C API to create BigDecimal objects

[byroot]

BigDecimal is used by various database clients, as well as various serialization libraries. Many of those are implemented in C, and for them creating BigDecimal objects is an important bottleneck.

For example, here's the relevant code in the Trilogy MySQL client gem: https://github.com/trilogy-libraries/trilogy/blob/7fcfe8c1c79208c6c56439d1d29c7dc591442c53/contrib/ruby/ext/trilogy-ruby/cast.c#L236-L241

It needs to:

• Allocate a Ruby String and cpy the bytes into it.
• Use rb_funcall to invoke BigDecimal().

The string allocation isn't too bad, but having to use method dispatch is quite costly.

It would be very useful if there was a set of C APIs to efficiently allocate BigDecimal objects:

VALUE BigDecimal_from_str(const char *, size_t len)`

[mrkn]

What approach are you assuming for referencing the BigDecimal_from_str symbol from the Trilogy extension library?

When I looked into this in the past while experimenting with Fiddle, based on my research and consultations, what I found was that if one extension library needs to reliably reference a symbol from another extension library, the only practical way is to use dlopen and dlsym directly.

[byroot]

I must confess that I lack knowledge and mastery in that area (build system, linkers, etc).

The precedent to gems exposing a C API is rb_digest_make_metadata from the digest gem.

But my understanding is that now that it has been extracted as a gem, it's only really possible to bind to the version installed with Ruby ruby/digest#34, and from what I understood from @hsbt is that rubygems/bundler is still lacking a proper mecanism for making this work.

Hence I'm open to any offered solution, but I'd understand if fixing rubygems/bundler was seen as a pre-requirement.

[rhenium]

Would rb_ext_resolve_symbol() (Ruby >= 3.3) be helpful? https://bugs.ruby-lang.org/issues/20005

[byroot]

Interesting. I never tried it, but it seems like it could work?