Question

I am trying to read a very large file in AS3 and am having problems with the runtime just crashing on me. I’m currently using a FileStream to open the file asynchronously. This does not work(crashes without an Exception) for files bigger than about 300MB.

_fileStream = new FileStream();
_fileStream.addEventListener(IOErrorEvent.IO_ERROR, loadError);
_fileStream.addEventListener(Event.COMPLETE, loadComplete);
_fileStream.openAsync(myFile, FileMode.READ);

In looking at the documentation, it sounds like the FileStream class still tries to read in the entire file to memory(which is bad for large files).

Is there a more suitable class to use for reading large files? I really would like something like a buffered FileStream class that only loads the bytes from the files that are going to be read next.

I’m expecting that I may need to write a class that does this for me, but then I would need to read only a piece of a file at a time. I’m assuming that I can do this by setting the position and readAhead properties of the FileStream to read a chunk out of a file at a time. I would love to save some time if there is a class like this that already exists.

Is there a good way to process large files in AS3, without loading entire contents into memory?

Answer 1

Can’t you create a stream, and read a chunk of bytes at a given offset, a chunk at a time… so:

function readPortionOfFile(starting:int, size:int):ByteArray
{
    var bytes:ByteArray ...
    var fileStream:FileStream ...    

    fileStream.open(myFile);
    fileStream.readBytes(bytes, starting, size);
    fileStream.close();

    return bytes;
}

and then repeat as required. I don’t know how this works, and haven’t tested it, but I was under the impression that this works.