state helpers

Cargo.toml

@@ -54,6 +54,8 @@ once_cell = { version = "1.19.0", optional = true }
 parking_lot = { version = "0.12.3", optional = true }
 parking_lot_rt = { version = "0.12.1", optional = true }
 quanta = { version = "=0.12.3", optional = true }
+serde_json = "1.0.134"
+rmp-serde = "1.3.0"
 
 [target.'cfg(windows)'.dependencies]
 parking_lot_rt = { version = "0.12.1" }

src/lib.rs

@@ -107,6 +107,9 @@ pub mod supervisor;
 /// Real-time thread functions to work with [`supervisor::Supervisor`] and standalone, Linux only
 pub mod thread_rt;
 
+/// State helper functions
+pub mod state;
+
 /// The crate result type
 pub type Result<T> = std::result::Result<T, Error>;
 

src/state.rs

+use std::{fs::File, io::Write, path::Path};
+
+use serde::{de::DeserializeOwned, Serialize};
+
+use crate::{Error, Result};
+
+enum Format {
+    Json,
+    Msgpack,
+}
+
+impl Format {
+    fn from_path<P: AsRef<Path>>(path: P) -> Self {
+        match path
+            .as_ref()
+            .extension()
+            .map_or("", |ext| ext.to_str().unwrap())
+        {
+            "json" => Self::Json,
+            _ => Self::Msgpack,
+        }
+    }
+}
+
+/// Load the state from a file. If "json" extension is specified, the state is loaded in JSON
+/// format. All errors, including missing state file, must be handled by the caller.
+pub fn load<S: DeserializeOwned, P: AsRef<Path>>(path: P) -> Result<S> {
+    let format = Format::from_path(&path);
+    let file = File::open(&path)?;
+    let data = match format {
+        Format::Json => serde_json::from_reader(file).map_err(Error::failed)?,
+        Format::Msgpack => rmp_serde::from_read(file).map_err(Error::failed)?,
+    };
+    Ok(data)
+}
+
+/// Save the state to a file. If "json" extension is specified, the state is saved in JSON
+/// format. Otherwise it is saved in MessagePack format.
+pub fn save<S: Serialize, P: AsRef<Path>>(state: &S, path: P) -> Result<()> {
+    let format = Format::from_path(&path);
+    let mut file = File::create(&path)?;
+    let data = match format {
+        Format::Json => serde_json::to_vec(state).map_err(Error::failed)?,
+        Format::Msgpack => rmp_serde::to_vec_named(state).map_err(Error::failed)?,
+    };
+    file.write_all(&data)?;
+    Ok(())
+}