Most efficient way (time and space wise) to send binary data in response

I solved the problem, and will write down the solution hoping it could save someone else's time.

Thank you, @dstromberg and @LukasGraf for your advices. I checked out BSON first, and found it sufficient for my needs, so never went into details of Procotol Buffer.

BSON on PyPi is available into two packages. In pymongo, it comes as a supplement to MongoDB. In bson, it is a standalone package, obviously suiting to my needs. However, it supports only Python2.So I looked around for a Python3 implementation before rolling out my own port, and found another implementation of BSON spec on bsonspec.org: Link to the module.

The simplest usage of that module goes like this:

>>> import bsonwarning: module typecheck.py cannot be imported, type checking is skipped>>> encoded = bson.serialize_to_bytes({'name': 'chunkfile', 'content': b'\xad\x03\xae\x03\xac\x03\xac\x03\xd4\x13'})>>> print(encoded)b'1\x00\x00\x00\x02name\x00\n\x00\x00\x00chunkfile\x00\x05content\x00\n\x00\x00\x00\x00\xad\x03\xae\x03\xac\x03\xac\x03\xd4\x13\x00'>>> decoded = bson.parse_bytes(encoded)>>> print(decoded)OrderedDict([('name', 'chunkfile'), ('content', b'\xad\x03\xae\x03\xac\x03\xac\x03\xd4\x13')])

As you can see, it can accommodate binary data as well.I sent the data from Flask as mimetype=application/bson, which was accurately parsed by the receiving JavaScript using this standalone BSON library provided by MongoDB team.