110 lines
2.9 KiB
JavaScript
110 lines
2.9 KiB
JavaScript
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//! stable.js 0.1.8, https://github.com/Two-Screen/stable
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//! © 2018 Angry Bytes and contributors. MIT licensed.
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(function (global, factory) {
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typeof exports === 'object' && typeof module !== 'undefined' ? module.exports = factory() :
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typeof define === 'function' && define.amd ? define(factory) :
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(global.stable = factory());
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}(this, (function () { 'use strict';
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// A stable array sort, because `Array#sort()` is not guaranteed stable.
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// This is an implementation of merge sort, without recursion.
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var stable = function (arr, comp) {
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return exec(arr.slice(), comp)
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};
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stable.inplace = function (arr, comp) {
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var result = exec(arr, comp);
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// This simply copies back if the result isn't in the original array,
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// which happens on an odd number of passes.
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if (result !== arr) {
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pass(result, null, arr.length, arr);
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}
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return arr
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};
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// Execute the sort using the input array and a second buffer as work space.
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// Returns one of those two, containing the final result.
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function exec(arr, comp) {
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if (typeof(comp) !== 'function') {
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comp = function (a, b) {
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return String(a).localeCompare(b)
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};
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}
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// Short-circuit when there's nothing to sort.
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var len = arr.length;
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if (len <= 1) {
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return arr
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}
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// Rather than dividing input, simply iterate chunks of 1, 2, 4, 8, etc.
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// Chunks are the size of the left or right hand in merge sort.
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// Stop when the left-hand covers all of the array.
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var buffer = new Array(len);
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for (var chk = 1; chk < len; chk *= 2) {
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pass(arr, comp, chk, buffer);
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var tmp = arr;
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arr = buffer;
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buffer = tmp;
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}
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return arr
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}
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// Run a single pass with the given chunk size.
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var pass = function (arr, comp, chk, result) {
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var len = arr.length;
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var i = 0;
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// Step size / double chunk size.
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var dbl = chk * 2;
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// Bounds of the left and right chunks.
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var l, r, e;
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// Iterators over the left and right chunk.
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var li, ri;
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// Iterate over pairs of chunks.
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for (l = 0; l < len; l += dbl) {
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r = l + chk;
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e = r + chk;
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if (r > len) r = len;
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if (e > len) e = len;
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// Iterate both chunks in parallel.
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li = l;
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ri = r;
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while (true) {
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// Compare the chunks.
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if (li < r && ri < e) {
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// This works for a regular `sort()` compatible comparator,
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// but also for a simple comparator like: `a > b`
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if (comp(arr[li], arr[ri]) <= 0) {
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result[i++] = arr[li++];
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}
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else {
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result[i++] = arr[ri++];
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}
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}
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// Nothing to compare, just flush what's left.
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else if (li < r) {
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result[i++] = arr[li++];
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}
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else if (ri < e) {
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result[i++] = arr[ri++];
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}
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// Both iterators are at the chunk ends.
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else {
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break
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}
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}
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}
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};
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return stable;
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})));
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