package copystructure
import (
"errors"
"reflect"
"sync"
"github.com/mitchellh/reflectwalk"
)
// Copy returns a deep copy of v.
func Copy(v interface{}) (interface{}, error) {
return Config{}.Copy(v)
}
// CopierFunc is a function that knows how to deep copy a specific type.
// Register these globally with the Copiers variable.
type CopierFunc func(interface{}) (interface{}, error)
// Copiers is a map of types that behave specially when they are copied.
// If a type is found in this map while deep copying, this function
// will be called to copy it instead of attempting to copy all fields.
//
// The key should be the type, obtained using: reflect.TypeOf(value with type).
//
// It is unsafe to write to this map after Copies have started. If you
// are writing to this map while also copying, wrap all modifications to
// this map as well as to Copy in a mutex.
var Copiers map[reflect.Type]CopierFunc = make(map[reflect.Type]CopierFunc)
// Must is a helper that wraps a call to a function returning
// (interface{}, error) and panics if the error is non-nil. It is intended
// for use in variable initializations and should only be used when a copy
// error should be a crashing case.
func Must(v interface{}, err error) interface{} {
if err != nil {
panic("copy error: " + err.Error())
}
return v
}
var errPointerRequired = errors.New("Copy argument must be a pointer when Lock is true")
type Config struct {
// Lock any types that are a sync.Locker and are not a mutex while copying.
// If there is an RLocker method, use that to get the sync.Locker.
Lock bool
// Copiers is a map of types associated with a CopierFunc. Use the global
// Copiers map if this is nil.
Copiers map[reflect.Type]CopierFunc
}
func (c Config) Copy(v interface{}) (interface{}, error) {
if c.Lock && reflect.ValueOf(v).Kind() != reflect.Ptr {
return nil, errPointerRequired
}
w := new(walker)
if c.Lock {
w.useLocks = true
}
if c.Copiers == nil {
c.Copiers = Copiers
}
err := reflectwalk.Walk(v, w)
if err != nil {
return nil, err
}
// Get the result. If the result is nil, then we want to turn it
// into a typed nil if we can.
result := w.Result
if result == nil {
val := reflect.ValueOf(v)
result = reflect.Indirect(reflect.New(val.Type())).Interface()
}
return result, nil
}
// Return the key used to index interfaces types we've seen. Store the number
// of pointers in the upper 32bits, and the depth in the lower 32bits. This is
// easy to calculate, easy to match a key with our current depth, and we don't
// need to deal with initializing and cleaning up nested maps or slices.
func ifaceKey(pointers, depth int) uint64 {
return uint64(pointers)<<32 | uint64(depth)
}
type walker struct {
Result interface{}
depth int
ignoreDepth int
vals []reflect.Value
cs []reflect.Value
// This stores the number of pointers we've walked over, indexed by depth.
ps []int
// If an interface is indirected by a pointer, we need to know the type of
// interface to create when creating the new value. Store the interface
// types here, indexed by both the walk depth and the number of pointers
// already seen at that depth. Use ifaceKey to calculate the proper uint64
// value.
ifaceTypes map[uint64]reflect.Type
// any locks we've taken, indexed by depth
locks []sync.Locker
// take locks while walking the structure
useLocks bool
}
func (w *walker) Enter(l reflectwalk.Location) error {
w.depth++
// ensure we have enough elements to index via w.depth
for w.depth >= len(w.locks) {
w.locks = append(w.locks, nil)
}
for len(w.ps) < w.depth+1 {
w.ps = append(w.ps, 0)
}
return nil
}
func (w *walker) Exit(l reflectwalk.Location) error {
locker := w.locks[w.depth]
w.locks[w.depth] = nil
if locker != nil {
defer locker.Unlock()
}
// clear out pointers and interfaces as we exit the stack
w.ps[w.depth] = 0
for k := range w.ifaceTypes {
mask := uint64(^uint32(0))
if k&mask == uint64(w.depth) {
delete(w.ifaceTypes, k)
}
}
w.depth--
if w.ignoreDepth > w.depth {
w.ignoreDepth = 0
}
if w.ignoring() {
return nil
}
switch l {
case reflectwalk.Map:
fallthrough
case reflectwalk.Slice:
// Pop map off our container
w.cs = w.cs[:len(w.cs)-1]
case reflectwalk.MapValue:
// Pop off the key and value
mv := w.valPop()
mk := w.valPop()
m := w.cs[len(w.cs)-1]
// If mv is the zero value, SetMapIndex deletes the key form the map,
// or in this case never adds it. We need to create a properly typed
// zero value so that this key can be set.
if !mv.IsValid() {
mv = reflect.Zero(m.Type().Elem())
}
m.SetMapIndex(mk, mv)
case reflectwalk.SliceElem:
// Pop off the value and the index and set it on the slice
v := w.valPop()
i := w.valPop().Interface().(int)
if v.IsValid() {
s := w.cs[len(w.cs)-1]
se := s.Index(i)
if se.CanSet() {
se.Set(v)
}
}
case reflectwalk.Struct:
w.replacePointerMaybe()
// Remove the struct from the container stack
w.cs = w.cs[:len(w.cs)-1]
case reflectwalk.StructField:
// Pop off the value and the field
v := w.valPop()
f := w.valPop().Interface().(reflect.StructField)
if v.IsValid() {
s := w.cs[len(w.cs)-1]
sf := reflect.Indirect(s).FieldByName(f.Name)
if sf.CanSet() {
sf.Set(v)
}
}
case reflectwalk.WalkLoc:
// Clear out the slices for GC
w.cs = nil
w.vals = nil
}
return nil
}
func (w *walker) Map(m reflect.Value) error {
if w.ignoring() {
return nil
}
w.lock(m)
// Create the map. If the map itself is nil, then just make a nil map
var newMap reflect.Value
if m.IsNil() {
newMap = reflect.Indirect(reflect.New(m.Type()))
} else {
newMap = reflect.MakeMap(m.Type())
}
w.cs = append(w.cs, newMap)
w.valPush(newMap)
return nil
}
func (w *walker) MapElem(m, k, v reflect.Value) error {
return nil
}
func (w *walker) PointerEnter(v bool) error {
if v {
w.ps[w.depth]++
}
return nil
}
func (w *walker) PointerExit(v bool) error {
if v {
w.ps[w.depth]--
}
return nil
}
func (w *walker) Interface(v reflect.Value) error {
if !v.IsValid() {
return nil
}
if w.ifaceTypes == nil {
w.ifaceTypes = make(map[uint64]reflect.Type)
}
w.ifaceTypes[ifaceKey(w.ps[w.depth], w.depth)] = v.Type()
return nil
}
func (w *walker) Primitive(v reflect.Value) error {
if w.ignoring() {
return nil
}
w.lock(v)
// IsValid verifies the v is non-zero and CanInterface verifies
// that we're allowed to read this value (unexported fields).
var newV reflect.Value
if v.IsValid() && v.CanInterface() {
newV = reflect.New(v.Type())
newV.Elem().Set(v)
}
w.valPush(newV)
w.replacePointerMaybe()
return nil
}
func (w *walker) Slice(s reflect.Value) error {
if w.ignoring() {
return nil
}
w.lock(s)
var newS reflect.Value
if s.IsNil() {
newS = reflect.Indirect(reflect.New(s.Type()))
} else {
newS = reflect.MakeSlice(s.Type(), s.Len(), s.Cap())
}
w.cs = append(w.cs, newS)
w.valPush(newS)
return nil
}
func (w *walker) SliceElem(i int, elem reflect.Value) error {
if w.ignoring() {
return nil
}
// We don't write the slice here because elem might still be
// arbitrarily complex. Just record the index and continue on.
w.valPush(reflect.ValueOf(i))
return nil
}
func (w *walker) Struct(s reflect.Value) error {
if w.ignoring() {
return nil
}
w.lock(s)
var v reflect.Value
if c, ok := Copiers[s.Type()]; ok {
// We have a Copier for this struct, so we use that copier to
// get the copy, and we ignore anything deeper than this.
w.ignoreDepth = w.depth
dup, err := c(s.Interface())
if err != nil {
return err
}
v = reflect.ValueOf(dup)
} else {
// No copier, we copy ourselves and allow reflectwalk to guide
// us deeper into the structure for copying.
v = reflect.New(s.Type())
}
// Push the value onto the value stack for setting the struct field,
// and add the struct itself to the containers stack in case we walk
// deeper so that its own fields can be modified.
w.valPush(v)
w.cs = append(w.cs, v)
return nil
}
func (w *walker) StructField(f reflect.StructField, v reflect.Value) error {
if w.ignoring() {
return nil
}
// If PkgPath is non-empty, this is a private (unexported) field.
// We do not set this unexported since the Go runtime doesn't allow us.
if f.PkgPath != "" {
return reflectwalk.SkipEntry
}
// Push the field onto the stack, we'll handle it when we exit
// the struct field in Exit...
w.valPush(reflect.ValueOf(f))
return nil
}
// ignore causes the walker to ignore any more values until we exit this on
func (w *walker) ignore() {
w.ignoreDepth = w.depth
}
func (w *walker) ignoring() bool {
return w.ignoreDepth > 0 && w.depth >= w.ignoreDepth
}
func (w *walker) pointerPeek() bool {
return w.ps[w.depth] > 0
}
func (w *walker) valPop() reflect.Value {
result := w.vals[len(w.vals)-1]
w.vals = w.vals[:len(w.vals)-1]
// If we're out of values, that means we popped everything off. In
// this case, we reset the result so the next pushed value becomes
// the result.
if len(w.vals) == 0 {
w.Result = nil
}
return result
}
func (w *walker) valPush(v reflect.Value) {
w.vals = append(w.vals, v)
// If we haven't set the result yet, then this is the result since
// it is the first (outermost) value we're seeing.
if w.Result == nil && v.IsValid() {
w.Result = v.Interface()
}
}
func (w *walker) replacePointerMaybe() {
// Determine the last pointer value. If it is NOT a pointer, then
// we need to push that onto the stack.
if !w.pointerPeek() {
w.valPush(reflect.Indirect(w.valPop()))
return
}
v := w.valPop()
for i := 1; i < w.ps[w.depth]; i++ {
if iType, ok := w.ifaceTypes[ifaceKey(w.ps[w.depth]-i, w.depth)]; ok {
iface := reflect.New(iType).Elem()
iface.Set(v)
v = iface
}
p := reflect.New(v.Type())
p.Elem().Set(v)
v = p
}
w.valPush(v)
}
// if this value is a Locker, lock it and add it to the locks slice
func (w *walker) lock(v reflect.Value) {
if !w.useLocks {
return
}
if !v.IsValid() || !v.CanInterface() {
return
}
type rlocker interface {
RLocker() sync.Locker
}
var locker sync.Locker
// We can't call Interface() on a value directly, since that requires
// a copy. This is OK, since the pointer to a value which is a sync.Locker
// is also a sync.Locker.
if v.Kind() == reflect.Ptr {
switch l := v.Interface().(type) {
case rlocker:
// don't lock a mutex directly
if _, ok := l.(*sync.RWMutex); !ok {
locker = l.RLocker()
}
case sync.Locker:
locker = l
}
} else if v.CanAddr() {
switch l := v.Addr().Interface().(type) {
case rlocker:
// don't lock a mutex directly
if _, ok := l.(*sync.RWMutex); !ok {
locker = l.RLocker()
}
case sync.Locker:
locker = l
}
}
// still no callable locker
if locker == nil {
return
}
// don't lock a mutex directly
switch locker.(type) {
case *sync.Mutex, *sync.RWMutex:
return
}
locker.Lock()
w.locks[w.depth] = locker
}
