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1 // Copyright 2015 The Chromium Authors. All rights reserved. | 1 // Copyright 2015 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 package datastore | 5 package datastore |
6 | 6 |
7 import ( | 7 import ( |
8 "reflect" | 8 "reflect" |
9 ) | 9 ) |
10 | 10 |
11 // GetPLS resolves obj into a PropertyLoadSaver. | 11 // GetPLS resolves obj into default struct PropertyLoadSaver and |
| 12 // MetaGetterSetter implementation. |
12 // | 13 // |
13 // obj must be a non-nil pointer to a struct of some sort. | 14 // obj must be a non-nil pointer to a struct of some sort. |
14 // | 15 // |
15 // By default, exported fields will be serialized to/from the datastore. If the | 16 // By default, exported fields will be serialized to/from the datastore. If the |
16 // field is not exported, it will be skipped by the serialization routines. | 17 // field is not exported, it will be skipped by the serialization routines. |
17 // | 18 // |
18 // If a field is of a non-supported type (see Property for the list of supported | 19 // If a field is of a non-supported type (see Property for the list of supported |
19 // property types), the resulting PropertyLoadSaver will have a non-nil | 20 // property types), the resulting PropertyLoadSaver will have a non-nil |
20 // Problem(). Other problems include duplicate field names (due to tagging), | 21 // Problem(). Other problems include duplicate field names (due to tagging), |
21 // recursively defined structs, nested structures with multiple slices (e.g. | 22 // recursively defined structs, nested structures with multiple slices (e.g. |
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86 // // 'Lines' will serialized to the datastore in the field 'Lines' | 87 // // 'Lines' will serialized to the datastore in the field 'Lines' |
87 // Lines []string | 88 // Lines []string |
88 // } | 89 // } |
89 // | 90 // |
90 // A pointer-to-struct may also implement MetaGetterSetter to provide more | 91 // A pointer-to-struct may also implement MetaGetterSetter to provide more |
91 // sophistocated metadata values. Explicitly defined fields (as shown above) | 92 // sophistocated metadata values. Explicitly defined fields (as shown above) |
92 // always take precedence over fields manipulated by the MetaGetterSetter | 93 // always take precedence over fields manipulated by the MetaGetterSetter |
93 // methods. So if your GetMeta handles "kind", but you explicitly have a | 94 // methods. So if your GetMeta handles "kind", but you explicitly have a |
94 // $kind field, the $kind field will take precedence and your GetMeta | 95 // $kind field, the $kind field will take precedence and your GetMeta |
95 // implementation will not be called for "kind". | 96 // implementation will not be called for "kind". |
96 func GetPLS(obj interface{}) PropertyLoadSaver { | 97 // |
| 98 // A struct overloading any of the PropertyLoadSaver or MetaGetterSetter |
| 99 // interfaces may evoke the default struct behavior by using GetPLS on itself. |
| 100 // For example: |
| 101 // |
| 102 // struct Special { |
| 103 // Name string |
| 104 // |
| 105 // foo string |
| 106 // } |
| 107 // |
| 108 // func (s *Special) Load(props PropertyMap) error { |
| 109 // if foo, ok := props["foo"]; ok && len(foo) == 1 { |
| 110 // s.foo = foo |
| 111 // delete(props, "foo") |
| 112 // } |
| 113 // return GetPLS(props) |
| 114 // } |
| 115 // |
| 116 // func (s *Special) Save(withMeta bool) (PropertyMap, error) { |
| 117 // props, err := GetPLS(withMeta) |
| 118 // if err != nil { |
| 119 // return nil, err |
| 120 // } |
| 121 // props["foo"] = []Property{MkProperty(s.foo)} |
| 122 // return props, nil |
| 123 // } |
| 124 // |
| 125 // func (s *Special) Problem() error { |
| 126 // return GetPLS(s).Problem() |
| 127 // } |
| 128 func GetPLS(obj interface{}) interface { |
| 129 » PropertyLoadSaver |
| 130 » MetaGetterSetter |
| 131 } { |
97 v := reflect.ValueOf(obj) | 132 v := reflect.ValueOf(obj) |
98 if v.Kind() != reflect.Ptr || v.Elem().Kind() != reflect.Struct { | 133 if v.Kind() != reflect.Ptr || v.Elem().Kind() != reflect.Struct { |
99 return &structPLS{c: &structCodec{problem: ErrInvalidEntityType}
} | 134 return &structPLS{c: &structCodec{problem: ErrInvalidEntityType}
} |
100 } | 135 } |
101 if v.IsNil() { | 136 if v.IsNil() { |
102 return &structPLS{c: &structCodec{problem: ErrInvalidEntityType}
} | 137 return &structPLS{c: &structCodec{problem: ErrInvalidEntityType}
} |
103 } | 138 } |
104 v = v.Elem() | 139 v = v.Elem() |
105 c := getCodec(v.Type()) | 140 c := getCodec(v.Type()) |
106 return &structPLS{v, c} | 141 return &structPLS{v, c} |
107 } | 142 } |
108 | 143 |
| 144 func getMGS(obj interface{}) MetaGetterSetter { |
| 145 if mgs, ok := obj.(MetaGetterSetter); ok { |
| 146 return mgs |
| 147 } |
| 148 return GetPLS(obj) |
| 149 } |
| 150 |
109 func getCodec(structType reflect.Type) *structCodec { | 151 func getCodec(structType reflect.Type) *structCodec { |
110 structCodecsMutex.RLock() | 152 structCodecsMutex.RLock() |
111 c, ok := structCodecs[structType] | 153 c, ok := structCodecs[structType] |
112 structCodecsMutex.RUnlock() | 154 structCodecsMutex.RUnlock() |
113 if ok { | 155 if ok { |
114 return c | 156 return c |
115 } | 157 } |
116 | 158 |
117 structCodecsMutex.Lock() | 159 structCodecsMutex.Lock() |
118 defer structCodecsMutex.Unlock() | 160 defer structCodecsMutex.Unlock() |
119 return getStructCodecLocked(structType) | 161 return getStructCodecLocked(structType) |
120 } | 162 } |
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