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util: improve readability of normalizeEncoding
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* Improve readability of util.normalizeEncoding
  and add some comments
* Add a benchmark for util.normalizeEncoding

PR-URL: #10439
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Andreas Madsen <amwebdk@gmail.com>
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joyeecheung authored and MylesBorins committed Mar 9, 2017
1 parent c086bdc commit 5321300
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Showing 2 changed files with 75 additions and 4 deletions.
65 changes: 65 additions & 0 deletions benchmark/util/normalize-encoding.js
Original file line number Diff line number Diff line change
@@ -0,0 +1,65 @@
'use strict';

const common = require('../common.js');
const assert = require('assert');

const groupedInputs = {
group_common: ['undefined', 'utf8', 'utf-8', 'base64', 'binary', 'latin1'],
group_upper: ['UTF-8', 'UTF8', 'UCS2', 'UTF-16LE', 'UTF16LE', 'BASE64'],
group_uncommon: [ 'foo', '1', 'false', 'undefined', '[]'],
group_misc: ['', 'utf16le', 'usc2', 'hex', 'HEX', 'BINARY']
};

const inputs = [
'', 'utf8', 'utf-8', 'UTF-8',
'UTF8', 'Utf8', 'uTf-8', 'utF-8', 'ucs2',
'UCS2', 'utf16le', 'utf-16le', 'UTF-16LE', 'UTF16LE',
'binary', 'BINARY', 'latin1', 'base64', 'BASE64',
'hex', 'HEX', 'foo', '1', 'false', 'undefined', '[]'];

const bench = common.createBenchmark(main, {
input: inputs.concat(Object.keys(groupedInputs)),
n: [1e5]
}, {
flags: '--expose-internals'
});

function getInput(input) {
switch (input) {
case 'group_common':
return groupedInputs.group_common;
case 'group_upper':
return groupedInputs.group_upper;
case 'group_uncommon':
return groupedInputs.group_uncommon;
case 'group_misc':
return groupedInputs.group_misc;
case '1':
return [1];
case 'false':
return [false];
case 'undefined':
return [undefined];
case '[]':
return [[]];
default:
return [input];
}
}

function main(conf) {
const normalizeEncoding = require('internal/util').normalizeEncoding;

const n = conf.n | 0;
const inputs = getInput(conf.input);
var noDead = '';

bench.start();
for (var i = 0; i < n; i += 1) {
for (var j = 0; j < inputs.length; ++j) {
noDead = normalizeEncoding(inputs[j]);
}
}
bench.end(n);
assert.ok(noDead === undefined || noDead.length > 0);
}
14 changes: 10 additions & 4 deletions lib/internal/util.js
Original file line number Diff line number Diff line change
Expand Up @@ -132,10 +132,16 @@ exports.cachedResult = function cachedResult(fn) {
};

exports.kIsEncodingSymbol = Symbol('node.isEncoding');

// The loop should only run at most twice, retrying with lowercased enc
// if there is no match in the first pass.
// We use a loop instead of branching to retry with a helper
// function in order to avoid the performance hit.
// Return undefined if there is no match.
exports.normalizeEncoding = function normalizeEncoding(enc) {
if (!enc) return 'utf8';
var low;
for (;;) {
var retried;
while (true) {
switch (enc) {
case 'utf8':
case 'utf-8':
Expand All @@ -153,9 +159,9 @@ exports.normalizeEncoding = function normalizeEncoding(enc) {
case 'hex':
return enc;
default:
if (low) return; // undefined
if (retried) return; // undefined
enc = ('' + enc).toLowerCase();
low = true;
retried = true;
}
}
};
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