface, Map, Ptr, or Slice. +func (v Value) IsNil() bool { + return v.internal().IsNil() +} + +func (iv internalValue) IsNil() bool { + switch iv.kind { + case Chan, Func, Map, Ptr: + if iv.method { + panic("reflect: IsNil of method Value") + } + return iv.word == 0 + case Interface, Slice: + // Both interface and slice are nil if first word is 0. + return *(*uintptr)(iv.addr) == 0 + } + panic(&ValueError{"reflect.Value.IsNil", iv.kind}) +} + +// IsValid returns true if v represents a value. +// It returns false if v is the zero Value. +// If IsValid returns false, all other methods except String panic. +// Most functions and methods never return an invalid value. +// If one does, its documentation states the conditions explicitly. +func (v Value) IsValid() bool { + return v.Internal != nil +} + +// Kind returns v's Kind. +// If v is the zero Value (IsValid returns false), Kind returns Invalid. +func (v Value) Kind() Kind { + return v.internal().kind +} + +// Len returns v's length. +// It panics if v's Kind is not Array, Chan, Map, Slice, or String. +func (v Value) Len() int { + iv := v.internal() + switch iv.kind { + case Array: + return iv.typ.Len() + case Chan: + return int(chanlen(iv.word)) + case Map: + return int(maplen(iv.word)) + case Slice: + return (*SliceHeader)(iv.addr).Len + case String: + return (*StringHeader)(iv.addr).Len + } + panic(&ValueError{"reflect.Value.Len", iv.kind}) +} + +// MapIndex returns the value associated with key in the map v. +// It panics if v's Kind is not Map. +// It returns the zero Value if key is not found in the map or if v represents a nil map. +// As in Go, the key's value must be assignable to the map's key type. +func (v Value) MapIndex(key Value) Value { + iv := v.internal() + iv.mustBe(Map) + typ := iv.typ.toType() + + // Do not require ikey to be exported, so that DeepEqual + // and other programs can use all the keys returned by + // MapKeys as arguments to MapIndex. If either the map + // or the key is unexported, though, the result will be + // considered unexported. + + ikey := key.internal() + ikey = convertForAssignment("reflect.Value.MapIndex", nil, typ.Key(), ikey) + if iv.word == 0 { + return Value{} + } + + flag := (iv.flag | ikey.flag) & flagRO + elemType := typ.Elem() + elemWord, ok := mapaccess(typ.runtimeType(), iv.word, ikey.word) + if !ok { + return Value{} + } + return valueFromIword(flag, elemType, elemWord) +} + +// MapKeys returns a slice containing all the keys present in the map, +// in unspecified order. +// It panics if v's Kind is not Map. +// It returns an empty slice if v represents a nil map. +func (v Value) MapKeys() []Value { + iv := v.internal() + iv.mustBe(Map) + keyType := iv.typ.Key() + + flag := iv.flag & flagRO + m := iv.word + mlen := int32(0) + if m != 0 { + mlen = maplen(m) + } + it := mapiterinit(iv.typ.runtimeType(), m) + a := make([]Value, mlen) + var i int + for i = 0; i < len(a); i++ { + keyWord, ok := mapiterkey(it) + if !ok { + break + } + a[i] = valueFromIword(flag, keyType, keyWord) + mapiternext(it) + } + return a[:i] +} + +// Method returns a function value corresponding to v's i'th method. +// The arguments to a Call on the returned function should not include +// a receiver; the returned function will always use v as the receiver. +// Method panics if i is out of range. +func (v Value) Method(i int) Value { + iv := v.internal() + if iv.kind == Invalid { + panic(&ValueError{"reflect.Value.Method", Invalid}) + } + if i < 0 || i >= iv.typ.NumMethod() { + panic("reflect: Method index out of range") + } + return Value{v.Internal, i + 1} +} + +// NumMethod returns the number of methods in the value's method set. +func (v Value) NumMethod() int { + iv := v.internal() + if iv.kind == Invalid { + panic(&ValueError{"reflect.Value.NumMethod", Invalid}) + } + return iv.typ.NumMethod() +} + +// MethodByName returns a function value corresponding to the method +// of v with the given name. +// The arguments to a Call on the returned function should not include +// a receiver; the returned function will always use v as the receiver. +// It returns the zero Value if no method was found. +func (v Value) MethodByName(name string) Value { + iv := v.internal() + if iv.kind == Invalid { + panic(&ValueError{"reflect.Value.MethodByName", Invalid}) + } + m, ok := iv.typ.MethodByName(name) + if ok { + return Value{v.Internal, m.Index + 1} + } + return Value{} +} + +// NumField returns the number of fields in the struct v. +// It panics if v's Kind is not Struct. +func (v Value) NumField() int { + iv := v.internal() + iv.mustBe(Struct) + return iv.typ.NumField() +} + +// OverflowComplex returns true if the complex128 x cannot be represented by v's type. +// It panics if v's Kind is not Complex64 or Complex128. +func (v Value) OverflowComplex(x complex128) bool { + iv := v.internal() + switch iv.kind { + case Complex64: + return overflowFloat32(real(x)) || overflowFloat32(imag(x)) + case Complex128: + return false + } + panic(&ValueError{"reflect.Value.OverflowComplex", iv.kind}) +} + +// OverflowFloat returns true if the float64 x cannot be represented by v's type. +// It panics if v's Kind is not Float32 or Float64. +func (v Value) OverflowFloat(x float64) bool { + iv := v.internal() + switch iv.kind { + case Float32: + return overflowFloat32(x) + case Float64: + return false + } + panic(&ValueError{"reflect.Value.OverflowFloat", iv.kind}) +} + +func overflowFloat32(x float64) bool { + if x < 0 { + x = -x + } + return math.MaxFloat32 <= x && x <= math.MaxFloat64 +} + +// OverflowInt returns true if the int64 x cannot be represented by v's type. +// It panics if v's Kind is not Int, Int8, int16, Int32, or Int64. +func (v Value) OverflowInt(x int64) bool { + iv := v.internal() + switch iv.kind { + case Int, Int8, Int16, Int32, Int64: + bitSize := iv.typ.size * 8 + trunc := (x << (64 - bitSize)) >> (64 - bitSize) + return x != trunc + } + panic(&ValueError{"reflect.Value.OverflowInt", iv.kind}) +} + +// OverflowUint returns true if the uint64 x cannot be represented by v's type. +// It panics if v's Kind is not Uint, Uintptr, Uint8, Uint16, Uint32, or Uint64. +func (v Value) OverflowUint(x uint64) bool { + iv := v.internal() + switch iv.kind { + case Uint, Uintptr, Uint8, Uint16, Uint32, Uint64: + bitSize := iv.typ.size * 8 + trunc := (x << (64 - bitSize)) >> (64 - bitSize) + return x != trunc + } + panic(&ValueError{"reflect.Value.OverflowUint", iv.kind}) +} + +// Pointer returns v's value as a uintptr. +// It returns uintptr instead of unsafe.Pointer so that +// code using reflect cannot obtain unsafe.Pointers +// without importing the unsafe package explicitly. +// It panics if v's Kind is not Chan, Func, Map, Ptr, Slice, or UnsafePointer. +func (v Value) Pointer() uintptr { + iv := v.internal() + switch iv.kind { + case Chan, Func, Map, Ptr, UnsafePointer: + if iv.kind == Func && v.InternalMethod != 0 { + panic("reflect.Value.Pointer of method Value") + } + return uintptr(iv.word) + case Slice: + return (*SliceHeader)(iv.addr).Data + } + panic(&ValueError{"reflect.Value.Pointer", iv.kind}) +} + +// Recv receives and returns a value from the channel v. +// It panics if v's Kind is not Chan. +// The receive blocks until a value is ready. +// The boolean value ok is true if the value x corresponds to a send +// on the channel, false if it is a zero value received because the channel is closed. +func (v Value) Recv() (x Value, ok bool) { + iv := v.internal() + iv.mustBe(Chan) + iv.mustBeExported() + return iv.recv(false) +} + +// internal recv, possibly non-blocking (nb) +func (iv internalValue) recv(nb bool) (val Value, ok bool) { + t := iv.typ.toType() + if t.ChanDir()&RecvDir == 0 { + panic("recv on send-only channel") + } + ch := iv.word + if ch == 0 { + panic("recv on nil channel") + } + valWord, selected, ok := chanrecv(iv.typ.runtimeType(), ch, nb) + if selected { + val = valueFromIword(0, t.Elem(), valWord) + } + return +} + +// Send sends x on the channel v. +// It panics if v's kind is not Chan or if x's type is not the same type as v's element type. +// As in Go, x's value must be assignable to the channel's element type. +func (v Value) Send(x Value) { + iv := v.internal() + iv.mustBe(Chan) + iv.mustBeExported() + iv.send(x, false) +} + +// internal send, possibly non-blocking +func (iv internalValue) send(x Value, nb bool) (selected bool) { + t := iv.typ.toType() + if t.ChanDir()&SendDir == 0 { + panic("send on recv-only channel") + } + ix := x.internal() + ix.mustBeExported() // do not let unexported x leak + ix = convertForAssignment("reflect.Value.Send", nil, t.Elem(), ix) + ch := iv.word + if ch == 0 { + panic("send on nil channel") + } + return chansend(iv.typ.runtimeType(), ch, ix.word, nb) +} + +// Set assigns x to the value v. +// It panics if CanSet returns false. +// As in Go, x's value must be assignable to v's type. +func (v Value) Set(x Value) { + iv := v.internal() + ix := x.internal() + + iv.mustBeAssignable() + ix.mustBeExported() // do not let unexported x leak + + ix = convertForAssignment("reflect.Set", iv.addr, iv.typ, ix) + + n := ix.typ.size + if n <= ptrSize { + storeIword(iv.addr, ix.word, n) + } else { + memmove(iv.addr, ix.addr, n) + } +} + +// SetBool sets v's underlying value. +// It panics if v's Kind is not Bool or if CanSet() is false. +func (v Value) SetBool(x bool) { + iv := v.internal() + iv.mustBeAssignable() + iv.mustBe(Bool) + *(*bool)(iv.addr) = x +} + +// SetComplex sets v's underlying value to x. +// It panics if v's Kind is not Complex64 or Complex128, or if CanSet() is false. +func (v Value) SetComplex(x complex128) { + iv := v.internal() + iv.mustBeAssignable() + switch iv.kind { + default: + panic(&ValueError{"reflect.Value.SetComplex", iv.kind}) + case Complex64: + *(*complex64)(iv.addr) = complex64(x) + case Complex128: + *(*complex128)(iv.addr) = x + } +} + +// SetFloat sets v's underlying value to x. +// It panics if v's Kind is not Float32 or Float64, or if CanSet() is false. +func (v Value) SetFloat(x float64) { + iv := v.internal() + iv.mustBeAssignable() + switch iv.kind { + default: + panic(&ValueError{"reflect.Value.SetFloat", iv.kind}) + case Float32: + *(*float32)(iv.addr) = float32(x) + case Float64: + *(*float64)(iv.addr) = x + } +} + +// SetInt sets v's underlying value to x. +// It panics if v's Kind is not Int, Int8, Int16, Int32, or Int64, or if CanSet() is false. +func (v Value) SetInt(x int64) { + iv := v.internal() + iv.mustBeAssignable() + switch iv.kind { + default: + panic(&ValueError{"reflect.Value.SetInt", iv.kind}) + case Int: + *(*int)(iv.addr) = int(x) + case Int8: + *(*int8)(iv.addr) = int8(x) + case Int16: + *(*int16)(iv.addr) = int16(x) + case Int32: + *(*int32)(iv.addr) = int32(x) + case Int64: + *(*int64)(iv.addr) = x + } +} + +// SetLen sets v's length to n. +// It panics if v's Kind is not Slice. +func (v Value) SetLen(n int) { + iv := v.internal() + iv.mustBeAssignable() + iv.mustBe(Slice) + s := (*SliceHeader)(iv.addr) + if n < 0 || n > int(s.Cap) { + panic("reflect: slice length out of range in SetLen") + } + s.Len = n +} + +// SetMapIndex sets the value associated with key in the map v to val. +// It panics if v's Kind is not Map. +// If val is the zero Value, SetMapIndex deletes the key from the map. +// As in Go, key's value must be assignable to the map's key type, +// and val's value must be assignable to the map's value type. +func (v Value) SetMapIndex(key, val Value) { + iv := v.internal() + ikey := key.internal() + ival := val.internal() + + iv.mustBe(Map) + iv.mustBeExported() + + ikey.mustBeExported() + ikey = convertForAssignment("reflect.Value.SetMapIndex", nil, iv.typ.Key(), ikey) + + if ival.kind != Invalid { + ival.mustBeExported() + ival = convertForAssignment("reflect.Value.SetMapIndex", nil, iv.typ.Elem(), ival) + } + + mapassign(iv.typ.runtimeType(), iv.word, ikey.word, ival.word, ival.kind != Invalid) +} + +// SetUint sets v's underlying value to x. +// It panics if v's Kind is not Uint, Uintptr, Uint8, Uint16, Uint32, or Uint64, or if CanSet() is false. +func (v Value) SetUint(x uint64) { + iv := v.internal() + iv.mustBeAssignable() + switch iv.kind { + default: + panic(&ValueError{"reflect.Value.SetUint", iv.kind}) + case Uint: + *(*uint)(iv.addr) = uint(x) + case Uint8: + *(*uint8)(iv.addr) = uint8(x) + case Uint16: + *(*uint16)(iv.addr) = uint16(x) + case Uint32: + *(*uint32)(iv.addr) = uint32(x) + case Uint64: + *(*uint64)(iv.addr) = x + case Uintptr: + *(*uintptr)(iv.addr) = uintptr(x) + } +} + +// SetPointer sets the unsafe.Pointer value v to x. +// It panics if v's Kind is not UnsafePointer. +func (v Value) SetPointer(x unsafe.Pointer) { + iv := v.internal() + iv.mustBeAssignable() + iv.mustBe(UnsafePointer) + *(*unsafe.Pointer)(iv.addr) = x +} + +// SetString sets v's underlying value to x. +// It panics if v's Kind is not String or if CanSet() is false. +func (v Value) SetString(x string) { + iv := v.internal() + iv.mustBeAssignable() + iv.mustBe(String) + *(*string)(iv.addr) = x +} + +// Slice returns a slice of v. +// It panics if v's Kind is not Array or Slice. +func (v Value) Slice(beg, end int) Value { + iv := v.internal() + if iv.kind != Array && iv.kind != Slice { + panic(&ValueError{"reflect.Value.Slice", iv.kind}) + } + cap := v.Cap() + if beg < 0 || end < beg || end > cap { + panic("reflect.Value.Slice: slice index out of bounds") + } + var typ Type + var base uintptr + switch iv.kind { + case Array: + if iv.flag&flagAddr == 0 { + panic("reflect.Value.Slice: slice of unaddressable array") + } + typ = toType((*arrayType)(unsafe.Pointer(iv.typ)).slice) + base = uintptr(iv.addr) + case Slice: + typ = iv.typ.toType() + base = (*SliceHeader)(iv.addr).Data + } + s := new(SliceHeader) + s.Data = base + uintptr(beg)*typ.Elem().Size() + s.Len = end - beg + s.Cap = cap - beg + return valueFromAddr(iv.flag&flagRO, typ, unsafe.Pointer(s)) +} + +// String returns the string v's underlying value, as a string. +// String is a special case because of Go's String method convention. +// Unlike the other getters, it does not panic if v's Kind is not String. +// Instead, it returns a string of the form "<T value>" where T is v's type. +func (v Value) String() string { + iv := v.internal() + switch iv.kind { + case Invalid: + return "<invalid Value>" + case String: + return *(*string)(iv.addr) + } + return "<" + iv.typ.String() + " Value>" +} + +// TryRecv attempts to receive a value from the channel v but will not block. +// It panics if v's Kind is not Chan. +// If the receive cannot finish without blocking, x is the zero Value. +// The boolean ok is true if the value x corresponds to a send +// on the channel, false if it is a zero value received because the channel is closed. +func (v Value) TryRecv() (x Value, ok bool) { + iv := v.internal() + iv.mustBe(Chan) + iv.mustBeExported() + return iv.recv(true) +} + +// TrySend attempts to send x on the channel v but will not block. +// It panics if v's Kind is not Chan. +// It returns true if the value was sent, false otherwise. +// As in Go, x's value must be assignable to the channel's element type. +func (v Value) TrySend(x Value) bool { + iv := v.internal() + iv.mustBe(Chan) + iv.mustBeExported() + return iv.send(x, true) +} + +// Type returns v's type. +func (v Value) Type() Type { + t := v.internal().typ + if t == nil { + panic(&ValueError{"reflect.Value.Type", Invalid}) + } + return t.toType() +} + +// Uint returns v's underlying value, as a uint64. +// It panics if v's Kind is not Uint, Uintptr, Uint8, Uint16, Uint32, or Uint64. +func (v Value) Uint() uint64 { + iv := v.internal() + switch iv.kind { + case Uint: + return uint64(*(*uint)(unsafe.Pointer(&iv.word))) + case Uint8: + return uint64(*(*uint8)(unsafe.Pointer(&iv.word))) + case Uint16: + return uint64(*(*uint16)(unsafe.Pointer(&iv.word))) + case Uint32: + return uint64(*(*uint32)(unsafe.Pointer(&iv.word))) + case Uintptr: + return uint64(*(*uintptr)(unsafe.Pointer(&iv.word))) + case Uint64: + if iv.addr == nil { + return *(*uint64)(unsafe.Pointer(&iv.word)) + } + return *(*uint64)(iv.addr) + } + panic(&ValueError{"reflect.Value.Uint", iv.kind}) +} + +// UnsafeAddr returns a pointer to v's data. +// It is for advanced clients that also import the "unsafe" package. +// It panics if v is not addressable. +func (v Value) UnsafeAddr() uintptr { + iv := v.internal() + if iv.kind == Invalid { + panic(&ValueError{"reflect.Value.UnsafeAddr", iv.kind}) + } + if iv.flag&flagAddr == 0 { + panic("reflect.Value.UnsafeAddr of unaddressable value") + } + return uintptr(iv.addr) +} + +// StringHeader is the runtime representation of a string. +// It cannot be used safely or portably. +type StringHeader struct { + Data uintptr + Len int +} + +// SliceHeader is the runtime representation of a slice. +// It cannot be used safely or portably. +type SliceHeader struct { + Data uintptr + Len int + Cap int +} + +func typesMustMatch(what string, t1, t2 Type) { + if t1 != t2 { + panic("reflect: " + what + ": " + t1.String() + " != " + t2.String()) + } +} + +// grow grows the slice s so that it can hold extra more values, allocating +// more capacity if needed. It also returns the old and new slice lengths. +func grow(s Value, extra int) (Value, int, int) { + i0 := s.Len() + i1 := i0 + extra + if i1 < i0 { + panic("reflect.Append: slice overflow") + } + m := s.Cap() + if i1 <= m { + return s.Slice(0, i1), i0, i1 + } + if m == 0 { + m = extra + } else { + for m < i1 { + if i0 < 1024 { + m += m + } else { + m += m / 4 + } + } + } + t := MakeSlice(s.Type(), i1, m) + Copy(t, s) + return t, i0, i1 +} + +// Append appends the values x to a slice s and returns the resulting slice. +// As in Go, each x's value must be assignable to the slice's element type. +func Append(s Value, x ...Value) Value { + s.internal().mustBe(Slice) + s, i0, i1 := grow(s, len(x)) + for i, j := i0, 0; i < i1; i, j = i+1, j+1 { + s.Index(i).Set(x[j]) + } + return s +} + +// AppendSlice appends a slice t to a slice s and returns the resulting slice. +// The slices s and t must have the same element type. +func AppendSlice(s, t Value) Value { + s.internal().mustBe(Slice) + t.internal().mustBe(Slice) + typesMustMatch("reflect.AppendSlice", s.Type().Elem(), t.Type().Elem()) + s, i0, i1 := grow(s, t.Len()) + Copy(s.Slice(i0, i1), t) + return s +} + +// Copy copies the contents of src into dst until either +// dst has been filled or src has been exhausted. +// It returns the number of elements copied. +// Dst and src each must have kind Slice or Array, and +// dst and src must have the same element type. +func Copy(dst, src Value) int { + idst := dst.internal() + isrc := src.internal() + + if idst.kind != Array && idst.kind != Slice { + panic(&ValueError{"reflect.Copy", idst.kind}) + } + if idst.kind == Array { + idst.mustBeAssignable() + } + idst.mustBeExported() + if isrc.kind != Array && isrc.kind != Slice { + panic(&ValueError{"reflect.Copy", isrc.kind}) + } + isrc.mustBeExported() + + de := idst.typ.Elem() + se := isrc.typ.Elem() + typesMustMatch("reflect.Copy", de, se) + + n := dst.Len() + if sn := src.Len(); n > sn { + n = sn + } + + // If sk is an in-line array, cannot take its address. + // Instead, copy element by element. + if isrc.addr == nil { + for i := 0; i < n; i++ { + dst.Index(i).Set(src.Index(i)) + } + return n + } + + // Copy via memmove. + var da, sa unsafe.Pointer + if idst.kind == Array { + da = idst.addr + } else { + da = unsafe.Pointer((*SliceHeader)(idst.addr).Data) + } + if isrc.kind == Array { + sa = isrc.addr + } else { + sa = unsafe.Pointer((*SliceHeader)(isrc.addr).Data) + } + memmove(da, sa, uintptr(n)*de.Size()) + return n +} + +/* + * constructors + */ + +// MakeSlice creates a new zero-initialized slice value +// for the specified slice type, length, and capacity. +func MakeSlice(typ Type, len, cap int) Value { + if typ.Kind() != Slice { + panic("reflect: MakeSlice of non-slice type") + } + s := &SliceHeader{ + Data: uintptr(unsafe.NewArray(typ.Elem(), cap)), + Len: len, + Cap: cap, + } + return valueFromAddr(0, typ, unsafe.Pointer(s)) +} + +// MakeChan creates a new channel with the specified type and buffer size. +func MakeChan(typ Type, buffer int) Value { + if typ.Kind() != Chan { + panic("reflect: MakeChan of non-chan type") + } + if buffer < 0 { + panic("MakeChan: negative buffer size") + } + if typ.ChanDir() != BothDir { + panic("MakeChan: unidirectional channel type") + } + ch := makechan(typ.runtimeType(), uint32(buffer)) + return valueFromIword(0, typ, ch) +} + +// MakeMap creates a new map of the specified type. +func MakeMap(typ Type) Value { + if typ.Kind() != Map { + panic("reflect: MakeMap of non-map type") + } + m := makemap(typ.runtimeType()) + return valueFromIword(0, typ, m) +} + +// Indirect returns the value that v points to. +// If v is a nil pointer, Indirect returns a nil Value. +// If v is not a pointer, Indirect returns v. +func Indirect(v Value) Value { + if v.Kind() != Ptr { + return v + } + return v.Elem() +} + +// ValueOf returns a new Value initialized to the concrete value +// stored in the interface i. ValueOf(nil) returns the zero Value. +func ValueOf(i interface{}) Value { + if i == nil { + return Value{} + } + // For an interface value with the noAddr bit set, + // the representation is identical to an empty interface. + eface := *(*emptyInterface)(unsafe.Pointer(&i)) + return packValue(0, eface.typ, eface.word) +} + +// Zero returns a Value representing a zero value for the specified type. +// The result is different from the zero value of the Value struct, +// which represents no value at all. +// For example, Zero(TypeOf(42)) returns a Value with Kind Int and value 0. +func Zero(typ Type) Value { + if typ == nil { + panic("reflect: Zero(nil)") + } + if typ.Size() <= ptrSize { + return valueFromIword(0, typ, 0) + } + return valueFromAddr(0, typ, unsafe.New(typ)) +} + +// New returns a Value representing a pointer to a new zero value +// for the specified type. That is, the returned Value's Type is PtrTo(t). +func New(typ Type) Value { + if typ == nil { + panic("reflect: New(nil)") + } + ptr := unsafe.New(typ) + return valueFromIword(0, PtrTo(typ), iword(ptr)) +} + +// convertForAssignment +func convertForAssignment(what string, addr unsafe.Pointer, dst Type, iv internalValue) internalValue { + if iv.method { + panic(what + ": cannot assign method value to type " + dst.String()) + } + + dst1 := dst.(*commonType) + if directlyAssignable(dst1, iv.typ) { + // Overwrite type so that they match. + // Same memory layout, so no harm done. + iv.typ = dst1 + return iv + } + if implements(dst1, iv.typ) { + if addr == nil { + addr = unsafe.Pointer(new(interface{})) + } + x := iv.Interface() + if dst.NumMethod() == 0 { + *(*interface{})(addr) = x + } else { + ifaceE2I(dst1.runtimeType(), x, addr) + } + iv.addr = addr + iv.word = iword(addr) + iv.typ = dst1 + return iv + } + + // Failed. + panic(what + ": value of type " + iv.typ.String() + " is not assignable to type " + dst.String()) +} + +// implemented in ../pkg/runtime +func chancap(ch iword) int32 +func chanclose(ch iword) +func chanlen(ch iword) int32 +func chanrecv(t *runtime.Type, ch iword, nb bool) (val iword, selected, received bool) +func chansend(t *runtime.Type, ch iword, val iword, nb bool) bool + +func makechan(typ *runtime.Type, size uint32) (ch iword) +func makemap(t *runtime.Type) iword +func mapaccess(t *runtime.Type, m iword, key iword) (val iword, ok bool) +func mapassign(t *runtime.Type, m iword, key, val iword, ok bool) +func mapiterinit(t *runtime.Type, m iword) *byte +func mapiterkey(it *byte) (key iword, ok bool) +func mapiternext(it *byte) +func maplen(m iword) int32 + +func call(fn, arg unsafe.Pointer, n uint32) +func ifaceE2I(t *runtime.Type, src interface{}, dst unsafe.Pointer) |