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 protoreflect
8
9import (
10	"unsafe"
11
12	"google.golang.org/protobuf/internal/pragma"
13)
14
15type (
16	stringHeader struct {
17		Data unsafe.Pointer
18		Len  int
19	}
20	sliceHeader struct {
21		Data unsafe.Pointer
22		Len  int
23		Cap  int
24	}
25	ifaceHeader struct {
26		Type unsafe.Pointer
27		Data unsafe.Pointer
28	}
29)
30
31var (
32	nilType     = typeOf(nil)
33	boolType    = typeOf(*new(bool))
34	int32Type   = typeOf(*new(int32))
35	int64Type   = typeOf(*new(int64))
36	uint32Type  = typeOf(*new(uint32))
37	uint64Type  = typeOf(*new(uint64))
38	float32Type = typeOf(*new(float32))
39	float64Type = typeOf(*new(float64))
40	stringType  = typeOf(*new(string))
41	bytesType   = typeOf(*new([]byte))
42	enumType    = typeOf(*new(EnumNumber))
43)
44
45// typeOf returns a pointer to the Go type information.
46// The pointer is comparable and equal if and only if the types are identical.
47func typeOf(t interface{}) unsafe.Pointer {
48	return (*ifaceHeader)(unsafe.Pointer(&t)).Type
49}
50
51// value is a union where only one type can be represented at a time.
52// The struct is 24B large on 64-bit systems and requires the minimum storage
53// necessary to represent each possible type.
54//
55// The Go GC needs to be able to scan variables containing pointers.
56// As such, pointers and non-pointers cannot be intermixed.
57type value struct {
58	pragma.DoNotCompare // 0B
59
60	// typ stores the type of the value as a pointer to the Go type.
61	typ unsafe.Pointer // 8B
62
63	// ptr stores the data pointer for a String, Bytes, or interface value.
64	ptr unsafe.Pointer // 8B
65
66	// num stores a Bool, Int32, Int64, Uint32, Uint64, Float32, Float64, or
67	// Enum value as a raw uint64.
68	//
69	// It is also used to store the length of a String or Bytes value;
70	// the capacity is ignored.
71	num uint64 // 8B
72}
73
74func valueOfString(v string) Value {
75	p := (*stringHeader)(unsafe.Pointer(&v))
76	return Value{typ: stringType, ptr: p.Data, num: uint64(len(v))}
77}
78func valueOfBytes(v []byte) Value {
79	p := (*sliceHeader)(unsafe.Pointer(&v))
80	return Value{typ: bytesType, ptr: p.Data, num: uint64(len(v))}
81}
82func valueOfIface(v interface{}) Value {
83	p := (*ifaceHeader)(unsafe.Pointer(&v))
84	return Value{typ: p.Type, ptr: p.Data}
85}
86
87func (v Value) getString() (x string) {
88	*(*stringHeader)(unsafe.Pointer(&x)) = stringHeader{Data: v.ptr, Len: int(v.num)}
89	return x
90}
91func (v Value) getBytes() (x []byte) {
92	*(*sliceHeader)(unsafe.Pointer(&x)) = sliceHeader{Data: v.ptr, Len: int(v.num), Cap: int(v.num)}
93	return x
94}
95func (v Value) getIface() (x interface{}) {
96	*(*ifaceHeader)(unsafe.Pointer(&x)) = ifaceHeader{Type: v.typ, Data: v.ptr}
97	return x
98}
99