Help with implementing ID3v3.2 spec in dart

[velia-vito]

Preface

I know this issue isn't directly relevant to mutagen but I am at my wits end trying to figure out what I'm doing wrong. That said, you can close this issue for irrelevancy without a second thought.

Details

The project I used to work on spotDL/spotify-downloader depended on mutagen. I'm currently working on transitioning the work into Dart (as it's multiplatform native.) This has meant that I've had to try and build a custom implementation of the ID3v2.

Here is my implementation that attempts to follow the spec via waybackmachine:

• FrameBuffer: Underlying code to simplify creating byte arrays.
• Frame: Creating individual ID3 frames (very very barebones.)
• Tag: Putting everything together.

I realize the syntax is different, but I hope it's similar enough that you can point out where I'm going wrong (windows refuses to read my tag data.)

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Update

• This is my testing code that has been applied to plain metadataless mp3 file.
• This is the resulting supposedly with metadata attached file