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