pointer_unsafe.go 6.6 KB

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  1. // Copyright 2018 The Go Authors. All rights reserved.
  2. // Use of this source code is governed by a BSD-style
  3. // license that can be found in the LICENSE file.
  4. // +build !purego,!appengine
  5. package impl
  6. import (
  7. "reflect"
  8. "sync/atomic"
  9. "unsafe"
  10. )
  11. const UnsafeEnabled = true
  12. // Pointer is an opaque pointer type.
  13. type Pointer unsafe.Pointer
  14. // offset represents the offset to a struct field, accessible from a pointer.
  15. // The offset is the byte offset to the field from the start of the struct.
  16. type offset uintptr
  17. // offsetOf returns a field offset for the struct field.
  18. func offsetOf(f reflect.StructField, x exporter) offset {
  19. return offset(f.Offset)
  20. }
  21. // IsValid reports whether the offset is valid.
  22. func (f offset) IsValid() bool { return f != invalidOffset }
  23. // invalidOffset is an invalid field offset.
  24. var invalidOffset = ^offset(0)
  25. // zeroOffset is a noop when calling pointer.Apply.
  26. var zeroOffset = offset(0)
  27. // pointer is a pointer to a message struct or field.
  28. type pointer struct{ p unsafe.Pointer }
  29. // pointerOf returns p as a pointer.
  30. func pointerOf(p Pointer) pointer {
  31. return pointer{p: unsafe.Pointer(p)}
  32. }
  33. // pointerOfValue returns v as a pointer.
  34. func pointerOfValue(v reflect.Value) pointer {
  35. return pointer{p: unsafe.Pointer(v.Pointer())}
  36. }
  37. // pointerOfIface returns the pointer portion of an interface.
  38. func pointerOfIface(v interface{}) pointer {
  39. type ifaceHeader struct {
  40. Type unsafe.Pointer
  41. Data unsafe.Pointer
  42. }
  43. return pointer{p: (*ifaceHeader)(unsafe.Pointer(&v)).Data}
  44. }
  45. // IsNil reports whether the pointer is nil.
  46. func (p pointer) IsNil() bool {
  47. return p.p == nil
  48. }
  49. // Apply adds an offset to the pointer to derive a new pointer
  50. // to a specified field. The pointer must be valid and pointing at a struct.
  51. func (p pointer) Apply(f offset) pointer {
  52. if p.IsNil() {
  53. panic("invalid nil pointer")
  54. }
  55. return pointer{p: unsafe.Pointer(uintptr(p.p) + uintptr(f))}
  56. }
  57. // AsValueOf treats p as a pointer to an object of type t and returns the value.
  58. // It is equivalent to reflect.ValueOf(p.AsIfaceOf(t))
  59. func (p pointer) AsValueOf(t reflect.Type) reflect.Value {
  60. return reflect.NewAt(t, p.p)
  61. }
  62. // AsIfaceOf treats p as a pointer to an object of type t and returns the value.
  63. // It is equivalent to p.AsValueOf(t).Interface()
  64. func (p pointer) AsIfaceOf(t reflect.Type) interface{} {
  65. // TODO: Use tricky unsafe magic to directly create ifaceHeader.
  66. return p.AsValueOf(t).Interface()
  67. }
  68. func (p pointer) Bool() *bool { return (*bool)(p.p) }
  69. func (p pointer) BoolPtr() **bool { return (**bool)(p.p) }
  70. func (p pointer) BoolSlice() *[]bool { return (*[]bool)(p.p) }
  71. func (p pointer) Int32() *int32 { return (*int32)(p.p) }
  72. func (p pointer) Int32Ptr() **int32 { return (**int32)(p.p) }
  73. func (p pointer) Int32Slice() *[]int32 { return (*[]int32)(p.p) }
  74. func (p pointer) Int64() *int64 { return (*int64)(p.p) }
  75. func (p pointer) Int64Ptr() **int64 { return (**int64)(p.p) }
  76. func (p pointer) Int64Slice() *[]int64 { return (*[]int64)(p.p) }
  77. func (p pointer) Uint32() *uint32 { return (*uint32)(p.p) }
  78. func (p pointer) Uint32Ptr() **uint32 { return (**uint32)(p.p) }
  79. func (p pointer) Uint32Slice() *[]uint32 { return (*[]uint32)(p.p) }
  80. func (p pointer) Uint64() *uint64 { return (*uint64)(p.p) }
  81. func (p pointer) Uint64Ptr() **uint64 { return (**uint64)(p.p) }
  82. func (p pointer) Uint64Slice() *[]uint64 { return (*[]uint64)(p.p) }
  83. func (p pointer) Float32() *float32 { return (*float32)(p.p) }
  84. func (p pointer) Float32Ptr() **float32 { return (**float32)(p.p) }
  85. func (p pointer) Float32Slice() *[]float32 { return (*[]float32)(p.p) }
  86. func (p pointer) Float64() *float64 { return (*float64)(p.p) }
  87. func (p pointer) Float64Ptr() **float64 { return (**float64)(p.p) }
  88. func (p pointer) Float64Slice() *[]float64 { return (*[]float64)(p.p) }
  89. func (p pointer) String() *string { return (*string)(p.p) }
  90. func (p pointer) StringPtr() **string { return (**string)(p.p) }
  91. func (p pointer) StringSlice() *[]string { return (*[]string)(p.p) }
  92. func (p pointer) Bytes() *[]byte { return (*[]byte)(p.p) }
  93. func (p pointer) BytesSlice() *[][]byte { return (*[][]byte)(p.p) }
  94. func (p pointer) WeakFields() *weakFields { return (*weakFields)(p.p) }
  95. func (p pointer) Extensions() *map[int32]ExtensionField { return (*map[int32]ExtensionField)(p.p) }
  96. func (p pointer) Elem() pointer {
  97. return pointer{p: *(*unsafe.Pointer)(p.p)}
  98. }
  99. // PointerSlice loads []*T from p as a []pointer.
  100. // The value returned is aliased with the original slice.
  101. // This behavior differs from the implementation in pointer_reflect.go.
  102. func (p pointer) PointerSlice() []pointer {
  103. // Super-tricky - p should point to a []*T where T is a
  104. // message type. We load it as []pointer.
  105. return *(*[]pointer)(p.p)
  106. }
  107. // AppendPointerSlice appends v to p, which must be a []*T.
  108. func (p pointer) AppendPointerSlice(v pointer) {
  109. *(*[]pointer)(p.p) = append(*(*[]pointer)(p.p), v)
  110. }
  111. // SetPointer sets *p to v.
  112. func (p pointer) SetPointer(v pointer) {
  113. *(*unsafe.Pointer)(p.p) = (unsafe.Pointer)(v.p)
  114. }
  115. // Static check that MessageState does not exceed the size of a pointer.
  116. const _ = uint(unsafe.Sizeof(unsafe.Pointer(nil)) - unsafe.Sizeof(MessageState{}))
  117. func (Export) MessageStateOf(p Pointer) *messageState {
  118. // Super-tricky - see documentation on MessageState.
  119. return (*messageState)(unsafe.Pointer(p))
  120. }
  121. func (ms *messageState) pointer() pointer {
  122. // Super-tricky - see documentation on MessageState.
  123. return pointer{p: unsafe.Pointer(ms)}
  124. }
  125. func (ms *messageState) messageInfo() *MessageInfo {
  126. return ms.LoadMessageInfo()
  127. }
  128. func (ms *messageState) LoadMessageInfo() *MessageInfo {
  129. return (*MessageInfo)(atomic.LoadPointer((*unsafe.Pointer)(unsafe.Pointer(&ms.mi))))
  130. }
  131. func (ms *messageState) StoreMessageInfo(mi *MessageInfo) {
  132. atomic.StorePointer((*unsafe.Pointer)(unsafe.Pointer(&ms.mi)), unsafe.Pointer(mi))
  133. }
  134. type atomicNilMessage struct{ p unsafe.Pointer } // p is a *messageReflectWrapper
  135. func (m *atomicNilMessage) Init(mi *MessageInfo) *messageReflectWrapper {
  136. if p := atomic.LoadPointer(&m.p); p != nil {
  137. return (*messageReflectWrapper)(p)
  138. }
  139. w := &messageReflectWrapper{mi: mi}
  140. atomic.CompareAndSwapPointer(&m.p, nil, (unsafe.Pointer)(w))
  141. return (*messageReflectWrapper)(atomic.LoadPointer(&m.p))
  142. }