Right, this is a problem, but it's orthogonal to TLV, but it's TLV I was arguing against, not necessarily for cap'n proto.
You can use OER without having to allocate all sub-parts of the structure from one flat buffer, with no "edits" that fragment the buffer, and no memmoves, and you won't get zero-copy, but you'll still get a more efficient codec than any TLV encoding. I just don't see any case where TLV is appealing, but TLV is appalling :)
I think we're on the same page.
EDIT: BTW, thanks for the clarification -- I thought that was the issue you meant, but what you linked to was lengthy and I didn't want to have to wade through all of it.
EDIT: Also, even if zero-copy schemes are inefficient for some uses on the encoder side, they can still be very efficient on the decode side, as you need essentially no memory allocations to decode (though you still need to traverse the encoded data).
You can use OER without having to allocate all sub-parts of the structure from one flat buffer, with no "edits" that fragment the buffer, and no memmoves, and you won't get zero-copy, but you'll still get a more efficient codec than any TLV encoding. I just don't see any case where TLV is appealing, but TLV is appalling :)
I think we're on the same page.
EDIT: BTW, thanks for the clarification -- I thought that was the issue you meant, but what you linked to was lengthy and I didn't want to have to wade through all of it.
EDIT: Also, even if zero-copy schemes are inefficient for some uses on the encoder side, they can still be very efficient on the decode side, as you need essentially no memory allocations to decode (though you still need to traverse the encoded data).