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package bare
import (
"fmt"
"reflect"
)
// Any type which is a union member must implement this interface. You must
// also call RegisterUnion for go-bare to marshal or unmarshal messages which
// utilize your union type.
type Union interface {
IsUnion()
}
type UnionTags struct {
iface reflect.Type
tags map[reflect.Type]uint64
types map[uint64]reflect.Type
}
var unionInterface = reflect.TypeOf((*Union)(nil)).Elem()
var unionRegistry map[reflect.Type]*UnionTags
func init() {
unionRegistry = make(map[reflect.Type]*UnionTags)
}
// Registers a union type in this context. Pass the union interface and the
// list of types associated with it, sorted ascending by their union tag.
func RegisterUnion(iface interface{}) *UnionTags {
ity := reflect.TypeOf(iface).Elem()
if _, ok := unionRegistry[ity]; ok {
panic(fmt.Errorf("Type %s has already been registered", ity.Name()))
}
if !ity.Implements(reflect.TypeOf((*Union)(nil)).Elem()) {
panic(fmt.Errorf("Type %s does not implement bare.Union", ity.Name()))
}
utypes := &UnionTags{
iface: ity,
tags: make(map[reflect.Type]uint64),
types: make(map[uint64]reflect.Type),
}
unionRegistry[ity] = utypes
return utypes
}
func (ut *UnionTags) Member(t interface{}, tag uint64) *UnionTags {
ty := reflect.TypeOf(t)
if !ty.AssignableTo(ut.iface) {
panic(fmt.Errorf("Type %s does not implement interface %s",
ty.Name(), ut.iface.Name()))
}
if _, ok := ut.tags[ty]; ok {
panic(fmt.Errorf("Type %s is already registered for union %s",
ty.Name(), ut.iface.Name()))
}
if _, ok := ut.types[tag]; ok {
panic(fmt.Errorf("Tag %d is already registered for union %s",
tag, ut.iface.Name()))
}
ut.tags[ty] = tag
ut.types[tag] = ty
return ut
}
func (ut *UnionTags) TagFor(v interface{}) (uint64, bool) {
tag, ok := ut.tags[reflect.TypeOf(v)]
return tag, ok
}
func (ut *UnionTags) TypeFor(tag uint64) (reflect.Type, bool) {
t, ok := ut.types[tag]
return t, ok
}
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