src: fix creating an ArrayBuffer from a Blob created with openAsBlob

Signed-off-by: Daeyeon Jeong <daeyeon.dev@gmail.com>
PR-URL: #47691
Fixes: #47683
Reviewed-By: James M Snell <jasnell@gmail.com>

src/dataqueue/queue.cc

@@ -817,7 +817,7 @@ class FdEntry final : public EntryImpl {
     uint64_t new_start = start_ + start;
     uint64_t new_end = end_;
     if (end.has_value()) {
-      new_end = std::min(end.value() + start, new_end);
+      new_end = std::min(end.value(), end_);
     }
 
     CHECK(new_start >= start_);
@@ -881,7 +881,7 @@ class FdEntry final : public EntryImpl {
               file,
               Local<Object>(),
               entry->start_,
-              entry->end_)),
+              entry->end_ - entry->start_)),
           entry);
     }
 

test/parallel/test-blob-file-backed.js

@@ -68,6 +68,23 @@ writeFileSync(testfile3, '');
   await unlink(testfile);
 })().then(common.mustCall());
 
+(async () => {
+  // Refs: https://github.com/nodejs/node/issues/47683
+  const blob = await openAsBlob(testfile);
+  const res = blob.slice(10, 20);
+  const ab = await res.arrayBuffer();
+  strictEqual(res.size, ab.byteLength);
+
+  let length = 0;
+  const stream = await res.stream();
+  for await (const chunk of stream)
+    length += chunk.length;
+  strictEqual(res.size, length);
+
+  const res1 = blob.slice(995, 1005);
+  strictEqual(await res1.text(), data.slice(995, 1005));
+})().then(common.mustCall());
+
 (async () => {
   const blob = await openAsBlob(testfile2);
   const stream = blob.stream();