121 lines
3.4 KiB
JavaScript
121 lines
3.4 KiB
JavaScript
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/**
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* Loads a file from disk and returns a binary string
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*
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* Copyright (C) 2012 Mike Gerwitz
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Affero General Public License for more details.
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*
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* You should have received a copy of the GNU Affero General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*
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*
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* The file uses a number of features introduced in the HTML5 and ECMAScript
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* specs, as it depends on FileReader.
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*/
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/**
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* Load file into memory as binary string from a given file element
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*
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* This class handles the loading of only a single file (as that is all this
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* project requires).
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*/
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ltjs.FileLoader = Class( 'FileLoader',
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{
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/**
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* DOM file element to watch
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* @type {HTMLInputElement}
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*/
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'private _element': null,
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/**
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* Callback to call on file load
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* @type {function(Error,string)}
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*/
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'private _callback': null,
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/**
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* Initialize file loader, monitoring the given file element
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*
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* @param {HtmlInputElement} element file element to monitor
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*/
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__construct: function( element )
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{
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if ( element.type !== 'file' )
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{
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throw TypeError( 'Expected file element, given ' + element.type );
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}
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this._element = element;
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},
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/**
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* Bind callback to file load event
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*
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* The given callback will be called when the file is loaded. It must accept
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* two arguments: the first will be used to indicate an error (otherwise
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* null) and the second argument will contain the binary string of data
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* (unless an error occurred, in which case it will be undefined).
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*
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* @param {function(Error,string)} callback file load callback
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*
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* @return {FileLoader} self
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*/
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'public onLoad': function( callback )
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{
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this._callback = callback;
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// we do not want to monitor the change event until *after* a callback
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// is registered (it is otherwise pointless)
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this._element.addEventListener( 'change', this._loadFile.bind( this ) );
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// attempt to load file immediately (in case a file has already been
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// selected)
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this._loadFile( { target: this._element } );
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return this;
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},
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/**
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* Process file and invokes callback with result
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*
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* Called on filename change.
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*
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* @param {Object} event change event
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*
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* @return {undefined}
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*/
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'private _loadFile': function( event )
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{
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var _self = this,
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files = event.target.files;
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if ( files.length === 0 ) return;
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var reader = new FileReader();
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reader.onload = function( revent )
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{
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_self._callback.call( this.__inst, null, revent.target.result );
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};
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reader.onerror = function( e )
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{
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_self._callback.call( this.__inst, e );
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};
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// load file
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reader.readAsBinaryString( files[ 0 ] );
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}
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} );
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