implement hashCode()

Author: sidepelican

Sources/JExtractSwiftLib/JNI/JNISwift2JavaGenerator+JavaBindingsPrinting.swift

@@ -380,6 +380,10 @@ extension JNISwift2JavaGenerator {
           return false;
         }
 
+        public int hashCode() {
+          return SwiftObjects.hashCode(this.$memoryAddress(), this.$typeMetadataAddress());
+        }
+
         public java.lang.String toString() {
           return SwiftObjects.toString(this.$memoryAddress(), this.$typeMetadataAddress());
         }

Sources/SwiftJava/SwiftObjects.swift

@@ -135,4 +135,24 @@ extension SwiftObjects {
     }
     return perform(lhsType: lhsMetatype, rhsType: rhsMetatype)
   }
+
+  @JavaMethod
+  public static func hashCode(environment: UnsafeMutablePointer<JNIEnv?>!, selfPointer: Int64, selfTypePointer: Int64) -> Int32 {
+    guard let selfType$ = UnsafeRawPointer(bitPattern: Int(selfTypePointer)) else {
+      fatalError("selfType metadata address was null")
+    }
+    let typeMetadata = unsafeBitCast(selfType$, to: Any.Type.self)
+    guard let typeMetadata = typeMetadata as? (any Hashable.Type) else {
+      // For value types, different instances may return different hash codes even if the values are same.
+      return Int32(truncatingIfNeeded: selfPointer.hashValue)
+    }
+
+    func perform<T: Hashable>(as type: T.Type) -> Int32 {
+      guard let self$ = UnsafeMutablePointer<T>(bitPattern: Int(selfPointer)) else {
+        fatalError("self memory address was null")
+      }
+      return Int32(truncatingIfNeeded: self$.pointee.hashValue)
+    }
+    return perform(as: typeMetadata)
+  }
 }

SwiftKitCore/src/main/java/org/swift/swiftkit/core/SwiftObjects.java

@@ -30,4 +30,5 @@ public static void requireNonZero(long number, String name) {
     public static native void destroy(long selfPointer, long selfTypePointer);
     public static native String typeDescription(long selfTypePointer);
     public static native boolean equals(long lhsPointer, long lhsTypePointer, long rhsPointer, long rhsTypePointer);
+    public static native int hashCode(long selfPointer, long selfTypePointer);
 }