3 files changed, 39 insertions, 3 deletions
diff --git a/ext/web/06_streams.js b/ext/web/06_streams.js
index 4f472984d..9fc15d1ad 100644
--- a/ext/web/06_streams.js
+++ b/ext/web/06_streams.js
@@ -12,6 +12,7 @@ const {
   op_arraybuffer_was_detached,
   op_transfer_arraybuffer,
   op_readable_stream_resource_allocate,
+  op_readable_stream_resource_allocate_sized,
   op_readable_stream_resource_get_sink,
   op_readable_stream_resource_write_error,
   op_readable_stream_resource_write_buf,
@@ -863,13 +864,16 @@ function readableStreamReadFn(reader, sink) {
  * read operations, and those read operations will be fed by the output of the
  * ReadableStream source.
  * @param {ReadableStream<Uint8Array>} stream
+ * @param {number | undefined} length
  * @returns {number}
  */
-function resourceForReadableStream(stream) {
+function resourceForReadableStream(stream, length) {
   const reader = acquireReadableStreamDefaultReader(stream);
 
   // Allocate the resource
-  const rid = op_readable_stream_resource_allocate();
+  const rid = typeof length == "number"
+    ? op_readable_stream_resource_allocate_sized(length)
+    : op_readable_stream_resource_allocate();
 
   // Close the Reader we get from the ReadableStream when the resource is closed, ignoring any errors
   PromisePrototypeCatch(
diff --git a/ext/web/lib.rs b/ext/web/lib.rs
index 4e0d97f5c..a68b6344e 100644
--- a/ext/web/lib.rs
+++ b/ext/web/lib.rs
@@ -91,6 +91,7 @@ deno_core::extension!(deno_web,
     op_sleep,
     op_transfer_arraybuffer,
     stream_resource::op_readable_stream_resource_allocate,
+    stream_resource::op_readable_stream_resource_allocate_sized,
     stream_resource::op_readable_stream_resource_get_sink,
     stream_resource::op_readable_stream_resource_write_error,
     stream_resource::op_readable_stream_resource_write_buf,
diff --git a/ext/web/stream_resource.rs b/ext/web/stream_resource.rs
index 93d10f806..8505be01a 100644
--- a/ext/web/stream_resource.rs
+++ b/ext/web/stream_resource.rs
@@ -197,7 +197,14 @@ impl BoundedBufferChannelInner {
   pub fn write(&mut self, buffer: V8Slice<u8>) -> Result<(), V8Slice<u8>> {
     let next_producer_index = (self.ring_producer + 1) % BUFFER_CHANNEL_SIZE;
     if next_producer_index == self.ring_consumer {
-      return Err(buffer);
+      // Note that we may have been allowed to write because of a close/error condition, but the
+      // underlying channel is actually closed. If this is the case, we return `Ok(())`` and just
+      // drop the bytes on the floor.
+      return if self.closed || self.error.is_some() {
+        Ok(())
+      } else {
+        Err(buffer)
+      };
     }
 
     self.current_size += buffer.len();
@@ -336,6 +343,7 @@ struct ReadableStreamResource {
   channel: BoundedBufferChannel,
   cancel_handle: CancelHandle,
   data: ReadableStreamResourceData,
+  size_hint: (u64, Option<u64>),
 }
 
 impl ReadableStreamResource {
@@ -378,6 +386,10 @@ impl Resource for ReadableStreamResource {
   fn close(self: Rc<Self>) {
     self.close_channel();
   }
+
+  fn size_hint(&self) -> (u64, Option<u64>) {
+    self.size_hint
+  }
 }
 
 impl Drop for ReadableStreamResource {
@@ -438,6 +450,25 @@ pub fn op_readable_stream_resource_allocate(state: &mut OpState) -> ResourceId {
     cancel_handle: Default::default(),
     channel: BoundedBufferChannel::default(),
     data: ReadableStreamResourceData { completion },
+    size_hint: (0, None),
+  };
+  state.resource_table.add(resource)
+}
+
+/// Allocate a resource that wraps a ReadableStream, with a size hint.
+#[op2(fast)]
+#[smi]
+pub fn op_readable_stream_resource_allocate_sized(
+  state: &mut OpState,
+  #[number] length: u64,
+) -> ResourceId {
+  let completion = CompletionHandle::default();
+  let resource = ReadableStreamResource {
+    read_queue: Default::default(),
+    cancel_handle: Default::default(),
+    channel: BoundedBufferChannel::default(),
+    data: ReadableStreamResourceData { completion },
+    size_hint: (length, Some(length)),
   };
   state.resource_table.add(resource)
 }