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deepcopy.go
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deepcopy.go
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package darkness
import (
"fmt"
"reflect"
"unsafe"
)
// deepCopier keeps track of the pointers we discovered so far.
type deepCopier struct {
pointers map[unsafe.Pointer]interface{}
}
func (c *deepCopier) deepCopy(i interface{}) interface{} {
if i == nil {
return nil
}
typ := reflect.TypeOf(i)
value := reflect.ValueOf(i)
// if the thing is nil from the start just leave, IsNil only works on
// certain types though.
switch typ.Kind() {
case reflect.Chan, reflect.Func, reflect.Interface,
reflect.Map, reflect.Ptr, reflect.Slice:
if value.IsNil() {
return value.Interface()
}
}
switch typ.Kind() {
case reflect.Bool:
return value.Bool()
case reflect.Int: // ints
return int(value.Int())
case reflect.Int8:
return int8(value.Int())
case reflect.Int16:
return int16(value.Int())
case reflect.Int32:
return int32(value.Int())
case reflect.Int64:
return int64(value.Int())
case reflect.Uint: // uints
return uint(value.Uint())
case reflect.Uint8:
return uint8(value.Uint())
case reflect.Uint16:
return uint16(value.Uint())
case reflect.Uint32:
return uint32(value.Uint())
case reflect.Uint64:
return uint64(value.Uint())
case reflect.Float32: // floats
return float32(value.Float())
case reflect.Float64:
return float64(value.Float())
case reflect.Complex64: // complexs
return complex64(value.Complex())
case reflect.Complex128:
return complex128(value.Complex())
case reflect.Uintptr:
// void* can't be recursively copied as the info of the type they point
// to is not accessible via reflection
return uintptr(value.Uint())
case reflect.UnsafePointer:
// same as reflect.Uintptr
return unsafe.Pointer(value.Pointer())
case reflect.String:
// ensure a proper copy of the strings content
src := []byte(value.String())
return string(src)
case reflect.Func:
// func cannot be copied per se, that means closures will remain closure.
return value.Interface()
case reflect.Array:
a := reflect.Indirect(reflect.New(typ))
for i := 0; i < value.Len(); i++ {
a.Index(i).Set(reflect.ValueOf(c.deepCopy(value.Index(i).Interface())))
}
return a.Interface()
case reflect.Slice:
// verify if we already have copied that slice
old, ok := c.pointers[unsafe.Pointer(value.Pointer())]
if ok {
return old
}
s := reflect.MakeSlice(typ, value.Len(), value.Cap())
// store the copy in the map for future references
c.pointers[unsafe.Pointer(value.Pointer())] = s.Interface()
for i := 0; i < value.Len(); i++ {
s.Index(i).Set(reflect.ValueOf(c.deepCopy(value.Index(i).Interface())))
}
return s.Interface()
case reflect.Chan:
// verify if we already have copied that channel
old, ok := c.pointers[unsafe.Pointer(value.Pointer())]
if ok {
return old
}
ch := reflect.MakeChan(typ, value.Len())
// store the copy in the map for future references
c.pointers[unsafe.Pointer(value.Pointer())] = ch.Interface()
return ch.Interface()
case reflect.Map:
// verify if we already have copied that map
old, ok := c.pointers[unsafe.Pointer(value.Pointer())]
if ok {
return old
}
m := reflect.MakeMap(typ)
// store the copy in the map for future references
c.pointers[unsafe.Pointer(value.Pointer())] = m.Interface()
// copy the data between maps
for _, key := range value.MapKeys() {
m.SetMapIndex(key, reflect.ValueOf(c.deepCopy(value.MapIndex(key).Interface())))
}
return m.Interface()
case reflect.Struct:
s := reflect.Indirect(reflect.New(typ))
for i := 0; i < value.NumField(); i++ {
Sudo(s.Field(i)).Set(reflect.ValueOf(c.deepCopy(Sudo(value.Field(i)).Interface())))
}
return s.Interface()
case reflect.Ptr:
// verify if we already have copied that pointer
pointto, ok := c.pointers[unsafe.Pointer(value.Pointer())]
if ok {
return pointto
}
// in this case we indirect before allocating so we get a reflect.Value
// already all set to receive data.
ptr := reflect.New(reflect.Indirect(value).Type())
interf := ptr.Interface()
// store the copy in the map for future references
c.pointers[unsafe.Pointer(value.Pointer())] = interf
cp := reflect.ValueOf(c.deepCopy(reflect.Indirect(value).Interface()))
reflect.Indirect(ptr).Set(cp)
return interf
}
panic(fmt.Sprintf("Problem copying a %s of kind %s, please file in a bug report on github with the type you tried to copy", typ, typ.Kind()))
}
// DeepCopy does a deep copy of the given data. It doesn't recursively copy
// function pointers, uintptrs or unsafe.Pointers as the data it points to is
// unaccessible via reflection but it will copy the pointer value. It does
// handle circular structures. It does not copy buffered channel content as
// there are no reflect.ChanHeader or similar provided by stdlib. It also isn't
// particularely efficient on string copy, by making a complete copy of every
// string it comes across we could effectively be allocating way more memory
// then needed. If anyone comes across this problem ping @hydroflame and he will
// implement something to reuse memory when possible.
func DeepCopy(i interface{}) interface{} {
c := deepCopier{
pointers: make(map[unsafe.Pointer]interface{}),
}
return c.deepCopy(i)
}