Matteo Scandolo | a428586 | 2020-12-01 18:10:10 -0800 | [diff] [blame] | 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 | |
| 5 | // +build !purego,!appengine |
| 6 | |
| 7 | package impl |
| 8 | |
| 9 | import ( |
| 10 | "reflect" |
| 11 | "sync/atomic" |
| 12 | "unsafe" |
| 13 | ) |
| 14 | |
| 15 | const UnsafeEnabled = true |
| 16 | |
| 17 | // Pointer is an opaque pointer type. |
| 18 | type Pointer unsafe.Pointer |
| 19 | |
| 20 | // offset represents the offset to a struct field, accessible from a pointer. |
| 21 | // The offset is the byte offset to the field from the start of the struct. |
| 22 | type offset uintptr |
| 23 | |
| 24 | // offsetOf returns a field offset for the struct field. |
| 25 | func offsetOf(f reflect.StructField, x exporter) offset { |
| 26 | return offset(f.Offset) |
| 27 | } |
| 28 | |
| 29 | // IsValid reports whether the offset is valid. |
| 30 | func (f offset) IsValid() bool { return f != invalidOffset } |
| 31 | |
| 32 | // invalidOffset is an invalid field offset. |
| 33 | var invalidOffset = ^offset(0) |
| 34 | |
| 35 | // zeroOffset is a noop when calling pointer.Apply. |
| 36 | var zeroOffset = offset(0) |
| 37 | |
| 38 | // pointer is a pointer to a message struct or field. |
| 39 | type pointer struct{ p unsafe.Pointer } |
| 40 | |
| 41 | // pointerOf returns p as a pointer. |
| 42 | func pointerOf(p Pointer) pointer { |
| 43 | return pointer{p: unsafe.Pointer(p)} |
| 44 | } |
| 45 | |
| 46 | // pointerOfValue returns v as a pointer. |
| 47 | func pointerOfValue(v reflect.Value) pointer { |
| 48 | return pointer{p: unsafe.Pointer(v.Pointer())} |
| 49 | } |
| 50 | |
| 51 | // pointerOfIface returns the pointer portion of an interface. |
| 52 | func pointerOfIface(v interface{}) pointer { |
| 53 | type ifaceHeader struct { |
| 54 | Type unsafe.Pointer |
| 55 | Data unsafe.Pointer |
| 56 | } |
| 57 | return pointer{p: (*ifaceHeader)(unsafe.Pointer(&v)).Data} |
| 58 | } |
| 59 | |
| 60 | // IsNil reports whether the pointer is nil. |
| 61 | func (p pointer) IsNil() bool { |
| 62 | return p.p == nil |
| 63 | } |
| 64 | |
| 65 | // Apply adds an offset to the pointer to derive a new pointer |
| 66 | // to a specified field. The pointer must be valid and pointing at a struct. |
| 67 | func (p pointer) Apply(f offset) pointer { |
| 68 | if p.IsNil() { |
| 69 | panic("invalid nil pointer") |
| 70 | } |
| 71 | return pointer{p: unsafe.Pointer(uintptr(p.p) + uintptr(f))} |
| 72 | } |
| 73 | |
| 74 | // AsValueOf treats p as a pointer to an object of type t and returns the value. |
| 75 | // It is equivalent to reflect.ValueOf(p.AsIfaceOf(t)) |
| 76 | func (p pointer) AsValueOf(t reflect.Type) reflect.Value { |
| 77 | return reflect.NewAt(t, p.p) |
| 78 | } |
| 79 | |
| 80 | // AsIfaceOf treats p as a pointer to an object of type t and returns the value. |
| 81 | // It is equivalent to p.AsValueOf(t).Interface() |
| 82 | func (p pointer) AsIfaceOf(t reflect.Type) interface{} { |
| 83 | // TODO: Use tricky unsafe magic to directly create ifaceHeader. |
| 84 | return p.AsValueOf(t).Interface() |
| 85 | } |
| 86 | |
| 87 | func (p pointer) Bool() *bool { return (*bool)(p.p) } |
| 88 | func (p pointer) BoolPtr() **bool { return (**bool)(p.p) } |
| 89 | func (p pointer) BoolSlice() *[]bool { return (*[]bool)(p.p) } |
| 90 | func (p pointer) Int32() *int32 { return (*int32)(p.p) } |
| 91 | func (p pointer) Int32Ptr() **int32 { return (**int32)(p.p) } |
| 92 | func (p pointer) Int32Slice() *[]int32 { return (*[]int32)(p.p) } |
| 93 | func (p pointer) Int64() *int64 { return (*int64)(p.p) } |
| 94 | func (p pointer) Int64Ptr() **int64 { return (**int64)(p.p) } |
| 95 | func (p pointer) Int64Slice() *[]int64 { return (*[]int64)(p.p) } |
| 96 | func (p pointer) Uint32() *uint32 { return (*uint32)(p.p) } |
| 97 | func (p pointer) Uint32Ptr() **uint32 { return (**uint32)(p.p) } |
| 98 | func (p pointer) Uint32Slice() *[]uint32 { return (*[]uint32)(p.p) } |
| 99 | func (p pointer) Uint64() *uint64 { return (*uint64)(p.p) } |
| 100 | func (p pointer) Uint64Ptr() **uint64 { return (**uint64)(p.p) } |
| 101 | func (p pointer) Uint64Slice() *[]uint64 { return (*[]uint64)(p.p) } |
| 102 | func (p pointer) Float32() *float32 { return (*float32)(p.p) } |
| 103 | func (p pointer) Float32Ptr() **float32 { return (**float32)(p.p) } |
| 104 | func (p pointer) Float32Slice() *[]float32 { return (*[]float32)(p.p) } |
| 105 | func (p pointer) Float64() *float64 { return (*float64)(p.p) } |
| 106 | func (p pointer) Float64Ptr() **float64 { return (**float64)(p.p) } |
| 107 | func (p pointer) Float64Slice() *[]float64 { return (*[]float64)(p.p) } |
| 108 | func (p pointer) String() *string { return (*string)(p.p) } |
| 109 | func (p pointer) StringPtr() **string { return (**string)(p.p) } |
| 110 | func (p pointer) StringSlice() *[]string { return (*[]string)(p.p) } |
| 111 | func (p pointer) Bytes() *[]byte { return (*[]byte)(p.p) } |
| 112 | func (p pointer) BytesSlice() *[][]byte { return (*[][]byte)(p.p) } |
| 113 | func (p pointer) WeakFields() *weakFields { return (*weakFields)(p.p) } |
| 114 | func (p pointer) Extensions() *map[int32]ExtensionField { return (*map[int32]ExtensionField)(p.p) } |
| 115 | |
| 116 | func (p pointer) Elem() pointer { |
| 117 | return pointer{p: *(*unsafe.Pointer)(p.p)} |
| 118 | } |
| 119 | |
| 120 | // PointerSlice loads []*T from p as a []pointer. |
| 121 | // The value returned is aliased with the original slice. |
| 122 | // This behavior differs from the implementation in pointer_reflect.go. |
| 123 | func (p pointer) PointerSlice() []pointer { |
| 124 | // Super-tricky - p should point to a []*T where T is a |
| 125 | // message type. We load it as []pointer. |
| 126 | return *(*[]pointer)(p.p) |
| 127 | } |
| 128 | |
| 129 | // AppendPointerSlice appends v to p, which must be a []*T. |
| 130 | func (p pointer) AppendPointerSlice(v pointer) { |
| 131 | *(*[]pointer)(p.p) = append(*(*[]pointer)(p.p), v) |
| 132 | } |
| 133 | |
| 134 | // SetPointer sets *p to v. |
| 135 | func (p pointer) SetPointer(v pointer) { |
| 136 | *(*unsafe.Pointer)(p.p) = (unsafe.Pointer)(v.p) |
| 137 | } |
| 138 | |
| 139 | // Static check that MessageState does not exceed the size of a pointer. |
| 140 | const _ = uint(unsafe.Sizeof(unsafe.Pointer(nil)) - unsafe.Sizeof(MessageState{})) |
| 141 | |
| 142 | func (Export) MessageStateOf(p Pointer) *messageState { |
| 143 | // Super-tricky - see documentation on MessageState. |
| 144 | return (*messageState)(unsafe.Pointer(p)) |
| 145 | } |
| 146 | func (ms *messageState) pointer() pointer { |
| 147 | // Super-tricky - see documentation on MessageState. |
| 148 | return pointer{p: unsafe.Pointer(ms)} |
| 149 | } |
| 150 | func (ms *messageState) messageInfo() *MessageInfo { |
| 151 | mi := ms.LoadMessageInfo() |
| 152 | if mi == nil { |
| 153 | panic("invalid nil message info; this suggests memory corruption due to a race or shallow copy on the message struct") |
| 154 | } |
| 155 | return mi |
| 156 | } |
| 157 | func (ms *messageState) LoadMessageInfo() *MessageInfo { |
| 158 | return (*MessageInfo)(atomic.LoadPointer((*unsafe.Pointer)(unsafe.Pointer(&ms.atomicMessageInfo)))) |
| 159 | } |
| 160 | func (ms *messageState) StoreMessageInfo(mi *MessageInfo) { |
| 161 | atomic.StorePointer((*unsafe.Pointer)(unsafe.Pointer(&ms.atomicMessageInfo)), unsafe.Pointer(mi)) |
| 162 | } |
| 163 | |
| 164 | type atomicNilMessage struct{ p unsafe.Pointer } // p is a *messageReflectWrapper |
| 165 | |
| 166 | func (m *atomicNilMessage) Init(mi *MessageInfo) *messageReflectWrapper { |
| 167 | if p := atomic.LoadPointer(&m.p); p != nil { |
| 168 | return (*messageReflectWrapper)(p) |
| 169 | } |
| 170 | w := &messageReflectWrapper{mi: mi} |
| 171 | atomic.CompareAndSwapPointer(&m.p, nil, (unsafe.Pointer)(w)) |
| 172 | return (*messageReflectWrapper)(atomic.LoadPointer(&m.p)) |
| 173 | } |