MPSC lock free queue

[C-implemented queue] (http://www.1024cores.net/home/lock-free-algorithms/queues/non-intrusive-mpsc-node-based-queue)

The following is an MPSC queue implemented by akka.

PS: the criterion for determining the end of a chain head in the Code is that the position of the added element is the end of the chain, which is in conflict with the name in the code.

PPS: single customer does not need to consider the consumer's competitive status at the same time

/*** Copyright (c) 2009-2014 typesafe Inc. */package akka. dispatch; import akka. util. unsafe; import Java. util. concurrent. atomic. atomicreference;/*** lock-free MPSC linked queue implementation based on Dmitriy vyukov's non-intrusive MPSC queue: * http://www.1024cores.net/home/lock-free-algorithms/queues/non-intrusive-mpsc-node-based-queue */@ suppresswarnings ("serial") Public Abstract class abstractnodequeue <t> extends atomicreference <abstractnodequeue. node <t> {// extends atomicreference for the "head" slot (which is the one that is appended) since unsafe does not expose xchg operation intrinsically // The value of atomicreference corresponds to the tail node of the queue @ suppresswarnings ("UNUSED") Private volatile node <t> _ blank; protected abstractnodequeue () {final node <t> N = ne W node <t> (); _ taildonotcallmedirectly = N; // initialize the root node, value = NULL, chainhead! Set (n); // initialize node at the end of the chain }/**!!! There is a copy of this Code in pollnode ()!!! * // @ Suppresswarnings ("unchecked") protected final node <t> peeknode () {// chain header (;;) {final node <t> tail = (node <t>) unsafe. instance. getobjectvolatile (this, tailoffset); final node <t> next = tail. next (); If (next! = NULL | get () = tail) // next! = NULL indicates that it is not the root node and is in the linked list; get () = tail indicates that there is no node in the entire linked list, and only return next ;}} public final t PEEK () {final node <t> N = peeknode (); Return (n! = NULL )? N. value: NULL;} public final void add (final T value) {final node <t> N = new node <t> (value); getandset (n ). setnext (n); // a classic sentence. Set the value of atomicreference to the latest node, link n to the end of the linked list.} public final void addnode (final node <t> N) {n. setnext (null); getandset (n ). setnext (n);} public final Boolean isempty () {return PEEK () = NULL;} public final int count () {// count is an inaccurate int COUNT = 0; For (node <t> N = peekno De (); n! = NULL; n = n. Next () + + count; return count ;}/**!!! There is a copy of this Code in pollnode ()!!! */Public final t poll () {final node <t> next = peeknode (); If (next = NULL) return NULL; else {final t ret = next. value; next. value = NULL; unsafe. instance. putorderedobject (this, tailoffset, next); // Replace the chain header with return ret; }}@ suppresswarnings ("unchecked") Public final node <t> pollnode () {node <t> tail; node <t> next; For (;) {tail = (node <t>) unsafe. instance. getobjectvolatile (this, tailoffset); n EXT = tail. Next (); If (next! = NULL | get () = tail) break;} If (next = NULL) return NULL; else {tail. value = next. value; next. value = NULL; unsafe. instance. putorderedobject (this, tailoffset, next); Return tail ;}} private final static long tailoffset; static {try {tailoffset = unsafe. instance. objectfieldoffset (abstractnodequeue. class. getdeclaredfield ("_ taildonotcallmedirectly");} catch (throwable t) {Throw new ti Onininitializererror (t) ;}} public static class node <t> {public T value; @ suppresswarnings ("UNUSED") Private volatile node <t> _ nextdonotcallmedirectly; // The next node. Next, directly use unsafe to operate public node () {This (null);} public node (final T value) {This. value = value ;}@ suppresswarnings ("unchecked") Public final node <t> next () {return (node <t>) unsafe. instance. getobjectvolatile (this, nextoffset);} protected final void setnext (final node <t> newnext) {unsafe. instance. putorderedobject (this, nextoffset, newnext);} private final static long nextoffset; static {try {nextoffset = unsafe. instance. objectfieldoffset (node. class. getdeclaredfield ("_ nextdonotcallmedirectly");} catch (throwable t) {Throw new exceptionininitializererror (t );}}}}

MPSC lock free queue