Merge pull request #314 from swiftwasm/yt/typed-array-init

Add `JSTypedArray.init(buffer:)` initializer

Author: kateinoigakukun

Sources/JavaScriptKit/BasicObjects/JSTypedArray.swift

@@ -46,20 +46,32 @@ public class JSTypedArray<Element>: JSBridgedClass, ExpressibleByArrayLiteral wh
     ///
     /// - Parameter array: The array that will be copied to create a new instance of TypedArray
     public convenience init(_ array: [Element]) {
-        let jsArrayRef = array.withUnsafeBufferPointer { ptr in
-            // Retain the constructor function to avoid it being released before calling `swjs_create_typed_array`
-            withExtendedLifetime(Self.constructor!) { ctor in
-                swjs_create_typed_array(ctor.id, ptr.baseAddress, Int32(array.count))
-            }
+        let object = array.withUnsafeBufferPointer { buffer in
+            Self.createTypedArray(from: buffer)
         }
-        self.init(unsafelyWrapping: JSObject(id: jsArrayRef))
+        self.init(unsafelyWrapping: object)
     }
 
     /// Convenience initializer for `Sequence`.
     public convenience init<S: Sequence>(_ sequence: S) where S.Element == Element {
         self.init(Array(sequence))
     }
 
+    /// Initialize a new instance of TypedArray in JavaScript environment with given buffer contents.
+    ///
+    /// - Parameter buffer: The buffer that will be copied to create a new instance of TypedArray
+    public convenience init(buffer: UnsafeBufferPointer<Element>) {
+        self.init(unsafelyWrapping: Self.createTypedArray(from: buffer))
+    }
+
+    private static func createTypedArray(from buffer: UnsafeBufferPointer<Element>) -> JSObject {
+        // Retain the constructor function to avoid it being released before calling `swjs_create_typed_array`
+        let jsArrayRef = withExtendedLifetime(Self.constructor!) { ctor in
+            swjs_create_typed_array(ctor.id, buffer.baseAddress, Int32(buffer.count))
+        }
+        return JSObject(id: jsArrayRef)
+    }
+
     /// Length (in bytes) of the typed array.
     /// The value is established when a TypedArray is constructed and cannot be changed.
     /// If the TypedArray is not specifying a `byteOffset` or a `length`, the `length` of the referenced `ArrayBuffer` will be returned.

Tests/JavaScriptKitTests/JSTypedArrayTests.swift

@@ -97,4 +97,16 @@ final class JSTypedArrayTests: XCTestCase {
 
         XCTAssertEqual(toString(array.jsValue.object!), jsStringify(Array(0..<100)))
     }
+
+    func testInitWithBufferPointer() {
+        let buffer = UnsafeMutableBufferPointer<Float32>.allocate(capacity: 20)
+        defer { buffer.deallocate() }
+        for i in 0..<20 {
+            buffer[i] = Float32(i)
+        }
+        let typedArray = JSTypedArray<Float32>(buffer: UnsafeBufferPointer(buffer))
+        for i in 0..<20 {
+            XCTAssertEqual(typedArray[i], Float32(i))
+        }
+    }
 }