| // Copyright 2009 The Go Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| package reflect |
| |
| import ( |
| "math" |
| "runtime" |
| "strconv" |
| "unsafe" |
| ) |
| |
| const bigEndian = false // can be smarter if we find a big-endian machine |
| const ptrSize = unsafe.Sizeof((*byte)(nil)) |
| const cannotSet = "cannot set value obtained from unexported struct field" |
| |
| // TODO: This will have to go away when |
| // the new gc goes in. |
| func memmove(adst, asrc unsafe.Pointer, n uintptr) { |
| dst := uintptr(adst) |
| src := uintptr(asrc) |
| switch { |
| case src < dst && src+n > dst: |
| // byte copy backward |
| // careful: i is unsigned |
| for i := n; i > 0; { |
| i-- |
| *(*byte)(unsafe.Pointer(dst + i)) = *(*byte)(unsafe.Pointer(src + i)) |
| } |
| case (n|src|dst)&(ptrSize-1) != 0: |
| // byte copy forward |
| for i := uintptr(0); i < n; i++ { |
| *(*byte)(unsafe.Pointer(dst + i)) = *(*byte)(unsafe.Pointer(src + i)) |
| } |
| default: |
| // word copy forward |
| for i := uintptr(0); i < n; i += ptrSize { |
| *(*uintptr)(unsafe.Pointer(dst + i)) = *(*uintptr)(unsafe.Pointer(src + i)) |
| } |
| } |
| } |
| |
| // Value is the reflection interface to a Go value. |
| // |
| // Not all methods apply to all kinds of values. Restrictions, |
| // if any, are noted in the documentation for each method. |
| // Use the Kind method to find out the kind of value before |
| // calling kind-specific methods. Calling a method |
| // inappropriate to the kind of type causes a run time panic. |
| // |
| // The zero Value represents no value. |
| // Its IsValid method returns false, its Kind method returns Invalid, |
| // its String method returns "<invalid Value>", and all other methods panic. |
| // Most functions and methods never return an invalid value. |
| // If one does, its documentation states the conditions explicitly. |
| type Value struct { |
| // typ holds the type of the value represented by a Value. |
| typ *commonType |
| |
| // val holds the 1-word representation of the value. |
| // If flag's flagIndir bit is set, then val is a pointer to the data. |
| // Otherwise val is a word holding the actual data. |
| // When the data is smaller than a word, it begins at |
| // the first byte (in the memory address sense) of val. |
| // We use unsafe.Pointer so that the garbage collector |
| // knows that val could be a pointer. |
| val unsafe.Pointer |
| |
| // flag holds metadata about the value. |
| // The lowest bits are flag bits: |
| // - flagRO: obtained via unexported field, so read-only |
| // - flagIndir: val holds a pointer to the data |
| // - flagAddr: v.CanAddr is true (implies flagIndir) |
| // - flagMethod: v is a method value. |
| // The next five bits give the Kind of the value. |
| // This repeats typ.Kind() except for method values. |
| // The remaining 23+ bits give a method number for method values. |
| // If flag.kind() != Func, code can assume that flagMethod is unset. |
| // If typ.size > ptrSize, code can assume that flagIndir is set. |
| flag |
| |
| // A method value represents a curried method invocation |
| // like r.Read for some receiver r. The typ+val+flag bits describe |
| // the receiver r, but the flag's Kind bits say Func (methods are |
| // functions), and the top bits of the flag give the method number |
| // in r's type's method table. |
| } |
| |
| type flag uintptr |
| |
| const ( |
| flagRO flag = 1 << iota |
| flagIndir |
| flagAddr |
| flagMethod |
| flagKindShift = iota |
| flagKindWidth = 5 // there are 27 kinds |
| flagKindMask flag = 1<<flagKindWidth - 1 |
| flagMethodShift = flagKindShift + flagKindWidth |
| ) |
| |
| func (f flag) kind() Kind { |
| return Kind((f >> flagKindShift) & flagKindMask) |
| } |
| |
| // A ValueError occurs when a Value method is invoked on |
| // a Value that does not support it. Such cases are documented |
| // in the description of each method. |
| type ValueError struct { |
| Method string |
| Kind Kind |
| } |
| |
| func (e *ValueError) Error() string { |
| if e.Kind == 0 { |
| return "reflect: call of " + e.Method + " on zero Value" |
| } |
| return "reflect: call of " + e.Method + " on " + e.Kind.String() + " Value" |
| } |
| |
| // methodName returns the name of the calling method, |
| // assumed to be two stack frames above. |
| func methodName() string { |
| pc, _, _, _ := runtime.Caller(2) |
| f := runtime.FuncForPC(pc) |
| if f == nil { |
| return "unknown method" |
| } |
| return f.Name() |
| } |
| |
| // An iword is the word that would be stored in an |
| // interface to represent a given value v. Specifically, if v is |
| // bigger than a pointer, its word is a pointer to v's data. |
| // Otherwise, its word holds the data stored |
| // in its leading bytes (so is not a pointer). |
| // Because the value sometimes holds a pointer, we use |
| // unsafe.Pointer to represent it, so that if iword appears |
| // in a struct, the garbage collector knows that might be |
| // a pointer. |
| type iword unsafe.Pointer |
| |
| func (v Value) iword() iword { |
| if v.flag&flagIndir != 0 && v.typ.size <= ptrSize { |
| // Have indirect but want direct word. |
| return loadIword(v.val, v.typ.size) |
| } |
| return iword(v.val) |
| } |
| |
| // loadIword loads n bytes at p from memory into an iword. |
| func loadIword(p unsafe.Pointer, n uintptr) iword { |
| // Run the copy ourselves instead of calling memmove |
| // to avoid moving w to the heap. |
| var w iword |
| switch n { |
| default: |
| panic("reflect: internal error: loadIword of " + strconv.Itoa(int(n)) + "-byte value") |
| case 0: |
| case 1: |
| *(*uint8)(unsafe.Pointer(&w)) = *(*uint8)(p) |
| case 2: |
| *(*uint16)(unsafe.Pointer(&w)) = *(*uint16)(p) |
| case 3: |
| *(*[3]byte)(unsafe.Pointer(&w)) = *(*[3]byte)(p) |
| case 4: |
| *(*uint32)(unsafe.Pointer(&w)) = *(*uint32)(p) |
| case 5: |
| *(*[5]byte)(unsafe.Pointer(&w)) = *(*[5]byte)(p) |
| case 6: |
| *(*[6]byte)(unsafe.Pointer(&w)) = *(*[6]byte)(p) |
| case 7: |
| *(*[7]byte)(unsafe.Pointer(&w)) = *(*[7]byte)(p) |
| case 8: |
| *(*uint64)(unsafe.Pointer(&w)) = *(*uint64)(p) |
| } |
| return w |
| } |
| |
| // storeIword stores n bytes from w into p. |
| func storeIword(p unsafe.Pointer, w iword, n uintptr) { |
| // Run the copy ourselves instead of calling memmove |
| // to avoid moving w to the heap. |
| switch n { |
| default: |
| panic("reflect: internal error: storeIword of " + strconv.Itoa(int(n)) + "-byte value") |
| case 0: |
| case 1: |
| *(*uint8)(p) = *(*uint8)(unsafe.Pointer(&w)) |
| case 2: |
| *(*uint16)(p) = *(*uint16)(unsafe.Pointer(&w)) |
| case 3: |
| *(*[3]byte)(p) = *(*[3]byte)(unsafe.Pointer(&w)) |
| case 4: |
| *(*uint32)(p) = *(*uint32)(unsafe.Pointer(&w)) |
| case 5: |
| *(*[5]byte)(p) = *(*[5]byte)(unsafe.Pointer(&w)) |
| case 6: |
| *(*[6]byte)(p) = *(*[6]byte)(unsafe.Pointer(&w)) |
| case 7: |
| *(*[7]byte)(p) = *(*[7]byte)(unsafe.Pointer(&w)) |
| case 8: |
| *(*uint64)(p) = *(*uint64)(unsafe.Pointer(&w)) |
| } |
| } |
| |
| // emptyInterface is the header for an interface{} value. |
| type emptyInterface struct { |
| typ *runtimeType |
| word iword |
| } |
| |
| // nonEmptyInterface is the header for a interface value with methods. |
| type nonEmptyInterface struct { |
| // see ../runtime/iface.c:/Itab |
| itab *struct { |
| ityp *runtimeType // static interface type |
| typ *runtimeType // dynamic concrete type |
| link unsafe.Pointer |
| bad int32 |
| unused int32 |
| fun [100000]unsafe.Pointer // method table |
| } |
| word iword |
| } |
| |
| // mustBe panics if f's kind is not expected. |
| // Making this a method on flag instead of on Value |
| // (and embedding flag in Value) means that we can write |
| // the very clear v.mustBe(Bool) and have it compile into |
| // v.flag.mustBe(Bool), which will only bother to copy the |
| // single important word for the receiver. |
| func (f flag) mustBe(expected Kind) { |
| k := f.kind() |
| if k != expected { |
| panic(&ValueError{methodName(), k}) |
| } |
| } |
| |
| // mustBeExported panics if f records that the value was obtained using |
| // an unexported field. |
| func (f flag) mustBeExported() { |
| if f == 0 { |
| panic(&ValueError{methodName(), 0}) |
| } |
| if f&flagRO != 0 { |
| panic(methodName() + " using value obtained using unexported field") |
| } |
| } |
| |
| // mustBeAssignable panics if f records that the value is not assignable, |
| // which is to say that either it was obtained using an unexported field |
| // or it is not addressable. |
| func (f flag) mustBeAssignable() { |
| if f == 0 { |
| panic(&ValueError{methodName(), Invalid}) |
| } |
| // Assignable if addressable and not read-only. |
| if f&flagRO != 0 { |
| panic(methodName() + " using value obtained using unexported field") |
| } |
| if f&flagAddr == 0 { |
| panic(methodName() + " using unaddressable value") |
| } |
| } |
| |
| // Addr returns a pointer value representing the address of v. |
| // It panics if CanAddr() returns false. |
| // Addr is typically used to obtain a pointer to a struct field |
| // or slice element in order to call a method that requires a |
| // pointer receiver. |
| func (v Value) Addr() Value { |
| if v.flag&flagAddr == 0 { |
| panic("reflect.Value.Addr of unaddressable value") |
| } |
| return Value{v.typ.ptrTo(), v.val, (v.flag & flagRO) | flag(Ptr)<<flagKindShift} |
| } |
| |
| // Bool returns v's underlying value. |
| // It panics if v's kind is not Bool. |
| func (v Value) Bool() bool { |
| v.mustBe(Bool) |
| if v.flag&flagIndir != 0 { |
| return *(*bool)(v.val) |
| } |
| return *(*bool)(unsafe.Pointer(&v.val)) |
| } |
| |
| // Bytes returns v's underlying value. |
| // It panics if v's underlying value is not a slice of bytes. |
| func (v Value) Bytes() []byte { |
| v.mustBe(Slice) |
| if v.typ.Elem().Kind() != Uint8 { |
| panic("reflect.Value.Bytes of non-byte slice") |
| } |
| // Slice is always bigger than a word; assume flagIndir. |
| return *(*[]byte)(v.val) |
| } |
| |
| // CanAddr returns true if the value's address can be obtained with Addr. |
| // Such values are called addressable. A value is addressable if it is |
| // an element of a slice, an element of an addressable array, |
| // a field of an addressable struct, or the result of dereferencing a pointer. |
| // If CanAddr returns false, calling Addr will panic. |
| func (v Value) CanAddr() bool { |
| return v.flag&flagAddr != 0 |
| } |
| |
| // CanSet returns true if the value of v can be changed. |
| // A Value can be changed only if it is addressable and was not |
| // obtained by the use of unexported struct fields. |
| // If CanSet returns false, calling Set or any type-specific |
| // setter (e.g., SetBool, SetInt64) will panic. |
| func (v Value) CanSet() bool { |
| return v.flag&(flagAddr|flagRO) == flagAddr |
| } |
| |
| // Call calls the function v with the input arguments in. |
| // For example, if len(in) == 3, v.Call(in) represents the Go call v(in[0], in[1], in[2]). |
| // Call panics if v's Kind is not Func. |
| // It returns the output results as Values. |
| // As in Go, each input argument must be assignable to the |
| // type of the function's corresponding input parameter. |
| // If v is a variadic function, Call creates the variadic slice parameter |
| // itself, copying in the corresponding values. |
| func (v Value) Call(in []Value) []Value { |
| v.mustBe(Func) |
| v.mustBeExported() |
| return v.call("Call", in) |
| } |
| |
| // CallSlice calls the variadic function v with the input arguments in, |
| // assigning the slice in[len(in)-1] to v's final variadic argument. |
| // For example, if len(in) == 3, v.Call(in) represents the Go call v(in[0], in[1], in[2]...). |
| // Call panics if v's Kind is not Func or if v is not variadic. |
| // It returns the output results as Values. |
| // As in Go, each input argument must be assignable to the |
| // type of the function's corresponding input parameter. |
| func (v Value) CallSlice(in []Value) []Value { |
| v.mustBe(Func) |
| v.mustBeExported() |
| return v.call("CallSlice", in) |
| } |
| |
| func (v Value) call(method string, in []Value) []Value { |
| // Get function pointer, type. |
| t := v.typ |
| var ( |
| fn unsafe.Pointer |
| rcvr iword |
| ) |
| if v.flag&flagMethod != 0 { |
| i := int(v.flag) >> flagMethodShift |
| if v.typ.Kind() == Interface { |
| tt := (*interfaceType)(unsafe.Pointer(v.typ)) |
| if i < 0 || i >= len(tt.methods) { |
| panic("reflect: broken Value") |
| } |
| m := &tt.methods[i] |
| if m.pkgPath != nil { |
| panic(method + " of unexported method") |
| } |
| t = toCommonType(m.typ) |
| iface := (*nonEmptyInterface)(v.val) |
| if iface.itab == nil { |
| panic(method + " of method on nil interface value") |
| } |
| fn = iface.itab.fun[i] |
| rcvr = iface.word |
| } else { |
| ut := v.typ.uncommon() |
| if ut == nil || i < 0 || i >= len(ut.methods) { |
| panic("reflect: broken Value") |
| } |
| m := &ut.methods[i] |
| if m.pkgPath != nil { |
| panic(method + " of unexported method") |
| } |
| fn = m.ifn |
| t = toCommonType(m.mtyp) |
| rcvr = v.iword() |
| } |
| } else if v.flag&flagIndir != 0 { |
| fn = *(*unsafe.Pointer)(v.val) |
| } else { |
| fn = v.val |
| } |
| |
| if fn == nil { |
| panic("reflect.Value.Call: call of nil function") |
| } |
| |
| isSlice := method == "CallSlice" |
| n := t.NumIn() |
| if isSlice { |
| if !t.IsVariadic() { |
| panic("reflect: CallSlice of non-variadic function") |
| } |
| if len(in) < n { |
| panic("reflect: CallSlice with too few input arguments") |
| } |
| if len(in) > n { |
| panic("reflect: CallSlice with too many input arguments") |
| } |
| } else { |
| if t.IsVariadic() { |
| n-- |
| } |
| if len(in) < n { |
| panic("reflect: Call with too few input arguments") |
| } |
| if !t.IsVariadic() && len(in) > n { |
| panic("reflect: Call with too many input arguments") |
| } |
| } |
| for _, x := range in { |
| if x.Kind() == Invalid { |
| panic("reflect: " + method + " using zero Value argument") |
| } |
| } |
| for i := 0; i < n; i++ { |
| if xt, targ := in[i].Type(), t.In(i); !xt.AssignableTo(targ) { |
| panic("reflect: " + method + " using " + xt.String() + " as type " + targ.String()) |
| } |
| } |
| if !isSlice && t.IsVariadic() { |
| // prepare slice for remaining values |
| m := len(in) - n |
| slice := MakeSlice(t.In(n), m, m) |
| elem := t.In(n).Elem() |
| for i := 0; i < m; i++ { |
| x := in[n+i] |
| if xt := x.Type(); !xt.AssignableTo(elem) { |
| panic("reflect: cannot use " + xt.String() + " as type " + elem.String() + " in " + method) |
| } |
| slice.Index(i).Set(x) |
| } |
| origIn := in |
| in = make([]Value, n+1) |
| copy(in[:n], origIn) |
| in[n] = slice |
| } |
| |
| nin := len(in) |
| if nin != t.NumIn() { |
| panic("reflect.Value.Call: wrong argument count") |
| } |
| nout := t.NumOut() |
| |
| // Compute arg size & allocate. |
| // This computation is 5g/6g/8g-dependent |
| // and probably wrong for gccgo, but so |
| // is most of this function. |
| size := uintptr(0) |
| if v.flag&flagMethod != 0 { |
| // extra word for receiver interface word |
| size += ptrSize |
| } |
| for i := 0; i < nin; i++ { |
| tv := t.In(i) |
| a := uintptr(tv.Align()) |
| size = (size + a - 1) &^ (a - 1) |
| size += tv.Size() |
| } |
| size = (size + ptrSize - 1) &^ (ptrSize - 1) |
| for i := 0; i < nout; i++ { |
| tv := t.Out(i) |
| a := uintptr(tv.Align()) |
| size = (size + a - 1) &^ (a - 1) |
| size += tv.Size() |
| } |
| |
| // size must be > 0 in order for &args[0] to be valid. |
| // the argument copying is going to round it up to |
| // a multiple of ptrSize anyway, so make it ptrSize to begin with. |
| if size < ptrSize { |
| size = ptrSize |
| } |
| |
| // round to pointer size |
| size = (size + ptrSize - 1) &^ (ptrSize - 1) |
| |
| // Copy into args. |
| // |
| // TODO(rsc): revisit when reference counting happens. |
| // The values are holding up the in references for us, |
| // but something must be done for the out references. |
| // For now make everything look like a pointer by pretending |
| // to allocate a []*int. |
| args := make([]*int, size/ptrSize) |
| ptr := uintptr(unsafe.Pointer(&args[0])) |
| off := uintptr(0) |
| if v.flag&flagMethod != 0 { |
| // Hard-wired first argument. |
| *(*iword)(unsafe.Pointer(ptr)) = rcvr |
| off = ptrSize |
| } |
| for i, v := range in { |
| v.mustBeExported() |
| targ := t.In(i).(*commonType) |
| a := uintptr(targ.align) |
| off = (off + a - 1) &^ (a - 1) |
| n := targ.size |
| addr := unsafe.Pointer(ptr + off) |
| v = v.assignTo("reflect.Value.Call", targ, (*interface{})(addr)) |
| if v.flag&flagIndir == 0 { |
| storeIword(addr, iword(v.val), n) |
| } else { |
| memmove(addr, v.val, n) |
| } |
| off += n |
| } |
| off = (off + ptrSize - 1) &^ (ptrSize - 1) |
| |
| // Call. |
| call(fn, unsafe.Pointer(ptr), uint32(size)) |
| |
| // Copy return values out of args. |
| // |
| // TODO(rsc): revisit like above. |
| ret := make([]Value, nout) |
| for i := 0; i < nout; i++ { |
| tv := t.Out(i) |
| a := uintptr(tv.Align()) |
| off = (off + a - 1) &^ (a - 1) |
| fl := flagIndir | flag(tv.Kind())<<flagKindShift |
| ret[i] = Value{tv.common(), unsafe.Pointer(ptr + off), fl} |
| off += tv.Size() |
| } |
| |
| return ret |
| } |
| |
| // Cap returns v's capacity. |
| // It panics if v's Kind is not Array, Chan, or Slice. |
| func (v Value) Cap() int { |
| k := v.kind() |
| switch k { |
| case Array: |
| return v.typ.Len() |
| case Chan: |
| return int(chancap(v.iword())) |
| case Slice: |
| // Slice is always bigger than a word; assume flagIndir. |
| return (*SliceHeader)(v.val).Cap |
| } |
| panic(&ValueError{"reflect.Value.Cap", k}) |
| } |
| |
| // Close closes the channel v. |
| // It panics if v's Kind is not Chan. |
| func (v Value) Close() { |
| v.mustBe(Chan) |
| v.mustBeExported() |
| chanclose(v.iword()) |
| } |
| |
| // Complex returns v's underlying value, as a complex128. |
| // It panics if v's Kind is not Complex64 or Complex128 |
| func (v Value) Complex() complex128 { |
| k := v.kind() |
| switch k { |
| case Complex64: |
| if v.flag&flagIndir != 0 { |
| return complex128(*(*complex64)(v.val)) |
| } |
| return complex128(*(*complex64)(unsafe.Pointer(&v.val))) |
| case Complex128: |
| // complex128 is always bigger than a word; assume flagIndir. |
| return *(*complex128)(v.val) |
| } |
| panic(&ValueError{"reflect.Value.Complex", k}) |
| } |
| |
| // Elem returns the value that the interface v contains |
| // or that the pointer v points to. |
| // It panics if v's Kind is not Interface or Ptr. |
| // It returns the zero Value if v is nil. |
| func (v Value) Elem() Value { |
| k := v.kind() |
| switch k { |
| case Interface: |
| var ( |
| typ *commonType |
| val unsafe.Pointer |
| ) |
| if v.typ.NumMethod() == 0 { |
| eface := (*emptyInterface)(v.val) |
| if eface.typ == nil { |
| // nil interface value |
| return Value{} |
| } |
| typ = toCommonType(eface.typ) |
| val = unsafe.Pointer(eface.word) |
| } else { |
| iface := (*nonEmptyInterface)(v.val) |
| if iface.itab == nil { |
| // nil interface value |
| return Value{} |
| } |
| typ = toCommonType(iface.itab.typ) |
| val = unsafe.Pointer(iface.word) |
| } |
| fl := v.flag & flagRO |
| fl |= flag(typ.Kind()) << flagKindShift |
| if typ.size > ptrSize { |
| fl |= flagIndir |
| } |
| return Value{typ, val, fl} |
| |
| case Ptr: |
| val := v.val |
| if v.flag&flagIndir != 0 { |
| val = *(*unsafe.Pointer)(val) |
| } |
| // The returned value's address is v's value. |
| if val == nil { |
| return Value{} |
| } |
| tt := (*ptrType)(unsafe.Pointer(v.typ)) |
| typ := toCommonType(tt.elem) |
| fl := v.flag&flagRO | flagIndir | flagAddr |
| fl |= flag(typ.Kind() << flagKindShift) |
| return Value{typ, val, fl} |
| } |
| panic(&ValueError{"reflect.Value.Elem", k}) |
| } |
| |
| // Field returns the i'th field of the struct v. |
| // It panics if v's Kind is not Struct or i is out of range. |
| func (v Value) Field(i int) Value { |
| v.mustBe(Struct) |
| tt := (*structType)(unsafe.Pointer(v.typ)) |
| if i < 0 || i >= len(tt.fields) { |
| panic("reflect: Field index out of range") |
| } |
| field := &tt.fields[i] |
| typ := toCommonType(field.typ) |
| |
| // Inherit permission bits from v. |
| fl := v.flag & (flagRO | flagIndir | flagAddr) |
| // Using an unexported field forces flagRO. |
| if field.pkgPath != nil { |
| fl |= flagRO |
| } |
| fl |= flag(typ.Kind()) << flagKindShift |
| |
| var val unsafe.Pointer |
| switch { |
| case fl&flagIndir != 0: |
| // Indirect. Just bump pointer. |
| val = unsafe.Pointer(uintptr(v.val) + field.offset) |
| case bigEndian: |
| // Direct. Discard leading bytes. |
| val = unsafe.Pointer(uintptr(v.val) << (field.offset * 8)) |
| default: |
| // Direct. Discard leading bytes. |
| val = unsafe.Pointer(uintptr(v.val) >> (field.offset * 8)) |
| } |
| |
| return Value{typ, val, fl} |
| } |
| |
| // FieldByIndex returns the nested field corresponding to index. |
| // It panics if v's Kind is not struct. |
| func (v Value) FieldByIndex(index []int) Value { |
| v.mustBe(Struct) |
| for i, x := range index { |
| if i > 0 { |
| if v.Kind() == Ptr && v.Elem().Kind() == Struct { |
| v = v.Elem() |
| } |
| } |
| v = v.Field(x) |
| } |
| return v |
| } |
| |
| // FieldByName returns the struct field with the given name. |
| // It returns the zero Value if no field was found. |
| // It panics if v's Kind is not struct. |
| func (v Value) FieldByName(name string) Value { |
| v.mustBe(Struct) |
| if f, ok := v.typ.FieldByName(name); ok { |
| return v.FieldByIndex(f.Index) |
| } |
| return Value{} |
| } |
| |
| // FieldByNameFunc returns the struct field with a name |
| // that satisfies the match function. |
| // It panics if v's Kind is not struct. |
| // It returns the zero Value if no field was found. |
| func (v Value) FieldByNameFunc(match func(string) bool) Value { |
| v.mustBe(Struct) |
| if f, ok := v.typ.FieldByNameFunc(match); ok { |
| return v.FieldByIndex(f.Index) |
| } |
| return Value{} |
| } |
| |
| // Float returns v's underlying value, as a float64. |
| // It panics if v's Kind is not Float32 or Float64 |
| func (v Value) Float() float64 { |
| k := v.kind() |
| switch k { |
| case Float32: |
| if v.flag&flagIndir != 0 { |
| return float64(*(*float32)(v.val)) |
| } |
| return float64(*(*float32)(unsafe.Pointer(&v.val))) |
| case Float64: |
| if v.flag&flagIndir != 0 { |
| return *(*float64)(v.val) |
| } |
| return *(*float64)(unsafe.Pointer(&v.val)) |
| } |
| panic(&ValueError{"reflect.Value.Float", k}) |
| } |
| |
| // Index returns v's i'th element. |
| // It panics if v's Kind is not Array or Slice or i is out of range. |
| func (v Value) Index(i int) Value { |
| k := v.kind() |
| switch k { |
| case Array: |
| tt := (*arrayType)(unsafe.Pointer(v.typ)) |
| if i < 0 || i > int(tt.len) { |
| panic("reflect: array index out of range") |
| } |
| typ := toCommonType(tt.elem) |
| fl := v.flag & (flagRO | flagIndir | flagAddr) // bits same as overall array |
| fl |= flag(typ.Kind()) << flagKindShift |
| offset := uintptr(i) * typ.size |
| |
| var val unsafe.Pointer |
| switch { |
| case fl&flagIndir != 0: |
| // Indirect. Just bump pointer. |
| val = unsafe.Pointer(uintptr(v.val) + offset) |
| case bigEndian: |
| // Direct. Discard leading bytes. |
| val = unsafe.Pointer(uintptr(v.val) << (offset * 8)) |
| default: |
| // Direct. Discard leading bytes. |
| val = unsafe.Pointer(uintptr(v.val) >> (offset * 8)) |
| } |
| return Value{typ, val, fl} |
| |
| case Slice: |
| // Element flag same as Elem of Ptr. |
| // Addressable, indirect, possibly read-only. |
| fl := flagAddr | flagIndir | v.flag&flagRO |
| s := (*SliceHeader)(v.val) |
| if i < 0 || i >= s.Len { |
| panic("reflect: slice index out of range") |
| } |
| tt := (*sliceType)(unsafe.Pointer(v.typ)) |
| typ := toCommonType(tt.elem) |
| fl |= flag(typ.Kind()) << flagKindShift |
| val := unsafe.Pointer(s.Data + uintptr(i)*typ.size) |
| return Value{typ, val, fl} |
| } |
| panic(&ValueError{"reflect.Value.Index", k}) |
| } |
| |
| // Int returns v's underlying value, as an int64. |
| // It panics if v's Kind is not Int, Int8, Int16, Int32, or Int64. |
| func (v Value) Int() int64 { |
| k := v.kind() |
| var p unsafe.Pointer |
| if v.flag&flagIndir != 0 { |
| p = v.val |
| } else { |
| // The escape analysis is good enough that &v.val |
| // does not trigger a heap allocation. |
| p = unsafe.Pointer(&v.val) |
| } |
| switch k { |
| case Int: |
| return int64(*(*int)(p)) |
| case Int8: |
| return int64(*(*int8)(p)) |
| case Int16: |
| return int64(*(*int16)(p)) |
| case Int32: |
| return int64(*(*int32)(p)) |
| case Int64: |
| return int64(*(*int64)(p)) |
| } |
| panic(&ValueError{"reflect.Value.Int", k}) |
| } |
| |
| // CanInterface returns true if Interface can be used without panicking. |
| func (v Value) CanInterface() bool { |
| if v.flag == 0 { |
| panic(&ValueError{"reflect.Value.CanInterface", Invalid}) |
| } |
| return v.flag&(flagMethod|flagRO) == 0 |
| } |
| |
| // Interface returns v's value as an interface{}. |
| // If v is a method obtained by invoking Value.Method |
| // (as opposed to Type.Method), Interface cannot return an |
| // interface value, so it panics. |
| // It also panics if the Value was obtained by accessing |
| // unexported struct fields. |
| func (v Value) Interface() interface{} { |
| return valueInterface(v, true) |
| } |
| |
| func valueInterface(v Value, safe bool) interface{} { |
| if v.flag == 0 { |
| panic(&ValueError{"reflect.Value.Interface", 0}) |
| } |
| if v.flag&flagMethod != 0 { |
| panic("reflect.Value.Interface: cannot create interface value for method with bound receiver") |
| } |
| |
| if safe && v.flag&flagRO != 0 { |
| // Do not allow access to unexported values via Interface, |
| // because they might be pointers that should not be |
| // writable or methods or function that should not be callable. |
| panic("reflect.Value.Interface: cannot return value obtained from unexported field or method") |
| } |
| |
| k := v.kind() |
| if k == Interface { |
| // Special case: return the element inside the interface. |
| // Empty interface has one layout, all interfaces with |
| // methods have a second layout. |
| if v.NumMethod() == 0 { |
| return *(*interface{})(v.val) |
| } |
| return *(*interface { |
| M() |
| })(v.val) |
| } |
| |
| // Non-interface value. |
| var eface emptyInterface |
| eface.typ = v.typ.runtimeType() |
| eface.word = v.iword() |
| return *(*interface{})(unsafe.Pointer(&eface)) |
| } |
| |
| // InterfaceData returns the interface v's value as a uintptr pair. |
| // It panics if v's Kind is not Interface. |
| func (v Value) InterfaceData() [2]uintptr { |
| v.mustBe(Interface) |
| // We treat this as a read operation, so we allow |
| // it even for unexported data, because the caller |
| // has to import "unsafe" to turn it into something |
| // that can be abused. |
| // Interface value is always bigger than a word; assume flagIndir. |
| return *(*[2]uintptr)(v.val) |
| } |
| |
| // IsNil returns true if v is a nil value. |
| // It panics if v's Kind is not Chan, Func, Interface, Map, Ptr, or Slice. |
| func (v Value) IsNil() bool { |
| k := v.kind() |
| switch k { |
| case Chan, Func, Map, Ptr: |
| if v.flag&flagMethod != 0 { |
| panic("reflect: IsNil of method Value") |
| } |
| ptr := v.val |
| if v.flag&flagIndir != 0 { |
| ptr = *(*unsafe.Pointer)(ptr) |
| } |
| return ptr == nil |
| case Interface, Slice: |
| // Both interface and slice are nil if first word is 0. |
| // Both are always bigger than a word; assume flagIndir. |
| return *(*unsafe.Pointer)(v.val) == nil |
| } |
| panic(&ValueError{"reflect.Value.IsNil", k}) |
| } |
| |
| // IsValid returns true if v represents a value. |
| // It returns false if v is the zero Value. |
| // If IsValid returns false, all other methods except String panic. |
| // Most functions and methods never return an invalid value. |
| // If one does, its documentation states the conditions explicitly. |
| func (v Value) IsValid() bool { |
| return v.flag != 0 |
| } |
| |
| // Kind returns v's Kind. |
| // If v is the zero Value (IsValid returns false), Kind returns Invalid. |
| func (v Value) Kind() Kind { |
| return v.kind() |
| } |
| |
| // Len returns v's length. |
| // It panics if v's Kind is not Array, Chan, Map, Slice, or String. |
| func (v Value) Len() int { |
| k := v.kind() |
| switch k { |
| case Array: |
| tt := (*arrayType)(unsafe.Pointer(v.typ)) |
| return int(tt.len) |
| case Chan: |
| return int(chanlen(v.iword())) |
| case Map: |
| return int(maplen(v.iword())) |
| case Slice: |
| // Slice is bigger than a word; assume flagIndir. |
| return (*SliceHeader)(v.val).Len |
| case String: |
| // String is bigger than a word; assume flagIndir. |
| return (*StringHeader)(v.val).Len |
| } |
| panic(&ValueError{"reflect.Value.Len", k}) |
| } |
| |
| // MapIndex returns the value associated with key in the map v. |
| // It panics if v's Kind is not Map. |
| // It returns the zero Value if key is not found in the map or if v represents a nil map. |
| // As in Go, the key's value must be assignable to the map's key type. |
| func (v Value) MapIndex(key Value) Value { |
| v.mustBe(Map) |
| tt := (*mapType)(unsafe.Pointer(v.typ)) |
| |
| // Do not require key to be exported, so that DeepEqual |
| // and other programs can use all the keys returned by |
| // MapKeys as arguments to MapIndex. If either the map |
| // or the key is unexported, though, the result will be |
| // considered unexported. This is consistent with the |
| // behavior for structs, which allow read but not write |
| // of unexported fields. |
| key = key.assignTo("reflect.Value.MapIndex", toCommonType(tt.key), nil) |
| |
| word, ok := mapaccess(v.typ.runtimeType(), v.iword(), key.iword()) |
| if !ok { |
| return Value{} |
| } |
| typ := toCommonType(tt.elem) |
| fl := (v.flag | key.flag) & flagRO |
| if typ.size > ptrSize { |
| fl |= flagIndir |
| } |
| fl |= flag(typ.Kind()) << flagKindShift |
| return Value{typ, unsafe.Pointer(word), fl} |
| } |
| |
| // MapKeys returns a slice containing all the keys present in the map, |
| // in unspecified order. |
| // It panics if v's Kind is not Map. |
| // It returns an empty slice if v represents a nil map. |
| func (v Value) MapKeys() []Value { |
| v.mustBe(Map) |
| tt := (*mapType)(unsafe.Pointer(v.typ)) |
| keyType := toCommonType(tt.key) |
| |
| fl := v.flag & flagRO |
| fl |= flag(keyType.Kind()) << flagKindShift |
| if keyType.size > ptrSize { |
| fl |= flagIndir |
| } |
| |
| m := v.iword() |
| mlen := int32(0) |
| if m != nil { |
| mlen = maplen(m) |
| } |
| it := mapiterinit(v.typ.runtimeType(), m) |
| a := make([]Value, mlen) |
| var i int |
| for i = 0; i < len(a); i++ { |
| keyWord, ok := mapiterkey(it) |
| if !ok { |
| break |
| } |
| a[i] = Value{keyType, unsafe.Pointer(keyWord), fl} |
| mapiternext(it) |
| } |
| return a[:i] |
| } |
| |
| // Method returns a function value corresponding to v's i'th method. |
| // The arguments to a Call on the returned function should not include |
| // a receiver; the returned function will always use v as the receiver. |
| // Method panics if i is out of range. |
| func (v Value) Method(i int) Value { |
| if v.typ == nil { |
| panic(&ValueError{"reflect.Value.Method", Invalid}) |
| } |
| if v.flag&flagMethod != 0 || i < 0 || i >= v.typ.NumMethod() { |
| panic("reflect: Method index out of range") |
| } |
| fl := v.flag & (flagRO | flagAddr | flagIndir) |
| fl |= flag(Func) << flagKindShift |
| fl |= flag(i)<<flagMethodShift | flagMethod |
| return Value{v.typ, v.val, fl} |
| } |
| |
| // NumMethod returns the number of methods in the value's method set. |
| func (v Value) NumMethod() int { |
| if v.typ == nil { |
| panic(&ValueError{"reflect.Value.NumMethod", Invalid}) |
| } |
| if v.flag&flagMethod != 0 { |
| return 0 |
| } |
| return v.typ.NumMethod() |
| } |
| |
| // MethodByName returns a function value corresponding to the method |
| // of v with the given name. |
| // The arguments to a Call on the returned function should not include |
| // a receiver; the returned function will always use v as the receiver. |
| // It returns the zero Value if no method was found. |
| func (v Value) MethodByName(name string) Value { |
| if v.typ == nil { |
| panic(&ValueError{"reflect.Value.MethodByName", Invalid}) |
| } |
| if v.flag&flagMethod != 0 { |
| return Value{} |
| } |
| m, ok := v.typ.MethodByName(name) |
| if !ok { |
| return Value{} |
| } |
| return v.Method(m.Index) |
| } |
| |
| // NumField returns the number of fields in the struct v. |
| // It panics if v's Kind is not Struct. |
| func (v Value) NumField() int { |
| v.mustBe(Struct) |
| tt := (*structType)(unsafe.Pointer(v.typ)) |
| return len(tt.fields) |
| } |
| |
| // OverflowComplex returns true if the complex128 x cannot be represented by v's type. |
| // It panics if v's Kind is not Complex64 or Complex128. |
| func (v Value) OverflowComplex(x complex128) bool { |
| k := v.kind() |
| switch k { |
| case Complex64: |
| return overflowFloat32(real(x)) || overflowFloat32(imag(x)) |
| case Complex128: |
| return false |
| } |
| panic(&ValueError{"reflect.Value.OverflowComplex", k}) |
| } |
| |
| // OverflowFloat returns true if the float64 x cannot be represented by v's type. |
| // It panics if v's Kind is not Float32 or Float64. |
| func (v Value) OverflowFloat(x float64) bool { |
| k := v.kind() |
| switch k { |
| case Float32: |
| return overflowFloat32(x) |
| case Float64: |
| return false |
| } |
| panic(&ValueError{"reflect.Value.OverflowFloat", k}) |
| } |
| |
| func overflowFloat32(x float64) bool { |
| if x < 0 { |
| x = -x |
| } |
| return math.MaxFloat32 <= x && x <= math.MaxFloat64 |
| } |
| |
| // OverflowInt returns true if the int64 x cannot be represented by v's type. |
| // It panics if v's Kind is not Int, Int8, int16, Int32, or Int64. |
| func (v Value) OverflowInt(x int64) bool { |
| k := v.kind() |
| switch k { |
| case Int, Int8, Int16, Int32, Int64: |
| bitSize := v.typ.size * 8 |
| trunc := (x << (64 - bitSize)) >> (64 - bitSize) |
| return x != trunc |
| } |
| panic(&ValueError{"reflect.Value.OverflowInt", k}) |
| } |
| |
| // OverflowUint returns true if the uint64 x cannot be represented by v's type. |
| // It panics if v's Kind is not Uint, Uintptr, Uint8, Uint16, Uint32, or Uint64. |
| func (v Value) OverflowUint(x uint64) bool { |
| k := v.kind() |
| switch k { |
| case Uint, Uintptr, Uint8, Uint16, Uint32, Uint64: |
| bitSize := v.typ.size * 8 |
| trunc := (x << (64 - bitSize)) >> (64 - bitSize) |
| return x != trunc |
| } |
| panic(&ValueError{"reflect.Value.OverflowUint", k}) |
| } |
| |
| // Pointer returns v's value as a uintptr. |
| // It returns uintptr instead of unsafe.Pointer so that |
| // code using reflect cannot obtain unsafe.Pointers |
| // without importing the unsafe package explicitly. |
| // It panics if v's Kind is not Chan, Func, Map, Ptr, Slice, or UnsafePointer. |
| func (v Value) Pointer() uintptr { |
| k := v.kind() |
| switch k { |
| case Chan, Func, Map, Ptr, UnsafePointer: |
| if k == Func && v.flag&flagMethod != 0 { |
| panic("reflect.Value.Pointer of method Value") |
| } |
| p := v.val |
| if v.flag&flagIndir != 0 { |
| p = *(*unsafe.Pointer)(p) |
| } |
| return uintptr(p) |
| case Slice: |
| return (*SliceHeader)(v.val).Data |
| } |
| panic(&ValueError{"reflect.Value.Pointer", k}) |
| } |
| |
| // Recv receives and returns a value from the channel v. |
| // It panics if v's Kind is not Chan. |
| // The receive blocks until a value is ready. |
| // The boolean value ok is true if the value x corresponds to a send |
| // on the channel, false if it is a zero value received because the channel is closed. |
| func (v Value) Recv() (x Value, ok bool) { |
| v.mustBe(Chan) |
| v.mustBeExported() |
| return v.recv(false) |
| } |
| |
| // internal recv, possibly non-blocking (nb). |
| // v is known to be a channel. |
| func (v Value) recv(nb bool) (val Value, ok bool) { |
| tt := (*chanType)(unsafe.Pointer(v.typ)) |
| if ChanDir(tt.dir)&RecvDir == 0 { |
| panic("recv on send-only channel") |
| } |
| word, selected, ok := chanrecv(v.typ.runtimeType(), v.iword(), nb) |
| if selected { |
| typ := toCommonType(tt.elem) |
| fl := flag(typ.Kind()) << flagKindShift |
| if typ.size > ptrSize { |
| fl |= flagIndir |
| } |
| val = Value{typ, unsafe.Pointer(word), fl} |
| } |
| return |
| } |
| |
| // Send sends x on the channel v. |
| // It panics if v's kind is not Chan or if x's type is not the same type as v's element type. |
| // As in Go, x's value must be assignable to the channel's element type. |
| func (v Value) Send(x Value) { |
| v.mustBe(Chan) |
| v.mustBeExported() |
| v.send(x, false) |
| } |
| |
| // internal send, possibly non-blocking. |
| // v is known to be a channel. |
| func (v Value) send(x Value, nb bool) (selected bool) { |
| tt := (*chanType)(unsafe.Pointer(v.typ)) |
| if ChanDir(tt.dir)&SendDir == 0 { |
| panic("send on recv-only channel") |
| } |
| x.mustBeExported() |
| x = x.assignTo("reflect.Value.Send", toCommonType(tt.elem), nil) |
| return chansend(v.typ.runtimeType(), v.iword(), x.iword(), nb) |
| } |
| |
| // Set assigns x to the value v. |
| // It panics if CanSet returns false. |
| // As in Go, x's value must be assignable to v's type. |
| func (v Value) Set(x Value) { |
| v.mustBeAssignable() |
| x.mustBeExported() // do not let unexported x leak |
| var target *interface{} |
| if v.kind() == Interface { |
| target = (*interface{})(v.val) |
| } |
| x = x.assignTo("reflect.Set", v.typ, target) |
| if x.flag&flagIndir != 0 { |
| memmove(v.val, x.val, v.typ.size) |
| } else { |
| storeIword(v.val, iword(x.val), v.typ.size) |
| } |
| } |
| |
| // SetBool sets v's underlying value. |
| // It panics if v's Kind is not Bool or if CanSet() is false. |
| func (v Value) SetBool(x bool) { |
| v.mustBeAssignable() |
| v.mustBe(Bool) |
| *(*bool)(v.val) = x |
| } |
| |
| // SetBytes sets v's underlying value. |
| // It panics if v's underlying value is not a slice of bytes. |
| func (v Value) SetBytes(x []byte) { |
| v.mustBeAssignable() |
| v.mustBe(Slice) |
| if v.typ.Elem().Kind() != Uint8 { |
| panic("reflect.Value.SetBytes of non-byte slice") |
| } |
| *(*[]byte)(v.val) = x |
| } |
| |
| // SetComplex sets v's underlying value to x. |
| // It panics if v's Kind is not Complex64 or Complex128, or if CanSet() is false. |
| func (v Value) SetComplex(x complex128) { |
| v.mustBeAssignable() |
| switch k := v.kind(); k { |
| default: |
| panic(&ValueError{"reflect.Value.SetComplex", k}) |
| case Complex64: |
| *(*complex64)(v.val) = complex64(x) |
| case Complex128: |
| *(*complex128)(v.val) = x |
| } |
| } |
| |
| // SetFloat sets v's underlying value to x. |
| // It panics if v's Kind is not Float32 or Float64, or if CanSet() is false. |
| func (v Value) SetFloat(x float64) { |
| v.mustBeAssignable() |
| switch k := v.kind(); k { |
| default: |
| panic(&ValueError{"reflect.Value.SetFloat", k}) |
| case Float32: |
| *(*float32)(v.val) = float32(x) |
| case Float64: |
| *(*float64)(v.val) = x |
| } |
| } |
| |
| // SetInt sets v's underlying value to x. |
| // It panics if v's Kind is not Int, Int8, Int16, Int32, or Int64, or if CanSet() is false. |
| func (v Value) SetInt(x int64) { |
| v.mustBeAssignable() |
| switch k := v.kind(); k { |
| default: |
| panic(&ValueError{"reflect.Value.SetInt", k}) |
| case Int: |
| *(*int)(v.val) = int(x) |
| case Int8: |
| *(*int8)(v.val) = int8(x) |
| case Int16: |
| *(*int16)(v.val) = int16(x) |
| case Int32: |
| *(*int32)(v.val) = int32(x) |
| case Int64: |
| *(*int64)(v.val) = x |
| } |
| } |
| |
| // SetLen sets v's length to n. |
| // It panics if v's Kind is not Slice or if n is negative or |
| // greater than the capacity of the slice. |
| func (v Value) SetLen(n int) { |
| v.mustBeAssignable() |
| v.mustBe(Slice) |
| s := (*SliceHeader)(v.val) |
| if n < 0 || n > int(s.Cap) { |
| panic("reflect: slice length out of range in SetLen") |
| } |
| s.Len = n |
| } |
| |
| // SetMapIndex sets the value associated with key in the map v to val. |
| // It panics if v's Kind is not Map. |
| // If val is the zero Value, SetMapIndex deletes the key from the map. |
| // As in Go, key's value must be assignable to the map's key type, |
| // and val's value must be assignable to the map's value type. |
| func (v Value) SetMapIndex(key, val Value) { |
| v.mustBe(Map) |
| v.mustBeExported() |
| key.mustBeExported() |
| tt := (*mapType)(unsafe.Pointer(v.typ)) |
| key = key.assignTo("reflect.Value.SetMapIndex", toCommonType(tt.key), nil) |
| if val.typ != nil { |
| val.mustBeExported() |
| val = val.assignTo("reflect.Value.SetMapIndex", toCommonType(tt.elem), nil) |
| } |
| mapassign(v.typ.runtimeType(), v.iword(), key.iword(), val.iword(), val.typ != nil) |
| } |
| |
| // SetUint sets v's underlying value to x. |
| // It panics if v's Kind is not Uint, Uintptr, Uint8, Uint16, Uint32, or Uint64, or if CanSet() is false. |
| func (v Value) SetUint(x uint64) { |
| v.mustBeAssignable() |
| switch k := v.kind(); k { |
| default: |
| panic(&ValueError{"reflect.Value.SetUint", k}) |
| case Uint: |
| *(*uint)(v.val) = uint(x) |
| case Uint8: |
| *(*uint8)(v.val) = uint8(x) |
| case Uint16: |
| *(*uint16)(v.val) = uint16(x) |
| case Uint32: |
| *(*uint32)(v.val) = uint32(x) |
| case Uint64: |
| *(*uint64)(v.val) = x |
| case Uintptr: |
| *(*uintptr)(v.val) = uintptr(x) |
| } |
| } |
| |
| // SetPointer sets the unsafe.Pointer value v to x. |
| // It panics if v's Kind is not UnsafePointer. |
| func (v Value) SetPointer(x unsafe.Pointer) { |
| v.mustBeAssignable() |
| v.mustBe(UnsafePointer) |
| *(*unsafe.Pointer)(v.val) = x |
| } |
| |
| // SetString sets v's underlying value to x. |
| // It panics if v's Kind is not String or if CanSet() is false. |
| func (v Value) SetString(x string) { |
| v.mustBeAssignable() |
| v.mustBe(String) |
| *(*string)(v.val) = x |
| } |
| |
| // Slice returns a slice of v. |
| // It panics if v's Kind is not Array or Slice. |
| func (v Value) Slice(beg, end int) Value { |
| var ( |
| cap int |
| typ *sliceType |
| base unsafe.Pointer |
| ) |
| switch k := v.kind(); k { |
| default: |
| panic(&ValueError{"reflect.Value.Slice", k}) |
| case Array: |
| if v.flag&flagAddr == 0 { |
| panic("reflect.Value.Slice: slice of unaddressable array") |
| } |
| tt := (*arrayType)(unsafe.Pointer(v.typ)) |
| cap = int(tt.len) |
| typ = (*sliceType)(unsafe.Pointer(toCommonType(tt.slice))) |
| base = v.val |
| case Slice: |
| typ = (*sliceType)(unsafe.Pointer(v.typ)) |
| s := (*SliceHeader)(v.val) |
| base = unsafe.Pointer(s.Data) |
| cap = s.Cap |
| |
| } |
| if beg < 0 || end < beg || end > cap { |
| panic("reflect.Value.Slice: slice index out of bounds") |
| } |
| |
| // Declare slice so that gc can see the base pointer in it. |
| var x []byte |
| |
| // Reinterpret as *SliceHeader to edit. |
| s := (*SliceHeader)(unsafe.Pointer(&x)) |
| s.Data = uintptr(base) + uintptr(beg)*toCommonType(typ.elem).Size() |
| s.Len = end - beg |
| s.Cap = cap - beg |
| |
| fl := v.flag&flagRO | flagIndir | flag(Slice)<<flagKindShift |
| return Value{typ.common(), unsafe.Pointer(&x), fl} |
| } |
| |
| // String returns the string v's underlying value, as a string. |
| // String is a special case because of Go's String method convention. |
| // Unlike the other getters, it does not panic if v's Kind is not String. |
| // Instead, it returns a string of the form "<T value>" where T is v's type. |
| func (v Value) String() string { |
| switch k := v.kind(); k { |
| case Invalid: |
| return "<invalid Value>" |
| case String: |
| return *(*string)(v.val) |
| } |
| // If you call String on a reflect.Value of other type, it's better to |
| // print something than to panic. Useful in debugging. |
| return "<" + v.typ.String() + " Value>" |
| } |
| |
| // TryRecv attempts to receive a value from the channel v but will not block. |
| // It panics if v's Kind is not Chan. |
| // If the receive cannot finish without blocking, x is the zero Value. |
| // The boolean ok is true if the value x corresponds to a send |
| // on the channel, false if it is a zero value received because the channel is closed. |
| func (v Value) TryRecv() (x Value, ok bool) { |
| v.mustBe(Chan) |
| v.mustBeExported() |
| return v.recv(true) |
| } |
| |
| // TrySend attempts to send x on the channel v but will not block. |
| // It panics if v's Kind is not Chan. |
| // It returns true if the value was sent, false otherwise. |
| // As in Go, x's value must be assignable to the channel's element type. |
| func (v Value) TrySend(x Value) bool { |
| v.mustBe(Chan) |
| v.mustBeExported() |
| return v.send(x, true) |
| } |
| |
| // Type returns v's type. |
| func (v Value) Type() Type { |
| f := v.flag |
| if f == 0 { |
| panic(&ValueError{"reflect.Value.Type", Invalid}) |
| } |
| if f&flagMethod == 0 { |
| // Easy case |
| return v.typ |
| } |
| |
| // Method value. |
| // v.typ describes the receiver, not the method type. |
| i := int(v.flag) >> flagMethodShift |
| if v.typ.Kind() == Interface { |
| // Method on interface. |
| tt := (*interfaceType)(unsafe.Pointer(v.typ)) |
| if i < 0 || i >= len(tt.methods) { |
| panic("reflect: broken Value") |
| } |
| m := &tt.methods[i] |
| return toCommonType(m.typ) |
| } |
| // Method on concrete type. |
| ut := v.typ.uncommon() |
| if ut == nil || i < 0 || i >= len(ut.methods) { |
| panic("reflect: broken Value") |
| } |
| m := &ut.methods[i] |
| return toCommonType(m.mtyp) |
| } |
| |
| // Uint returns v's underlying value, as a uint64. |
| // It panics if v's Kind is not Uint, Uintptr, Uint8, Uint16, Uint32, or Uint64. |
| func (v Value) Uint() uint64 { |
| k := v.kind() |
| var p unsafe.Pointer |
| if v.flag&flagIndir != 0 { |
| p = v.val |
| } else { |
| // The escape analysis is good enough that &v.val |
| // does not trigger a heap allocation. |
| p = unsafe.Pointer(&v.val) |
| } |
| switch k { |
| case Uint: |
| return uint64(*(*uint)(p)) |
| case Uint8: |
| return uint64(*(*uint8)(p)) |
| case Uint16: |
| return uint64(*(*uint16)(p)) |
| case Uint32: |
| return uint64(*(*uint32)(p)) |
| case Uint64: |
| return uint64(*(*uint64)(p)) |
| case Uintptr: |
| return uint64(*(*uintptr)(p)) |
| } |
| panic(&ValueError{"reflect.Value.Uint", k}) |
| } |
| |
| // UnsafeAddr returns a pointer to v's data. |
| // It is for advanced clients that also import the "unsafe" package. |
| // It panics if v is not addressable. |
| func (v Value) UnsafeAddr() uintptr { |
| if v.typ == nil { |
| panic(&ValueError{"reflect.Value.UnsafeAddr", Invalid}) |
| } |
| if v.flag&flagAddr == 0 { |
| panic("reflect.Value.UnsafeAddr of unaddressable value") |
| } |
| return uintptr(v.val) |
| } |
| |
| // StringHeader is the runtime representation of a string. |
| // It cannot be used safely or portably. |
| type StringHeader struct { |
| Data uintptr |
| Len int |
| } |
| |
| // SliceHeader is the runtime representation of a slice. |
| // It cannot be used safely or portably. |
| type SliceHeader struct { |
| Data uintptr |
| Len int |
| Cap int |
| } |
| |
| func typesMustMatch(what string, t1, t2 Type) { |
| if t1 != t2 { |
| panic(what + ": " + t1.String() + " != " + t2.String()) |
| } |
| } |
| |
| // grow grows the slice s so that it can hold extra more values, allocating |
| // more capacity if needed. It also returns the old and new slice lengths. |
| func grow(s Value, extra int) (Value, int, int) { |
| i0 := s.Len() |
| i1 := i0 + extra |
| if i1 < i0 { |
| panic("reflect.Append: slice overflow") |
| } |
| m := s.Cap() |
| if i1 <= m { |
| return s.Slice(0, i1), i0, i1 |
| } |
| if m == 0 { |
| m = extra |
| } else { |
| for m < i1 { |
| if i0 < 1024 { |
| m += m |
| } else { |
| m += m / 4 |
| } |
| } |
| } |
| t := MakeSlice(s.Type(), i1, m) |
| Copy(t, s) |
| return t, i0, i1 |
| } |
| |
| // Append appends the values x to a slice s and returns the resulting slice. |
| // As in Go, each x's value must be assignable to the slice's element type. |
| func Append(s Value, x ...Value) Value { |
| s.mustBe(Slice) |
| s, i0, i1 := grow(s, len(x)) |
| for i, j := i0, 0; i < i1; i, j = i+1, j+1 { |
| s.Index(i).Set(x[j]) |
| } |
| return s |
| } |
| |
| // AppendSlice appends a slice t to a slice s and returns the resulting slice. |
| // The slices s and t must have the same element type. |
| func AppendSlice(s, t Value) Value { |
| s.mustBe(Slice) |
| t.mustBe(Slice) |
| typesMustMatch("reflect.AppendSlice", s.Type().Elem(), t.Type().Elem()) |
| s, i0, i1 := grow(s, t.Len()) |
| Copy(s.Slice(i0, i1), t) |
| return s |
| } |
| |
| // Copy copies the contents of src into dst until either |
| // dst has been filled or src has been exhausted. |
| // It returns the number of elements copied. |
| // Dst and src each must have kind Slice or Array, and |
| // dst and src must have the same element type. |
| func Copy(dst, src Value) int { |
| dk := dst.kind() |
| if dk != Array && dk != Slice { |
| panic(&ValueError{"reflect.Copy", dk}) |
| } |
| if dk == Array { |
| dst.mustBeAssignable() |
| } |
| dst.mustBeExported() |
| |
| sk := src.kind() |
| if sk != Array && sk != Slice { |
| panic(&ValueError{"reflect.Copy", sk}) |
| } |
| src.mustBeExported() |
| |
| de := dst.typ.Elem() |
| se := src.typ.Elem() |
| typesMustMatch("reflect.Copy", de, se) |
| |
| n := dst.Len() |
| if sn := src.Len(); n > sn { |
| n = sn |
| } |
| |
| // If sk is an in-line array, cannot take its address. |
| // Instead, copy element by element. |
| if src.flag&flagIndir == 0 { |
| for i := 0; i < n; i++ { |
| dst.Index(i).Set(src.Index(i)) |
| } |
| return n |
| } |
| |
| // Copy via memmove. |
| var da, sa unsafe.Pointer |
| if dk == Array { |
| da = dst.val |
| } else { |
| da = unsafe.Pointer((*SliceHeader)(dst.val).Data) |
| } |
| if sk == Array { |
| sa = src.val |
| } else { |
| sa = unsafe.Pointer((*SliceHeader)(src.val).Data) |
| } |
| memmove(da, sa, uintptr(n)*de.Size()) |
| return n |
| } |
| |
| /* |
| * constructors |
| */ |
| |
| // implemented in package runtime |
| func unsafe_New(Type) unsafe.Pointer |
| func unsafe_NewArray(Type, int) unsafe.Pointer |
| |
| // MakeSlice creates a new zero-initialized slice value |
| // for the specified slice type, length, and capacity. |
| func MakeSlice(typ Type, len, cap int) Value { |
| if typ.Kind() != Slice { |
| panic("reflect.MakeSlice of non-slice type") |
| } |
| |
| // Declare slice so that gc can see the base pointer in it. |
| var x []byte |
| |
| // Reinterpret as *SliceHeader to edit. |
| s := (*SliceHeader)(unsafe.Pointer(&x)) |
| s.Data = uintptr(unsafe_NewArray(typ.Elem(), cap)) |
| s.Len = len |
| s.Cap = cap |
| |
| return Value{typ.common(), unsafe.Pointer(&x), flagIndir | flag(Slice)<<flagKindShift} |
| } |
| |
| // MakeChan creates a new channel with the specified type and buffer size. |
| func MakeChan(typ Type, buffer int) Value { |
| if typ.Kind() != Chan { |
| panic("reflect.MakeChan of non-chan type") |
| } |
| if buffer < 0 { |
| panic("reflect.MakeChan: negative buffer size") |
| } |
| if typ.ChanDir() != BothDir { |
| panic("reflect.MakeChan: unidirectional channel type") |
| } |
| ch := makechan(typ.runtimeType(), uint32(buffer)) |
| return Value{typ.common(), unsafe.Pointer(ch), flag(Chan) << flagKindShift} |
| } |
| |
| // MakeMap creates a new map of the specified type. |
| func MakeMap(typ Type) Value { |
| if typ.Kind() != Map { |
| panic("reflect.MakeMap of non-map type") |
| } |
| m := makemap(typ.runtimeType()) |
| return Value{typ.common(), unsafe.Pointer(m), flag(Map) << flagKindShift} |
| } |
| |
| // Indirect returns the value that v points to. |
| // If v is a nil pointer, Indirect returns a zero Value. |
| // If v is not a pointer, Indirect returns v. |
| func Indirect(v Value) Value { |
| if v.Kind() != Ptr { |
| return v |
| } |
| return v.Elem() |
| } |
| |
| // ValueOf returns a new Value initialized to the concrete value |
| // stored in the interface i. ValueOf(nil) returns the zero Value. |
| func ValueOf(i interface{}) Value { |
| if i == nil { |
| return Value{} |
| } |
| |
| // TODO(rsc): Eliminate this terrible hack. |
| // In the call to packValue, eface.typ doesn't escape, |
| // and eface.word is an integer. So it looks like |
| // i (= eface) doesn't escape. But really it does, |
| // because eface.word is actually a pointer. |
| escapes(i) |
| |
| // For an interface value with the noAddr bit set, |
| // the representation is identical to an empty interface. |
| eface := *(*emptyInterface)(unsafe.Pointer(&i)) |
| typ := toCommonType(eface.typ) |
| fl := flag(typ.Kind()) << flagKindShift |
| if typ.size > ptrSize { |
| fl |= flagIndir |
| } |
| return Value{typ, unsafe.Pointer(eface.word), fl} |
| } |
| |
| // Zero returns a Value representing a zero value for the specified type. |
| // The result is different from the zero value of the Value struct, |
| // which represents no value at all. |
| // For example, Zero(TypeOf(42)) returns a Value with Kind Int and value 0. |
| func Zero(typ Type) Value { |
| if typ == nil { |
| panic("reflect: Zero(nil)") |
| } |
| t := typ.common() |
| fl := flag(t.Kind()) << flagKindShift |
| if t.size <= ptrSize { |
| return Value{t, nil, fl} |
| } |
| return Value{t, unsafe_New(typ), fl | flagIndir} |
| } |
| |
| // New returns a Value representing a pointer to a new zero value |
| // for the specified type. That is, the returned Value's Type is PtrTo(t). |
| func New(typ Type) Value { |
| if typ == nil { |
| panic("reflect: New(nil)") |
| } |
| ptr := unsafe_New(typ) |
| fl := flag(Ptr) << flagKindShift |
| return Value{typ.common().ptrTo(), ptr, fl} |
| } |
| |
| // NewAt returns a Value representing a pointer to a value of the |
| // specified type, using p as that pointer. |
| func NewAt(typ Type, p unsafe.Pointer) Value { |
| fl := flag(Ptr) << flagKindShift |
| return Value{typ.common().ptrTo(), p, fl} |
| } |
| |
| // assignTo returns a value v that can be assigned directly to typ. |
| // It panics if v is not assignable to typ. |
| // For a conversion to an interface type, target is a suggested scratch space to use. |
| func (v Value) assignTo(context string, dst *commonType, target *interface{}) Value { |
| if v.flag&flagMethod != 0 { |
| panic(context + ": cannot assign method value to type " + dst.String()) |
| } |
| |
| switch { |
| case directlyAssignable(dst, v.typ): |
| // Overwrite type so that they match. |
| // Same memory layout, so no harm done. |
| v.typ = dst |
| fl := v.flag & (flagRO | flagAddr | flagIndir) |
| fl |= flag(dst.Kind()) << flagKindShift |
| return Value{dst, v.val, fl} |
| |
| case implements(dst, v.typ): |
| if target == nil { |
| target = new(interface{}) |
| } |
| x := valueInterface(v, false) |
| if dst.NumMethod() == 0 { |
| *target = x |
| } else { |
| ifaceE2I(dst.runtimeType(), x, unsafe.Pointer(target)) |
| } |
| return Value{dst, unsafe.Pointer(target), flagIndir | flag(Interface)<<flagKindShift} |
| } |
| |
| // Failed. |
| panic(context + ": value of type " + v.typ.String() + " is not assignable to type " + dst.String()) |
| } |
| |
| // implemented in ../pkg/runtime |
| func chancap(ch iword) int32 |
| func chanclose(ch iword) |
| func chanlen(ch iword) int32 |
| func chanrecv(t *runtimeType, ch iword, nb bool) (val iword, selected, received bool) |
| func chansend(t *runtimeType, ch iword, val iword, nb bool) bool |
| |
| func makechan(typ *runtimeType, size uint32) (ch iword) |
| func makemap(t *runtimeType) (m iword) |
| func mapaccess(t *runtimeType, m iword, key iword) (val iword, ok bool) |
| func mapassign(t *runtimeType, m iword, key, val iword, ok bool) |
| func mapiterinit(t *runtimeType, m iword) *byte |
| func mapiterkey(it *byte) (key iword, ok bool) |
| func mapiternext(it *byte) |
| func maplen(m iword) int32 |
| |
| func call(fn, arg unsafe.Pointer, n uint32) |
| func ifaceE2I(t *runtimeType, src interface{}, dst unsafe.Pointer) |
| |
| // Dummy annotation marking that the value x escapes, |
| // for use in cases where the reflect code is so clever that |
| // the compiler cannot follow. |
| func escapes(x interface{}) { |
| if dummy.b { |
| dummy.x = x |
| } |
| } |
| |
| var dummy struct { |
| b bool |
| x interface{} |
| } |