Add bignum feature

[ghost]

I've experimented with enabling Bignum extension (seems to be working just fine, can be enabled just by changing static lib name in Rust flags from quickjs to quickjs.bn). However I'm not sure what would be the correct types to map.

My idea is to have num-bigint feature that would use num-bigint crate to store values from JavaScript BigInt, which is currently stage3 and implemented by major browsers. At the same time I think maybeQuickJS's BigFloat can be ignored for now, as it is something non-standard, and also I haven't found a crate that would be a good fit to store BigFloat values in Rust.

[theduke]

I'm all for it.
For decimal, this might be a good fit: https://github.com/paupino/rust-decimal
It's used by diesel for postgres I think.

Are you interested in implementing this?

[ghost]

For decimal, this might be a good fit: https://github.com/paupino/rust-decimal

It is big decimal (fixed-point), which might not be practical to store QuickJS BigFloat (floating point), as numbers like 1e2000 would take enormous space when stored as fixed point.

[ghost]

Are you interested in implementing this?

Yes, want to try to add BigInt.

[theduke]

Happy to help if you run into any questions.

[theduke]

Ah yeah,

The binary representation consists of a 96 bit integer number, a scaling factor used to specify the decimal fraction and a 1 bit sign

I thought decimal was arbitrary precision.

[ghost]

@theduke It turns out that only functions for converting BigInt to i64 and back are exposed publicly in QuickJS:

• create BigInt from i64
• convert BigInt to i64

The structure JSBigFloat that is needed for extracting QuickJS big float type bf_t from JSValue is defined in quickjs.c and thus private.