Deduplicate arbitrator RustBytes types

arbitrator/prover/src/lib.rs

@@ -36,6 +36,7 @@ use once_cell::sync::OnceCell;
 use static_assertions::const_assert_eq;
 use std::{
     ffi::CStr,
+    marker::PhantomData,
     num::NonZeroUsize,
     os::raw::{c_char, c_int},
     path::Path,
@@ -59,11 +60,67 @@ pub struct CByteArray {
 }
 
 #[repr(C)]
-#[derive(Clone, Copy)]
-pub struct RustByteArray {
+pub struct RustSlice<'a> {
+    pub ptr: *const u8,
+    pub len: usize,
+    pub phantom: PhantomData<&'a [u8]>,
+}
+
+impl<'a> RustSlice<'a> {
+    pub fn new(slice: &'a [u8]) -> Self {
+        if slice.is_empty() {
+            return Self {
+                ptr: ptr::null(),
+                len: 0,
+                phantom: PhantomData,
+            };
+        }
+        Self {
+            ptr: slice.as_ptr(),
+            len: slice.len(),
+            phantom: PhantomData,
+        }
+    }
+}
+
+#[repr(C)]
+pub struct RustBytes {
     pub ptr: *mut u8,
     pub len: usize,
-    pub capacity: usize,
+    pub cap: usize,
+}
+
+impl RustBytes {
+    pub unsafe fn into_vec(self) -> Vec<u8> {
+        Vec::from_raw_parts(self.ptr, self.len, self.cap)
+    }
+
+    pub unsafe fn write(&mut self, mut vec: Vec<u8>) {
+        if vec.capacity() == 0 {
+            *self = RustBytes {
+                ptr: ptr::null_mut(),
+                len: 0,
+                cap: 0,
+            };
+            return;
+        }
+        self.ptr = vec.as_mut_ptr();
+        self.len = vec.len();
+        self.cap = vec.capacity();
+        std::mem::forget(vec);
+    }
+}
+
+/// Frees the vector. Does nothing when the vector is null.
+///
+/// # Safety
+///
+/// Must only be called once per vec.
+#[no_mangle]
+pub unsafe extern "C" fn free_rust_bytes(vec: RustBytes) {
+    if !vec.ptr.is_null() {
+        drop(vec.into_vec())
+    }
 }
 
 #[no_mangle]
@@ -410,18 +467,6 @@ pub unsafe extern "C" fn arbitrator_module_root(mach: *mut Machine) -> Bytes32 {
 
 #[no_mangle]
 #[cfg(feature = "native")]
-pub unsafe extern "C" fn arbitrator_gen_proof(mach: *mut Machine) -> RustByteArray {
-    let mut proof = (*mach).serialize_proof();
-    let ret = RustByteArray {
-        ptr: proof.as_mut_ptr(),
-        len: proof.len(),
-        capacity: proof.capacity(),
-    };
-    std::mem::forget(proof);
-    ret
-}
-
-#[no_mangle]
-pub unsafe extern "C" fn arbitrator_free_proof(proof: RustByteArray) {
-    drop(Vec::from_raw_parts(proof.ptr, proof.len, proof.capacity))
+pub unsafe extern "C" fn arbitrator_gen_proof(mach: *mut Machine, out: *mut RustBytes) {
+    (*out).write((*mach).serialize_proof());
 }

arbitrator/stylus/src/evm_api.rs

@@ -1,11 +1,12 @@
 // Copyright 2022-2024, Offchain Labs, Inc.
 // For license information, see https://github.com/OffchainLabs/nitro/blob/master/LICENSE
 
-use crate::{GoSliceData, RustSlice};
+use crate::GoSliceData;
 use arbutil::evm::{
     api::{EvmApiMethod, Gas, EVM_API_METHOD_REQ_OFFSET},
     req::RequestHandler,
 };
+use prover::RustSlice;
 
 #[repr(C)]
 pub struct NativeRequestHandler {

arbitrator/stylus/src/lib.rs

@@ -15,9 +15,12 @@ use cache::{deserialize_module, CacheMetrics, InitCache};
 use evm_api::NativeRequestHandler;
 use eyre::ErrReport;
 use native::NativeInstance;
-use prover::programs::{prelude::*, StylusData};
+use prover::{
+    programs::{prelude::*, StylusData},
+    RustBytes,
+};
 use run::RunProgram;
-use std::{marker::PhantomData, mem, ptr};
+use std::ptr;
 use target_cache::{target_cache_get, target_cache_set};
 
 pub use brotli;
@@ -76,52 +79,15 @@ impl DataReader for GoSliceData {
     }
 }
 
-#[repr(C)]
-pub struct RustSlice<'a> {
-    ptr: *const u8,
-    len: usize,
-    phantom: PhantomData<&'a [u8]>,
-}
-
-impl<'a> RustSlice<'a> {
-    fn new(slice: &'a [u8]) -> Self {
-        Self {
-            ptr: slice.as_ptr(),
-            len: slice.len(),
-            phantom: PhantomData,
-        }
-    }
-}
-
-#[repr(C)]
-pub struct RustBytes {
-    ptr: *mut u8,
-    len: usize,
-    cap: usize,
+unsafe fn write_err(output: &mut RustBytes, err: ErrReport) -> UserOutcomeKind {
+    output.write(err.debug_bytes());
+    UserOutcomeKind::Failure
 }
 
-impl RustBytes {
-    unsafe fn into_vec(self) -> Vec<u8> {
-        Vec::from_raw_parts(self.ptr, self.len, self.cap)
-    }
-
-    unsafe fn write(&mut self, mut vec: Vec<u8>) {
-        self.ptr = vec.as_mut_ptr();
-        self.len = vec.len();
-        self.cap = vec.capacity();
-        mem::forget(vec);
-    }
-
-    unsafe fn write_err(&mut self, err: ErrReport) -> UserOutcomeKind {
-        self.write(err.debug_bytes());
-        UserOutcomeKind::Failure
-    }
-
-    unsafe fn write_outcome(&mut self, outcome: UserOutcome) -> UserOutcomeKind {
-        let (status, outs) = outcome.into_data();
-        self.write(outs);
-        status
-    }
+unsafe fn write_outcome(output: &mut RustBytes, outcome: UserOutcome) -> UserOutcomeKind {
+    let (status, outs) = outcome.into_data();
+    output.write(outs);
+    status
 }
 
 /// "activates" a user wasm.
@@ -164,7 +130,7 @@ pub unsafe extern "C" fn stylus_activate(
         gas,
     ) {
         Ok(val) => val,
-        Err(err) => return output.write_err(err),
+        Err(err) => return write_err(output, err),
     };
 
     *module_hash = module.hash();
@@ -194,16 +160,16 @@ pub unsafe extern "C" fn stylus_compile(
     let output = &mut *output;
     let name = match String::from_utf8(name.slice().to_vec()) {
         Ok(val) => val,
-        Err(err) => return output.write_err(err.into()),
+        Err(err) => return write_err(output, err.into()),
     };
     let target = match target_cache_get(&name) {
         Ok(val) => val,
-        Err(err) => return output.write_err(err),
+        Err(err) => return write_err(output, err),
     };
 
     let asm = match native::compile(wasm, version, debug, target) {
         Ok(val) => val,
-        Err(err) => return output.write_err(err),
+        Err(err) => return write_err(output, err),
     };
 
     output.write(asm);
@@ -218,7 +184,7 @@ pub unsafe extern "C" fn wat_to_wasm(wat: GoSliceData, output: *mut RustBytes) -
     let output = &mut *output;
     let wasm = match wasmer::wat2wasm(wat.slice()) {
         Ok(val) => val,
-        Err(err) => return output.write_err(err.into()),
+        Err(err) => return write_err(output, err.into()),
     };
     output.write(wasm.into_owned());
     UserOutcomeKind::Success
@@ -241,16 +207,16 @@ pub unsafe extern "C" fn stylus_target_set(
     let output = &mut *output;
     let name = match String::from_utf8(name.slice().to_vec()) {
         Ok(val) => val,
-        Err(err) => return output.write_err(err.into()),
+        Err(err) => return write_err(output, err.into()),
     };
 
     let desc_str = match String::from_utf8(description.slice().to_vec()) {
         Ok(val) => val,
-        Err(err) => return output.write_err(err.into()),
+        Err(err) => return write_err(output, err.into()),
     };
 
     if let Err(err) = target_cache_set(name, desc_str, native) {
-        return output.write_err(err);
+        return write_err(output, err);
     };
 
     UserOutcomeKind::Success
@@ -298,8 +264,8 @@ pub unsafe extern "C" fn stylus_call(
     };
 
     let status = match instance.run_main(&calldata, config, ink) {
-        Err(e) | Ok(UserOutcome::Failure(e)) => output.write_err(e.wrap_err("call failed")),
-        Ok(outcome) => output.write_outcome(outcome),
+        Err(e) | Ok(UserOutcome::Failure(e)) => write_err(output, e.wrap_err("call failed")),
+        Ok(outcome) => write_outcome(output, outcome),
     };
     let ink_left = match status {
         UserOutcomeKind::OutOfStack => Ink(0), // take all gas when out of stack
@@ -352,18 +318,6 @@ pub extern "C" fn stylus_reorg_vm(_block: u64, arbos_tag: u32) {
     InitCache::clear_long_term(arbos_tag);
 }
 
-/// Frees the vector. Does nothing when the vector is null.
-///
-/// # Safety
-///
-/// Must only be called once per vec.
-#[no_mangle]
-pub unsafe extern "C" fn stylus_drop_vec(vec: RustBytes) {
-    if !vec.ptr.is_null() {
-        mem::drop(vec.into_vec())
-    }
-}
-
 /// Gets cache metrics.
 ///
 /// # Safety

arbos/programs/native.go

@@ -450,10 +450,16 @@ func addressToBytes20(addr common.Address) bytes20 {
 }
 
 func (slice *rustSlice) read() []byte {
+	if slice.len == 0 {
+		return nil
+	}
 	return arbutil.PointerToSlice((*byte)(slice.ptr), int(slice.len))
 }
 
 func (vec *rustBytes) read() []byte {
+	if vec.len == 0 {
+		return nil
+	}
 	return arbutil.PointerToSlice((*byte)(vec.ptr), int(vec.len))
 }
 
@@ -464,7 +470,7 @@ func (vec *rustBytes) intoBytes() []byte {
 }
 
 func (vec *rustBytes) drop() {
-	C.stylus_drop_vec(*vec)
+	C.free_rust_bytes(*vec)
 }
 
 func goSlice(slice []byte) C.GoSliceData {

validator/server_arb/machine.go

@@ -304,9 +304,13 @@ func (m *ArbitratorMachine) ProveNextStep() []byte {
 	m.mutex.Lock()
 	defer m.mutex.Unlock()
 
-	rustProof := C.arbitrator_gen_proof(m.ptr)
-	proofBytes := C.GoBytes(unsafe.Pointer(rustProof.ptr), C.int(rustProof.len))
-	C.arbitrator_free_proof(rustProof)
+	output := &C.RustBytes{}
+	C.arbitrator_gen_proof(m.ptr, output)
+	defer C.free_rust_bytes(*output)
+	if output.len == 0 {
+		return nil
+	}
+	proofBytes := C.GoBytes(unsafe.Pointer(output.ptr), C.int(output.len))
 
 	return proofBytes
 }