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