not-modified/notModified.js

HTTP cache validator

var crypto = require('crypto');
var fs = require('fs');

function notModified(req, res, mtime) {
	var etag = (mtime - 0).toString(16);
	return notModified.compare(req, res, etag);
}

notModified.compare = function(req, res, etag) {
	res.setHeader('ETag', '"' + etag + '"');
	var ifnonematch = req.headers['if-none-match'];
	if (ifnonematch && ifnonematch.indexOf(etag) != -1) {
		res.statusCode = 304;
		return true;
	}
	return false;
};

notModified.ex = function(req, res, files, data, cb) {
	if (!files) {
		files = [];
	} else if (files.constructor == String) {
		files = [files];
	}

	var hash = crypto.createHash('md5');
	files.map(function(file) {
		hash.update(notModified.fileHash(file));
	});

	data && hash.update(JSON.stringify(data), 'utf8');
	var etag = hash.digest('hex');
	cb(null, notModified.compare(req, res, etag));
};

notModified.fileHash = function(file) {
	if (notModified.fileHashCache[file])
		return notModified.fileHashCache[file];

	notModified.fileHashCache[file] = crypto.createHash('md5').update(fs.readFileSync(file)).digest();
	return notModified.fileHashCache[file];
};

notModified.fileHashCache = {};

module.exports = notModified;