feat: FNV hasher crate

.tangled/workflows/test.yml

···
   - name: Format check
     command: cargo fmt --all --check
   - name: Tests
-    command: cargo test --workspace
+    command: cargo test --workspace --locked

Cargo.lock

···
 ]
 
 [[package]]
+name = "sachy-fnv"
+version = "0.1.0"
+
+[[package]]
 name = "sachy-shtc3"
 version = "0.1.0"
 dependencies = [

Cargo.toml

···
 [workspace]
 resolver = "3"
-members = ["sachy-battery","sachy-bthome", "sachy-fmt", "sachy-shtc3"]
+members = ["sachy-battery","sachy-bthome", "sachy-fmt", "sachy-fnv", "sachy-shtc3"]
 
 [workspace.package]
 authors = ["Sachymetsu <[e-mail]>"]

sachy-fnv/Cargo.toml

···
+[package]
+name = "sachy-fnv"
+authors.workspace = true
+edition.workspace = true
+repository.workspace = true
+license.workspace = true
+version.workspace = true
+rust-version.workspace = true
+
+[dependencies]

sachy-fnv/src/lib.rs

···
+//! This crate provides a `const` FNV32 hasher for the purpose of supporting the ESPHome/Home Assistant protocol where required.
+//!
+//! ```
+//! use sachy_fnv::fnv32_hash;
+//! 
+//! let hash = fnv32_hash("water_pump_1");
+//!
+//! assert_eq!(hash, 3557162331);
+//! ```
+#![no_std]
+
+const FNV_OFFSET_BASIS_32:  u32  = 0x811c9dc5;
+const FNV_PRIME_32:  u32  = 0x01000193;
+
+/// `const` FNV32 hasher. Takes a `&str` and returns a `u32` hash.
+pub const fn fnv32_hash(str: &str) -> u32 {
+    let bytes = str.as_bytes();
+
+    let mut hash = FNV_OFFSET_BASIS_32;
+    let mut i = 0;
+    let len = bytes.len();
+
+    while i < len {
+        hash = hash.wrapping_mul(FNV_PRIME_32);
+        hash ^= bytes[i] as u32;
+        i += 1;
+    }
+
+    hash
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn it_works() {
+        let result = fnv32_hash("water_pump_1");
+        assert_eq!(result, 3557162331);
+        let result = fnv32_hash("pump_1_duration");
+        assert_eq!(result, 931766070);
+    }
+}