[boost] [serialization] deserializing asynchronously serialized types

Subject: [boost] [serialization] deserializing asynchronously serialized types
From: Andrew Hundt (athundt_at_[hidden])
Date: 2011-09-03 22:56:45

I have an unusual use case for boost.serialization, and I was wondering if
it would be possible to adapt it to my needs:

- I have a set of over 100 types, and instances of each are generated
asynchronously then serialized to a file in that order.
- The most interesting serialized data will be written just before the power
is unexpectedly cut.
- I need to load in and run on as much data as possible when reading the
serialized data back, ignoring incomplete data at the end (due to a power
cut).
- The basic Boost serialization examples require you to know the type of the
next piece of data to be loaded when reading. Since these types are
generated asynchronously they are not known in advance.
- I need to write the data out immediately when it arrives because of the
power issue.
- Files will be getting up to around 150GB in size for binary archives, so
it can't be marshaled in memory, it needs to be written immediately even if
it is redundant.

Is there a way to read in that serialized file using the facilities provided
in boost.serialization?

Here are my current ideas:
- I tried using boost.variant, but it loses its will to compile when I
increase the typelist limit to around ~60 types on gcc 4.4, and I have more
than a hundred.
- Use preprocessor metaprogramming to do something equivalent to
boost.variant, but I would very much prefer a more pleasant option.
- Serialize an index or custom headers indicating the next type to appear
- One way of achieving some of these goals is writing one piece at a time
using a binary archive to an fstream, with the index mentioned above
separating data types.

I don't know what aspects of my requirements will prove to be a problem, so
if anyone can provide advice that would help me avoid a major pitfall, it
would be greatly appreciated.

Thanks for your thoughts.

Cheers!
Andrew Hundt