add napi_create_buffer_from_arraybuffer (nodejs/node#54505)

Author: toyobayashi

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

@@ -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)!
+    const buffer = handle.value
+    if (!(buffer instanceof ArrayBuffer)) {
+      return envObject.setLastError(napi_status.napi_invalid_arg)
+    }
+
+    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
  */

packages/test/buffer/binding.c

@@ -190,6 +190,64 @@ static napi_value getMemoryDataAsArray(napi_env env, napi_callback_info info) {
   return ret;
 }
 
+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);
+
+static napi_value testBufferFromArrayBuffer(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 = node_api_create_buffer_from_arraybuffer(
+      env, arraybuffer, byte_offset, byte_length, &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");
+
+  bool is_buffer;
+  status = napi_is_buffer(env, buffer, &is_buffer);
+  NODE_API_ASSERT(env, status == napi_ok, "Failed to check if value is buffer");
+  NODE_API_ASSERT(env, is_buffer, "Expected a Buffer but did not get one");
+
+  status = node_api_create_buffer_from_arraybuffer(
+      env, arraybuffer, byte_length, byte_length + 1, &buffer);
+  NODE_API_ASSERT(env,
+                  status == 10,
+                  "Expected range error for invalid byte offset");
+  napi_value last_error;
+  status = napi_get_and_clear_last_exception(env, &last_error);
+  NODE_API_ASSERT(env, status == napi_ok, "Failed to call napi_get_and_clear_last_exception");
+
+  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 = node_api_create_buffer_from_arraybuffer(
+      env, non_arraybuffer, byte_offset, byte_length, &buffer);
+  NODE_API_ASSERT(env,
+                  status == napi_invalid_arg,
+                  "Expected invalid arg error for non-arraybuffer input");
+
+  return arraybuffer;
+}
+
 static napi_value Init(napi_env env, napi_value exports) {
   napi_value theValue;
 
@@ -208,6 +266,8 @@ 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("testBufferFromArrayBuffer",
+                                testBufferFromArrayBuffer),
   };
 
   NODE_API_CALL(env, napi_define_properties(

packages/test/buffer/buffer.test.js

@@ -58,4 +58,6 @@ module.exports = load('buffer').then(async binding => {
   assert.deepStrictEqual(binding.getMemoryDataAsArray(buffer), Array(6).fill(99))
   assert.deepStrictEqual(binding.getMemoryDataAsArray(typedArray), Array(6).fill(99))
   assert.deepStrictEqual(binding.getMemoryDataAsArray(dataView), Array(6).fill(99))
+
+  binding.testBufferFromArrayBuffer()
 })