n-api: add support for DataView

Basic support for Dataview is added in this commit. This is achieved
by using three functions, napi_create_dataview(), napi_is_dataview()
and napi_get_dataview_info().

PR-URL: nodejs#14382
Fixes: nodejs#13926
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

doc/api/n-api.md

@@ -1331,6 +1331,40 @@ JavaScript TypedArray Objects are described in
 [Section 22.2](https://tc39.github.io/ecma262/#sec-typedarray-objects)
 of the ECMAScript Language Specification.
 
+
+#### *napi_create_dataview*
+<!-- YAML
+added: REPLACEME
+-->
+
+```C
+napi_status napi_create_dataview(napi_env env,
+                                 size_t byte_length,
+                                 napi_value arraybuffer,
+                                 size_t byte_offset,
+                                 napi_value* result)
+
+```
+
+- `[in] env`: The environment that the API is invoked under.
+- `[in] length`: Number of elements in the DataView.
+- `[in] arraybuffer`: ArrayBuffer underlying the DataView.
+- `[in] byte_offset`: The byte offset within the ArrayBuffer from which to
+  start projecting the DataView.
+- `[out] result`: A `napi_value` representing a JavaScript DataView.
+
+Returns `napi_ok` if the API succeeded.
+
+This API creates a JavaScript DataView object over an existing ArrayBuffer.
+DataView objects provide an array-like view over an underlying data buffer,
+but one which allows items of different size and type in the ArrayBuffer.
+
+It is required that `byte_length + byte_offset` is less than or equal to the
+size in bytes of the array passed in. If not, a RangeError exception is raised.
+
+JavaScript DataView Objects are described in
+[Section 24.3][] of the ECMAScript Language Specification.
+
 ### Functions to convert from C types to N-API
 #### *napi_create_number*
 <!-- YAML
@@ -1552,6 +1586,36 @@ This API returns various properties of a typed array.
 *Warning*: Use caution while using this API since the underlying data buffer
 is managed by the VM
 
+
+
+#### *napi_get_dataview_info*
+<!-- YAML
+added: REPLACEME
+-->
+
+```C
+napi_status napi_get_dataview_info(napi_env env,
+                                   napi_value dataview,
+                                   size_t* byte_length,
+                                   void** data,
+                                   napi_value* arraybuffer,
+                                   size_t* byte_offset)
+```
+
+- `[in] env`: The environment that the API is invoked under.
+- `[in] dataview`: `napi_value` representing the DataView whose
+  properties to query.
+- `[out] byte_length`: Number of bytes in the DataView.
+- `[out] data`: The data buffer underlying the DataView.
+- `[out] arraybuffer`: ArrayBuffer underlying the DataView.
+- `[out] byte_offset`: The byte offset within the data buffer from which
+  to start projecting the DataView.
+
+Returns `napi_ok` if the API succeeded.
+
+This API returns various properties of a DataView.
+
+
 #### *napi_get_value_bool*
 <!-- YAML
 added: v8.0.0
@@ -2019,6 +2083,25 @@ Returns `napi_ok` if the API succeeded.
 
 This API checks if the Object passsed in is a typed array.
 
+
+
+### *napi_is_dataview*
+<!-- YAML
+added: REPLACEME
+-->
+
+```C
+napi_status napi_is_dataview(napi_env env, napi_value value, bool* result)
+```
+
+- `[in] env`: The environment that the API is invoked under.
+- `[in] value`: The JavaScript value to check.
+- `[out] result`: Whether the given `napi_value` represents a DataView.
+
+Returns `napi_ok` if the API succeeded.
+
+This API checks if the Object passed in is a DataView.
+
 ### *napi_strict_equals*
 <!-- YAML
 added: v8.0.0
@@ -3165,6 +3248,7 @@ support it:
 [Object Wrap]: #n_api_object_wrap
 [Section 9.1.6]: https://tc39.github.io/ecma262/#sec-ordinary-object-internal-methods-and-internal-slots-defineownproperty-p-desc
 [Section 12.5.5]: https://tc39.github.io/ecma262/#sec-typeof-operator
+[Section 24.3]: https://tc39.github.io/ecma262/#sec-dataview-objects
 [Working with JavaScript Functions]: #n_api_working_with_javascript_functions
 [Working with JavaScript Properties]: #n_api_working_with_javascript_properties
 [Working with JavaScript Values]: #n_api_working_with_javascript_values

src/node_api.cc

@@ -3019,6 +3019,72 @@ napi_status napi_get_typedarray_info(napi_env env,
   return napi_clear_last_error(env);
 }
 
+napi_status napi_create_dataview(napi_env env,
+                                 size_t byte_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> value = v8impl::V8LocalValueFromJsValue(arraybuffer);
+  RETURN_STATUS_IF_FALSE(env, value->IsArrayBuffer(), napi_invalid_arg);
+
+  v8::Local<v8::ArrayBuffer> buffer = value.As<v8::ArrayBuffer>();
+  v8::Local<v8::DataView> DataView = v8::DataView::New(buffer, byte_offset,
+                                                       byte_length);
+
+  *result = v8impl::JsValueFromV8LocalValue(DataView);
+  return GET_RETURN_STATUS(env);
+}
+
+napi_status napi_is_dataview(napi_env env, napi_value value, bool* result) {
+  CHECK_ENV(env);
+  CHECK_ARG(env, value);
+  CHECK_ARG(env, result);
+
+  v8::Local<v8::Value> val = v8impl::V8LocalValueFromJsValue(value);
+  *result = val->IsDataView();
+
+  return napi_clear_last_error(env);
+}
+
+napi_status napi_get_dataview_info(napi_env env,
+                                   napi_value dataview,
+                                   size_t* byte_length,
+                                   void** data,
+                                   napi_value* arraybuffer,
+                                   size_t* byte_offset) {
+  CHECK_ENV(env);
+  CHECK_ARG(env, dataview);
+
+  v8::Local<v8::Value> value = v8impl::V8LocalValueFromJsValue(dataview);
+  RETURN_STATUS_IF_FALSE(env, value->IsDataView(), napi_invalid_arg);
+
+  v8::Local<v8::DataView> array = value.As<v8::DataView>();
+
+  if (byte_length != nullptr) {
+    *byte_length = array->ByteLength();
+  }
+
+  v8::Local<v8::ArrayBuffer> buffer = array->Buffer();
+  if (data != nullptr) {
+    *data = static_cast<uint8_t*>(buffer->GetContents().Data()) +
+            array->ByteOffset();
+  }
+
+  if (arraybuffer != nullptr) {
+    *arraybuffer = v8impl::JsValueFromV8LocalValue(buffer);
+  }
+
+  if (byte_offset != nullptr) {
+    *byte_offset = array->ByteOffset();
+  }
+
+  return napi_clear_last_error(env);
+}
+
 napi_status napi_get_version(napi_env env, uint32_t* result) {
   CHECK_ENV(env);
   CHECK_ARG(env, result);

src/node_api.h

@@ -494,6 +494,21 @@ NAPI_EXTERN napi_status napi_get_typedarray_info(napi_env env,
                                                  napi_value* arraybuffer,
                                                  size_t* byte_offset);
 
+NAPI_EXTERN napi_status napi_create_dataview(napi_env env,
+                                             size_t length,
+                                             napi_value arraybuffer,
+                                             size_t byte_offset,
+                                             napi_value* result);
+NAPI_EXTERN napi_status napi_is_dataview(napi_env env,
+                                         napi_value value,
+                                         bool* result);
+NAPI_EXTERN napi_status napi_get_dataview_info(napi_env env,
+                                               napi_value dataview,
+                                               size_t* bytelength,
+                                               void** data,
+                                               napi_value* arraybuffer,
+                                               size_t* byte_offset);
+
 // Methods to manage simple async operations
 NAPI_EXTERN
 napi_status napi_create_async_work(napi_env env,

test/addons-napi/test_dataview/binding.gyp

@@ -0,0 +1,8 @@
+{
+  "targets": [
+    {
+      "target_name": "test_dataview",
+      "sources": [ "test_dataview.c" ]
+    }
+  ]
+}

test/addons-napi/test_dataview/test.js

@@ -0,0 +1,14 @@
+'use strict';
+const common = require('../../common');
+const assert = require('assert');
+
+// Testing api calls for arrays
+const test_dataview = require(`./build/${common.buildType}/test_dataview`);
+
+//create dataview
+const buffer = new ArrayBuffer(128);
+const template = Reflect.construct(DataView, [buffer]);
+
+const theDataview = test_dataview.CreateDataView(template);
+assert.ok(theDataview instanceof DataView,
+          'The new variable should be of type Dataview');

test/addons-napi/test_dataview/test_dataview.c

@@ -0,0 +1,49 @@
+#include <node_api.h>
+#include <string.h>
+#include "../common.h"
+
+napi_value CreateDataView(napi_env env, napi_callback_info info) {
+  size_t argc = 1;
+  napi_value args [1];
+  NAPI_CALL(env, napi_get_cb_info(env, info, &argc, args, NULL, NULL));
+
+  NAPI_ASSERT(env, argc == 1, "Wrong number of arguments");
+
+  napi_valuetype valuetype;
+  napi_value input_dataview = args[0];
+
+  NAPI_CALL(env, napi_typeof(env, input_dataview, &valuetype));
+  NAPI_ASSERT(env, valuetype == napi_object,
+              "Wrong type of arguments. Expects a DataView as the first "
+              "argument.");
+
+  bool is_dataview;
+  NAPI_CALL(env, napi_is_dataview(env, input_dataview, &is_dataview));
+  NAPI_ASSERT(env, is_dataview,
+              "Wrong type of arguments. Expects a DataView as the first "
+              "argument.");
+  size_t byte_offset = 0;
+  size_t length = 0;
+  napi_value buffer;
+  NAPI_CALL(env,
+            napi_get_dataview_info(env, input_dataview, &length, NULL,
+                                   &buffer, &byte_offset));
+
+  napi_value output_dataview;
+  NAPI_CALL(env,
+            napi_create_dataview(env, length, buffer,
+                                 byte_offset, &output_dataview));
+
+  return output_dataview;
+}
+
+void Init(napi_env env, napi_value exports, napi_value module, void* priv) {
+  napi_property_descriptor descriptors[] = {
+    DECLARE_NAPI_PROPERTY("CreateDataView", CreateDataView)
+  };
+
+  NAPI_CALL_RETURN_VOID(env, napi_define_properties(
+      env, exports, sizeof(descriptors) / sizeof(*descriptors), descriptors));
+}
+
+NAPI_MODULE(addon, Init)