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