| // Copyright 2014 Google Inc. All rights reserved. |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| package proptools |
| |
| import ( |
| "fmt" |
| "reflect" |
| "sync" |
| "sync/atomic" |
| ) |
| |
| func CloneProperties(structValue reflect.Value) reflect.Value { |
| result := reflect.New(structValue.Type()) |
| CopyProperties(result.Elem(), structValue) |
| return result |
| } |
| |
| func CopyProperties(dstValue, srcValue reflect.Value) { |
| typ := dstValue.Type() |
| if srcValue.Type() != typ { |
| panic(fmt.Errorf("can't copy mismatching types (%s <- %s)", |
| dstValue.Kind(), srcValue.Kind())) |
| } |
| |
| for i, field := range typeFields(typ) { |
| if field.PkgPath != "" { |
| // The field is not exported so just skip it. |
| continue |
| } |
| |
| srcFieldValue := srcValue.Field(i) |
| dstFieldValue := dstValue.Field(i) |
| dstFieldInterfaceValue := reflect.Value{} |
| origDstFieldValue := dstFieldValue |
| |
| switch srcFieldValue.Kind() { |
| case reflect.Bool, reflect.String, reflect.Int, reflect.Uint: |
| dstFieldValue.Set(srcFieldValue) |
| case reflect.Struct: |
| CopyProperties(dstFieldValue, srcFieldValue) |
| case reflect.Slice: |
| if !srcFieldValue.IsNil() { |
| if srcFieldValue != dstFieldValue { |
| newSlice := reflect.MakeSlice(field.Type, srcFieldValue.Len(), |
| srcFieldValue.Len()) |
| reflect.Copy(newSlice, srcFieldValue) |
| dstFieldValue.Set(newSlice) |
| } |
| } else { |
| dstFieldValue.Set(srcFieldValue) |
| } |
| case reflect.Interface: |
| if srcFieldValue.IsNil() { |
| dstFieldValue.Set(srcFieldValue) |
| break |
| } |
| |
| srcFieldValue = srcFieldValue.Elem() |
| |
| if srcFieldValue.Kind() != reflect.Ptr { |
| panic(fmt.Errorf("can't clone field %q: interface refers to a non-pointer", |
| field.Name)) |
| } |
| if srcFieldValue.Type().Elem().Kind() != reflect.Struct { |
| panic(fmt.Errorf("can't clone field %q: interface points to a non-struct", |
| field.Name)) |
| } |
| |
| if dstFieldValue.IsNil() || dstFieldValue.Elem().Type() != srcFieldValue.Type() { |
| // We can't use the existing destination allocation, so |
| // clone a new one. |
| newValue := reflect.New(srcFieldValue.Type()).Elem() |
| dstFieldValue.Set(newValue) |
| dstFieldInterfaceValue = dstFieldValue |
| dstFieldValue = newValue |
| } else { |
| dstFieldValue = dstFieldValue.Elem() |
| } |
| fallthrough |
| case reflect.Ptr: |
| if srcFieldValue.IsNil() { |
| origDstFieldValue.Set(srcFieldValue) |
| break |
| } |
| |
| srcFieldValue := srcFieldValue.Elem() |
| |
| switch srcFieldValue.Kind() { |
| case reflect.Struct: |
| if !dstFieldValue.IsNil() { |
| // Re-use the existing allocation. |
| CopyProperties(dstFieldValue.Elem(), srcFieldValue) |
| break |
| } else { |
| newValue := CloneProperties(srcFieldValue) |
| if dstFieldInterfaceValue.IsValid() { |
| dstFieldInterfaceValue.Set(newValue) |
| } else { |
| origDstFieldValue.Set(newValue) |
| } |
| } |
| case reflect.Bool, reflect.Int64, reflect.String: |
| newValue := reflect.New(srcFieldValue.Type()) |
| newValue.Elem().Set(srcFieldValue) |
| origDstFieldValue.Set(newValue) |
| default: |
| panic(fmt.Errorf("can't clone field %q: points to a %s", |
| field.Name, srcFieldValue.Kind())) |
| } |
| default: |
| panic(fmt.Errorf("unexpected kind for property struct field %q: %s", |
| field.Name, srcFieldValue.Kind())) |
| } |
| } |
| } |
| |
| func ZeroProperties(structValue reflect.Value) { |
| typ := structValue.Type() |
| |
| for i, field := range typeFields(typ) { |
| if field.PkgPath != "" { |
| // The field is not exported so just skip it. |
| continue |
| } |
| |
| fieldValue := structValue.Field(i) |
| |
| switch fieldValue.Kind() { |
| case reflect.Bool, reflect.String, reflect.Slice, reflect.Int, reflect.Uint: |
| fieldValue.Set(reflect.Zero(fieldValue.Type())) |
| case reflect.Interface: |
| if fieldValue.IsNil() { |
| break |
| } |
| |
| // We leave the pointer intact and zero out the struct that's |
| // pointed to. |
| fieldValue = fieldValue.Elem() |
| if fieldValue.Kind() != reflect.Ptr { |
| panic(fmt.Errorf("can't zero field %q: interface refers to a non-pointer", |
| field.Name)) |
| } |
| if fieldValue.Type().Elem().Kind() != reflect.Struct { |
| panic(fmt.Errorf("can't zero field %q: interface points to a non-struct", |
| field.Name)) |
| } |
| fallthrough |
| case reflect.Ptr: |
| switch fieldValue.Type().Elem().Kind() { |
| case reflect.Struct: |
| if fieldValue.IsNil() { |
| break |
| } |
| ZeroProperties(fieldValue.Elem()) |
| case reflect.Bool, reflect.Int64, reflect.String: |
| fieldValue.Set(reflect.Zero(fieldValue.Type())) |
| default: |
| panic(fmt.Errorf("can't zero field %q: points to a %s", |
| field.Name, fieldValue.Elem().Kind())) |
| } |
| case reflect.Struct: |
| ZeroProperties(fieldValue) |
| default: |
| panic(fmt.Errorf("unexpected kind for property struct field %q: %s", |
| field.Name, fieldValue.Kind())) |
| } |
| } |
| } |
| |
| func CloneEmptyProperties(structValue reflect.Value) reflect.Value { |
| result := reflect.New(structValue.Type()) |
| cloneEmptyProperties(result.Elem(), structValue) |
| return result |
| } |
| |
| func cloneEmptyProperties(dstValue, srcValue reflect.Value) { |
| typ := srcValue.Type() |
| for i, field := range typeFields(typ) { |
| if field.PkgPath != "" { |
| // The field is not exported so just skip it. |
| continue |
| } |
| |
| srcFieldValue := srcValue.Field(i) |
| dstFieldValue := dstValue.Field(i) |
| dstFieldInterfaceValue := reflect.Value{} |
| |
| switch srcFieldValue.Kind() { |
| case reflect.Bool, reflect.String, reflect.Slice, reflect.Int, reflect.Uint: |
| // Nothing |
| case reflect.Struct: |
| cloneEmptyProperties(dstFieldValue, srcFieldValue) |
| case reflect.Interface: |
| if srcFieldValue.IsNil() { |
| break |
| } |
| |
| srcFieldValue = srcFieldValue.Elem() |
| if srcFieldValue.Kind() != reflect.Ptr { |
| panic(fmt.Errorf("can't clone empty field %q: interface refers to a non-pointer", |
| field.Name)) |
| } |
| if srcFieldValue.Type().Elem().Kind() != reflect.Struct { |
| panic(fmt.Errorf("can't clone empty field %q: interface points to a non-struct", |
| field.Name)) |
| } |
| |
| newValue := reflect.New(srcFieldValue.Type()).Elem() |
| dstFieldValue.Set(newValue) |
| dstFieldInterfaceValue = dstFieldValue |
| dstFieldValue = newValue |
| fallthrough |
| case reflect.Ptr: |
| switch srcFieldValue.Type().Elem().Kind() { |
| case reflect.Struct: |
| if srcFieldValue.IsNil() { |
| break |
| } |
| newValue := CloneEmptyProperties(srcFieldValue.Elem()) |
| if dstFieldInterfaceValue.IsValid() { |
| dstFieldInterfaceValue.Set(newValue) |
| } else { |
| dstFieldValue.Set(newValue) |
| } |
| case reflect.Bool, reflect.Int64, reflect.String: |
| // Nothing |
| default: |
| panic(fmt.Errorf("can't clone empty field %q: points to a %s", |
| field.Name, srcFieldValue.Elem().Kind())) |
| } |
| |
| default: |
| panic(fmt.Errorf("unexpected kind for property struct field %q: %s", |
| field.Name, srcFieldValue.Kind())) |
| } |
| } |
| } |
| |
| // reflect.Type.Field allocates a []int{} to hold the index every time it is called, which ends up |
| // being a significant portion of the GC pressure. It can't reuse the same one in case a caller |
| // modifies the backing array through the slice. Since we don't modify it, cache the result |
| // locally to reduce allocations. |
| type typeFieldMap map[reflect.Type][]reflect.StructField |
| |
| var ( |
| // Stores an atomic pointer to map caching Type to its StructField |
| typeFieldCache atomic.Value |
| // Lock used by slow path updating the cache pointer |
| typeFieldCacheWriterLock sync.Mutex |
| ) |
| |
| func init() { |
| typeFieldCache.Store(make(typeFieldMap)) |
| } |
| |
| func typeFields(typ reflect.Type) []reflect.StructField { |
| // Fast path |
| cache := typeFieldCache.Load().(typeFieldMap) |
| if typeFields, ok := cache[typ]; ok { |
| return typeFields |
| } |
| |
| // Slow path |
| typeFields := make([]reflect.StructField, typ.NumField()) |
| |
| for i := range typeFields { |
| typeFields[i] = typ.Field(i) |
| } |
| |
| typeFieldCacheWriterLock.Lock() |
| defer typeFieldCacheWriterLock.Unlock() |
| |
| old := typeFieldCache.Load().(typeFieldMap) |
| cache = make(typeFieldMap) |
| for k, v := range old { |
| cache[k] = v |
| } |
| |
| cache[typ] = typeFields |
| |
| typeFieldCache.Store(cache) |
| |
| return typeFields |
| } |