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 package protoreflect
6 7 import (
8 "unsafe"
9 10 "google.golang.org/protobuf/internal/pragma"
11 )
12 13 type (
14 ifaceHeader struct {
15 _ [0]any // if interfaces have greater alignment than unsafe.Pointer, this will enforce it.
16 Type unsafe.Pointer
17 Data unsafe.Pointer
18 }
19 )
20 21 var (
22 nilType = typeOf(nil)
23 boolType = typeOf(*new(bool))
24 int32Type = typeOf(*new(int32))
25 int64Type = typeOf(*new(int64))
26 uint32Type = typeOf(*new(uint32))
27 uint64Type = typeOf(*new(uint64))
28 float32Type = typeOf(*new(float32))
29 float64Type = typeOf(*new(float64))
30 stringType = typeOf(*new(string))
31 bytesType = typeOf(*new([]byte))
32 enumType = typeOf(*new(EnumNumber))
33 )
34 35 // typeOf returns a pointer to the Go type information.
36 // The pointer is comparable and equal if and only if the types are identical.
37 func typeOf(t any) unsafe.Pointer {
38 return (*ifaceHeader)(unsafe.Pointer(&t)).Type
39 }
40 41 // value is a union where only one type can be represented at a time.
42 // The struct is 24B large on 64-bit systems and requires the minimum storage
43 // necessary to represent each possible type.
44 //
45 // The Go GC needs to be able to scan variables containing pointers.
46 // As such, pointers and non-pointers cannot be intermixed.
47 type value struct {
48 pragma.DoNotCompare // 0B
49 50 // typ stores the type of the value as a pointer to the Go type.
51 typ unsafe.Pointer // 8B
52 53 // ptr stores the data pointer for a String, Bytes, or interface value.
54 ptr unsafe.Pointer // 8B
55 56 // num stores a Bool, Int32, Int64, Uint32, Uint64, Float32, Float64, or
57 // Enum value as a raw uint64.
58 //
59 // It is also used to store the length of a String or Bytes value;
60 // the capacity is ignored.
61 num uint64 // 8B
62 }
63 64 func valueOfString(v string) Value {
65 return Value{typ: stringType, ptr: unsafe.Pointer(unsafe.StringData(v)), num: uint64(len(v))}
66 }
67 func valueOfBytes(v []byte) Value {
68 return Value{typ: bytesType, ptr: unsafe.Pointer(unsafe.SliceData(v)), num: uint64(len(v))}
69 }
70 func valueOfIface(v any) Value {
71 p := (*ifaceHeader)(unsafe.Pointer(&v))
72 return Value{typ: p.Type, ptr: p.Data}
73 }
74 75 func (v Value) getString() string {
76 return unsafe.String((*byte)(v.ptr), v.num)
77 }
78 func (v Value) getBytes() []byte {
79 return unsafe.Slice((*byte)(v.ptr), v.num)
80 }
81 func (v Value) getIface() (x any) {
82 *(*ifaceHeader)(unsafe.Pointer(&x)) = ifaceHeader{Type: v.typ, Data: v.ptr}
83 return x
84 }
85