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Deian Stefan
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0 parents  commit ef29f49

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‎lib/low-level.js

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var assert = require('assert');
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var util = require('util');
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// The heap (not yet initialized properly)
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var heap = new Array(1000);
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// Heap objects
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function HeapObject(next) {
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if (!this instanceof HeapObject) {
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return new HeapObject(next);
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}
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assert(isPointer(next));
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// Pointers to other objects
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this.fst = null;
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this.snd = null;
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this._free = true; // Is this object free?
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this._next = next; // Next object on free list
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this._refcount = 0;
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this._traced = false;
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}
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exports.HeapObject = HeapObject;
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function isHeapObject(obj) {
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return (obj instanceof HeapObject);
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}
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// Low level pointers
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function Ptr(idx) {
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if (!this instanceof Ptr) {
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return new Ptr(idx);
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}
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assert(idx < heap.length);
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this._idx = idx;
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}
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exports.Ptr = Ptr;
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Ptr.prototype.equals = function(other) {
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if (other instanceof Ptr) {
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return (this._idx === other._idx);
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}
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return false;
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};
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Ptr.prototype.deref = function() {
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// Task 1 {{
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// }}
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};
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Ptr.prototype.write = function(v) {
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if (!isHeapObject(v)) {
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throw new Error('Can only write HeapObject to the heap');
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}
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// Task 1 {{
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// }}
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};
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Ptr.prototype.toString = function() {
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return this._idx.toString();
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};
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function isPointer(p) {
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return (p instanceof Ptr) || p === null;
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}
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exports.isPointer = isPointer;
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// Initialize the heap
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function initHeap() {
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// Task 2(a) {{
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// }}
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}
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var free_list_head = new Ptr(0);
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var free_list_tail = new Ptr(heap.length - 1);
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initHeap();
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// Exposed function for iterating over whole heap:
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exports.heapIterate = function(f) {
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for (var i = 0; i < heap.length - 1; i++) {
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f(new Ptr(i));
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}
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};
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// Memory allocation
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function malloc() {
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// Task 2(b) {{
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// }}
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}
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exports.malloc = malloc;
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function free(ptr) {
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assert(isPointer(ptr));
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if (ptr === null) {
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throw new Error('Cannot free a null pointer');
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}
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// Task 2(b) {{
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// }}
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}
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exports.free = free;
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// An easier way of freeing the object pointed to by this pointer:
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Ptr.prototype.free = function() { free(this); };
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// Diagnostics
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function showUsage() {
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var total = heap.length;
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var free = 1;
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var ptr = free_list_head;
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while (!ptr.equals(free_list_tail)) {
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free++;
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ptr = ptr.deref()._next;
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}
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return '[ free: ' + free +
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', used: ' + (total - free) +
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', total: ' + total + ' ]';
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}
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exports.showUsage = showUsage;
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exports.showHeap = function(type) {
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var res = [];
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for (var i = 0; i < heap.length; i++) {
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var obj = heap[i];
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var fst = obj.fst ? obj.fst._idx : null;
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var snd = obj.snd ? obj.snd._idx : null;
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if (!obj._free) {
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switch (type) {
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case 'ref':
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res.push(util.format('{%d @ [%d] : (%s, %s)}', i,
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obj._refcount, fst, snd));
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break;
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case 'trace':
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res.push(util.format('{%d @ [%s] : (%s, %s)}', i,
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obj._traced ? '*' : '-', fst, snd));
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break;
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default:
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res.push(util.format('{%d @ [%d|%s] : (%s, %s)}', i,
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obj._refcount,
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obj._traced ? '*' : '-', fst, snd));
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break;
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};
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}
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}
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return '[ ' + res.toString() + ' ]';
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};

‎lib/marksweep.js

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var assert = require('assert');
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var util = require('util');
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var ll = require('./low-level');
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var HeapObject = ll.HeapObject;
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var Ptr = ll.Ptr;
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Ptr.prototype.setfst = function(x) {
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assert(ll.isPointer(x));
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this.deref().fst = x;
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};
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Ptr.prototype.setsnd = function(x) {
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assert(ll.isPointer(x));
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this.deref().snd = x;
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};
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Ptr.prototype.withfst = function(f) {
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// Task 4(a) {{
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// }}
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};
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Ptr.prototype.withsnd = function(f) {
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// Task 4(a) {{
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// }}
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};
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function create(fst, snd, f) {
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// Task 4(a) {{
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// }}
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}
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exports.create = create;
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// Roots
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var root = { root: null, stack: [] };
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function setroot(ptr) {
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assert(ll.isPointer(ptr));
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root.root = ptr;
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}
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exports.setroot = setroot;
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function withroot(f) {
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// Task 4(a) {{
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// }}
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};
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exports.withroot = withroot;
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exports.showRoots = function () {
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var a = root.stack.map(function(e) { return e.toString() });
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return util.format('[%s%s%s]', root.root ? root.root : ''
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, (root.root && a.length > 0) ? ',' : ''
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, a);
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}
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// GC
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function mark() {
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// Task 4(b) {{
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// }}
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}
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exports.mark = mark;
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function sweep() {
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ll.heapIterate(function (ptr) {
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// Task 4(b) {{
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// }}
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});
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}
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exports.sweep = sweep;
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function gc() {
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mark();
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sweep();
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}
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exports.gc = gc;
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/* Task 4(c):
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*/

‎lib/refcount.js

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var assert = require('assert');
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var ll = require('./low-level');
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var HeapObject = ll.HeapObject;
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var Ptr = ll.Ptr;
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Ptr.prototype.addref = function() {
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// Task 3(a){{
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// }}
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};
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Ptr.prototype.release = function() {
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// Task 3(a){{
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// }}
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};
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Ptr.prototype.setfst = function(x) {
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assert(ll.isPointer(x));
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// Task 3(b){{
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// }}
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};
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Ptr.prototype.setsnd = function(x) {
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assert(ll.isPointer(x));
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// Task 3(b){{
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// }}
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};
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Ptr.prototype.withfst = function(f) {
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// Task 3(b){{
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// }}
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};
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Ptr.prototype.withsnd = function(f) {
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// Task 3(b){{
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// }}
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};
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function create(fst, snd, f) {
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// Task 3(b){{
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// }}
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}
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exports.create = create;
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// Roots
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var root = null;
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function setroot(ptr) {
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// Task 3(b){{
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// }}
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}
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exports.setroot = setroot;
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function withroot(f) {
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// Task 3(b){{
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// }}
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}
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exports.withroot = withroot;

‎task2a.js

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var ll = require('./lib/low-level');
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console.log(ll.showUsage());

‎task2b.js

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var ll = require('./lib/low-level');
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console.log('init: %s', ll.showUsage());
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var ptr = ll.malloc();
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console.log('after 1 malloc: %s', ll.showUsage());
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ll.free(ptr);
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console.log('after free: %s', ll.showUsage());
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try {
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ll.free(ptr);
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} catch (e) {
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console.log('Failed to free again: %s', e);
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}
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try {
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while (true) {
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ll.malloc();
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}
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} catch (e) {
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console.log('Infinite alloc stopped: %s', e);
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}
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console.log('end: %s', ll.showUsage());

‎task3a.js

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var ll = require('./lib/low-level');
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var rc = require('./lib/refcount');
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// create a new object
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var ptr1 = ll.malloc();
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ptr1.addref();
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// set the object's fst field to a newly allocated pointer
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ptr1.deref().fst = ll.malloc();
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ptr1.deref().fst.addref();
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console.log(ll.showUsage());
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console.log('1 addref: %s', ll.showHeap('ref'));
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var ptr2 = ptr1;
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ptr2.addref();
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console.log('2 addref: %s', ll.showHeap('ref'));
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ptr1.release();
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console.log(ll.showHeap('ref'));
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console.log('1 release: %s', ll.showHeap('ref'));
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ptr2.release();
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console.log('2 release: %s', ll.showHeap('ref'));
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console.log(ll.showUsage());

‎task3b-create-1.js

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var ll = require('./lib/low-level');
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var rc = require('./lib/refcount');
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rc.create(null, null, function (ptr1) {
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console.log('a: create ptr1: %s', ll.showHeap('ref'));
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rc.create(null, null, function (ptr1_fst) {
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console.log('b: create fst: %s', ll.showHeap('ref'));
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ptr1.setfst(ptr1_fst);
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console.log('b: ptr1.setfst(fst): %s', ll.showHeap('ref'));
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});
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console.log('a: %s', ll.showHeap('ref'));
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});
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console.log('end: %s', ll.showHeap('ref'));

‎task3b-create-2.js

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var ll = require('./lib/low-level');
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var rc = require('./lib/refcount');
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rc.create(null, null, function (ptr1_fst) {
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console.log('a: create fst : %s', ll.showHeap('ref'));
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rc.create(ptr1_fst, null, function (ptr1) {
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console.log('b: create ptr: %s', ll.showHeap('ref'));
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});
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console.log('a: %s', ll.showHeap('ref'));
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});
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console.log('end: %s', ll.showHeap('ref'));

‎task3b-cycle.js

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var ll = require('./lib/low-level');
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var rc = require('./lib/refcount');
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rc.create(null, null, function (ptr1_fst) {
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console.log('a: create fst : %s', ll.showHeap('ref'));
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rc.create(ptr1_fst, null, function (ptr1) {
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console.log('b: create ptr: %s', ll.showHeap('ref'));
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ptr1_fst.setfst(ptr1);
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console.log('b: fst.setfst(ptr): %s', ll.showHeap('ref'));
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});
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console.log('a: %s', ll.showHeap('ref'));
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});
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console.log('end: %s', ll.showHeap('ref'));

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