Add crate int-to-c-enum

Cargo.lock

@@ -758,6 +758,22 @@ version = "1.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1674845326ee10d37ca60470760d4288a6f80f304007d92e5c53bab78c9cfd79"
 
+[[package]]
+name = "value-enum"
+version = "0.1.0"
+dependencies = [
+ "value-enum-derive",
+]
+
+[[package]]
+name = "value-enum-derive"
+version = "0.1.0"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "version_check"
 version = "0.9.4"

Cargo.toml

@@ -35,6 +35,7 @@ members = [
     "services/libs/typeflags-util",
     "services/libs/jinux-util",
     "services/libs/cpio-decoder",
+    "services/libs/int-to-c-enum",
 ]
 
 exclude = ["services/libs/comp-sys/controlled", "services/libs/comp-sys/cargo-component"]

services/libs/int-to-c-enum/.gitignore

@@ -0,0 +1,2 @@
+/target
+/Cargo.lock

services/libs/int-to-c-enum/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "int-to-c-enum"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+int-to-c-enum-derive = { path = "derive", optional = true }
+
+[features]
+default = ["derive"]
+derive = ["int-to-c-enum-derive"]

services/libs/int-to-c-enum/README.md

@@ -0,0 +1,35 @@
+# TryFromInt - A convenient derive macro for converting an integer to an enum
+
+## Quick Start
+To use this crate, first add this crate to your `Cargo.toml`.
+
+```toml
+[dependencies]
+int-to-c-enum = "0.1.0"
+```
+
+You can use this macro for a [C-like enum](https://doc.rust-lang.org/stable/rust-by-example/custom_types/enum/c_like.html).
+
+```rust 
+use int_to_c_enum::TryFromInt;
+#[repr(u8)]
+#[derive(TryFromInt, Debug)]
+pub enum Color {
+    Red = 1,
+    Blue = 2,
+    Green = 3,
+}
+```
+
+Then, you can use `try_from` function for this enum.
+```rust
+fn main() {
+    let color = Color::try_from(1).unwrap();
+    println!("color = {color:?}"); // color = Red;
+}
+```
+
+## Introduction
+This crate provides a derive procedural macro named `TryFromInt`. This macro will automatically implement [TryFrom](https://doc.rust-lang.org/core/convert/trait.TryFrom.html) trait for enums that meet the following requirements:
+1. The enum must have a primitive repr, i.e., the enum should have attribute like #[repr(u8)], #[repr(u32)], etc. The type parameter of TryFrom will be the repr, e.g., in the `QuickStart` example, the macro will implment `TryFrom<u8>` for `Color`.
+2. The enum must consist solely of unit variants, which is called [units only enum](https://doc.rust-lang.org/reference/items/enumerations.html#unit-only-enum). Each field should have an **explicit discriminant**.

services/libs/int-to-c-enum/derive/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "int-to-c-enum-derive"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[lib]
+proc-macro = true
+
+[dependencies]
+proc-macro2 = "1.0"
+quote = "1.0"
+syn = { version = "2.0.15", features = ["parsing"] }

services/libs/int-to-c-enum/derive/src/lib.rs

@@ -0,0 +1,106 @@
+use proc_macro2::{Ident, TokenStream};
+use quote::{format_ident, quote, TokenStreamExt};
+use syn::{parse_macro_input, Attribute, Data, DataEnum, DeriveInput, Generics};
+
+const ALLOWED_REPRS: &[&str] = &[
+    "u8", "i8", "u16", "i16", "u32", "i32", "u64", "i64", "usize", "isize",
+];
+const VALUE_NAME: &str = "value";
+const REPR_PATH: &str = "repr";
+
+#[proc_macro_derive(TryFromInt)]
+pub fn derive_try_from_num(input_token: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    let input = parse_macro_input!(input_token as DeriveInput);
+    expand_derive_try_from_num(input).into()
+}
+
+fn expand_derive_try_from_num(input: DeriveInput) -> TokenStream {
+    let attrs = input.attrs;
+    let ident = input.ident;
+    let generics = input.generics;
+    if let Data::Enum(data_enum) = input.data {
+        impl_try_from(data_enum, attrs, generics, ident)
+    } else {
+        panic!("cannot derive TryFromInt for structs or union.")
+    }
+}
+
+fn impl_try_from(
+    data_enum: DataEnum,
+    attrs: Vec<Attribute>,
+    generics: Generics,
+    ident: Ident,
+) -> TokenStream {
+    let valid_repr = if let Some(valid_repr) = has_valid_repr(attrs) {
+        format_ident!("{}", valid_repr)
+    } else {
+        panic!(
+            "{} does not have invalid repr to implement TryFromInt.",
+            ident.to_string()
+        );
+    };
+
+    for variant in &data_enum.variants {
+        if variant.discriminant.is_none() {
+            panic!("Enum can only have fields like Variant=1");
+        }
+    }
+
+    let (impl_generics, type_generics, where_clause) = generics.split_for_impl();
+    let fn_body = fn_body_tokens(VALUE_NAME, &data_enum, ident.clone());
+    let param = format_ident!("{}", VALUE_NAME);
+    quote!(
+        #[automatically_derived]
+        impl #impl_generics ::core::convert::TryFrom<#valid_repr> #type_generics for #ident #where_clause  {
+            type Error = ::int_to_c_enum::TryFromIntError;
+            fn try_from(#param: #valid_repr) -> ::core::result::Result<Self, Self::Error> {
+                #fn_body
+            }
+        }
+    )
+}
+
+fn fn_body_tokens(value_name: &str, data_enum: &DataEnum, ident: Ident) -> TokenStream {
+    let mut match_bodys = quote!();
+    for variant in &data_enum.variants {
+        let (_, value) = variant
+            .discriminant
+            .as_ref()
+            .expect("Each field must be assigned a discriminant value explicitly");
+        let vairant_ident = &variant.ident;
+        let statement = quote!(#value => ::core::result::Result::Ok(#ident::#vairant_ident),);
+        match_bodys.append_all(statement);
+    }
+    match_bodys.append_all(quote!(_ => core::result::Result::Err(::int_to_c_enum::TryFromIntError::InvalidValue),));
+    let param = format_ident!("{}", value_name);
+    quote!(match #param {
+        #match_bodys
+    })
+}
+
+fn has_valid_repr(attrs: Vec<Attribute>) -> Option<&'static str> {
+    for attr in attrs {
+        if let Some(repr) = parse_repr(attr) {
+            return Some(repr);
+        }
+    }
+    None
+}
+
+fn parse_repr(attr: Attribute) -> Option<&'static str> {
+    if !attr.path().is_ident(REPR_PATH) {
+        return None;
+    }
+    let mut repr = None;
+    attr.parse_nested_meta(|meta| {
+        for allowed_repr in ALLOWED_REPRS {
+            if meta.path.is_ident(*allowed_repr) {
+                repr = Some(*allowed_repr);
+                break;
+            }
+        }
+        Ok(())
+    })
+    .ok()?;
+    repr
+}

services/libs/int-to-c-enum/src/lib.rs

@@ -0,0 +1,47 @@
+//! This crate provides a derive macro named TryFromInt. This macro can be used to automatically implement TryFrom trait
+//! for [C-like enums](https://doc.rust-lang.org/stable/rust-by-example/custom_types/enum/c_like.html).
+//!
+//! Currently, this macro only supports enums with [explicit discriminants](https://doc.rust-lang.org/reference/items/enumerations.html#explicit-discriminants).
+//!
+//! Below is a simple example. We derive macro `TryFromInt` for an enum `Color`.
+//! ```rust
+//! use int_to_c_enum::TryFromInt;
+//! #[repr(u8)]
+//! #[derive(TryFromInt, Eq, PartialEq)]
+//! pub enum Color {
+//!     Red = 1,
+//!     Yellow = 2,
+//!     Blue = 3,
+//! }
+//! // Then, we can use method `try_from` for `Color`.
+//! let color = Color::try_from(1).unwrap();
+//! assert!(color == Color::Red);
+//! ```
+//!
+//! The `TryFromInt` macro will automatically implement trait `TryFrom<u8>` for `Color`.
+//! After macro expansion, the generated code looks like as follows:
+//! ```ignore
+//! impl TryFrom<u8> for Color {
+//!     type Error = TryFromIntError;
+//!     fn try_from(value: u8) -> Result<Self, Self::Error> {
+//!         match value {
+//!             1 => Ok(Color::Red),
+//!             2 => Ok(Color::Yellow),
+//!             3 => Ok(Color::Blue),
+//!             _ => Err(TryFromIntError::InvalidValue),
+//!         }
+//!     }
+//! }
+//! ```
+//! 
+
+#![no_std]
+
+/// Error type for TryFromInt derive macro
+#[derive(Debug, Clone, Copy)]
+pub enum TryFromIntError {
+    InvalidValue,
+}
+
+#[cfg(feature = "derive")]
+pub use int_to_c_enum_derive::TryFromInt;

services/libs/int-to-c-enum/tests/regression.rs

@@ -0,0 +1,22 @@
+use int_to_c_enum::TryFromInt;
+
+#[derive(TryFromInt, Debug, PartialEq, Eq)]
+#[repr(u8)]
+enum Color {
+    Red = 1,
+    Blue = 2,
+    Green = 3,
+}
+
+#[test]
+fn conversion() {
+    let color = Color::try_from(1).unwrap();
+    println!("color = {color:?}");
+    assert!(color == Color::Red);
+}
+
+#[test]
+fn invalid_value() {
+    let color = Color::try_from(4);
+    assert!(color.is_err());
+}