1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
|
// Copyright (C) 2022-2023 Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later
package lowmemjson
import (
"reflect"
"git.lukeshu.com/go/lowmemjson/internal"
)
type structField struct {
Name string
Path []int
Tagged bool
OmitEmpty bool
Quote bool
}
// A structIndex is used by Decoder.Decode() and Encoder.Encode() when
// decoding-to or encoding-from a struct.
type structIndex struct {
byPos []structField
byName map[string]int
}
// indexStruct takes a struct Type, and indexes its fields for use by
// Decoder.Decode() and Encoder.Encode().
func indexStruct(typ reflect.Type) structIndex {
var byPos []structField
byName := make(map[string][]int)
indexStructInner(typ, &byPos, byName, nil, map[reflect.Type]struct{}{})
ret := structIndex{
byName: make(map[string]int),
}
for curPos, _field := range byPos {
name := _field.Name
fieldPoss := byName[name]
switch len(fieldPoss) {
case 0:
// do nothing
case 1:
ret.byName[name] = len(ret.byPos)
ret.byPos = append(ret.byPos, _field)
default:
// To quote the encoding/json docs (version 1.18.4):
//
// If there are multiple fields at the same level, and that level is the
// least nested (and would therefore be the nesting level selected by the
// usual Go rules), the following extra rules apply:
//
// 1) Of those fields, if any are JSON-tagged, only tagged fields are
// considered, even if there are multiple untagged fields that would
// otherwise conflict.
//
// 2) If there is exactly one field (tagged or not according to the first
// rule), that is selected.
//
// 3) Otherwise there are multiple fields, and all are ignored; no error
// occurs.
leastLevel := len(byPos[fieldPoss[0]].Path)
for _, fieldPos := range fieldPoss[1:] {
field := byPos[fieldPos]
if len(field.Path) < leastLevel {
leastLevel = len(field.Path)
}
}
var numUntagged, numTagged int
var untaggedPos, taggedPos int
for _, fieldPos := range fieldPoss {
field := byPos[fieldPos]
if len(field.Path) != leastLevel {
continue
}
if field.Tagged {
numTagged++
taggedPos = fieldPos
if numTagged > 1 {
break // optimization
}
} else {
numUntagged++
untaggedPos = fieldPos
}
}
switch numTagged {
case 0:
switch numUntagged {
case 0:
// do nothing
case 1:
if curPos == untaggedPos {
ret.byName[name] = len(ret.byPos)
ret.byPos = append(ret.byPos, byPos[curPos])
}
}
case 1:
if curPos == taggedPos {
ret.byName[name] = len(ret.byPos)
ret.byPos = append(ret.byPos, byPos[curPos])
}
}
}
}
return ret
}
// indexStructInner crawls the struct `typ`, storing information on
// all struct fields foun in to `byPos` and `byName`. If `typ`
// contains other structs as fields, indexStructInner will recurse and
// call itself; keeping track of stack information with `stackPath`
// (which identifies where we are in the parent struct) and
// `stackSeen` (which is used for detecting loops).
func indexStructInner(typ reflect.Type, byPos *[]structField, byName map[string][]int, stackPath []int, stackSeen map[reflect.Type]struct{}) {
if _, ok := stackSeen[typ]; ok {
return
}
stackSeen[typ] = struct{}{}
defer delete(stackSeen, typ)
n := typ.NumField()
for i := 0; i < n; i++ {
stackPath := append(stackPath, i)
fTyp := typ.Field(i)
var embed bool
if fTyp.Anonymous {
t := fTyp.Type
if t.Kind() == reflect.Pointer {
t = t.Elem()
}
if !fTyp.IsExported() && t.Kind() != reflect.Struct {
continue
}
embed = t.Kind() == reflect.Struct
} else if !fTyp.IsExported() {
continue
}
tag := fTyp.Tag.Get("json")
if tag == "-" {
continue
}
tagName, opts := internal.ParseTag(tag)
name := tagName
if !isValidTag(name) {
name = ""
}
if name == "" {
name = fTyp.Name
}
if embed && tagName == "" {
t := fTyp.Type
if t.Kind() == reflect.Pointer {
t = t.Elem()
}
indexStructInner(t, byPos, byName, stackPath, stackSeen)
} else {
byName[name] = append(byName[name], len(*byPos))
*byPos = append(*byPos, structField{
Name: name,
Path: append([]int(nil), stackPath...),
Tagged: tagName != "",
OmitEmpty: opts.Contains("omitempty"),
Quote: opts.Contains("string") && isQuotable(fTyp.Type),
})
}
}
}
// isQuotable returns whether a type is eligible for `json:,string`
// quoting.
func isQuotable(typ reflect.Type) bool {
for typ.Kind() == reflect.Pointer {
typ = typ.Elem()
}
switch typ.Kind() {
case reflect.Bool,
reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64,
reflect.Uintptr,
reflect.Float32, reflect.Float64,
reflect.String:
return true
default:
return false
}
}
|
