node-api: add napi_create_buffer_from_arraybuffer method

Author: Mert Can Altin

doc/api/n-api.md

@@ -2696,6 +2696,35 @@ is raised.
 JavaScript `TypedArray` objects are described in
 [Section 22.2][] of the ECMAScript Language Specification.
 
+#### `napi_create_buffer_from_arraybuffer`
+
+<!-- YAML
+added: v22.7.0
+napiVersion: 1
+-->
+
+```c
+napi_status NAPI_CDECL napi_create_buffer_from_arraybuffer(napi_env env,
+                                                          size_t length,
+                                                          napi_value arraybuffer,
+                                                          size_t byte_offset,
+                                                          napi_value* result)
+```
+
+* `[in] env`: The environment that the API is invoked under.
+* `[in] length`: The length of the buffer to be created from the `ArrayBuffer`.
+* `[in] arraybuffer`: The `ArrayBuffer` from which the buffer will be created.
+* `[in] byte_offset`: The byte offset within the `ArrayBuffer` from which to start creating the buffer.
+* `[out] result`: A `napi_value` representing a JavaScript `Buffer` object.
+
+Returns `napi_ok` if the API succeeded.
+
+This API creates a JavaScript `Buffer` object from an existing `ArrayBuffer`.
+The `Buffer` object is a node-specific class that provides a way to work with binary data directly in JavaScript.
+
+The byte range `[byte_offset, byte_offset + length)` must be within the bounds of the `ArrayBuffer`.
+If `byte_offset + length` exceeds the size of the `ArrayBuffer`, a `RangeError` exception is raised.
+
 #### `napi_create_dataview`
 
 <!-- YAML

src/js_native_api.h

@@ -450,6 +450,12 @@ napi_create_typedarray(napi_env env,
                        size_t byte_offset,
                        napi_value* result);
 NAPI_EXTERN napi_status NAPI_CDECL
+napi_create_buffer_from_arraybuffer(napi_env env,
+                                    napi_value arraybuffer,
+                                    size_t byte_offset,
+                                    size_t byte_length,
+                                    napi_value* result);
+NAPI_EXTERN napi_status NAPI_CDECL
 napi_get_typedarray_info(napi_env env,
                          napi_value typedarray,
                          napi_typedarray_type* type,

src/js_native_api_v8.cc

@@ -3535,3 +3535,33 @@ napi_status NAPI_CDECL napi_is_detached_arraybuffer(napi_env env,
 
   return napi_clear_last_error(env);
 }
+
+napi_status NAPI_CDECL
+napi_create_buffer_from_arraybuffer(napi_env env,
+                                    size_t length,
+                                    napi_value arraybuffer,
+                                    size_t byte_offset,
+                                    napi_value* result) {
+  NAPI_PREAMBLE(env);
+  CHECK_ARG(env, arraybuffer);
+  CHECK_ARG(env, result);
+
+  v8::Local<v8::Value> arraybuffer_value =
+      v8impl::V8LocalValueFromJsValue(arraybuffer);
+  if (!arraybuffer_value->IsArrayBuffer()) {
+    return napi_invalid_arg;
+  }
+
+  v8::Local<v8::ArrayBuffer> arraybuffer_obj =
+      arraybuffer_value.As<v8::ArrayBuffer>();
+  if (byte_offset + length > arraybuffer_obj->ByteLength()) {
+    return napi_throw_range_error(
+        env, "ERR_OUT_OF_RANGE", "The byte offset + length is out of range");
+  }
+
+  v8::Local<v8::Uint8Array> buffer_view =
+      v8::Uint8Array::New(arraybuffer_obj, byte_offset, length);
+
+  *result = v8impl::JsValueFromV8LocalValue(buffer_view);
+  return napi_ok;
+}

test/js-native-api/test_typedarray/test_typedarray.c

@@ -230,6 +230,48 @@ static napi_value IsDetached(napi_env env, napi_callback_info info) {
   return result;
 }
 
+static napi_value BufferFromArrayBuffer(napi_env env, napi_callback_info info) {
+  napi_status status;
+  napi_value arraybuffer;
+  void* data;
+  napi_value buffer;
+  size_t byte_length = 1024;
+  size_t byte_offset = 0;
+
+  status = napi_create_arraybuffer(env, byte_length, &data, &arraybuffer);
+  NODE_API_ASSERT(env, status == napi_ok, "Failed to create arraybuffer");
+
+  status = napi_create_buffer_from_arraybuffer(
+      env, byte_length, arraybuffer, byte_offset, &buffer);
+  NODE_API_ASSERT(
+      env, status == napi_ok, "Failed to create buffer from arraybuffer");
+
+  void* buffer_data;
+  size_t buffer_length;
+  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");
+
+  status = napi_create_buffer_from_arraybuffer(
+      env, byte_length, arraybuffer, byte_length + 1, &buffer);
+  NODE_API_ASSERT(env,
+                  status == napi_range_error,
+                  "Expected range error for invalid byte offset");
+
+  napi_value non_arraybuffer;
+  status = napi_create_uint32(env, 123, &non_arraybuffer);
+  NODE_API_ASSERT(
+      env, status == napi_ok, "Failed to create non-arraybuffer value");
+
+  status = napi_create_buffer_from_arraybuffer(
+      env, byte_length, non_arraybuffer, byte_offset, &buffer);
+  NODE_API_ASSERT(env,
+                  status == napi_invalid_arg,
+                  "Expected invalid arg error for non-arraybuffer input");
+
+  return NULL;
+}
+
 EXTERN_C_START
 napi_value Init(napi_env env, napi_value exports) {
   napi_property_descriptor descriptors[] = {
@@ -239,6 +281,7 @@ napi_value Init(napi_env env, napi_value exports) {
     DECLARE_NODE_API_PROPERTY("CreateTypedArray", CreateTypedArray),
     DECLARE_NODE_API_PROPERTY("Detach", Detach),
     DECLARE_NODE_API_PROPERTY("IsDetached", IsDetached),
+    DECLARE_NODE_API_PROPERTY("BufferFromArrayBuffer", BufferFromArrayBuffer),
   };
 
   NODE_API_CALL(env, napi_define_properties(