Support no_std in roto-runtime

Add #![no_std] to the runtime crate and introduce optional std and
alloc features. Update the code generator to be compatible and add a
no_std_test example. Remove the generator binary.

Cargo.lock

@@ -832,6 +832,13 @@ version = "0.10.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1d87ecb2933e8aeadb3e3a02b828fed80a7528047e68b4f424523a0981a3a084"
 
+[[package]]
+name = "no_std_test"
+version = "0.1.0"
+dependencies = [
+ "roto-runtime",
+]
+
 [[package]]
 name = "num-traits"
 version = "0.2.19"

Cargo.toml

@@ -6,8 +6,15 @@ members = [
     "benches",
     "roto-tonic",
     "examples/hello_world",
+    "examples/no_std_test",
 ]
 
 exclude = [
     "test_gen_project"
 ]
+
+[profile.dev]
+panic = "abort"
+
+[profile.release]
+panic = "abort"

codegen/src/bin/generator.rs

@@ -1,42 +0,0 @@
-use clap::Parser;
-use roto_codegen::generator::generate_rust_code;
-use roto_codegen::google::protobuf::descriptor::FileDescriptorSet;
-use std::fs;
-use std::path::PathBuf;
-
-#[derive(Parser)]
-#[command(
-    author,
-    version,
-    about = "Generates Rust accessor and builder code from a protobuf descriptor set"
-)]
-struct Args {
-    /// Path to the descriptor set file (.desc)
-    #[arg(short, long)]
-    input: PathBuf,
-
-    /// Path to the output directory
-    #[arg(short, long)]
-    output: PathBuf,
-
-    /// Files to generate. If omitted, all files are generated.
-    #[arg(short, long, value_delimiter = ',')]
-    files: Option<Vec<String>>,
-}
-
-fn main() -> Result<(), Box<dyn std::error::Error>> {
-    let args = Args::parse();
-    let data = fs::read(&args.input)?;
-    let set = FileDescriptorSet::new(&data).expect("Failed to parse FileDescriptorSet");
-
-    let files = generate_rust_code(&set, args.files.as_deref(), true);
-
-    for (filename, content) in files {
-        let path = args.output.join(filename);
-        if let Some(parent) = path.parent() {
-            fs::create_dir_all(parent)?;
-        }
-        fs::write(path, content)?;
-    }
-    Ok(())
-}

codegen/src/generator.rs

@@ -6,7 +6,7 @@ use roto_runtime::ProtoAccessor;
 use std::collections::{HashMap, HashSet};
 use std::str;
 
-const DATA_IMPORTS: &str = "use roto_runtime::{ProtoAccessor, ProtoBuilder, Result, RotoError, read_varint, RepeatedFieldIterator, RotoMessage};\nuse std::str;\nuse bytes::{Bytes, BytesMut, Buf, BufMut};\n";
+const DATA_IMPORTS: &str = "use roto_runtime::{ProtoAccessor, ProtoBuilder, Result, RotoError, read_varint, RepeatedFieldIterator, RotoMessage};\nuse core::str;\nuse bytes::{Bytes, BytesMut, Buf, BufMut};\n";
 const SERVICE_IMPORTS: &str = "use tonic::{Request, Response, Status};\nuse tokio_stream::Stream;\nuse std::pin::Pin;\nuse std::sync::Arc;\nuse std::task::{Context, Poll};\nuse std::future::Future;\nuse tonic::body::BoxBody;\nuse tower::Service;\nuse futures_util::StreamExt;\nuse http_body_util::BodyExt;\nuse http_body::Body;\nuse crate::{BufferPool, StatusBody};\n";
 
 pub fn to_pascal_case(s: &str) -> String {
@@ -440,18 +440,18 @@ fn write_message(msg_proto: &DescriptorProto, output: &mut String) {
 
     output.push_str(&format!("    pub fn finish(self) -> roto_runtime::Result<&'b mut [u8]> {{\n        self.builder.finish()\n    }}\n}}\n\n"));
 
-    output.push_str(&format!("pub struct Owned{} {{\n", msg_name));
+    output.push_str(&format!("#[cfg(feature = \"alloc\")]\npub struct Owned{} {{\n", msg_name));
     output.push_str("    pub data: bytes::Bytes,\n");
     output.push_str("}\n\n");
 
-    output.push_str(&format!("impl roto_runtime::RotoOwned for Owned{} {{\n", msg_name));
+    output.push_str(&format!("#[cfg(feature = \"alloc\")]\nimpl roto_runtime::RotoOwned for Owned{} {{\n", msg_name));
     output.push_str(&format!("    type Reader<'a> = {}<'a>;\n", msg_name));
     output.push_str(&format!("    fn reader(&self) -> {}<'_> {{\n", msg_name));
     output.push_str(&format!("        {}::new(&self.data).expect(\"failed to create reader\")\n", msg_name));
     output.push_str("    }\n");
     output.push_str("}\n\n");
 
-    output.push_str(&format!("impl roto_runtime::RotoMessage for Owned{} {{\n", msg_name));
+    output.push_str(&format!("#[cfg(feature = \"alloc\")]\nimpl roto_runtime::RotoMessage for Owned{} {{\n", msg_name));
     output.push_str("    fn decode(buf: bytes::Bytes) -> roto_runtime::Result<Self> {\n");
     output.push_str(&format!("        Ok(Owned{} {{ data: buf }})\n", msg_name));
     output.push_str("    }\n\n");

examples/no_std_test/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "no_std_test"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+roto-runtime = { path = "../../runtime", default-features = false }
+
+[profile.dev]
+panic = "abort"
+
+[profile.release]
+panic = "abort"

examples/no_std_test/src/main.rs

@@ -0,0 +1,16 @@
+#![no_std]
+#![no_main]
+
+use roto_runtime::ProtoAccessor;
+
+#[panic_handler]
+fn panic(_info: &core::panic::PanicInfo) -> ! {
+    loop {}
+}
+
+#[unsafe(no_mangle)]
+pub extern "C" fn _start() -> ! {
+    let _data = [0u8; 0];
+    let _ = ProtoAccessor::new(&_data);
+    loop {}
+}

runtime/Cargo.toml

@@ -4,4 +4,9 @@ version = "0.1.0"
 edition = "2024"
 
 [dependencies]
-bytes = "1.7"
+bytes = { version = "1.7", default-features = false }
+
+[features]
+default = ["std", "alloc"]
+std = []
+alloc = []

runtime/src/lib.rs

@@ -1,4 +1,9 @@
-use std::fmt;
+#![no_std]
+
+#[cfg(feature = "std")]
+extern crate std;
+
+use core::fmt;
 use bytes::BufMut;
 
 pub struct MapFieldIterator<'a> {
@@ -51,9 +56,10 @@ impl fmt::Display for RotoError {
     }
 }
 
+#[cfg(feature = "std")]
 impl std::error::Error for RotoError {}
 
-pub type Result<T> = std::result::Result<T, RotoError>;
+pub type Result<T> = core::result::Result<T, RotoError>;
 
 pub trait RotoOwned {
     type Reader<'a> where Self: 'a;
@@ -686,7 +692,7 @@ mod tests {
             .iter_repeated(18)
             .map(|r| {
                 let (val, _) = r.expect("Failed to decode repeated string");
-                std::str::from_utf8(val).expect("Invalid utf8")
+                core::str::from_utf8(val).expect("Invalid utf8")
             })
             .collect();
         assert_eq!(repeated_strings, vec!["one", "two", "three"]);