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1 // Copyright 2018 The Go Authors. All rights reserved. |
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2 // Use of this source code is governed by a BSD-style |
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3 // license that can be found in the LICENSE file. |
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4 |
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5 // +build !purego,!appengine |
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6 |
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7 package impl |
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8 |
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9 import ( |
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10 "reflect" |
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11 "sync/atomic" |
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12 "unsafe" |
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13 ) |
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14 |
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15 const UnsafeEnabled = true |
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16 |
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17 // Pointer is an opaque pointer type. |
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18 type Pointer unsafe.Pointer |
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19 |
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20 // offset represents the offset to a struct field, accessible from a pointer. |
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21 // The offset is the byte offset to the field from the start of the struct. |
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22 type offset uintptr |
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23 |
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24 // offsetOf returns a field offset for the struct field. |
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25 func offsetOf(f reflect.StructField, x exporter) offset { |
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26 return offset(f.Offset) |
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27 } |
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28 |
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29 // IsValid reports whether the offset is valid. |
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30 func (f offset) IsValid() bool { return f != invalidOffset } |
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31 |
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32 // invalidOffset is an invalid field offset. |
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33 var invalidOffset = ^offset(0) |
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34 |
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35 // zeroOffset is a noop when calling pointer.Apply. |
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36 var zeroOffset = offset(0) |
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37 |
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38 // pointer is a pointer to a message struct or field. |
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39 type pointer struct{ p unsafe.Pointer } |
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40 |
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41 // pointerOf returns p as a pointer. |
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42 func pointerOf(p Pointer) pointer { |
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43 return pointer{p: unsafe.Pointer(p)} |
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44 } |
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45 |
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46 // pointerOfValue returns v as a pointer. |
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47 func pointerOfValue(v reflect.Value) pointer { |
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48 return pointer{p: unsafe.Pointer(v.Pointer())} |
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49 } |
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50 |
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51 // pointerOfIface returns the pointer portion of an interface. |
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52 func pointerOfIface(v interface{}) pointer { |
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53 type ifaceHeader struct { |
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54 Type unsafe.Pointer |
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55 Data unsafe.Pointer |
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56 } |
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57 return pointer{p: (*ifaceHeader)(unsafe.Pointer(&v)).Data} |
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58 } |
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59 |
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60 // IsNil reports whether the pointer is nil. |
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61 func (p pointer) IsNil() bool { |
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62 return p.p == nil |
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63 } |
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64 |
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65 // Apply adds an offset to the pointer to derive a new pointer |
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66 // to a specified field. The pointer must be valid and pointing at a struct. |
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67 func (p pointer) Apply(f offset) pointer { |
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68 if p.IsNil() { |
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69 panic("invalid nil pointer") |
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70 } |
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71 return pointer{p: unsafe.Pointer(uintptr(p.p) + uintptr(f))} |
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72 } |
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73 |
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74 // AsValueOf treats p as a pointer to an object of type t and returns the value. |
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75 // It is equivalent to reflect.ValueOf(p.AsIfaceOf(t)) |
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76 func (p pointer) AsValueOf(t reflect.Type) reflect.Value { |
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77 return reflect.NewAt(t, p.p) |
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78 } |
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79 |
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80 // AsIfaceOf treats p as a pointer to an object of type t and returns the value. |
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81 // It is equivalent to p.AsValueOf(t).Interface() |
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82 func (p pointer) AsIfaceOf(t reflect.Type) interface{} { |
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83 // TODO: Use tricky unsafe magic to directly create ifaceHeader. |
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84 return p.AsValueOf(t).Interface() |
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85 } |
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86 |
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87 func (p pointer) Bool() *bool { return (*bool)(p.p) } |
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88 func (p pointer) BoolPtr() **bool { return (**bool)(p.p) } |
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89 func (p pointer) BoolSlice() *[]bool { return (*[]bool)(p.p) } |
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90 func (p pointer) Int32() *int32 { return (*int32)(p.p) } |
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91 func (p pointer) Int32Ptr() **int32 { return (**int32)(p.p) } |
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92 func (p pointer) Int32Slice() *[]int32 { return (*[]int32)(p.p) } |
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93 func (p pointer) Int64() *int64 { return (*int64)(p.p) } |
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94 func (p pointer) Int64Ptr() **int64 { return (**int64)(p.p) } |
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95 func (p pointer) Int64Slice() *[]int64 { return (*[]int64)(p.p) } |
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96 func (p pointer) Uint32() *uint32 { return (*uint32)(p.p) } |
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97 func (p pointer) Uint32Ptr() **uint32 { return (**uint32)(p.p) } |
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98 func (p pointer) Uint32Slice() *[]uint32 { return (*[]uint32)(p.p) } |
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99 func (p pointer) Uint64() *uint64 { return (*uint64)(p.p) } |
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100 func (p pointer) Uint64Ptr() **uint64 { return (**uint64)(p.p) } |
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101 func (p pointer) Uint64Slice() *[]uint64 { return (*[]uint64)(p.p) } |
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102 func (p pointer) Float32() *float32 { return (*float32)(p.p) } |
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103 func (p pointer) Float32Ptr() **float32 { return (**float32)(p.p) } |
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104 func (p pointer) Float32Slice() *[]float32 { return (*[]float32)(p.p) } |
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105 func (p pointer) Float64() *float64 { return (*float64)(p.p) } |
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106 func (p pointer) Float64Ptr() **float64 { return (**float64)(p.p) } |
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107 func (p pointer) Float64Slice() *[]float64 { return (*[]float64)(p.p) } |
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108 func (p pointer) String() *string { return (*string)(p.p) } |
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109 func (p pointer) StringPtr() **string { return (**string)(p.p) } |
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110 func (p pointer) StringSlice() *[]string { return (*[]string)(p.p) } |
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111 func (p pointer) Bytes() *[]byte { return (*[]byte)(p.p) } |
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112 func (p pointer) BytesPtr() **[]byte { return (**[]byte)(p.p) } |
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113 func (p pointer) BytesSlice() *[][]byte { return (*[][]byte)(p.p) } |
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114 func (p pointer) WeakFields() *weakFields { return (*weakFields)(p.p) } |
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115 func (p pointer) Extensions() *map[int32]ExtensionField { return (*map[int32]ExtensionField)(p.p) } |
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116 |
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117 func (p pointer) Elem() pointer { |
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118 return pointer{p: *(*unsafe.Pointer)(p.p)} |
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119 } |
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120 |
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121 // PointerSlice loads []*T from p as a []pointer. |
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122 // The value returned is aliased with the original slice. |
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123 // This behavior differs from the implementation in pointer_reflect.go. |
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124 func (p pointer) PointerSlice() []pointer { |
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125 // Super-tricky - p should point to a []*T where T is a |
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126 // message type. We load it as []pointer. |
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127 return *(*[]pointer)(p.p) |
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128 } |
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129 |
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130 // AppendPointerSlice appends v to p, which must be a []*T. |
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131 func (p pointer) AppendPointerSlice(v pointer) { |
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132 *(*[]pointer)(p.p) = append(*(*[]pointer)(p.p), v) |
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133 } |
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134 |
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135 // SetPointer sets *p to v. |
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136 func (p pointer) SetPointer(v pointer) { |
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137 *(*unsafe.Pointer)(p.p) = (unsafe.Pointer)(v.p) |
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138 } |
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139 |
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140 // Static check that MessageState does not exceed the size of a pointer. |
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141 const _ = uint(unsafe.Sizeof(unsafe.Pointer(nil)) - unsafe.Sizeof(MessageState{})) |
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142 |
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143 func (Export) MessageStateOf(p Pointer) *messageState { |
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144 // Super-tricky - see documentation on MessageState. |
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145 return (*messageState)(unsafe.Pointer(p)) |
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146 } |
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147 func (ms *messageState) pointer() pointer { |
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148 // Super-tricky - see documentation on MessageState. |
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149 return pointer{p: unsafe.Pointer(ms)} |
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150 } |
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151 func (ms *messageState) messageInfo() *MessageInfo { |
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152 mi := ms.LoadMessageInfo() |
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153 if mi == nil { |
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154 panic("invalid nil message info; this suggests memory corruption due to a race or shallow copy on the message struct") |
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155 } |
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156 return mi |
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157 } |
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158 func (ms *messageState) LoadMessageInfo() *MessageInfo { |
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159 return (*MessageInfo)(atomic.LoadPointer((*unsafe.Pointer)(unsafe.Pointer(&ms.atomicMessageInfo)))) |
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160 } |
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161 func (ms *messageState) StoreMessageInfo(mi *MessageInfo) { |
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162 atomic.StorePointer((*unsafe.Pointer)(unsafe.Pointer(&ms.atomicMessageInfo)), unsafe.Pointer(mi)) |
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163 } |
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164 |
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165 type atomicNilMessage struct{ p unsafe.Pointer } // p is a *messageReflectWrapper |
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166 |
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167 func (m *atomicNilMessage) Init(mi *MessageInfo) *messageReflectWrapper { |
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168 if p := atomic.LoadPointer(&m.p); p != nil { |
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169 return (*messageReflectWrapper)(p) |
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170 } |
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171 w := &messageReflectWrapper{mi: mi} |
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172 atomic.CompareAndSwapPointer(&m.p, nil, (unsafe.Pointer)(w)) |
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173 return (*messageReflectWrapper)(atomic.LoadPointer(&m.p)) |
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174 } |