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/* global XPCOMUtils, BackgroundPageThumbs, FileUtils, PageThumbsStorage, Task, MIMEService */
/* exported PreviewProvider */
"use strict";
this.EXPORTED_SYMBOLS = ["PreviewProvider"];
const {utils: Cu} = Components;
Cu.import("resource://gre/modules/XPCOMUtils.jsm");
Cu.import("resource://gre/modules/Task.jsm");
Cu.import("resource://gre/modules/PageThumbs.jsm");
Cu.import("resource://gre/modules/FileUtils.jsm");
const {OS} = Cu.import("resource://gre/modules/osfile.jsm", {});
XPCOMUtils.defineLazyModuleGetter(this, "BackgroundPageThumbs",
"resource://gre/modules/BackgroundPageThumbs.jsm");
XPCOMUtils.defineLazyServiceGetter(this, "MIMEService",
"@mozilla.org/mime;1", "nsIMIMEService");
let PreviewProvider = {
/**
* Returns a thumbnail as a data URI for a url, creating it if necessary
*
* @param {String} url
* a url to obtain a thumbnail for
* @return {Promise} A Promise that resolves with a base64 encoded thumbnail
*/
getThumbnail: Task.async(function* PreviewProvider_getThumbnail(url) {
try {
yield BackgroundPageThumbs.captureIfMissing(url);
let imgPath = PageThumbsStorage.getFilePathForURL(url);
// OS.File object used to easily read off-thread
let file = yield OS.File.open(imgPath, {read: true, existing: true});
// nsIFile object needed for MIMEService
let nsFile = FileUtils.File(imgPath);
let contentType = MIMEService.getTypeFromFile(nsFile);
let bytes = yield file.read();
let encodedData = btoa(String.fromCharCode.apply(null, bytes));
file.close();
return `data:${contentType};base64,${encodedData}`;
} catch (err) {
Cu.reportError(`PreviewProvider_getThumbnail error: ${err}`);
throw err;
}
})
};
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