/*! * compression * Copyright(c) 2010 Sencha Inc. * Copyright(c) 2011 TJ Holowaychuk * Copyright(c) 2014 Jonathan Ong * Copyright(c) 2014-2015 Douglas Christopher Wilson * MIT Licensed */ 'use strict' /** * Module dependencies. * @private */ var accepts = require('accepts') var Buffer = require('safe-buffer').Buffer var bytes = require('bytes') var compressible = require('compressible') var debug = require('debug')('compression') var onHeaders = require('on-headers') var vary = require('vary') var zlib = require('zlib') /** * Module exports. */ module.exports = compression module.exports.filter = shouldCompress /** * Module variables. * @private */ var cacheControlNoTransformRegExp = /(?:^|,)\s*?no-transform\s*?(?:,|$)/ /** * Compress response data with gzip / deflate. * * @param {Object} [options] * @return {Function} middleware * @public */ function compression (options) { var opts = options || {} // options var filter = opts.filter || shouldCompress var threshold = bytes.parse(opts.threshold) if (threshold == null) { threshold = 1024 } return function compression (req, res, next) { var ended = false var length var listeners = [] var stream var _end = res.end var _on = res.on var _write = res.write // flush res.flush = function flush () { if (stream) { stream.flush() } } // proxy res.write = function write (chunk, encoding) { if (ended) { return false } if (!this._header) { this._implicitHeader() } return stream ? stream.write(Buffer.from(chunk, encoding)) : _write.call(this, chunk, encoding) } res.end = function end (chunk, encoding) { if (ended) { return false } if (!this._header) { // estimate the length if (!this.getHeader('Content-Length')) { length = chunkLength(chunk, encoding) } this._implicitHeader() } if (!stream) { return _end.call(this, chunk, encoding) } // mark ended ended = true // write Buffer for Node.js 0.8 return chunk ? stream.end(Buffer.from(chunk, encoding)) : stream.end() } res.on = function on (type, listener) { if (!listeners || type !== 'drain') { return _on.call(this, type, listener) } if (stream) { return stream.on(type, listener) } // buffer listeners for future stream listeners.push([type, listener]) return this } function nocompress (msg) { debug('no compression: %s', msg) addListeners(res, _on, listeners) listeners = null } onHeaders(res, function onResponseHeaders () { // determine if request is filtered if (!filter(req, res)) { nocompress('filtered') return } // determine if the entity should be transformed if (!shouldTransform(req, res)) { nocompress('no transform') return } // vary vary(res, 'Accept-Encoding') // content-length below threshold if (Number(res.getHeader('Content-Length')) < threshold || length < threshold) { nocompress('size below threshold') return } var encoding = res.getHeader('Content-Encoding') || 'identity' // already encoded if (encoding !== 'identity') { nocompress('already encoded') return } // head if (req.method === 'HEAD') { nocompress('HEAD request') return } // compression method var accept = accepts(req) var method = accept.encoding(['gzip', 'deflate', 'identity']) // we really don't prefer deflate if (method === 'deflate' && accept.encoding(['gzip'])) { method = accept.encoding(['gzip', 'identity']) } // negotiation failed if (!method || method === 'identity') { nocompress('not acceptable') return } // compression stream debug('%s compression', method) stream = method === 'gzip' ? zlib.createGzip(opts) : zlib.createDeflate(opts) // add buffered listeners to stream addListeners(stream, stream.on, listeners) // header fields res.setHeader('Content-Encoding', method) res.removeHeader('Content-Length') // compression stream.on('data', function onStreamData (chunk) { if (_write.call(res, chunk) === false) { stream.pause() } }) stream.on('end', function onStreamEnd () { _end.call(res) }) _on.call(res, 'drain', function onResponseDrain () { stream.resume() }) }) next() } } /** * Add bufferred listeners to stream * @private */ function addListeners (stream, on, listeners) { for (var i = 0; i < listeners.length; i++) { on.apply(stream, listeners[i]) } } /** * Get the length of a given chunk */ function chunkLength (chunk, encoding) { if (!chunk) { return 0 } return !Buffer.isBuffer(chunk) ? Buffer.byteLength(chunk, encoding) : chunk.length } /** * Default filter function. * @private */ function shouldCompress (req, res) { var type = res.getHeader('Content-Type') if (type === undefined || !compressible(type)) { debug('%s not compressible', type) return false } return true } /** * Determine if the entity should be transformed. * @private */ function shouldTransform (req, res) { var cacheControl = res.getHeader('Cache-Control') // Don't compress for Cache-Control: no-transform // https://tools.ietf.org/html/rfc7234#section-5.2.2.4 return !cacheControl || !cacheControlNoTransformRegExp.test(cacheControl) }