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registry.go
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registry.go
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package bsoncodec
import (
"errors"
"reflect"
"sync"
)
// ErrNilType is returned when nil is passed to either LookupEncoder or LookupDecoder.
var ErrNilType = errors.New("cannot perform an encoder or decoder lookup on <nil>")
// ErrNoEncoder is returned when there wasn't an encoder available for a type.
type ErrNoEncoder struct {
Type reflect.Type
}
func (ene ErrNoEncoder) Error() string {
return "no encoder found for " + ene.Type.String()
}
// ErrNoDecoder is returned when there wasn't a decoder available for a type.
type ErrNoDecoder struct {
Type reflect.Type
}
func (end ErrNoDecoder) Error() string {
return "no decoder found for " + end.Type.String()
}
// ErrNotInterface is returned when the provided type is not an interface.
var ErrNotInterface = errors.New("The provided type is not an interface")
var defaultRegistry *Registry
func init() {
defaultRegistry = buildDefaultRegistry()
}
// A RegistryBuilder is used to build a Registry. This type is not goroutine
// safe.
type RegistryBuilder struct {
typeEncoders map[reflect.Type]ValueEncoder
interfaceEncoders []interfaceValueEncoder
kindEncoders map[reflect.Kind]ValueEncoder
typeDecoders map[reflect.Type]ValueDecoder
interfaceDecoders []interfaceValueDecoder
kindDecoders map[reflect.Kind]ValueDecoder
}
// A Registry is used to store and retrieve codecs for types and interfaces. This type is the main
// typed passed around and Encoders and Decoders are constructed from it.
type Registry struct {
typeEncoders map[reflect.Type]ValueEncoder
typeDecoders map[reflect.Type]ValueDecoder
interfaceEncoders []interfaceValueEncoder
interfaceDecoders []interfaceValueDecoder
kindEncoders map[reflect.Kind]ValueEncoder
kindDecoders map[reflect.Kind]ValueDecoder
mu sync.RWMutex
}
// NewRegistryBuilder creates a new empty RegistryBuilder.
func NewRegistryBuilder() *RegistryBuilder {
return &RegistryBuilder{
typeEncoders: make(map[reflect.Type]ValueEncoder),
typeDecoders: make(map[reflect.Type]ValueDecoder),
interfaceEncoders: make([]interfaceValueEncoder, 0),
interfaceDecoders: make([]interfaceValueDecoder, 0),
kindEncoders: make(map[reflect.Kind]ValueEncoder),
kindDecoders: make(map[reflect.Kind]ValueDecoder),
}
}
func buildDefaultRegistry() *Registry {
rb := NewRegistryBuilder()
defaultValueEncoders.RegisterDefaultEncoders(rb)
defaultValueDecoders.RegisterDefaultDecoders(rb)
return rb.Build()
}
// RegisterCodec will register the provided ValueCodec for the provided type.
func (rb *RegistryBuilder) RegisterCodec(t reflect.Type, codec ValueCodec) *RegistryBuilder {
rb.RegisterEncoder(t, codec)
rb.RegisterDecoder(t, codec)
return rb
}
// RegisterEncoder will register the provided ValueEncoder to the provided type.
func (rb *RegistryBuilder) RegisterEncoder(t reflect.Type, enc ValueEncoder) *RegistryBuilder {
switch t.Kind() {
case reflect.Interface:
for idx, ir := range rb.interfaceEncoders {
if ir.i == t {
rb.interfaceEncoders[idx].ve = enc
return rb
}
}
rb.interfaceEncoders = append(rb.interfaceEncoders, interfaceValueEncoder{i: t, ve: enc})
default:
if t.Kind() != reflect.Ptr {
t = reflect.PtrTo(t)
}
rb.typeEncoders[t] = enc
}
return rb
}
// RegisterDecoder will register the provided ValueDecoder to the provided type.
func (rb *RegistryBuilder) RegisterDecoder(t reflect.Type, dec ValueDecoder) *RegistryBuilder {
switch t.Kind() {
case reflect.Interface:
for idx, ir := range rb.interfaceDecoders {
if ir.i == t {
rb.interfaceDecoders[idx].vd = dec
return rb
}
}
rb.interfaceDecoders = append(rb.interfaceDecoders, interfaceValueDecoder{i: t, vd: dec})
default:
if t.Kind() != reflect.Ptr {
t = reflect.PtrTo(t)
}
rb.typeDecoders[t] = dec
}
return rb
}
// RegisterDefaultEncoder will registr the provided ValueEncoder to the provided
// kind.
func (rb *RegistryBuilder) RegisterDefaultEncoder(kind reflect.Kind, enc ValueEncoder) *RegistryBuilder {
rb.kindEncoders[kind] = enc
return rb
}
// RegisterDefaultDecoder will register the provided ValueDecoder to the
// provided kind.
func (rb *RegistryBuilder) RegisterDefaultDecoder(kind reflect.Kind, dec ValueDecoder) *RegistryBuilder {
rb.kindDecoders[kind] = dec
return rb
}
// Build creates a Registry from the current state of this RegistryBuilder.
func (rb *RegistryBuilder) Build() *Registry {
registry := new(Registry)
registry.typeEncoders = make(map[reflect.Type]ValueEncoder)
for t, enc := range rb.typeEncoders {
registry.typeEncoders[t] = enc
}
registry.typeDecoders = make(map[reflect.Type]ValueDecoder)
for t, dec := range rb.typeDecoders {
registry.typeDecoders[t] = dec
}
registry.interfaceEncoders = make([]interfaceValueEncoder, len(rb.interfaceEncoders))
copy(registry.interfaceEncoders, rb.interfaceEncoders)
registry.interfaceDecoders = make([]interfaceValueDecoder, len(rb.interfaceDecoders))
copy(registry.interfaceDecoders, rb.interfaceDecoders)
registry.kindEncoders = make(map[reflect.Kind]ValueEncoder)
for kind, enc := range rb.kindEncoders {
registry.kindEncoders[kind] = enc
}
registry.kindDecoders = make(map[reflect.Kind]ValueDecoder)
for kind, dec := range rb.kindDecoders {
registry.kindDecoders[kind] = dec
}
return registry
}
// LookupEncoder will inspect the registry for an encoder that satisfies the
// type provided. An encoder registered for a specific type will take
// precedence over an encoder registered for an interface the type satisfies,
// which takes precedence over an encoder for the reflect.Kind of the value. If
// no encoder can be found, an error is returned.
func (r *Registry) LookupEncoder(t reflect.Type) (ValueEncoder, error) {
if t == nil {
return nil, ErrNilType
}
encodererr := ErrNoEncoder{Type: t}
r.mu.RLock()
enc, found := r.lookupTypeEncoder(t)
r.mu.RUnlock()
if found {
if enc == nil {
return nil, ErrNoEncoder{Type: t}
}
return enc, nil
}
enc, found = r.lookupInterfaceEncoder(t)
if found {
r.mu.Lock()
if t.Kind() != reflect.Ptr {
t = reflect.PtrTo(t)
}
r.typeEncoders[t] = enc
r.mu.Unlock()
return enc, nil
}
if t.Kind() == reflect.Map && t.Key().Kind() != reflect.String {
r.mu.Lock()
r.typeEncoders[t] = nil
r.mu.Unlock()
return nil, encodererr
}
if t.Kind() == reflect.Ptr {
t = t.Elem()
}
enc, found = r.kindEncoders[t.Kind()]
if !found {
r.mu.Lock()
r.typeEncoders[t] = nil
r.mu.Unlock()
return nil, encodererr
}
r.mu.Lock()
r.typeEncoders[t] = enc
r.mu.Unlock()
return enc, nil
}
func (r *Registry) lookupTypeEncoder(t reflect.Type) (ValueEncoder, bool) {
if t.Kind() != reflect.Ptr {
t = reflect.PtrTo(t)
}
enc, found := r.typeEncoders[t]
return enc, found
}
func (r *Registry) lookupInterfaceEncoder(t reflect.Type) (ValueEncoder, bool) {
for _, ienc := range r.interfaceEncoders {
if !t.Implements(ienc.i) {
continue
}
return ienc.ve, true
}
return nil, false
}
// LookupDecoder will inspect the registry for a decoder that satisfies the
// type provided. A decoder registered for a specific type will take
// precedence over a decoder registered for an interface the type satisfies,
// which takes precedence over a decoder for the reflect.Kind of the value. If
// no decoder can be found, an error is returned.
func (r *Registry) LookupDecoder(t reflect.Type) (ValueDecoder, error) {
if t == nil {
return nil, ErrNilType
}
decodererr := ErrNoDecoder{Type: t}
r.mu.RLock()
dec, found := r.lookupTypeDecoder(t)
r.mu.RUnlock()
if found {
if dec == nil {
return nil, ErrNoDecoder{Type: t}
}
return dec, nil
}
dec, found = r.lookupInterfaceDecoder(t)
if found {
r.mu.Lock()
if t.Kind() != reflect.Ptr {
t = reflect.PtrTo(t)
}
r.typeDecoders[t] = dec
r.mu.Unlock()
return dec, nil
}
if t.Kind() == reflect.Map && t.Key().Kind() != reflect.String {
r.mu.Lock()
r.typeDecoders[t] = nil
r.mu.Unlock()
return nil, decodererr
}
if t.Kind() == reflect.Ptr {
t = t.Elem()
}
dec, found = r.kindDecoders[t.Kind()]
if !found {
r.mu.Lock()
r.typeDecoders[t] = nil
r.mu.Unlock()
return nil, decodererr
}
r.mu.Lock()
r.typeDecoders[t] = dec
r.mu.Unlock()
return dec, nil
}
func (r *Registry) lookupTypeDecoder(t reflect.Type) (ValueDecoder, bool) {
if t.Kind() != reflect.Ptr {
t = reflect.PtrTo(t)
}
dec, found := r.typeDecoders[t]
return dec, found
}
func (r *Registry) lookupInterfaceDecoder(t reflect.Type) (ValueDecoder, bool) {
for _, idec := range r.interfaceDecoders {
if !t.Implements(idec.i) {
continue
}
return idec.vd, true
}
return nil, false
}
type interfaceValueEncoder struct {
i reflect.Type
ve ValueEncoder
}
type interfaceValueDecoder struct {
i reflect.Type
vd ValueDecoder
}