add napi_create_buffer_from_arraybuffer (#126)

packages/emnapi/include/node/node_api.h

@@ -145,6 +145,18 @@ napi_create_external_buffer(napi_env env,
                             void* finalize_hint,
                             napi_value* result);
 #endif  // NODE_API_NO_EXTERNAL_BUFFERS_ALLOWED
+
+#ifdef NAPI_EXPERIMENTAL
+#define NODE_API_EXPERIMENTAL_HAS_CREATE_BUFFER_FROM_ARRAYBUFFER
+
+NAPI_EXTERN napi_status NAPI_CDECL
+node_api_create_buffer_from_arraybuffer(napi_env env,
+                                        napi_value arraybuffer,
+                                        size_t byte_offset,
+                                        size_t byte_length,
+                                        napi_value* result);
+#endif  // NAPI_EXPERIMENTAL
+
 NAPI_EXTERN napi_status NAPI_CDECL napi_create_buffer_copy(napi_env env,
                                                            size_t length,
                                                            const void* data,

packages/emnapi/src/value/create.ts

@@ -229,10 +229,10 @@ export function napi_create_typedarray (
     $CHECK_ARG!(envObject, result)
 
     const handle = emnapiCtx.handleStore.get(arraybuffer)!
-    const buffer = handle.value
-    if (!(buffer instanceof ArrayBuffer)) {
+    if (!handle.isArrayBuffer()) {
       return envObject.setLastError(napi_status.napi_invalid_arg)
     }
+    const buffer = handle.value
 
     from64('byte_offset')
     from64('length')
@@ -412,6 +412,63 @@ export function napi_create_external_buffer (
   )
 }
 
+/**
+ * @__sig ippppp
+ */
+export function node_api_create_buffer_from_arraybuffer (
+  env: napi_env,
+  arraybuffer: napi_value,
+  byte_offset: size_t,
+  byte_length: size_t,
+  result: Pointer<napi_value>
+): napi_status {
+  // eslint-disable-next-line @typescript-eslint/no-unused-vars
+  let value: number
+
+  return $PREAMBLE!(env, (envObject) => {
+    $CHECK_ARG!(envObject, arraybuffer)
+    $CHECK_ARG!(envObject, result)
+    from64('byte_offset')
+    from64('byte_length')
+    byte_offset = byte_offset >>> 0
+    byte_length = byte_length >>> 0
+    const handle = emnapiCtx.handleStore.get(arraybuffer)!
+    if (!handle.isArrayBuffer()) {
+      return envObject.setLastError(napi_status.napi_invalid_arg)
+    }
+    const buffer = handle.value
+
+    if ((byte_length + byte_offset) > buffer.byteLength) {
+      const err: RangeError & { code?: string } = new RangeError('The byte offset + length is out of range')
+      err.code = 'ERR_OUT_OF_RANGE'
+      throw err
+    }
+
+    const Buffer = emnapiCtx.feature.Buffer!
+    if (!Buffer) {
+      throw emnapiCtx.createNotSupportBufferError('node_api_create_buffer_from_arraybuffer', '')
+    }
+    const out = Buffer.from(buffer, byte_offset, byte_length)
+    if (buffer === wasmMemory.buffer) {
+      if (!emnapiExternalMemory.wasmMemoryViewTable.has(out)) {
+        emnapiExternalMemory.wasmMemoryViewTable.set(out, {
+          Ctor: Buffer,
+          address: byte_offset,
+          length: byte_length,
+          ownership: ReferenceOwnership.kUserland,
+          runtimeAllocated: 0
+        })
+      }
+    }
+    from64('result')
+
+    // eslint-disable-next-line @typescript-eslint/no-unused-vars
+    value = emnapiCtx.addToCurrentScope(out).id
+    makeSetValue('result', 0, 'value', '*')
+    return envObject.getReturnStatus()
+  })
+}
+
 /**
  * @__sig ippppp
  */
@@ -433,10 +490,10 @@ export function napi_create_dataview (
     byte_length = byte_length >>> 0
     byte_offset = byte_offset >>> 0
     const handle = emnapiCtx.handleStore.get(arraybuffer)!
-    const buffer = handle.value
-    if (!(buffer instanceof ArrayBuffer)) {
+    if (!handle.isArrayBuffer()) {
       return envObject.setLastError(napi_status.napi_invalid_arg)
     }
+    const buffer = handle.value
 
     if ((byte_length + byte_offset) > buffer.byteLength) {
       const err: RangeError & { code?: string } = new RangeError('byte_offset + byte_length should be less than or equal to the size in bytes of the array passed in')

packages/test/CMakeLists.txt

@@ -294,6 +294,7 @@ add_test("number" "./number/binding.c;./number/test_null.c" OFF)
 add_test("symbol" "./symbol/binding.c" OFF)
 add_test("typedarray" "./typedarray/binding.c" OFF)
 add_test("buffer" "./buffer/binding.c" OFF)
+target_compile_definitions("buffer" PRIVATE "NAPI_EXPERIMENTAL")
 add_test("buffer_finalizer" "./buffer_finalizer/binding.c" OFF)
 add_test("fatal_exception" "./fatal_exception/binding.c" OFF)
 add_test("cleanup_hook" "./cleanup_hook/binding.c" OFF)

packages/test/buffer/binding.c

@@ -38,17 +38,23 @@ static const char theText[] =
 const unsigned int theTextSize = sizeof(theText);
 
 static int deleterCallCount = 0;
-static void deleteTheText(napi_env env, void* data, void* finalize_hint) {
-  NODE_API_ASSERT_RETURN_VOID(
-      env, data != NULL && strcmp(data, theText) == 0, "invalid data");
+
+static void deleteTheText(node_api_basic_env env,
+                          void* data,
+                          void* finalize_hint) {
+  NODE_API_BASIC_ASSERT_RETURN_VOID(data != NULL && strcmp(data, theText) == 0,
+                                    "invalid data");
+
   (void)finalize_hint;
   free(data);
   deleterCallCount++;
 }
 
-static void noopDeleter(napi_env env, void* data, void* finalize_hint) {
-  NODE_API_ASSERT_RETURN_VOID(
-      env, data != NULL && strcmp(data, theText) == 0, "invalid data");
+static void noopDeleter(node_api_basic_env env,
+                        void* data,
+                        void* finalize_hint) {
+  NODE_API_BASIC_ASSERT_RETURN_VOID(data != NULL && strcmp(data, theText) == 0,
+                                    "invalid data");
   (void)finalize_hint;
   deleterCallCount++;
 }
@@ -75,9 +81,12 @@ static napi_value newExternalBuffer(napi_env env, napi_callback_info info) {
   NODE_API_ASSERT(
       env, theCopy, "Failed to copy static text for newExternalBuffer");
   NODE_API_CALL(env,
-      napi_create_external_buffer(
-          env, theTextSize, theCopy, deleteTheText,
-          NULL /* finalize_hint */, &theBuffer));
+                napi_create_external_buffer(env,
+                                            sizeof(theText),
+                                            theCopy,
+                                            deleteTheText,
+                                            NULL /* finalize_hint */,
+                                            &theBuffer));
 
   return theBuffer;
 }
@@ -134,9 +143,12 @@ static napi_value bufferInfo(napi_env env, napi_callback_info info) {
 static napi_value staticBuffer(napi_env env, napi_callback_info info) {
   napi_value theBuffer;
   NODE_API_CALL(env,
-      napi_create_external_buffer(
-          env, sizeof(theText), (void*)theText, noopDeleter,
-          NULL /* finalize_hint */, &theBuffer));
+                napi_create_external_buffer(env,
+                                            sizeof(theText),
+                                            (void*)theText,
+                                            noopDeleter,
+                                            NULL /* finalize_hint */,
+                                            &theBuffer));
   return theBuffer;
 }
 
@@ -190,6 +202,32 @@ static napi_value getMemoryDataAsArray(napi_env env, napi_callback_info info) {
   return ret;
 }
 
+static napi_value bufferFromArrayBuffer(napi_env env,
+                                        napi_callback_info info) {
+  napi_status status;
+  napi_value arraybuffer;
+  napi_value buffer;
+  size_t byte_length = 1024;
+  void* data = NULL;
+  size_t buffer_length = 0;
+  void* buffer_data = NULL;
+
+  status = napi_create_arraybuffer(env, byte_length, &data, &arraybuffer);
+  NODE_API_ASSERT(env, status == napi_ok, "Failed to create arraybuffer");
+
+  status = node_api_create_buffer_from_arraybuffer(
+      env, arraybuffer, 0, byte_length, &buffer);
+  NODE_API_ASSERT(
+      env, status == napi_ok, "Failed to create buffer from arraybuffer");
+
+  status = napi_get_buffer_info(env, buffer, &buffer_data, &buffer_length);
+  NODE_API_ASSERT(env, status == napi_ok, "Failed to get buffer info");
+
+  NODE_API_ASSERT(env, buffer_length == byte_length, "Buffer length mismatch");
+
+  return buffer;
+}
+
 static napi_value Init(napi_env env, napi_value exports) {
   napi_value theValue;
 
@@ -208,6 +246,7 @@ static napi_value Init(napi_env env, napi_value exports) {
     DECLARE_NODE_API_PROPERTY("staticBuffer", staticBuffer),
     DECLARE_NODE_API_PROPERTY("invalidObjectAsBuffer", invalidObjectAsBuffer),
     DECLARE_NODE_API_PROPERTY("getMemoryDataAsArray", getMemoryDataAsArray),
+    DECLARE_NODE_API_PROPERTY("bufferFromArrayBuffer", bufferFromArrayBuffer),
   };
 
   NODE_API_CALL(env, napi_define_properties(

packages/test/buffer/buffer.test.js

@@ -21,6 +21,9 @@ module.exports = load('buffer').then(async binding => {
 
     // To test this doesn't crash
     binding.invalidObjectAsBuffer({})
+
+    const testBuffer = binding.bufferFromArrayBuffer()
+    assert(testBuffer instanceof Buffer, 'Expected a Buffer')
   })().then(common.mustCall())
 
   process.externalBuffer = binding.newExternalBuffer()