Train a fast (FIFO) queue with a rollback mechanism. Behind the scenes it uses 2 arrays to simulate and perform fast shifting and popping operations without using the Array#shift() method..
Train, a fast (FIFO) queue with rollback mechanism.
Behind the scenes, it uses 2 arrays, to simulate and perform fast shifting and popping operations, without using the Array#shift() method.
Array#shift method shows an high loss of performances when the array is very long; for example, on my laptop the bottleneck occurs when I fill an array with more than 2^17 items. It implies that for shorter array lengths, is still possible to use Array#shift.
If you need a simple (LIFO) Stack, try Peela.
$ npm install train [-g]
var Train = require 'train' ;
$ cd train/$ npm test
$ cd train/$ npm run bench
Create an instance, argument within [ ] is optional.
Train Object opt// orObject opt
Default options are listed.
// init queue with some elementshead :// max limit for 'xpush', 'xconcat', 'x..' methodsxlim : Infinity// max size for the rollback queuerlim : Infinity
Don't mess with these properties!
/** Property to get the queue length.** NOTE: Accessors are very slow,* use size() method instead.*/Trainlength : Number/** Property to set the queue size limit.** NOTE: Only #xpush(), #xconcat() are affected by this limit.*/Trainxlim : Number/** Property to set the size limit for the rollback queue.*/Trainrlim : Number/** Property to get current iterator position in the queue.** NOTE: manually changing this value directly affects the* behaviour of iterator methods like #next() and #curr.*/Trainipos : Number/** Property that indicates the current head element* position/index in the queue.** WARNING: private property, don't mess with it.*/Trainhpos : Number/** Property that indicates the current roll position/index* in the head queue.** WARNING: private property, don't mess with it.*/Trainrpos : Number/** Property that indicates if the mechanism of rolling up* is enabled or not. It is set by #rollUp() and unset by* #rollBack() or #rollUp( false ).** WARNING: private property, don't mess with it.*/Trainroll : Boolean/** An array that represents the current head of the queue.** WARNING: private property, don't mess with it.*/Trainqhead : Array/** An array that represents the current tail of queue.** NOTE: private property, don't mess with it.*/Trainqtail : Array/** An array for rollback mechanism.** NOTE: private property, don't mess with it.*/Trainqroll : Array
Arguments within [ ] are optional.
/** Get an element at a certain index.*/Train#get Number index : Object/** Circular get.*/Train#cget Number index : Object/** Return the index of an element in the queue, optionally* starting the search from an offset index.* If element was not found, it returns -1.*/Train#indexOf Object el Number offset : Object/** Evict the first (head) element from the queue.*/Train#shift : Object/** Evict one or multiple elements, if a number k was specified,* it returns an array of K elements, with K <= k.* If k > # size(), all elements are returned.** NOTE: #pop(k) elements is faster than executing #shift() * k times.* NOTE: For popping all elements you could do Train#pop( Infinity )*/Train#pop Number k : Array/** Slice a portion of train queue into a new array,* from begin to end index.** NOTE: Usage is the same as Array#slice method; it* accepts negative indexes and numbers as strings.*/Train#slice Number begin Number end : Array/** Start rolling up.* From now, all items evicted from the queue could be* restored, executing #rollBack().* Disable rollUp passing false.* It returns the current Train instance.** NOTE: For now, there is no implemented mechanism, to* directly limit the roll queue size.*/Train#rollUp Boolean on : Train/** Do rollback; previously evicted items are restored* to the head of queue. Optionally, it is possible to* re-enable rollUp mechanism after the rollback, passing* a true argument.* It returns the current Train instance.*/Train#rollBack Boolean rollUp : Train/** Return current element through the circular iterator.*/Train#curr : Object/** Get the current element through a circular iterator, also* incrementing the iterator counter/position by one; optionally,* it is possible to specify a number as the next iterator* position / index in the queue.*/Train#next Number index : Object/** Push one or multiple objects into the queue. it uses* the same signature as Array#push.* It returns the current number of items.*/Train#push Object obj1 Object obj2 : Number/** Push one or multiple objects into the queue,* Unlike #push, if the addition of elements exceeds the* xlim value, items aren't added but silently dropped.* It returns the current number of items in the queue,* or -1 if the current arguments/items were dropped.*/Train#xpush Object obj1 Object obj2 : Number/** A slightly faster push, ~15% than #push.* It is still possible to increase speed ( bypassing function call )* pushing element(s) directly to the tail of the queue and to calculate* current size, using:** var t = Train()* , size = t.qtail.push( .. ) + t.qhead.length - me.hpos* // or for multiple arguments* , size = t.qtail.apply( t.qtail, [..] ) + t.qhead.length - me.hpos* ;** See Benchmarks.*/Train#fpush Object obj : Number/** Concatenate an Array to the queue.* It returns the current Train instance.** NOTE: It accepts a single argument, that could be also a generic element.*/Train#concat Array array : Train/** Concatenate an Array to the queue.* Unlike #concat, if the addition of elements, contained in the array,* exceeds the xlim value, array is silently dropped.* It returns the current number of items in the queue,* or -1 if the current array was dropped.** NOTE: It accepts a single argument, that could be also a generic element.*/Train#xconcat Array array : Number/** Melt a list of Objects, preferably Train or Arrays to this queue;* all Train queues will be emptied, all Arrays will be concatenated.* Optionally, when boolean 'all' is true, it melts all items contained* in the tlist argument.* It returns the current queue size.** NOTE: When 'all' is set to true, if an item in the tlist is not an* instance of Train or Array, it will be added to the queue as is,* also null, NaN and undefined values.*/Train#melt Array tlist Boolean all : Number/** Get the queue size.*/Train#size : Number/** Empty the queue for default.* If bool is set to false, no action will be done.* It returns the number of elements evicted.*/Train#flush Boolean bool : Number/** Apply a fn to every element of the queue, like Array#forEach;* fn will get 3 arguments: ( Object element, Number index, Number qsize ).** NOTE: on iteration, the size is fixed to the current queue size,* then it is possible to push other elements to the tail, these* added elements are not affected by iteration.*/Train#forEach Function fn Object scope : Train/** Apply a fn to every element of the queue;* fn will get 3 arguments: Object element, Number index, Function done.* After that every fn will have called done(), the callback will be launched* with an err argument ( if any has occurred ) and a number, representing* the total processed / iterated elements in the queue.** If boolean "evict" was set to true, after the last fn call to done(),* the queue will be flushed.** NOTE: when queue size is 0, the callback will be immediately executed* with arguments: ( null, 0 ).** NOTE: on iteration, the size is fixed to the current queue size,* then it is possible to push other elements to the tail, these* added elements are not affected by iteration.*/Train#iterate Function fn Object scope Function cback Boolean evict : Train
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