You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
109 lines
2.9 KiB
109 lines
2.9 KiB
//! 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; |
|
|
|
})));
|
|
|