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 7package impl 8 9import ( 10 "reflect" 11 "sync/atomic" 12 "unsafe" 13) 14 15const UnsafeEnabled = true 16 17// Pointer is an opaque pointer type. 18type 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. 22type offset uintptr 23 24// offsetOf returns a field offset for the struct field. 25func offsetOf(f reflect.StructField, x exporter) offset { 26 return offset(f.Offset) 27} 28 29// IsValid reports whether the offset is valid. 30func (f offset) IsValid() bool { return f != invalidOffset } 31 32// invalidOffset is an invalid field offset. 33var invalidOffset = ^offset(0) 34 35// zeroOffset is a noop when calling pointer.Apply. 36var zeroOffset = offset(0) 37 38// pointer is a pointer to a message struct or field. 39type pointer struct{ p unsafe.Pointer } 40 41// pointerOf returns p as a pointer. 42func pointerOf(p Pointer) pointer { 43 return pointer{p: unsafe.Pointer(p)} 44} 45 46// pointerOfValue returns v as a pointer. 47func pointerOfValue(v reflect.Value) pointer { 48 return pointer{p: unsafe.Pointer(v.Pointer())} 49} 50 51// pointerOfIface returns the pointer portion of an interface. 52func 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. 61func (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. 67func (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)) 76func (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() 82func (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 87func (p pointer) Bool() *bool { return (*bool)(p.p) } 88func (p pointer) BoolPtr() **bool { return (**bool)(p.p) } 89func (p pointer) BoolSlice() *[]bool { return (*[]bool)(p.p) } 90func (p pointer) Int32() *int32 { return (*int32)(p.p) } 91func (p pointer) Int32Ptr() **int32 { return (**int32)(p.p) } 92func (p pointer) Int32Slice() *[]int32 { return (*[]int32)(p.p) } 93func (p pointer) Int64() *int64 { return (*int64)(p.p) } 94func (p pointer) Int64Ptr() **int64 { return (**int64)(p.p) } 95func (p pointer) Int64Slice() *[]int64 { return (*[]int64)(p.p) } 96func (p pointer) Uint32() *uint32 { return (*uint32)(p.p) } 97func (p pointer) Uint32Ptr() **uint32 { return (**uint32)(p.p) } 98func (p pointer) Uint32Slice() *[]uint32 { return (*[]uint32)(p.p) } 99func (p pointer) Uint64() *uint64 { return (*uint64)(p.p) } 100func (p pointer) Uint64Ptr() **uint64 { return (**uint64)(p.p) } 101func (p pointer) Uint64Slice() *[]uint64 { return (*[]uint64)(p.p) } 102func (p pointer) Float32() *float32 { return (*float32)(p.p) } 103func (p pointer) Float32Ptr() **float32 { return (**float32)(p.p) } 104func (p pointer) Float32Slice() *[]float32 { return (*[]float32)(p.p) } 105func (p pointer) Float64() *float64 { return (*float64)(p.p) } 106func (p pointer) Float64Ptr() **float64 { return (**float64)(p.p) } 107func (p pointer) Float64Slice() *[]float64 { return (*[]float64)(p.p) } 108func (p pointer) String() *string { return (*string)(p.p) } 109func (p pointer) StringPtr() **string { return (**string)(p.p) } 110func (p pointer) StringSlice() *[]string { return (*[]string)(p.p) } 111func (p pointer) Bytes() *[]byte { return (*[]byte)(p.p) } 112func (p pointer) BytesPtr() **[]byte { return (**[]byte)(p.p) } 113func (p pointer) BytesSlice() *[][]byte { return (*[][]byte)(p.p) } 114func (p pointer) WeakFields() *weakFields { return (*weakFields)(p.p) } 115func (p pointer) Extensions() *map[int32]ExtensionField { return (*map[int32]ExtensionField)(p.p) } 116 117func (p pointer) Elem() pointer { 118 return pointer{p: *(*unsafe.Pointer)(p.p)} 119} 120 121// PointerSlice loads []*T from p as a []pointer. 122// The value returned is aliased with the original slice. 123// This behavior differs from the implementation in pointer_reflect.go. 124func (p pointer) PointerSlice() []pointer { 125 // Super-tricky - p should point to a []*T where T is a 126 // message type. We load it as []pointer. 127 return *(*[]pointer)(p.p) 128} 129 130// AppendPointerSlice appends v to p, which must be a []*T. 131func (p pointer) AppendPointerSlice(v pointer) { 132 *(*[]pointer)(p.p) = append(*(*[]pointer)(p.p), v) 133} 134 135// SetPointer sets *p to v. 136func (p pointer) SetPointer(v pointer) { 137 *(*unsafe.Pointer)(p.p) = (unsafe.Pointer)(v.p) 138} 139 140// Static check that MessageState does not exceed the size of a pointer. 141const _ = uint(unsafe.Sizeof(unsafe.Pointer(nil)) - unsafe.Sizeof(MessageState{})) 142 143func (Export) MessageStateOf(p Pointer) *messageState { 144 // Super-tricky - see documentation on MessageState. 145 return (*messageState)(unsafe.Pointer(p)) 146} 147func (ms *messageState) pointer() pointer { 148 // Super-tricky - see documentation on MessageState. 149 return pointer{p: unsafe.Pointer(ms)} 150} 151func (ms *messageState) messageInfo() *MessageInfo { 152 mi := ms.LoadMessageInfo() 153 if mi == nil { 154 panic("invalid nil message info; this suggests memory corruption due to a race or shallow copy on the message struct") 155 } 156 return mi 157} 158func (ms *messageState) LoadMessageInfo() *MessageInfo { 159 return (*MessageInfo)(atomic.LoadPointer((*unsafe.Pointer)(unsafe.Pointer(&ms.atomicMessageInfo)))) 160} 161func (ms *messageState) StoreMessageInfo(mi *MessageInfo) { 162 atomic.StorePointer((*unsafe.Pointer)(unsafe.Pointer(&ms.atomicMessageInfo)), unsafe.Pointer(mi)) 163} 164 165type atomicNilMessage struct{ p unsafe.Pointer } // p is a *messageReflectWrapper 166 167func (m *atomicNilMessage) Init(mi *MessageInfo) *messageReflectWrapper { 168 if p := atomic.LoadPointer(&m.p); p != nil { 169 return (*messageReflectWrapper)(p) 170 } 171 w := &messageReflectWrapper{mi: mi} 172 atomic.CompareAndSwapPointer(&m.p, nil, (unsafe.Pointer)(w)) 173 return (*messageReflectWrapper)(atomic.LoadPointer(&m.p)) 174} 175