Generate ISO-8601 timestamps for Deno using Rust/FFI

NOTE: This is a test project, not suitable to be used for anything except testing.

The main use case of this project is to see whether we can speed up generating ISO-8601 timestamp strings using a native library and how efficient different FFI interface declarations will be (essentially, where are the bottlenecks).

Benchmarks

This project includes a set of benchmarks with comparison to the basic JavaScript forms of:

// 1. generate an ISO-8601 string from given (static) milliseconds
new Date(millis).toISOString()

// 2. generate an ISO-8601 string for the current time
new Date().toISOString()

While the first merely tests the performance of the FFI interface overhead as well as the performance of the underlying Rust library iso8601-timestamp for generating a string for a given timestamp, the second includes the time for retrieving the current time, which is quite significant.

Absolute results are mostly irrelevant, but the comparison shows where bottlenecks exist:

$ make bench
cargo build --release
    Finished `release` profile [optimized] target(s) in 0.04s
deno bench --allow-ffi --allow-env bench.ts
    CPU | AMD Ryzen 7 5700G with Radeon Graphics
Runtime | Deno 1.46.3 (x86_64-unknown-linux-gnu)

file:///home/ancoron/dev/ancoron/deno-iso8601-rs/bench.ts

benchmark                                time/iter (avg)        iter/s      (min … max)           p75      p99     p995
---------------------------------------- ----------------------------- --------------------- --------------------------

group From Milliseconds
standard JavaScript (new Date(millis))          606.2 ns     1,650,000 (537.9 ns …   1.2 µs) 555.2 ns   1.2 µs   1.2 µs
FFI (bindgen; return String)                      1.5 µs       675,000 (  1.3 µs …   2.0 µs)   1.6 µs   2.0 µs   2.0 µs
FFI (bindgen; pass a buffer)                    769.0 ns     1,300,000 (473.6 ns …   1.3 µs) 868.0 ns   1.3 µs   1.3 µs
FFI (manual; return CString + free)             228.8 ns     4,370,000 (209.6 ns … 354.7 ns) 225.4 ns 342.7 ns 352.8 ns
FFI (manual; fill buffer with CString)            1.6 µs       641,600 (843.7 ns …   3.4 µs)   2.0 µs   3.4 µs   3.4 µs

summary
  standard JavaScript (new Date(millis))
     2.65x slower than FFI (manual; return CString + free)
     1.27x faster than FFI (bindgen; pass a buffer)
     2.44x faster than FFI (bindgen; return String)
     2.57x faster than FFI (manual; fill buffer with CString)

group Current Timestamp
standard JavaScript (new Date())                  2.1 µs       485,200 (  1.8 µs …   2.8 µs)   2.1 µs   2.8 µs   2.8 µs
FFI (bindgen; return String)                      2.8 µs       357,700 (  2.4 µs …   3.2 µs)   2.9 µs   3.2 µs   3.2 µs
FFI (bindgen; pass a buffer)                      3.3 µs       307,500 (  1.8 µs … 941.3 µs)   3.4 µs   4.7 µs   5.3 µs
FFI (manual; return CString + free)               1.5 µs       660,700 (  1.4 µs …   3.6 µs)   1.5 µs   3.6 µs   3.6 µs
FFI (manual; fill buffer with CString)            3.1 µs       326,700 (  2.3 µs …   5.2 µs)   3.6 µs   5.2 µs   5.2 µs

summary
  standard JavaScript (new Date())
     1.36x slower than FFI (manual; return CString + free)
     1.36x faster than FFI (bindgen; return String)
     1.49x faster than FFI (manual; fill buffer with CString)
     1.58x faster than FFI (bindgen; pass a buffer)

Contributing

Contributions are welcome on any area (within the scope/use-case of this project).