// +build !safe
// +build !appengine
// +build go1.7

// Copyright (c) 2012-2015 Ugorji Nwoke. All rights reserved.
// Use of this source code is governed by a MIT license found in the LICENSE file.

package codec

import (
	"reflect"
	"sync/atomic"
	"unsafe"
)

// This file has unsafe variants of some helper methods.
// NOTE: See helper_not_unsafe.go for the usage information.

// var zeroRTv [4]uintptr

const unsafeFlagIndir = 1 << 7 // keep in sync with GO_ROOT/src/reflect/value.go

type unsafeString struct {
	Data uintptr
	Len  int
}

type unsafeSlice struct {
	Data uintptr
	Len  int
	Cap  int
}

type unsafeIntf struct {
	typ  unsafe.Pointer
	word unsafe.Pointer
}

type unsafeReflectValue struct {
	typ  unsafe.Pointer
	ptr  unsafe.Pointer
	flag uintptr
}

func stringView(v []byte) string {
	if len(v) == 0 {
		return ""
	}

	bx := (*unsafeSlice)(unsafe.Pointer(&v))
	sx := unsafeString{bx.Data, bx.Len}
	return *(*string)(unsafe.Pointer(&sx))
}

func bytesView(v string) []byte {
	if len(v) == 0 {
		return zeroByteSlice
	}

	sx := (*unsafeString)(unsafe.Pointer(&v))
	bx := unsafeSlice{sx.Data, sx.Len, sx.Len}
	return *(*[]byte)(unsafe.Pointer(&bx))
}

func definitelyNil(v interface{}) bool {
	return (*unsafeIntf)(unsafe.Pointer(&v)).word == nil
}

// func keepAlive4BytesView(v string) {
// 	runtime.KeepAlive(v)
// }

// func keepAlive4StringView(v []byte) {
// 	runtime.KeepAlive(v)
// }

// TODO: consider a more generally-known optimization for reflect.Value ==> Interface
//
// Currently, we use this fragile method that taps into implememtation details from
// the source go stdlib reflect/value.go,
// and trims the implementation.
func rv2i(rv reflect.Value) interface{} {
	if false {
		return rv.Interface()
	}
	urv := (*unsafeReflectValue)(unsafe.Pointer(&rv))
	// references that are single-words (map, ptr) may be double-referenced as flagIndir
	kk := urv.flag & (1<<5 - 1)
	if (kk == uintptr(reflect.Map) || kk == uintptr(reflect.Ptr)) && urv.flag&unsafeFlagIndir != 0 {
		return *(*interface{})(unsafe.Pointer(&unsafeIntf{word: *(*unsafe.Pointer)(urv.ptr), typ: urv.typ}))
	}
	return *(*interface{})(unsafe.Pointer(&unsafeIntf{word: urv.ptr, typ: urv.typ}))
}

func rt2id(rt reflect.Type) uintptr {
	return uintptr(((*unsafeIntf)(unsafe.Pointer(&rt))).word)
}

func rv2rtid(rv reflect.Value) uintptr {
	return uintptr((*unsafeReflectValue)(unsafe.Pointer(&rv)).typ)
}

// func rv0t(rt reflect.Type) reflect.Value {
// 	ut := (*unsafeIntf)(unsafe.Pointer(&rt))
// 	// we need to determine whether ifaceIndir, and then whether to just pass 0 as the ptr
// 	uv := unsafeReflectValue{ut.word, &zeroRTv, flag(rt.Kind())}
// 	return *(*reflect.Value)(unsafe.Pointer(&uv})
// }

// --------------------------
type atomicTypeInfoSlice struct {
	v unsafe.Pointer
}

func (x *atomicTypeInfoSlice) load() *[]rtid2ti {
	return (*[]rtid2ti)(atomic.LoadPointer(&x.v))
}

func (x *atomicTypeInfoSlice) store(p *[]rtid2ti) {
	atomic.StorePointer(&x.v, unsafe.Pointer(p))
}

// --------------------------
func (d *Decoder) raw(f *codecFnInfo, rv reflect.Value) {
	urv := (*unsafeReflectValue)(unsafe.Pointer(&rv))
	// if urv.flag&unsafeFlagIndir != 0 {
	// 	urv.ptr = *(*unsafe.Pointer)(urv.ptr)
	// }
	*(*[]byte)(urv.ptr) = d.rawBytes()
}

func (d *Decoder) kString(f *codecFnInfo, rv reflect.Value) {
	urv := (*unsafeReflectValue)(unsafe.Pointer(&rv))
	*(*string)(urv.ptr) = d.d.DecodeString()
}

func (d *Decoder) kBool(f *codecFnInfo, rv reflect.Value) {
	urv := (*unsafeReflectValue)(unsafe.Pointer(&rv))
	*(*bool)(urv.ptr) = d.d.DecodeBool()
}

func (d *Decoder) kFloat32(f *codecFnInfo, rv reflect.Value) {
	urv := (*unsafeReflectValue)(unsafe.Pointer(&rv))
	*(*float32)(urv.ptr) = float32(d.d.DecodeFloat(true))
}

func (d *Decoder) kFloat64(f *codecFnInfo, rv reflect.Value) {
	urv := (*unsafeReflectValue)(unsafe.Pointer(&rv))
	*(*float64)(urv.ptr) = d.d.DecodeFloat(false)
}

func (d *Decoder) kInt(f *codecFnInfo, rv reflect.Value) {
	urv := (*unsafeReflectValue)(unsafe.Pointer(&rv))
	*(*int)(urv.ptr) = int(d.d.DecodeInt(intBitsize))
}

func (d *Decoder) kInt8(f *codecFnInfo, rv reflect.Value) {
	urv := (*unsafeReflectValue)(unsafe.Pointer(&rv))
	*(*int8)(urv.ptr) = int8(d.d.DecodeInt(8))
}

func (d *Decoder) kInt16(f *codecFnInfo, rv reflect.Value) {
	urv := (*unsafeReflectValue)(unsafe.Pointer(&rv))
	*(*int16)(urv.ptr) = int16(d.d.DecodeInt(16))
}

func (d *Decoder) kInt32(f *codecFnInfo, rv reflect.Value) {
	urv := (*unsafeReflectValue)(unsafe.Pointer(&rv))
	*(*int32)(urv.ptr) = int32(d.d.DecodeInt(32))
}

func (d *Decoder) kInt64(f *codecFnInfo, rv reflect.Value) {
	urv := (*unsafeReflectValue)(unsafe.Pointer(&rv))
	*(*int64)(urv.ptr) = d.d.DecodeInt(64)
}

func (d *Decoder) kUint(f *codecFnInfo, rv reflect.Value) {
	urv := (*unsafeReflectValue)(unsafe.Pointer(&rv))
	*(*uint)(urv.ptr) = uint(d.d.DecodeUint(uintBitsize))
}

func (d *Decoder) kUintptr(f *codecFnInfo, rv reflect.Value) {
	urv := (*unsafeReflectValue)(unsafe.Pointer(&rv))
	*(*uintptr)(urv.ptr) = uintptr(d.d.DecodeUint(uintBitsize))
}

func (d *Decoder) kUint8(f *codecFnInfo, rv reflect.Value) {
	urv := (*unsafeReflectValue)(unsafe.Pointer(&rv))
	*(*uint8)(urv.ptr) = uint8(d.d.DecodeUint(8))
}

func (d *Decoder) kUint16(f *codecFnInfo, rv reflect.Value) {
	urv := (*unsafeReflectValue)(unsafe.Pointer(&rv))
	*(*uint16)(urv.ptr) = uint16(d.d.DecodeUint(16))
}

func (d *Decoder) kUint32(f *codecFnInfo, rv reflect.Value) {
	urv := (*unsafeReflectValue)(unsafe.Pointer(&rv))
	*(*uint32)(urv.ptr) = uint32(d.d.DecodeUint(32))
}

func (d *Decoder) kUint64(f *codecFnInfo, rv reflect.Value) {
	urv := (*unsafeReflectValue)(unsafe.Pointer(&rv))
	*(*uint64)(urv.ptr) = d.d.DecodeUint(64)
}

// ------------

// func rt2id(rt reflect.Type) uintptr {
// 	return uintptr(((*unsafeIntf)(unsafe.Pointer(&rt))).word)
// 	// var i interface{} = rt
// 	// // ui := (*unsafeIntf)(unsafe.Pointer(&i))
// 	// return ((*unsafeIntf)(unsafe.Pointer(&i))).word
// }

// func rv2i(rv reflect.Value) interface{} {
// 	urv := (*unsafeReflectValue)(unsafe.Pointer(&rv))
// 	// non-reference type: already indir
// 	// reference type: depend on flagIndir property ('cos maybe was double-referenced)
// 	// const (unsafeRvFlagKindMask    = 1<<5 - 1 , unsafeRvFlagIndir       = 1 << 7 )
// 	// rvk := reflect.Kind(urv.flag & (1<<5 - 1))
// 	// if (rvk == reflect.Chan ||
// 	// 	rvk == reflect.Func ||
// 	// 	rvk == reflect.Interface ||
// 	// 	rvk == reflect.Map ||
// 	// 	rvk == reflect.Ptr ||
// 	// 	rvk == reflect.UnsafePointer) && urv.flag&(1<<8) != 0 {
// 	// 	fmt.Printf(">>>>> ---- double indirect reference: %v, %v\n", rvk, rv.Type())
// 	// 	return *(*interface{})(unsafe.Pointer(&unsafeIntf{word: *(*unsafe.Pointer)(urv.ptr), typ: urv.typ}))
// 	// }
// 	if urv.flag&(1<<5-1) == uintptr(reflect.Map) && urv.flag&(1<<7) != 0 {
// 		// fmt.Printf(">>>>> ---- double indirect reference: %v, %v\n", rvk, rv.Type())
// 		return *(*interface{})(unsafe.Pointer(&unsafeIntf{word: *(*unsafe.Pointer)(urv.ptr), typ: urv.typ}))
// 	}
// 	// fmt.Printf(">>>>> ++++ direct reference: %v, %v\n", rvk, rv.Type())
// 	return *(*interface{})(unsafe.Pointer(&unsafeIntf{word: urv.ptr, typ: urv.typ}))
// }

// const (
// 	unsafeRvFlagKindMask    = 1<<5 - 1
// 	unsafeRvKindDirectIface = 1 << 5
// 	unsafeRvFlagIndir       = 1 << 7
// 	unsafeRvFlagAddr        = 1 << 8
// 	unsafeRvFlagMethod      = 1 << 9

// 	_USE_RV_INTERFACE bool = false
// 	_UNSAFE_RV_DEBUG       = true
// )

// type unsafeRtype struct {
// 	_    [2]uintptr
// 	_    uint32
// 	_    uint8
// 	_    uint8
// 	_    uint8
// 	kind uint8
// 	_    [2]uintptr
// 	_    int32
// }

// func _rv2i(rv reflect.Value) interface{} {
// 	// Note: From use,
// 	//   - it's never an interface
// 	//   - the only calls here are for ifaceIndir types.
// 	//     (though that conditional is wrong)
// 	//     To know for sure, we need the value of t.kind (which is not exposed).
// 	//
// 	// Need to validate the path: type is indirect ==> only value is indirect ==> default (value is direct)
// 	//    - Type indirect, Value indirect: ==> numbers, boolean, slice, struct, array, string
// 	//    - Type Direct,   Value indirect: ==> map???
// 	//    - Type Direct,   Value direct:   ==> pointers, unsafe.Pointer, func, chan, map
// 	//
// 	// TRANSLATES TO:
// 	//    if typeIndirect { } else if valueIndirect { } else { }
// 	//
// 	// Since we don't deal with funcs, then "flagNethod" is unset, and can be ignored.

// 	if _USE_RV_INTERFACE {
// 		return rv.Interface()
// 	}
// 	urv := (*unsafeReflectValue)(unsafe.Pointer(&rv))

// 	// if urv.flag&unsafeRvFlagMethod != 0 || urv.flag&unsafeRvFlagKindMask == uintptr(reflect.Interface) {
// 	// 	println("***** IS flag method or interface: delegating to rv.Interface()")
// 	// 	return rv.Interface()
// 	// }

// 	// if urv.flag&unsafeRvFlagKindMask == uintptr(reflect.Interface) {
// 	// 	println("***** IS Interface: delegate to rv.Interface")
// 	// 	return rv.Interface()
// 	// }
// 	// if urv.flag&unsafeRvFlagKindMask&unsafeRvKindDirectIface == 0 {
// 	// 	if urv.flag&unsafeRvFlagAddr == 0 {
// 	// 		println("***** IS ifaceIndir typ")
// 	// 		// ui := unsafeIntf{word: urv.ptr, typ: urv.typ}
// 	// 		// return *(*interface{})(unsafe.Pointer(&ui))
// 	// 		// return *(*interface{})(unsafe.Pointer(&unsafeIntf{word: urv.ptr, typ: urv.typ}))
// 	// 	}
// 	// } else if urv.flag&unsafeRvFlagIndir != 0 {
// 	// 	println("***** IS flagindir")
// 	// 	// return *(*interface{})(unsafe.Pointer(&unsafeIntf{word: *(*unsafe.Pointer)(urv.ptr), typ: urv.typ}))
// 	// } else {
// 	// 	println("***** NOT flagindir")
// 	// 	return *(*interface{})(unsafe.Pointer(&unsafeIntf{word: urv.ptr, typ: urv.typ}))
// 	// }
// 	// println("***** default: delegate to rv.Interface")

// 	urt := (*unsafeRtype)(unsafe.Pointer(urv.typ))
// 	if _UNSAFE_RV_DEBUG {
// 		fmt.Printf(">>>> start: %v: ", rv.Type())
// 		fmt.Printf("%v - %v\n", *urv, *urt)
// 	}
// 	if urt.kind&unsafeRvKindDirectIface == 0 {
// 		if _UNSAFE_RV_DEBUG {
// 			fmt.Printf("**** +ifaceIndir type: %v\n", rv.Type())
// 		}
// 		// println("***** IS ifaceIndir typ")
// 		// if true || urv.flag&unsafeRvFlagAddr == 0 {
// 		// 	// println("    ***** IS NOT addr")
// 		return *(*interface{})(unsafe.Pointer(&unsafeIntf{word: urv.ptr, typ: urv.typ}))
// 		// }
// 	} else if urv.flag&unsafeRvFlagIndir != 0 {
// 		if _UNSAFE_RV_DEBUG {
// 			fmt.Printf("**** +flagIndir type: %v\n", rv.Type())
// 		}
// 		// println("***** IS flagindir")
// 		return *(*interface{})(unsafe.Pointer(&unsafeIntf{word: *(*unsafe.Pointer)(urv.ptr), typ: urv.typ}))
// 	} else {
// 		if _UNSAFE_RV_DEBUG {
// 			fmt.Printf("**** -flagIndir type: %v\n", rv.Type())
// 		}
// 		// println("***** NOT flagindir")
// 		return *(*interface{})(unsafe.Pointer(&unsafeIntf{word: urv.ptr, typ: urv.typ}))
// 	}
// 	// println("***** default: delegating to rv.Interface()")
// 	// return rv.Interface()
// }

// var staticM0 = make(map[string]uint64)
// var staticI0 = (int32)(-5)

// func staticRv2iTest() {
// 	i0 := (int32)(-5)
// 	m0 := make(map[string]uint16)
// 	m0["1"] = 1
// 	for _, i := range []interface{}{
// 		(int)(7),
// 		(uint)(8),
// 		(int16)(-9),
// 		(uint16)(19),
// 		(uintptr)(77),
// 		(bool)(true),
// 		float32(-32.7),
// 		float64(64.9),
// 		complex(float32(19), 5),
// 		complex(float64(-32), 7),
// 		[4]uint64{1, 2, 3, 4},
// 		(chan<- int)(nil), // chan,
// 		rv2i,              // func
// 		io.Writer(ioutil.Discard),
// 		make(map[string]uint),
// 		(map[string]uint)(nil),
// 		staticM0,
// 		m0,
// 		&m0,
// 		i0,
// 		&i0,
// 		&staticI0,
// 		&staticM0,
// 		[]uint32{6, 7, 8},
// 		"abc",
// 		Raw{},
// 		RawExt{},
// 		&Raw{},
// 		&RawExt{},
// 		unsafe.Pointer(&i0),
// 	} {
// 		i2 := rv2i(reflect.ValueOf(i))
// 		eq := reflect.DeepEqual(i, i2)
// 		fmt.Printf(">>>> %v == %v? %v\n", i, i2, eq)
// 	}
// 	// os.Exit(0)
// }

// func init() {
// 	staticRv2iTest()
// }

// func rv2i(rv reflect.Value) interface{} {
// 	if _USE_RV_INTERFACE || rv.Kind() == reflect.Interface || rv.CanAddr() {
// 		return rv.Interface()
// 	}
// 	// var i interface{}
// 	// ui := (*unsafeIntf)(unsafe.Pointer(&i))
// 	var ui unsafeIntf
// 	urv := (*unsafeReflectValue)(unsafe.Pointer(&rv))
// 	// fmt.Printf("urv: flag: %b, typ: %b, ptr: %b\n", urv.flag, uintptr(urv.typ), uintptr(urv.ptr))
// 	if (urv.flag&unsafeRvFlagKindMask)&unsafeRvKindDirectIface == 0 {
// 		if urv.flag&unsafeRvFlagAddr != 0 {
// 			println("***** indirect and addressable! Needs typed move - delegate to rv.Interface()")
// 			return rv.Interface()
// 		}
// 		println("****** indirect type/kind")
// 		ui.word = urv.ptr
// 	} else if urv.flag&unsafeRvFlagIndir != 0 {
// 		println("****** unsafe rv flag indir")
// 		ui.word = *(*unsafe.Pointer)(urv.ptr)
// 	} else {
// 		println("****** default: assign prt to word directly")
// 		ui.word = urv.ptr
// 	}
// 	// ui.word = urv.ptr
// 	ui.typ = urv.typ
// 	// fmt.Printf("(pointers) ui.typ: %p, word: %p\n", ui.typ, ui.word)
// 	// fmt.Printf("(binary)   ui.typ: %b, word: %b\n", uintptr(ui.typ), uintptr(ui.word))
// 	return *(*interface{})(unsafe.Pointer(&ui))
// 	// return i
// }