fs.readFile anomaly

Question

fs.readFile anomaly

Trying to run a script that opens a bunch of files asynchronously and reads their content. I am getting an error where fs.readFile's callback comes in with no data, yet the file is there, and is not currently being opened by anything else. Totally confused.

The error is:

Error: OK, open 'D:\Workspace\fasttrack\public\cloudmade\images\998\256\6\31\61.png'

More info:

The program runs through a loop that has a bunch of objects in it that look like this:

newObject = {
    filePath:filePath,
    scanPixels:function(parent){
        ....
    }
}

The loop calls each object's scanPixels function, which then does an fs.readFile on the parent.filePath

Here is the for loop

for(var index=0;index<objects.length;index++){
    objects[index].scanPixels(objects[index]);
}

The scanPixels function is essentially this:

scanPixels:function(parent){

            png_js.decode(parent.filePath, function(pixels){

                ...more stuff

And in the png_js file:

PNG.decode = function(path, fn) {

  return fs.readFile(path, function(err, file) {

    var png;
    png = new PNG(file);
    return png.decode(function(pixels) {
      return fn(pixels);
    });
  });
};

node.js

Answer 1

the problem is that fs.readFile does not return a value. You would want fs.readFileSync for that

var buffer1 = fs.fileReadSync('./hello1.txt');

var buffer2;
fs.fileRead('./hello2.txt', function (err, file) {
    buffer = file;
});