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utils.js
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utils.js
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/**
* Module dependencies.
*/
var mime = require('send').mime;
var crc32 = require('buffer-crc32');
var crypto = require('crypto');
var basename = require('path').basename;
var proxyaddr = require('proxy-addr');
var typer = require('media-typer');
/**
* Return strong ETag for `body`.
*
* @param {String|Buffer} body
* @param {String} [encoding]
* @return {String}
* @api private
*/
exports.etag = function etag(body, encoding){
if (body.length === 0) {
// fast-path empty body
return '"1B2M2Y8AsgTpgAmY7PhCfg=="'
}
var hash = crypto
.createHash('md5')
.update(body, encoding)
.digest('base64')
return '"' + hash + '"'
};
/**
* Return weak ETag for `body`.
*
* @param {String|Buffer} body
* @param {String} [encoding]
* @return {String}
* @api private
*/
exports.wetag = function wetag(body, encoding){
if (body.length === 0) {
// fast-path empty body
return 'W/"0-0"'
}
var buf = Buffer.isBuffer(body)
? body
: new Buffer(body, encoding)
var len = buf.length
return 'W/"' + len.toString(16) + '-' + crc32.unsigned(buf) + '"'
};
/**
* Check if `path` looks absolute.
*
* @param {String} path
* @return {Boolean}
* @api private
*/
exports.isAbsolute = function(path){
if ('/' == path[0]) return true;
if (':' == path[1] && '\\' == path[2]) return true;
if ('\\\\' == path.substring(0, 2)) return true; // Microsoft Azure absolute path
};
/**
* Flatten the given `arr`.
*
* @param {Array} arr
* @return {Array}
* @api private
*/
exports.flatten = function(arr, ret){
ret = ret || [];
var len = arr.length;
for (var i = 0; i < len; ++i) {
if (Array.isArray(arr[i])) {
exports.flatten(arr[i], ret);
} else {
ret.push(arr[i]);
}
}
return ret;
};
/**
* Normalize the given `type`, for example "html" becomes "text/html".
*
* @param {String} type
* @return {Object}
* @api private
*/
exports.normalizeType = function(type){
return ~type.indexOf('/')
? acceptParams(type)
: { value: mime.lookup(type), params: {} };
};
/**
* Normalize `types`, for example "html" becomes "text/html".
*
* @param {Array} types
* @return {Array}
* @api private
*/
exports.normalizeTypes = function(types){
var ret = [];
for (var i = 0; i < types.length; ++i) {
ret.push(exports.normalizeType(types[i]));
}
return ret;
};
/**
* Generate Content-Disposition header appropriate for the filename.
* non-ascii filenames are urlencoded and a filename* parameter is added
*
* @param {String} filename
* @return {String}
* @api private
*/
exports.contentDisposition = function(filename){
var ret = 'attachment';
if (filename) {
filename = basename(filename);
// if filename contains non-ascii characters, add a utf-8 version ala RFC 5987
ret = /[^\040-\176]/.test(filename)
? 'attachment; filename="' + encodeURI(filename) + '"; filename*=UTF-8\'\'' + encodeURI(filename)
: 'attachment; filename="' + filename + '"';
}
return ret;
};
/**
* Parse accept params `str` returning an
* object with `.value`, `.quality` and `.params`.
* also includes `.originalIndex` for stable sorting
*
* @param {String} str
* @return {Object}
* @api private
*/
function acceptParams(str, index) {
var parts = str.split(/ *; */);
var ret = { value: parts[0], quality: 1, params: {}, originalIndex: index };
for (var i = 1; i < parts.length; ++i) {
var pms = parts[i].split(/ *= */);
if ('q' == pms[0]) {
ret.quality = parseFloat(pms[1]);
} else {
ret.params[pms[0]] = pms[1];
}
}
return ret;
}
/**
* Compile "etag" value to function.
*
* @param {Boolean|String|Function} val
* @return {Function}
* @api private
*/
exports.compileETag = function(val) {
var fn;
if (typeof val === 'function') {
return val;
}
switch (val) {
case true:
fn = exports.wetag;
break;
case false:
break;
case 'strong':
fn = exports.etag;
break;
case 'weak':
fn = exports.wetag;
break;
default:
throw new TypeError('unknown value for etag function: ' + val);
}
return fn;
}
/**
* Compile "proxy trust" value to function.
*
* @param {Boolean|String|Number|Array|Function} val
* @return {Function}
* @api private
*/
exports.compileTrust = function(val) {
if (typeof val === 'function') return val;
if (val === true) {
// Support plain true/false
return function(){ return true };
}
if (typeof val === 'number') {
// Support trusting hop count
return function(a, i){ return i < val };
}
if (typeof val === 'string') {
// Support comma-separated values
val = val.split(/ *, */);
}
return proxyaddr.compile(val || []);
}
/**
* Set the charset in a given Content-Type string.
*
* @param {String} type
* @param {String} charset
* @return {String}
* @api private
*/
exports.setCharset = function(type, charset){
if (!type || !charset) return type;
// parse type
var parsed = typer.parse(type);
// set charset
parsed.parameters.charset = charset;
// format type
return typer.format(parsed);
};