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package json
import (
"fmt"
"reflect"
"strings"
"sync"
"unicode"
)
var (
// cache caches struct info.
cache = newStructInfoCache()
)
// structCache is a cache of struct info.
type structInfoCache struct {
sync.RWMutex
structInfos map[reflect.Type]*structInfo
}
func newStructInfoCache() *structInfoCache {
return &structInfoCache{
structInfos: make(map[reflect.Type]*structInfo),
}
}
func (c *structInfoCache) get(rt reflect.Type) *structInfo {
c.RLock()
defer c.RUnlock()
return c.structInfos[rt]
}
func (c *structInfoCache) set(rt reflect.Type, sInfo *structInfo) {
c.Lock()
defer c.Unlock()
c.structInfos[rt] = sInfo
}
// structInfo contains JSON info for a struct.
type structInfo struct {
fields []*fieldInfo
}
// fieldInfo contains JSON info for a struct field.
type fieldInfo struct {
jsonName string
omitEmpty bool
hidden bool
}
// makeStructInfo generates structInfo for a struct as a reflect.Value.
func makeStructInfo(rt reflect.Type) *structInfo {
if rt.Kind() != reflect.Struct {
panic(fmt.Sprintf("can't make struct info for non-struct value %v", rt))
}
if sInfo := cache.get(rt); sInfo != nil {
return sInfo
}
fields := make([]*fieldInfo, 0, rt.NumField())
for i := 0; i < cap(fields); i++ {
frt := rt.Field(i)
fInfo := &fieldInfo{
jsonName: frt.Name,
omitEmpty: false,
hidden: frt.Name == "" || !unicode.IsUpper(rune(frt.Name[0])),
}
o := frt.Tag.Get("json")
if o == "-" {
fInfo.hidden = true
} else if o != "" {
opts := strings.Split(o, ",")
if opts[0] != "" {
fInfo.jsonName = opts[0]
}
for _, o := range opts[1:] {
if o == "omitempty" {
fInfo.omitEmpty = true
}
}
}
fields = append(fields, fInfo)
}
sInfo := &structInfo{fields: fields}
cache.set(rt, sInfo)
return sInfo
}