Optimize RustStr's Equatable implementation (#151)

SwiftRustIntegrationTestRunner/SwiftRustIntegrationTestRunnerTests/StringTests.swift

@@ -46,5 +46,26 @@ class StringTests: XCTestCase {
             "hi"
         )
     }
+
+    func testRustStrEqualityOperator() throws {
+        XCTContext.runActivity(named: "Should be equal"){
+            _ in
+            let hello1 = create_string("hello")
+            let hello2 = create_string("hello")
+            XCTAssertEqual(hello1.as_str(), hello2.as_str())
+        }
+        XCTContext.runActivity(named: "Should not be equal"){
+            _ in
+            //Not equal length
+            let hi    = create_string("hi")
+            let hello = create_string("hello")
+            XCTAssertNotEqual(hi.as_str(), hello.as_str())
+
+            //Equal length
+            let foo  = create_string("foo")
+            let bar = create_string("bar")
+            XCTAssertNotEqual(foo.as_str(), bar.as_str())
+        }
+    }
 }
 

crates/swift-bridge-build/src/generate_core/rust_string.c.h

@@ -15,4 +15,5 @@ void* __swift_bridge__$RustString$new(void);
 void* __swift_bridge__$RustString$new_with_str(struct RustStr str);
 uintptr_t __swift_bridge__$RustString$len(void* self);
 struct RustStr __swift_bridge__$RustString$as_str(void* self);
-struct RustStr __swift_bridge__$RustString$trim(void* self);
+struct RustStr __swift_bridge__$RustString$trim(void* self);
+bool __swift_bridge__$RustStr$partial_eq(struct RustStr lhs, struct RustStr rhs);

crates/swift-bridge-build/src/generate_core/string.swift

@@ -27,10 +27,7 @@ extension RustStr: Identifiable {
 }
 extension RustStr: Equatable {
     public static func == (lhs: RustStr, rhs: RustStr) -> Bool {
-        // TODO: Rather than compare Strings, we can avoid allocating by calling a function
-        // on the Rust side that compares the underlying byte slices.
-        return
-            lhs.toString() == rhs.toString()
+        return __swift_bridge__$RustStr$partial_eq(lhs, rhs);
     }
 }
 

src/std_bridge.rs

@@ -1,3 +1,5 @@
+//! The corresponding C and Swift code can be found in
+//! crates/swift-bridge-build/src/generate_core/*
 #![allow(missing_docs)]
 
 pub mod option;

src/std_bridge/string.rs

@@ -1,3 +1,5 @@
+//! The corresponding C and Swift code can be found in
+//! crates/swift-bridge-build/src/generate_core/rust_string.{c.h,swift}
 pub use self::ffi::*;
 
 #[swift_bridge_macro::bridge(swift_bridge_path = crate)]
@@ -80,3 +82,18 @@ impl RustStr {
         }
     }
 }
+
+impl PartialEq for RustStr {
+    fn eq(&self, other: &Self) -> bool {
+        unsafe {
+            std::slice::from_raw_parts(self.start, self.len)
+                == std::slice::from_raw_parts(other.start, other.len)
+        }
+    }
+}
+
+#[export_name = "__swift_bridge__$RustStr$partial_eq"]
+#[allow(non_snake_case)]
+pub extern "C" fn __swift_bridge__RustStr_partial_eq(lhs: RustStr, rhs: RustStr) -> bool {
+    lhs == rhs
+}