| // Copyright 2018 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. |
| |
| // +build !purego,!appengine |
| |
| package impl |
| |
| import ( |
| "reflect" |
| "sync/atomic" |
| "unsafe" |
| ) |
| |
| const UnsafeEnabled = true |
| |
| // Pointer is an opaque pointer type. |
| type Pointer unsafe.Pointer |
| |
| // offset represents the offset to a struct field, accessible from a pointer. |
| // The offset is the byte offset to the field from the start of the struct. |
| type offset uintptr |
| |
| // offsetOf returns a field offset for the struct field. |
| func offsetOf(f reflect.StructField, x exporter) offset { |
| return offset(f.Offset) |
| } |
| |
| // IsValid reports whether the offset is valid. |
| func (f offset) IsValid() bool { return f != invalidOffset } |
| |
| // invalidOffset is an invalid field offset. |
| var invalidOffset = ^offset(0) |
| |
| // zeroOffset is a noop when calling pointer.Apply. |
| var zeroOffset = offset(0) |
| |
| // pointer is a pointer to a message struct or field. |
| type pointer struct{ p unsafe.Pointer } |
| |
| // pointerOf returns p as a pointer. |
| func pointerOf(p Pointer) pointer { |
| return pointer{p: unsafe.Pointer(p)} |
| } |
| |
| // pointerOfValue returns v as a pointer. |
| func pointerOfValue(v reflect.Value) pointer { |
| return pointer{p: unsafe.Pointer(v.Pointer())} |
| } |
| |
| // pointerOfIface returns the pointer portion of an interface. |
| func pointerOfIface(v interface{}) pointer { |
| type ifaceHeader struct { |
| Type unsafe.Pointer |
| Data unsafe.Pointer |
| } |
| return pointer{p: (*ifaceHeader)(unsafe.Pointer(&v)).Data} |
| } |
| |
| // IsNil reports whether the pointer is nil. |
| func (p pointer) IsNil() bool { |
| return p.p == nil |
| } |
| |
| // Apply adds an offset to the pointer to derive a new pointer |
| // to a specified field. The pointer must be valid and pointing at a struct. |
| func (p pointer) Apply(f offset) pointer { |
| if p.IsNil() { |
| panic("invalid nil pointer") |
| } |
| return pointer{p: unsafe.Pointer(uintptr(p.p) + uintptr(f))} |
| } |
| |
| // AsValueOf treats p as a pointer to an object of type t and returns the value. |
| // It is equivalent to reflect.ValueOf(p.AsIfaceOf(t)) |
| func (p pointer) AsValueOf(t reflect.Type) reflect.Value { |
| return reflect.NewAt(t, p.p) |
| } |
| |
| // AsIfaceOf treats p as a pointer to an object of type t and returns the value. |
| // It is equivalent to p.AsValueOf(t).Interface() |
| func (p pointer) AsIfaceOf(t reflect.Type) interface{} { |
| // TODO: Use tricky unsafe magic to directly create ifaceHeader. |
| return p.AsValueOf(t).Interface() |
| } |
| |
| func (p pointer) Bool() *bool { return (*bool)(p.p) } |
| func (p pointer) BoolPtr() **bool { return (**bool)(p.p) } |
| func (p pointer) BoolSlice() *[]bool { return (*[]bool)(p.p) } |
| func (p pointer) Int32() *int32 { return (*int32)(p.p) } |
| func (p pointer) Int32Ptr() **int32 { return (**int32)(p.p) } |
| func (p pointer) Int32Slice() *[]int32 { return (*[]int32)(p.p) } |
| func (p pointer) Int64() *int64 { return (*int64)(p.p) } |
| func (p pointer) Int64Ptr() **int64 { return (**int64)(p.p) } |
| func (p pointer) Int64Slice() *[]int64 { return (*[]int64)(p.p) } |
| func (p pointer) Uint32() *uint32 { return (*uint32)(p.p) } |
| func (p pointer) Uint32Ptr() **uint32 { return (**uint32)(p.p) } |
| func (p pointer) Uint32Slice() *[]uint32 { return (*[]uint32)(p.p) } |
| func (p pointer) Uint64() *uint64 { return (*uint64)(p.p) } |
| func (p pointer) Uint64Ptr() **uint64 { return (**uint64)(p.p) } |
| func (p pointer) Uint64Slice() *[]uint64 { return (*[]uint64)(p.p) } |
| func (p pointer) Float32() *float32 { return (*float32)(p.p) } |
| func (p pointer) Float32Ptr() **float32 { return (**float32)(p.p) } |
| func (p pointer) Float32Slice() *[]float32 { return (*[]float32)(p.p) } |
| func (p pointer) Float64() *float64 { return (*float64)(p.p) } |
| func (p pointer) Float64Ptr() **float64 { return (**float64)(p.p) } |
| func (p pointer) Float64Slice() *[]float64 { return (*[]float64)(p.p) } |
| func (p pointer) String() *string { return (*string)(p.p) } |
| func (p pointer) StringPtr() **string { return (**string)(p.p) } |
| func (p pointer) StringSlice() *[]string { return (*[]string)(p.p) } |
| func (p pointer) Bytes() *[]byte { return (*[]byte)(p.p) } |
| func (p pointer) BytesPtr() **[]byte { return (**[]byte)(p.p) } |
| func (p pointer) BytesSlice() *[][]byte { return (*[][]byte)(p.p) } |
| func (p pointer) WeakFields() *weakFields { return (*weakFields)(p.p) } |
| func (p pointer) Extensions() *map[int32]ExtensionField { return (*map[int32]ExtensionField)(p.p) } |
| |
| func (p pointer) Elem() pointer { |
| return pointer{p: *(*unsafe.Pointer)(p.p)} |
| } |
| |
| // PointerSlice loads []*T from p as a []pointer. |
| // The value returned is aliased with the original slice. |
| // This behavior differs from the implementation in pointer_reflect.go. |
| func (p pointer) PointerSlice() []pointer { |
| // Super-tricky - p should point to a []*T where T is a |
| // message type. We load it as []pointer. |
| return *(*[]pointer)(p.p) |
| } |
| |
| // AppendPointerSlice appends v to p, which must be a []*T. |
| func (p pointer) AppendPointerSlice(v pointer) { |
| *(*[]pointer)(p.p) = append(*(*[]pointer)(p.p), v) |
| } |
| |
| // SetPointer sets *p to v. |
| func (p pointer) SetPointer(v pointer) { |
| *(*unsafe.Pointer)(p.p) = (unsafe.Pointer)(v.p) |
| } |
| |
| // Static check that MessageState does not exceed the size of a pointer. |
| const _ = uint(unsafe.Sizeof(unsafe.Pointer(nil)) - unsafe.Sizeof(MessageState{})) |
| |
| func (Export) MessageStateOf(p Pointer) *messageState { |
| // Super-tricky - see documentation on MessageState. |
| return (*messageState)(unsafe.Pointer(p)) |
| } |
| func (ms *messageState) pointer() pointer { |
| // Super-tricky - see documentation on MessageState. |
| return pointer{p: unsafe.Pointer(ms)} |
| } |
| func (ms *messageState) messageInfo() *MessageInfo { |
| mi := ms.LoadMessageInfo() |
| if mi == nil { |
| panic("invalid nil message info; this suggests memory corruption due to a race or shallow copy on the message struct") |
| } |
| return mi |
| } |
| func (ms *messageState) LoadMessageInfo() *MessageInfo { |
| return (*MessageInfo)(atomic.LoadPointer((*unsafe.Pointer)(unsafe.Pointer(&ms.atomicMessageInfo)))) |
| } |
| func (ms *messageState) StoreMessageInfo(mi *MessageInfo) { |
| atomic.StorePointer((*unsafe.Pointer)(unsafe.Pointer(&ms.atomicMessageInfo)), unsafe.Pointer(mi)) |
| } |
| |
| type atomicNilMessage struct{ p unsafe.Pointer } // p is a *messageReflectWrapper |
| |
| func (m *atomicNilMessage) Init(mi *MessageInfo) *messageReflectWrapper { |
| if p := atomic.LoadPointer(&m.p); p != nil { |
| return (*messageReflectWrapper)(p) |
| } |
| w := &messageReflectWrapper{mi: mi} |
| atomic.CompareAndSwapPointer(&m.p, nil, (unsafe.Pointer)(w)) |
| return (*messageReflectWrapper)(atomic.LoadPointer(&m.p)) |
| } |