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Emscripten: Allow replacing the filesystem used for "Save" folder #1173

merged 2 commits into from May 21, 2017


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3 participants

Ghabry commented May 20, 2017

This allows replacing the storage used by simply editing the index.html emscripten shell (Module.EASYRPG_FS = MY_FS) and implementing MY_FS.

Motivation: This allows somebody who hosts our Player to provide e.g. a web based storage (session based) instead of the default local storage.

Mostly for rmarchiv because it wants to provide server-baked storage.


Reference client implementation of a FS doing AJAX via VanillaJS to transmit save files. The server part is more work ;)

Format is in both directions.

    "1": "BASE64 OF SAVE01.LSD",
    "14": "BASE64 OF SAVE14.LSD"

Request URL hardcoded to "/save"

var SAMPLEFS = {
    mount: function(mount) {
    // reuse all of the core MEMFS functionality
    return MEMFS.mount.apply(null, arguments);
  to_binary: function(dataURI){
    var base64 = dataURI.substring(0);
    var raw = window.atob(base64);
    var rawLength = raw.length;
    var array = new Uint8Array(new ArrayBuffer(rawLength));

    for(i = 0; i < rawLength; i++) {
      array[i] = raw.charCodeAt(i);
    return array;
  syncfs: function(mount, populate, callback) {
    //if (err) return callback(err); TODO Error handling
    if (populate) {
      var xhr = new XMLHttpRequest();
      xhr.withCredentials = true;
      xhr.onreadystatechange = function () {
        if (xhr.readyState === 4) {
          if (xhr.status === 200) {
            var obj = JSON.parse(xhr.responseText);

            for (var property in obj) {
              if (obj.hasOwnProperty(property)) {
                var nal = property.length == 1 ? "0" : "";
                var bin = SAMPLEFS.to_binary(obj[property]);
                var stream = + "/Save" + nal + property + ".lsd", "w");
                FS.write(stream, bin, 0, bin.length, 0);
          } else {
            console.log('Error: ' + xhr.status);
      };'GET', '/save');
    } else {
      var xhr = new XMLHttpRequest();
      xhr.withCredentials = true;
      xhr.onreadystatechange = function () {
        if (xhr.readyState === 4) {
          if (xhr.status !== 200) {
            console.log('Error: ' + xhr.status);
      };'POST', '/save');

      var obj = {}
        FS.readdir(mount.mountpoint).forEach(function(x) {
        var num = parseInt(x.substr(4,2));
        if (!isNaN(num) && num >= 1 && num <= 15) {
          obj[num.toString()] = btoa(String.fromCharCode.apply(null, FS.readFile(mount.mountpoint + "/" + x)));


Super basic test server (Lacks sanity checks!)

Put emscripten shell with the client code in the same folder as the python-script. Put a game in subfolder "game" (don't forget to create a index.json), run the script and visit localhost:5000

from flask import Flask,send_file
app = Flask(__name__)
from flask import request
import json

def mem():
    return send_file(open("index.html.mem", "rb"),mimetype="application/octet-stream")

def index():
    return open("index.html", "r").read()

def start(f):
    return open(f, "r").read()

@app.route("/save", methods=['GET', 'POST'])
def save():
    if request.method == "POST":
        j = request.get_json(force=True)
        f=open("save.json", "w")
        return ""
        return open("save.json", "r").read()

def game(f):
    return send_file(open("game/"+f, "rb"),mimetype="application/octet-stream")

if __name__ == "__main__":
Emscripten: Allow replacing the filesystem used for "Save" (by defaul…
…t IDBFS) with a custom file system.

This can be achived by providing a custom emscripten shell file which sets Module.EASYRPG_FS.
Cancel fast forward when the webplayer waits for important files.
Resulted in "Map not found" errors because they waiting was skipped.

Fixes #1174

@fdelapena fdelapena added this to the 0.5.2 milestone May 21, 2017

@carstene1ns carstene1ns merged commit 2e8352f into EasyRPG:master May 21, 2017

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@Ghabry Ghabry deleted the Ghabry:emscripten-custom-save branch May 28, 2017

Ghabry pushed a commit to libretro/easyrpg-libretro that referenced this pull request May 22, 2018

Merge pull request #1173 from Ghabry/emscripten-custom-save
Emscripten: Allow replacing the filesystem used for "Save" folder
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