Merge pull request #3097 from cloudflare/jsnell/blob-use-buffersource…

…-for-reads
cloudflare · Nov 12, 2024 · 88eab86 · 88eab86
2 parents f117326 + 56c6529
commit 88eab86
Show file tree

Hide file tree

Showing 2 changed files with 14 additions and 5 deletions.
diff --git a/src/workerd/api/blob.c++ b/src/workerd/api/blob.c++
@@ -200,14 +200,23 @@ jsg::Ref<Blob> Blob::slice(
       JSG_THIS, data.slice(start, end), normalizeType(kj::mv(type).orDefault(nullptr)));
 }
 
-jsg::Promise<kj::Array<kj::byte>> Blob::arrayBuffer(jsg::Lock& js) {
-  // TODO(perf): Find a way to avoid the copy.
+jsg::Promise<jsg::BufferSource> Blob::arrayBuffer(jsg::Lock& js) {
   FeatureObserver::maybeRecordUse(FeatureObserver::Feature::BLOB_AS_ARRAY_BUFFER);
-  return js.resolvedPromise(kj::heapArray<byte>(data));
+  // We use BufferSource here instead of kj::Array<kj::byte> to ensure that the
+  // resulting backing store is associated with the isolate, which is necessary
+  // for when we start making use of v8 sandboxing.
+  auto backing = jsg::BackingStore::alloc<v8::ArrayBuffer>(js, data.size());
+  backing.asArrayPtr().copyFrom(data);
+  return js.resolvedPromise(jsg::BufferSource(js, kj::mv(backing)));
 }
 
 jsg::Promise<jsg::BufferSource> Blob::bytes(jsg::Lock& js) {
-  return js.resolvedPromise(js.bytes(kj::heapArray<byte>(data)));
+  // We use BufferSource here instead of kj::Array<kj::byte> to ensure that the
+  // resulting backing store is associated with the isolate, which is necessary
+  // for when we start making use of v8 sandboxing.
+  auto backing = jsg::BackingStore::alloc<v8::Uint8Array>(js, data.size());
+  backing.asArrayPtr().copyFrom(data);
+  return js.resolvedPromise(jsg::BufferSource(js, kj::mv(backing)));
 }
 
 jsg::Promise<kj::String> Blob::text(jsg::Lock& js) {

diff --git a/src/workerd/api/blob.h b/src/workerd/api/blob.h
@@ -44,7 +44,7 @@ class Blob: public jsg::Object {
   jsg::Ref<Blob> slice(
       jsg::Optional<int> start, jsg::Optional<int> end, jsg::Optional<kj::String> type);
 
-  jsg::Promise<kj::Array<kj::byte>> arrayBuffer(jsg::Lock& js);
+  jsg::Promise<jsg::BufferSource> arrayBuffer(jsg::Lock& js);
   jsg::Promise<jsg::BufferSource> bytes(jsg::Lock& js);
   jsg::Promise<kj::String> text(jsg::Lock& js);
   jsg::Ref<ReadableStream> stream();