Tensor constructor to create with an existing Tensor.

Differential Revision: D71906972

Pull Request resolved: #9677

Author: shoumikhin

extension/apple/ExecuTorch/Exported/ExecuTorchTensor.h

@@ -151,6 +151,15 @@ __attribute__((deprecated("This API is experimental.")))
 - (instancetype)initWithNativeInstance:(void *)nativeInstance
     NS_DESIGNATED_INITIALIZER NS_SWIFT_UNAVAILABLE("");
 
+/**
+ * Creates a new tensor by copying an existing tensor.
+ *
+ * @param otherTensor The tensor instance to copy.
+ * @return A new ExecuTorchTensor instance that is a copy of otherTensor.
+ */
+- (instancetype)initWithTensor:(ExecuTorchTensor *)otherTensor
+    NS_SWIFT_NAME(init(_:));
+
 /**
  * Executes a block with a pointer to the tensor's immutable byte data.
  *

extension/apple/ExecuTorch/Exported/ExecuTorchTensor.mm

@@ -44,6 +44,14 @@ - (instancetype)initWithNativeInstance:(void *)nativeInstance {
   return self;
 }
 
+- (instancetype)initWithTensor:(ExecuTorchTensor *)otherTensor {
+  ET_CHECK(otherTensor);
+  auto tensor = make_tensor_ptr(
+    **reinterpret_cast<TensorPtr *>(otherTensor.nativeInstance)
+  );
+  return [self initWithNativeInstance:&tensor];
+}
+
 - (void *)nativeInstance {
   return &_tensor;
 }

extension/apple/ExecuTorch/__tests__/TensorTest.swift

@@ -137,4 +137,18 @@ class TensorTest: XCTestCase {
       XCTAssertEqual(updatedData, [2, 4, 6, 8])
     }
   }
+
+  func testInitWithTensor() {
+    var data: [Int] = [10, 20, 30, 40]
+    let tensor1 = data.withUnsafeMutableBytes {
+      Tensor(bytesNoCopy: $0.baseAddress!, shape: [2, 2], dataType: .int)
+    }
+    let tensor2 = Tensor(tensor1)
+
+    XCTAssertEqual(tensor2.dataType, tensor1.dataType)
+    XCTAssertEqual(tensor2.shape, tensor1.shape)
+    XCTAssertEqual(tensor2.strides, tensor1.strides)
+    XCTAssertEqual(tensor2.dimensionOrder, tensor1.dimensionOrder)
+    XCTAssertEqual(tensor2.count, tensor1.count)
+  }
 }