Rust -> Nim ABI (#62)

* Use correct build hook

* force sret like return from rust code for nim compatibility

* Fix target mismatch

* Update usages

.cargo/config.toml

@@ -0,0 +1,7 @@
+[env]
+# Pin the macOS deployment target so vendored C/C++ builds (SQLCipher, OpenSSL)
+# compile with the same minimum version as the Nim linker expects.
+# Without this, the host SDK version is used (currently 15.5), causing
+# "was built for newer macOS version" linker warnings.
+# This is caused by nimble and cargo defaulting to different targets.
+MACOSX_DEPLOYMENT_TARGET = { value = "15.0", force = false }

conversations/src/api.rs

@@ -55,9 +55,12 @@ pub fn create_context(name: repr_c::String) -> repr_c::Box<ContextHandle> {
 }
 
 /// Returns the friendly name of the contexts installation.
+///
+/// # ABI note
+/// The result is written through `out` (Nim's calling convention for large struct returns).
 #[ffi_export]
-pub fn installation_name(ctx: &ContextHandle) -> repr_c::String {
-    ctx.0.installation_name().to_string().into()
+pub fn installation_name(ctx: &ContextHandle, out: &mut repr_c::String) {
+    *out = ctx.0.installation_name().to_string().into();
 }
 
 /// Destroys a conversation store and frees its memory
@@ -74,11 +77,13 @@ pub fn destroy_context(ctx: repr_c::Box<ContextHandle>) {
 /// Creates an intro bundle for sharing with other users
 ///
 /// # Returns
-/// Returns the number of bytes written to bundle_out
 /// Check error_code field: 0 means success, negative values indicate errors (see ErrorCode).
+///
+/// # ABI note
+/// The result is written through `out` (Nim's calling convention for large struct returns).
 #[ffi_export]
-pub fn create_intro_bundle(ctx: &mut ContextHandle) -> CreateIntroResult {
-    match ctx.0.create_intro_bundle() {
+pub fn create_intro_bundle(ctx: &mut ContextHandle, out: &mut CreateIntroResult) {
+    *out = match ctx.0.create_intro_bundle() {
         Ok(v) => CreateIntroResult {
             error_code: ErrorCode::None as i32,
             intro_bytes: v.into(),
@@ -87,7 +92,7 @@ pub fn create_intro_bundle(ctx: &mut ContextHandle) -> CreateIntroResult {
             error_code: ErrorCode::UnknownError as i32,
             intro_bytes: repr_c::Vec::EMPTY,
         },
-    }
+    };
 }
 
 /// Creates a new private conversation
@@ -95,19 +100,24 @@ pub fn create_intro_bundle(ctx: &mut ContextHandle) -> CreateIntroResult {
 /// # Returns
 /// Returns a struct with payloads that must be sent, the conversation_id that was created.
 /// The NewConvoResult must be freed.
+///
+/// # ABI note
+/// The result is written through `out` (Nim's calling convention for large struct returns).
 #[ffi_export]
 pub fn create_new_private_convo(
     ctx: &mut ContextHandle,
     bundle: c_slice::Ref<'_, u8>,
     content: c_slice::Ref<'_, u8>,
-) -> NewConvoResult {
+    out: &mut NewConvoResult,
+) {
     // Convert input bundle to Introduction
     let Ok(intro) = Introduction::try_from(bundle.as_slice()) else {
-        return NewConvoResult {
+        *out = NewConvoResult {
             error_code: ErrorCode::BadIntro as i32,
             convo_id: "".into(),
             payloads: Vec::new().into(),
         };
+        return;
     };
 
     // Create conversation
@@ -122,11 +132,11 @@ pub fn create_new_private_convo(
         })
         .collect();
 
-    NewConvoResult {
+    *out = NewConvoResult {
         error_code: 0,
         convo_id: convo_id.to_string().into(),
         payloads: ffi_payloads.into(),
-    }
+    };
 }
 
 /// Sends content to an existing conversation
@@ -134,19 +144,24 @@ pub fn create_new_private_convo(
 /// # Returns
 /// Returns a PayloadResult with payloads that must be delivered to participants.
 /// Check error_code field: 0 means success, negative values indicate errors (see ErrorCode).
+///
+/// # ABI note
+/// The result is written through `out` (Nim's calling convention for large struct returns).
 #[ffi_export]
 pub fn send_content(
     ctx: &mut ContextHandle,
     convo_id: repr_c::String,
     content: c_slice::Ref<'_, u8>,
-) -> SendContentResult {
+    out: &mut SendContentResult,
+) {
     let payloads = match ctx.0.send_content(&convo_id, &content) {
         Ok(p) => p,
         Err(_) => {
-            return SendContentResult {
+            *out = SendContentResult {
                 error_code: ErrorCode::UnknownError as i32,
                 payloads: safer_ffi::Vec::EMPTY,
             };
+            return;
         }
     };
 
@@ -158,10 +173,10 @@ pub fn send_content(
         })
         .collect();
 
-    SendContentResult {
+    *out = SendContentResult {
         error_code: 0,
         payloads: ffi_payloads.into(),
-    }
+    };
 }
 
 /// Handles an incoming payload
@@ -170,15 +185,19 @@ pub fn send_content(
 /// Returns HandlePayloadResult
 /// This call does not always generate content. If data is zero bytes long then there
 /// is no data, and the converation_id should be ignored.
+///
+/// # ABI note
+/// The result is written through `out` (Nim's calling convention for large struct returns).
 #[ffi_export]
 pub fn handle_payload(
     ctx: &mut ContextHandle,
     payload: c_slice::Ref<'_, u8>,
-) -> HandlePayloadResult {
-    match ctx.0.handle_payload(&payload) {
+    out: &mut HandlePayloadResult,
+) {
+    *out = match ctx.0.handle_payload(&payload) {
         Ok(o) => o.into(),
         Err(e) => e.into(),
-    }
+    };
 }
 
 // ------------------------------------------

conversations/src/lib.rs

@@ -25,7 +25,11 @@ mod tests {
         let mut raya = create_context("raya".into());
 
         // Raya Creates Bundle and Sends to Saro
-        let intro_result = create_intro_bundle(&mut raya);
+        let mut intro_result = CreateIntroResult {
+            error_code: -99,
+            intro_bytes: safer_ffi::Vec::EMPTY,
+        };
+        create_intro_bundle(&mut raya, &mut intro_result);
         assert!(is_ok(intro_result.error_code));
 
         let raya_bundle = intro_result.intro_bytes.as_ref();
@@ -33,13 +37,24 @@ mod tests {
         // Saro creates a new conversation with Raya
         let content: &[u8] = "hello".as_bytes();
 
-        let convo_result = create_new_private_convo(&mut saro, raya_bundle, content.into());
+        let mut convo_result = NewConvoResult {
+            error_code: -99,
+            convo_id: "".into(),
+            payloads: safer_ffi::Vec::EMPTY,
+        };
+        create_new_private_convo(&mut saro, raya_bundle, content.into(), &mut convo_result);
         assert!(is_ok(convo_result.error_code));
 
         // Raya recieves initial message
         let payload = convo_result.payloads.first().unwrap();
 
-        let handle_result = handle_payload(&mut raya, payload.data.as_ref());
+        let mut handle_result: HandlePayloadResult = HandlePayloadResult {
+            error_code: -99,
+            convo_id: "".into(),
+            content: safer_ffi::Vec::EMPTY,
+            is_new_convo: false,
+        };
+        handle_payload(&mut raya, payload.data.as_ref(), &mut handle_result);
         assert!(is_ok(handle_result.error_code));
 
         // Check that the Content sent was the content received

nim-bindings/conversations_example.nimble

@@ -13,9 +13,14 @@ bin           = @["libchat"]
 requires "nim >= 2.2.4"
 requires "results"
 
-# Build Rust library before compiling Nim
-before build:
+proc buildRust() =
   exec "cargo build --release --manifest-path ../Cargo.toml"
 
+
+# Build Rust library before compiling Nim
+before build:
+  buildRust()
+
 task pingpong, "Run pingpong example":
+  buildRust()
   exec "nim c -r --path:src --passL:../target/release/liblibchat.a examples/pingpong.nim"