Static Config

What is this?

If configuration values are obtained from env or toml, Rust compiler considers those values as dynamic values. Thus, Rust compiler cannot optimized them as constant values. Furthermore, a fixed-length array only accepts integers with const types. A constant with non-const type (e.g. let val = 3;) cannot be used.

static-config reads the content of static_config.toml at the crate root and embedded the values as a static rust source file. Values from static_config.toml can be accessed as pre-defined constants.

How to use

1. Add this library to your dependency list.
2. Put static_config.toml to the root of your crate/workspace (where you type cargo commands).
3. (Warning) This library will not work if the target directory is changed via env vars or cargo options.
4. Values from the TOML file is obtained through static_config::config API.
5. To use integer values as length of a fixed-length array, all integer values within the system's usize range are also defined in static_config::CONST_USIZE.

Example of static_config.toml

[level1]
string = "string value with escape \"!!\""
bool = true
i8 = -128
i16 = -32768
i32 = -2147483648
i64 = -9223372036854775808
# i128 is not yet supported in toml 0.5

[level1.level2]
string = "string value with escape \"\\\""
bool = false
u8 = 255
u16 = 65535
u32 = 4294967295
u64 = 9223372036854775807 # Max int type is i64
# u128 is not yet supported in toml 0.5

The following command is fully optimized-out into a const value.

assert!(true == static_config::config("level1.bool").try_into().unwrap());

If you want a const usize type to be used in array length:

assert!(255usize == static_config::CONST_USIZE.LEVEL1_LEVEL2_U8);

static_config::CPU_COUNT

static_config provides a CPU_COUNT constant measured by num_cpus crate.