src: allow not materializing ArrayBuffers from C++

Where appropriate, use a helper that wraps around
`ArrayBufferView::Buffer()` or `ArrayBufferView::CopyContents()`
rather than `Buffer::Data()`, as that may help to avoid materializing
the underlying `ArrayBuffer` when reading small typed arrays from C++.
This allows keeping the performance benefits of the faster creation of
heap-allocated small typed arrays in many cases.

PR-URL: https://github.com/nodejs/node/pull/26301
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/src/string_decoder.cc b/src/string_decoder.cc
index 9cf1bd671b3..1441ca86936 100644
--- a/src/string_decoder.cc
+++ b/src/string_decoder.cc
@@ -4,6 +4,7 @@
 #include "string_decoder-inl.h"
 
 using v8::Array;
+using v8::ArrayBufferView;
 using v8::Context;
 using v8::FunctionCallbackInfo;
 using v8::Integer;
@@ -252,9 +253,13 @@ void DecodeData(const FunctionCallbackInfo<Value>& args) {
   StringDecoder* decoder =
       reinterpret_cast<StringDecoder*>(Buffer::Data(args[0]));
   CHECK_NOT_NULL(decoder);
-  size_t nread = Buffer::Length(args[1]);
+
+  CHECK(args[1]->IsArrayBufferView());
+  ArrayBufferViewContents<char> content(args[1].As<ArrayBufferView>());
+  size_t length = content.length();
+
   MaybeLocal<String> ret =
-      decoder->DecodeData(args.GetIsolate(), Buffer::Data(args[1]), &nread);
+      decoder->DecodeData(args.GetIsolate(), content.data(), &length);
   if (!ret.IsEmpty())
     args.GetReturnValue().Set(ret.ToLocalChecked());
 }