92 lines
2.0 KiB
JavaScript
92 lines
2.0 KiB
JavaScript
/*!
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* on-headers
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* Copyright(c) 2014 Douglas Christopher Wilson
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* MIT Licensed
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*/
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/**
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* Reference to Array slice.
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*/
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var slice = Array.prototype.slice
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/**
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* Execute a listener when a response is about to write headers.
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*
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* @param {Object} res
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* @return {Function} listener
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* @api public
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*/
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module.exports = function onHeaders(res, listener) {
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if (!res) {
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throw new TypeError('argument res is required')
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}
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if (typeof listener !== 'function') {
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throw new TypeError('argument listener must be a function')
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}
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res.writeHead = createWriteHead(res.writeHead, listener)
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}
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function createWriteHead(prevWriteHead, listener) {
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var fired = false;
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// return function with core name and argument list
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return function writeHead(statusCode) {
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// set headers from arguments
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var args = setWriteHeadHeaders.apply(this, arguments);
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// fire listener
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if (!fired) {
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fired = true
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listener.call(this)
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// pass-along an updated status code
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if (typeof args[0] === 'number' && this.statusCode !== args[0]) {
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args[0] = this.statusCode
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args.length = 1
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}
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}
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prevWriteHead.apply(this, args);
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}
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}
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function setWriteHeadHeaders(statusCode) {
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var length = arguments.length
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var headerIndex = length > 1 && typeof arguments[1] === 'string'
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? 2
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: 1
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var headers = length >= headerIndex + 1
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? arguments[headerIndex]
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: undefined
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this.statusCode = statusCode
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// the following block is from node.js core
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if (Array.isArray(headers)) {
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// handle array case
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for (var i = 0, len = headers.length; i < len; ++i) {
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this.setHeader(headers[i][0], headers[i][1])
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}
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} else if (headers) {
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// handle object case
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var keys = Object.keys(headers)
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for (var i = 0; i < keys.length; i++) {
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var k = keys[i]
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if (k) this.setHeader(k, headers[k])
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}
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}
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// copy leading arguments
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var args = new Array(Math.min(length, headerIndex))
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for (var i = 0; i < args.length; i++) {
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args[i] = arguments[i]
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}
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return args
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}
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