Writing Int32 to ByteBuffer yields strange result in DataView

[tfalencar]

Hello,

I'm not familiar with ByteBuffer (trying it for the first time due protobuf.js), but I'm trying to simply write an int32 to the buffer, convert it to a ArrayBuffers and see this value in 4 bytes in a file output. I'm pretty sure I'm doing some nasty mistake and it's not the library's fault, but this is one of the ways I've tried:

var ByteBuffer = dcodeIO.ByteBuffer;
//below is run inside a loop
var byteBuffer = new ByteBuffer(ByteBuffer.DEFAULT_CAPACITY, ByteBuffer.LITTLE_ENDIAN);
byteBuffer.append(new ByteBuffer().writeInt32(data.calculate()));

//finally, generate the file for download
var data = new Blob([new DataView(byteBuffer.toArrayBuffer())], {type: 'application/octet-stream'});
this.url = ($window.URL || $window.webkitURL).createObjectURL(data);

then in html there's a field to download the file, as in:

<a download="vat.scope" ng-href="{{ vatEditor.url }}">download</a>

For example, when data.calculate() yields 32, I'd expect to see 0x 20 00 00 00, but what I got is 0x 28 00 38 05 (which in little endian integer is 87556136). Anyone would be kind to help me pinpoint the mistake(s) here?

A more extensive explanation of what I'm trying to accomplish can be found here.

[dcodeIO]

Make sure to call flip() once all relative write operations are complete. See: https://github.com/dcodeIO/ByteBuffer.js/wiki/Offset-and-limit

var bb = new ByteBuffer().LE();
for (...) {
  // bb.append(new ByteBuffer().LE().writeInt32(data.calculate()).flip());
  bb.writeInt32(data.calculate());
}
var ab = bb.flip().toArrayBuffer();
...

[tfalencar]

HOORAY! it works now! I actually tried the short version as well before, but it didn't come to me that when using .toArrayBuffer() that is effectively performing a read operation, and per docs if I understood it right when switching from read/write operations a flip() is necessary, so that explains it (I forgot to add it when creating the DataView() after using .toArrayBuffer().

Just for clarity writing both mentioned ways works now:

byteBuffer.writeInt32(data.calculate());
//or
byteBuffer.append(new ByteBuffer(ByteBuffer.DEFAULT_CAPACITY, ByteBuffer.LITTLE_ENDIAN).writeInt32(data.calculate()).flip());

//the important, forgotten flip() - 'implicit' read operation:
new Blob([new DataView(byteBuffer.flip().toArrayBuffer())]

Thanks a lot !