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1 // Copyright 2018 The Go Authors. All rights reserved. |
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2 // Use of this source code is governed by a BSD-style |
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3 // license that can be found in the LICENSE file. |
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4 |
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5 // +build !purego,!appengine |
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6 |
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7 package protoreflect |
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8 |
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9 import ( |
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10 "unsafe" |
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11 |
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12 "google.golang.org/protobuf/internal/pragma" |
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13 ) |
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14 |
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15 type ( |
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16 stringHeader struct { |
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17 Data unsafe.Pointer |
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18 Len int |
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19 } |
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20 sliceHeader struct { |
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21 Data unsafe.Pointer |
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22 Len int |
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23 Cap int |
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24 } |
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25 ifaceHeader struct { |
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26 Type unsafe.Pointer |
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27 Data unsafe.Pointer |
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28 } |
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29 ) |
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30 |
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31 var ( |
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32 nilType = typeOf(nil) |
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33 boolType = typeOf(*new(bool)) |
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34 int32Type = typeOf(*new(int32)) |
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35 int64Type = typeOf(*new(int64)) |
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36 uint32Type = typeOf(*new(uint32)) |
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37 uint64Type = typeOf(*new(uint64)) |
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38 float32Type = typeOf(*new(float32)) |
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39 float64Type = typeOf(*new(float64)) |
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40 stringType = typeOf(*new(string)) |
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41 bytesType = typeOf(*new([]byte)) |
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42 enumType = typeOf(*new(EnumNumber)) |
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43 ) |
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44 |
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45 // typeOf returns a pointer to the Go type information. |
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46 // The pointer is comparable and equal if and only if the types are identical. |
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47 func typeOf(t interface{}) unsafe.Pointer { |
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48 return (*ifaceHeader)(unsafe.Pointer(&t)).Type |
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49 } |
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50 |
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51 // value is a union where only one type can be represented at a time. |
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52 // The struct is 24B large on 64-bit systems and requires the minimum storage |
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53 // necessary to represent each possible type. |
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54 // |
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55 // The Go GC needs to be able to scan variables containing pointers. |
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56 // As such, pointers and non-pointers cannot be intermixed. |
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57 type value struct { |
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58 pragma.DoNotCompare // 0B |
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59 |
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60 // typ stores the type of the value as a pointer to the Go type. |
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61 typ unsafe.Pointer // 8B |
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62 |
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63 // ptr stores the data pointer for a String, Bytes, or interface value. |
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64 ptr unsafe.Pointer // 8B |
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65 |
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66 // num stores a Bool, Int32, Int64, Uint32, Uint64, Float32, Float64, or |
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67 // Enum value as a raw uint64. |
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68 // |
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69 // It is also used to store the length of a String or Bytes value; |
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70 // the capacity is ignored. |
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71 num uint64 // 8B |
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72 } |
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73 |
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74 func valueOfString(v string) Value { |
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75 p := (*stringHeader)(unsafe.Pointer(&v)) |
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76 return Value{typ: stringType, ptr: p.Data, num: uint64(len(v))} |
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77 } |
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78 func valueOfBytes(v []byte) Value { |
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79 p := (*sliceHeader)(unsafe.Pointer(&v)) |
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80 return Value{typ: bytesType, ptr: p.Data, num: uint64(len(v))} |
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81 } |
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82 func valueOfIface(v interface{}) Value { |
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83 p := (*ifaceHeader)(unsafe.Pointer(&v)) |
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84 return Value{typ: p.Type, ptr: p.Data} |
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85 } |
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86 |
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87 func (v Value) getString() (x string) { |
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88 *(*stringHeader)(unsafe.Pointer(&x)) = stringHeader{Data: v.ptr, Len: int(v.num)} |
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89 return x |
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90 } |
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91 func (v Value) getBytes() (x []byte) { |
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92 *(*sliceHeader)(unsafe.Pointer(&x)) = sliceHeader{Data: v.ptr, Len: int(v.num), Cap: int(v.num)} |
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93 return x |
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94 } |
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95 func (v Value) getIface() (x interface{}) { |
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96 *(*ifaceHeader)(unsafe.Pointer(&x)) = ifaceHeader{Type: v.typ, Data: v.ptr} |
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97 return x |
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98 } |