Read binary file with extendscript - binary

Question

Limited to using Extendscript in Photoshop I'm trying to write and then read in the same binary file.
I can write the file okay, but I'm not sure where I'm going wrong with the read part.
The data will be RGB colours in hex, so I'll either want to return the data from the read function as array or a string. Only I can't even get it to tell me the file just written exists. And I'm not sure if I should be using seek() or read(). Confused.
var f = new File("D:\\temp\\bin.act");
var w = write_binary(f);
var r = read_binary(w);
alert(r);
function write_binary(afile)
{
afile.encoding = "BINARY";
afile.open ("w");
for(i = 0; i < 256; i++)
{
afile.write(String.fromCharCode (i));
}
afile.close();
}
function read_binary(afile)
{
var f = new File(afile);
f.open("r");
f.encoding = "BINARY";
//var data = f.read();
//if(f.exists) alert(afile);
//alert (data);
var arr = [];
for (var i = 0; i < f.length; i+=4)
{
f.seek(i, 0);
var hex = f.readch().charCodeAt(0).toString(16);
if(hex.length === 1) hex = "0" + hex;
arr.push(hex);
}
return arr;
}

Answer 1

You can read it like this:
// Open binary file
var afile = "/Users/mark/StackOverflow/data.bin"
var f = new File(afile);
f.open("r");
f.encoding = "BINARY";
alert('OK');
var hexstring=""
while (true){
var b = f.readch().charCodeAt(0);
if(f.eof){break;}
var hex = b.toString(16);
if(hex.length === 1) hex = "0" + hex;
hexstring += hex;
}
alert(hexstring);
The corresponding writing part of this answer is here.