On the second pass of the file, this turns up empty

[jcalfee]

In other words, if I filter a file and save it this appears to work fine. However, if I filter that file again, I do not get the same file (expected), instead I get no data at all.

Here is a trace of what is happening:

offset < dv.byteLength true,
app1 == 0xffe1 false,
app1 == 0xffe1 false,
app1 == 0xffe1 false,
app1 == 0xffe1 false,
app1 == 0xffe1 false,
app1 == 0xffe1 false,
app1 == 0xffe1 false,
app1 == 0xffe1 false,
app1 == 0xffda true,
pieces.length > 0 false