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|
package scfg
import (
"fmt"
"reflect"
"strings"
"sync"
)
// structInfo contains scfg metadata for structs.
type structInfo struct {
param int // index of field storing parameters
children map[string]int // indices of fields storing child directives
}
var (
structCacheMutex sync.Mutex
structCache = make(map[reflect.Type]*structInfo)
)
func getStructInfo(t reflect.Type) (*structInfo, error) {
structCacheMutex.Lock()
defer structCacheMutex.Unlock()
if info := structCache[t]; info != nil {
return info, nil
}
info := &structInfo{
param: -1,
children: make(map[string]int),
}
for i := 0; i < t.NumField(); i++ {
f := t.Field(i)
if f.Anonymous {
return nil, fmt.Errorf("scfg: anonymous struct fields are not supported")
} else if !f.IsExported() {
continue
}
tag := f.Tag.Get("scfg")
parts := strings.Split(tag, ",")
k, options := parts[0], parts[1:]
if k == "-" {
continue
} else if k == "" {
k = f.Name
}
isParam := false
for _, opt := range options {
switch opt {
case "param":
isParam = true
default:
return nil, fmt.Errorf("scfg: invalid option %q in struct tag", opt)
}
}
if isParam {
if info.param >= 0 {
return nil, fmt.Errorf("scfg: param option specified multiple times in struct tag in %v", t)
}
if parts[0] != "" {
return nil, fmt.Errorf("scfg: name must be empty when param option is specified in struct tag in %v", t)
}
info.param = i
} else {
if _, ok := info.children[k]; ok {
return nil, fmt.Errorf("scfg: key %q specified multiple times in struct tag in %v", k, t)
}
info.children[k] = i
}
}
structCache[t] = info
return info, nil
}
|
