// Copyright 2014 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package atomic

import (
	
)

// A Value provides an atomic load and store of a consistently typed value.
// The zero value for a Value returns nil from Load.
// Once Store has been called, a Value must not be copied.
//
// A Value must not be copied after first use.
type Value struct {
	v interface{}
}

// ifaceWords is interface{} internal representation.
type ifaceWords struct {
	typ  unsafe.Pointer
	data unsafe.Pointer
}

// Load returns the value set by the most recent Store.
// It returns nil if there has been no call to Store for this Value.
func ( *Value) () ( interface{}) {
	 := (*ifaceWords)(unsafe.Pointer())
	 := LoadPointer(&.typ)
	if  == nil || uintptr() == ^uintptr(0) {
		// First store not yet completed.
		return nil
	}
	 := LoadPointer(&.data)
	 := (*ifaceWords)(unsafe.Pointer(&))
	.typ = 
	.data = 
	return
}

// Store sets the value of the Value to x.
// All calls to Store for a given Value must use values of the same concrete type.
// Store of an inconsistent type panics, as does Store(nil).
func ( *Value) ( interface{}) {
	if  == nil {
		panic("sync/atomic: store of nil value into Value")
	}
	 := (*ifaceWords)(unsafe.Pointer())
	 := (*ifaceWords)(unsafe.Pointer(&))
	for {
		 := LoadPointer(&.typ)
		if  == nil {
			// Attempt to start first store.
			// Disable preemption so that other goroutines can use
			// active spin wait to wait for completion; and so that
			// GC does not see the fake type accidentally.
			runtime_procPin()
			if !CompareAndSwapPointer(&.typ, nil, unsafe.Pointer(^uintptr(0))) {
				runtime_procUnpin()
				continue
			}
			// Complete first store.
			StorePointer(&.data, .data)
			StorePointer(&.typ, .typ)
			runtime_procUnpin()
			return
		}
		if uintptr() == ^uintptr(0) {
			// First store in progress. Wait.
			// Since we disable preemption around the first store,
			// we can wait with active spinning.
			continue
		}
		// First store completed. Check type and overwrite data.
		if  != .typ {
			panic("sync/atomic: store of inconsistently typed value into Value")
		}
		StorePointer(&.data, .data)
		return
	}
}

// Swap stores new into Value and returns the previous value. It returns nil if
// the Value is empty.
//
// All calls to Swap for a given Value must use values of the same concrete
// type. Swap of an inconsistent type panics, as does Swap(nil).
func ( *Value) ( interface{}) ( interface{}) {
	if  == nil {
		panic("sync/atomic: swap of nil value into Value")
	}
	 := (*ifaceWords)(unsafe.Pointer())
	 := (*ifaceWords)(unsafe.Pointer(&))
	for {
		 := LoadPointer(&.typ)
		if  == nil {
			// Attempt to start first store.
			// Disable preemption so that other goroutines can use
			// active spin wait to wait for completion; and so that
			// GC does not see the fake type accidentally.
			runtime_procPin()
			if !CompareAndSwapPointer(&.typ, nil, unsafe.Pointer(^uintptr(0))) {
				runtime_procUnpin()
				continue
			}
			// Complete first store.
			StorePointer(&.data, .data)
			StorePointer(&.typ, .typ)
			runtime_procUnpin()
			return nil
		}
		if uintptr() == ^uintptr(0) {
			// First store in progress. Wait.
			// Since we disable preemption around the first store,
			// we can wait with active spinning.
			continue
		}
		// First store completed. Check type and overwrite data.
		if  != .typ {
			panic("sync/atomic: swap of inconsistently typed value into Value")
		}
		 := (*ifaceWords)(unsafe.Pointer(&))
		.typ, .data = .typ, SwapPointer(&.data, .data)
		return 
	}
}

// CompareAndSwapPointer executes the compare-and-swap operation for the Value.
//
// All calls to CompareAndSwap for a given Value must use values of the same
// concrete type. CompareAndSwap of an inconsistent type panics, as does
// CompareAndSwap(old, nil).
func ( *Value) (,  interface{}) ( bool) {
	if  == nil {
		panic("sync/atomic: compare and swap of nil value into Value")
	}
	 := (*ifaceWords)(unsafe.Pointer())
	 := (*ifaceWords)(unsafe.Pointer(&))
	 := (*ifaceWords)(unsafe.Pointer(&))
	if .typ != nil && .typ != .typ {
		panic("sync/atomic: compare and swap of inconsistently typed values")
	}
	for {
		 := LoadPointer(&.typ)
		if  == nil {
			if  != nil {
				return false
			}
			// Attempt to start first store.
			// Disable preemption so that other goroutines can use
			// active spin wait to wait for completion; and so that
			// GC does not see the fake type accidentally.
			runtime_procPin()
			if !CompareAndSwapPointer(&.typ, nil, unsafe.Pointer(^uintptr(0))) {
				runtime_procUnpin()
				continue
			}
			// Complete first store.
			StorePointer(&.data, .data)
			StorePointer(&.typ, .typ)
			runtime_procUnpin()
			return true
		}
		if uintptr() == ^uintptr(0) {
			// First store in progress. Wait.
			// Since we disable preemption around the first store,
			// we can wait with active spinning.
			continue
		}
		// First store completed. Check type and overwrite data.
		if  != .typ {
			panic("sync/atomic: compare and swap of inconsistently typed value into Value")
		}
		// Compare old and current via runtime equality check.
		// This allows value types to be compared, something
		// not offered by the package functions.
		// CompareAndSwapPointer below only ensures vp.data
		// has not changed since LoadPointer.
		 := LoadPointer(&.data)
		var  interface{}
		(*ifaceWords)(unsafe.Pointer(&)).typ = 
		(*ifaceWords)(unsafe.Pointer(&)).data = 
		if  !=  {
			return false
		}
		return CompareAndSwapPointer(&.data, , .data)
	}
}

// Disable/enable preemption, implemented in runtime.
func runtime_procPin()
func runtime_procUnpin()