1 unstable release

0.1.0 Oct 8, 2018

#1004 in Embedded development


Used in mcf-config-demo-lib

MIT license

2KB

A demo using const-fn as a configuration medium

The gist here:

  • Embedded devices often need many tweaks to their libraries, to tune the behavior of a driver to a particular use case
    • This is often seen with things like Buffer Sizes, where sometimes 512 bytes is enough, but other times 4K is needed
  • Cargo's cfg feature flags are binary, and act as a union, so it is hard to provide compile-time settings, especially non-binary ones like size parameters, via feature flags
  • min_const_fn just stabilized, and will make it in time for 1.31

This demo is a PoC of using const fn to tweak compile time settings of a library, rather than relying solely on cfg features.

The parts of this demo

  1. mcf-config-demo-lib - an example library, published on crates.io
  2. mcf-config-demo-settings - a library crate, published on crates.io, containing default settings
  3. mcf-config-demo-app - a binary crate, that consumes the library above (not published on crates.io)
  4. mcf-config-demo-override - a copy of mcf-config-demo-settings, but with some configuration items changed

To see how the demo works:

$ cd mcf-config-demo-app
$ cargo run

$ cargo run
        Finished dev [unoptimized + debuginfo] target(s) in 0.00s
         Running `target/debug/mcf-config-demo-app`
    000: 0xac
    001: 0xac
    002: 0xac
    003: 0xac
    004: 0xac
    005: 0xac
    006: 0xac
    007: 0xac
    Hello, world!

# uncomment the lines from Cargo.toml in the app folder
nano Cargo.toml
# ...

cargo run
cargo run
        Finished dev [unoptimized + debuginfo] target(s) in 0.01s
         Running `target/debug/mcf-config-demo-app`
    000: 0xac
    001: 0xac
    002: 0xac
    003: 0xac
    004: 0xac
    005: 0xac
    006: 0xac
    007: 0xac
    008: 0xac
    009: 0xac
    010: 0xac
    011: 0xac
    012: 0xac
    013: 0xac
    014: 0xac
    015: 0xac
    y halo thar!

License

Licensed under either of

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

No runtime deps