lib/common/plugin/FileReader.js

var exec = require('cordova/exec'),
    FileError = require('cordova/plugin/FileError'),
    ProgressEvent = require('cordova/plugin/ProgressEvent');

/**
 * This class reads the mobile device file system.
 *
 * For Android:
 *      The root directory is the root of the file system.
 *      To read from the SD card, the file name is "sdcard/my_file.txt"
 * @constructor
 */
var FileReader = function() {
    this.fileName = "";

    this.readyState = 0; // FileReader.EMPTY

    // File data
    this.result = null;

    // Error
    this.error = null;

    // Event handlers
    this.onloadstart = null;    // When the read starts.
    this.onprogress = null;     // While reading (and decoding) file or fileBlob data, and reporting partial file data (progess.loaded/progress.total)
    this.onload = null;         // When the read has successfully completed.
    this.onerror = null;        // When the read has failed (see errors).
    this.onloadend = null;      // When the request has completed (either in success or failure).
    this.onabort = null;        // When the read has been aborted. For instance, by invoking the abort() method.
};

// States
FileReader.EMPTY = 0;
FileReader.LOADING = 1;
FileReader.DONE = 2;

/**
 * Abort reading file.
 */
FileReader.prototype.abort = function() {
    this.result = null;

    if (this.readyState == FileReader.DONE || this.readyState == FileReader.EMPTY) {
      return;
    }

    this.readyState = FileReader.DONE;

    // If abort callback
    if (typeof this.onabort === 'function') {
        this.onabort(new ProgressEvent('abort', {target:this}));
    }
    // If load end callback
    if (typeof this.onloadend === 'function') {
        this.onloadend(new ProgressEvent('loadend', {target:this}));
    }
};

/**
 * Read text file.
 *
 * @param file          {File} File object containing file properties
 * @param encoding      [Optional] (see http://www.iana.org/assignments/character-sets)
 */
FileReader.prototype.readAsText = function(file, encoding) {
    // Figure out pathing
    this.fileName = '';
    if (typeof file.fullPath === 'undefined') {
        this.fileName = file;
    } else {
        this.fileName = file.fullPath;
    }

    // Already loading something
    if (this.readyState == FileReader.LOADING) {
        throw new FileError(FileError.INVALID_STATE_ERR);
    }

    // LOADING state
    this.readyState = FileReader.LOADING;

    // If loadstart callback
    if (typeof this.onloadstart === "function") {
        this.onloadstart(new ProgressEvent("loadstart", {target:this}));
    }

    // Default encoding is UTF-8
    var enc = encoding ? encoding : "UTF-8";

    var me = this;

    // Read file
    exec(
        // Success callback
        function(r) {
            // If DONE (cancelled), then don't do anything
            if (me.readyState === FileReader.DONE) {
                return;
            }

            // Save result
            me.result = r;

            // If onload callback
            if (typeof me.onload === "function") {
                me.onload(new ProgressEvent("load", {target:me}));
            }

            // DONE state
            me.readyState = FileReader.DONE;

            // If onloadend callback
            if (typeof me.onloadend === "function") {
                me.onloadend(new ProgressEvent("loadend", {target:me}));
            }
        },
        // Error callback
        function(e) {
            // If DONE (cancelled), then don't do anything
            if (me.readyState === FileReader.DONE) {
                return;
            }

            // DONE state
            me.readyState = FileReader.DONE;

            // null result
            me.result = null;

            // Save error
            me.error = new FileError(e);

            // If onerror callback
            if (typeof me.onerror === "function") {
                me.onerror(new ProgressEvent("error", {target:me}));
            }

            // If onloadend callback
            if (typeof me.onloadend === "function") {
                me.onloadend(new ProgressEvent("loadend", {target:me}));
            }
        }, "File", "readAsText", [this.fileName, enc]);
};


/**
 * Read file and return data as a base64 encoded data url.
 * A data url is of the form:
 *      data:[<mediatype>][;base64],<data>
 *
 * @param file          {File} File object containing file properties
 */
FileReader.prototype.readAsDataURL = function(file) {
    this.fileName = "";
    if (typeof file.fullPath === "undefined") {
        this.fileName = file;
    } else {
        this.fileName = file.fullPath;
    }

    // Already loading something
    if (this.readyState == FileReader.LOADING) {
        throw new FileError(FileError.INVALID_STATE_ERR);
    }

    // LOADING state
    this.readyState = FileReader.LOADING;

    // If loadstart callback
    if (typeof this.onloadstart === "function") {
        this.onloadstart(new ProgressEvent("loadstart", {target:this}));
    }

    var me = this;

    // Read file
    exec(
        // Success callback
        function(r) {
            // If DONE (cancelled), then don't do anything
            if (me.readyState === FileReader.DONE) {
                return;
            }

            // DONE state
            me.readyState = FileReader.DONE;

            // Save result
            me.result = r;

            // If onload callback
            if (typeof me.onload === "function") {
                me.onload(new ProgressEvent("load", {target:me}));
            }

            // If onloadend callback
            if (typeof me.onloadend === "function") {
                me.onloadend(new ProgressEvent("loadend", {target:me}));
            }
        },
        // Error callback
        function(e) {
            // If DONE (cancelled), then don't do anything
            if (me.readyState === FileReader.DONE) {
                return;
            }

            // DONE state
            me.readyState = FileReader.DONE;

            me.result = null;

            // Save error
            me.error = new FileError(e);

            // If onerror callback
            if (typeof me.onerror === "function") {
                me.onerror(new ProgressEvent("error", {target:me}));
            }

            // If onloadend callback
            if (typeof me.onloadend === "function") {
                me.onloadend(new ProgressEvent("loadend", {target:me}));
            }
        }, "File", "readAsDataURL", [this.fileName]);
};

/**
 * Read file and return data as a binary data.
 *
 * @param file          {File} File object containing file properties
 */
FileReader.prototype.readAsBinaryString = function(file) {
    // TODO - Can't return binary data to browser.
    console.log('method "readAsBinaryString" is not supported at this time.');
};

/**
 * Read file and return data as a binary data.
 *
 * @param file          {File} File object containing file properties
 */
FileReader.prototype.readAsArrayBuffer = function(file) {
    // TODO - Can't return binary data to browser.
    console.log('This method is not supported at this time.');
};

module.exports = FileReader;