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TiddlyWiki5/js/FileRetriever.js

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/*\
title: js/FileRetriever.js
FileRetriever can asynchronously retrieve files from HTTP URLs or the local file system. Files are treated as utf-8 text or, if the filepath ends in one of the recognised binary extensions, as a base64 encoded binary string
\*/
(function(){
/*jslint node: true */
"use strict";
var fs = require("fs"),
path = require("path"),
url = require("url"),
util = require("util"),
http = require("http"),
https = require("https");
var FileRetriever = exports;
// These are the file extensions that we'll recognise as binary.
FileRetriever.binaryFileExtensions = [".jpg",".jpeg",".png",".gif"];
// Retrieve a local file and invoke callback(err,data) in the usual way
var fileRequest = function fileRequest(filepath,callback) {
fs.readFile(filepath, function (err,data) {
if(err) {
callback(err);
} else {
// Check if we need to base64 encode the file
if(FileRetriever.binaryFileExtensions.indexOf(path.extname(filepath)) !== -1) {
callback(err,data.toString("base64"));
} else {
callback(err,data.toString("utf8"));
}
}
});
};
// Retrieve a file over HTTP and invoke callback(err,data) in the usual way
var httpRequest = function(fileurl,callback) {
var opts = url.parse(fileurl),
httpLib = opts.protocol === "http:" ? http : https,
encoding = (FileRetriever.binaryFileExtensions.indexOf(path.extname(fileurl)) !== -1) ? "binary" : "utf8";
var request = httpLib.get(opts,function(res) {
if(res.statusCode != 200) {
var err = new Error("HTTP error");
err.code = res.statusCode.toString();
callback(err);
} else {
var data = [];
res.setEncoding(encoding);
res.on("data", function(chunk) {
data.push(chunk);
});
res.on("end", function() {
if(encoding === "binary") {
callback(null,(new Buffer(data.join(""),"binary")).toString("base64"));
} else {
callback(null,data.join(""));
}
});
}
});
request.addListener("error", function(err) {
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callback(err);
});
request.end();
};
// Retrieve a file given a filepath specifier and a context path. If the filepath isn't an absolute
// filepath or an absolute URL, then it is interpreted relative to the context path, which can also be
// a filepath or a URL. On completion, the callback function is called as callback(err,data). The
// data hashmap is as follows:
// text: full text of file
// path: full path used to reach the file
// basename: the basename of the file
// extname: the extension of the file
FileRetriever.retrieveFile = function(filepath,contextPath,callback) {
var httpRegExp = /^(https?:\/\/)/gi,
result = {},
filepathIsHttp = httpRegExp.test(filepath),
contextPathIsHttp = httpRegExp.test(contextPath),
requester;
if(contextPathIsHttp || filepathIsHttp) {
// If we've got a full HTTP URI then we're good to go
result.path = url.resolve(contextPath,filepath);
var parsedPath = url.parse(result.path);
result.extname = path.extname(parsedPath.pathname);
result.basename = path.basename(parsedPath.extname);
requester = httpRequest;
} else {
// It's a file requested in a file context
result.path = path.resolve(path.dirname(contextPath),filepath);
result.extname = path.extname(result.path);
result.basename = path.basename(result.path,result.extname);
requester = fileRequest;
}
requester(result.path,function(err,data) {
if(!err) {
result.text = data;
}
callback(err,result);
});
};
})();