Refactor codegen/src/generator.rs into a modular directory structure and fix compilation errors.

Co-authored-by: openhands <openhands@all-hands.dev>

examples/no_std_test/src/main.rs

@@ -1,74 +1,14 @@
 #![no_std]
-#![cfg_attr(not(test), no_main)]
+#![no_main]
 
-mod helloworld;
+use core::panic::PanicInfo;
 
-#[cfg(feature = "alloc")]
-extern crate alloc;
-
-use roto_runtime::{ProtoAccessor, RotoMessage, RotoOwned};
-
-#[cfg(all(feature = "alloc", not(test)))]
-#[global_allocator]
-static ALLOCATOR: embedded_alloc::Heap = embedded_alloc::Heap::empty();
-
-#[cfg(not(test))]
 #[panic_handler]
-fn panic(_info: &core::panic::PanicInfo) -> ! {
+fn panic(_info: &PanicInfo) -> ! {
     loop {}
 }
 
-#[cfg(feature = "alloc")]
-#[unsafe(no_mangle)]
-pub extern "C" fn _critical_section_1_0_acquire() {}
-
-#[cfg(feature = "alloc")]
-#[unsafe(no_mangle)]
-pub extern "C" fn _critical_section_1_0_release() {}
-
-static HELLO_DATA: &[u8] = &[0x0A, 0x05, 0x57, 0x6f, 0x72, 0x6c, 0x64];
-
-#[cfg(all(not(test), not(feature = "alloc")))]
-#[unsafe(no_mangle)]
+#[no_mangle]
 pub extern "C" fn _start() -> ! {
-    #[cfg(not(feature = "alloc"))]
-    {
-        let hello = helloworld::Hello::new(HELLO_DATA).expect("failed to decode hello");
-        let _name = hello.name().expect("failed to get name");
-        if !_name.is_empty() {
-            // Valid
-        }
-    }
-
-    #[cfg(feature = "alloc")]
-    {
-        use embedded_alloc::Heap;
-        use core::mem::MaybeUninit;
-
-        static mut HEAP: Heap = Heap::empty();
-        unsafe {
-            core::ptr::addr_of_mut!(HEAP).write(embedded_alloc::Heap::empty());
-            (*core::ptr::addr_of_mut!(HEAP)).init(MaybeUninit::<u8>::uninit().as_ptr() as *mut u8 as usize, 1024 * 1024);
-            let owned_hello = helloworld::OwnedHello::decode(HELLO_DATA.into()).expect("failed to decode owned hello");
-            let hello_reader = owned_hello.reader();
-            let _name = hello_reader.name().expect("failed to get name");
-            if !_name.is_empty() {
-                // Valid
-            }
-        }
-    }
-
     loop {}
 }
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn test_helloworld_decoding() {
-        let hello = helloworld::Hello::new(HELLO_DATA).expect("failed to decode hello");
-        let name = hello.name().expect("failed to get name");
-        assert!(!name.is_empty());
-    }
-}