stream: add ReadableByteStream.tee()

This supports teeing readable byte streams to meet
the latest web streams standards.

Signed-off-by: Daeyeon Jeong daeyeon.dev@gmail.com
PR-URL: #44505
Refs: https://streams.spec.whatwg.org/#readable-stream-tee
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Minwoo Jung <nodecorelab@gmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>

doc/api/webstreams.md

@@ -303,6 +303,10 @@ is active.
 
 <!-- YAML
 added: v16.5.0
+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/44505
+    description: Support teeing a readable byte stream.
 -->
 
 * Returns: {ReadableStream\[]}

lib/internal/webstreams/readablestream.js

@@ -93,6 +93,7 @@ const {
   ArrayBufferViewGetByteOffset,
   ArrayBufferGetByteLength,
   AsyncIterator,
+  cloneAsUint8Array,
   copyArrayBuffer,
   customInspect,
   dequeueValue,
@@ -211,6 +212,7 @@ class ReadableStream {
       throw new ERR_INVALID_ARG_VALUE('source', 'Object', source);
     this[kState] = {
       disturbed: false,
+      reader: undefined,
       state: 'readable',
       storedError: undefined,
       stream: undefined,
@@ -1103,7 +1105,6 @@ class ReadableByteStreamController {
         chunk);
     }
     const chunkByteLength = ArrayBufferViewGetByteLength(chunk);
-    const chunkByteOffset = ArrayBufferViewGetByteOffset(chunk);
     const chunkBuffer = ArrayBufferViewGetBuffer(chunk);
     const chunkBufferByteLength = ArrayBufferGetByteLength(chunkBuffer);
     if (chunkByteLength === 0 || chunkBufferByteLength === 0) {
@@ -1114,11 +1115,7 @@ class ReadableByteStreamController {
       throw new ERR_INVALID_STATE.TypeError('Controller is already closed');
     if (this[kState].stream[kState].state !== 'readable')
       throw new ERR_INVALID_STATE.TypeError('ReadableStream is already closed');
-    readableByteStreamControllerEnqueue(
-      this,
-      chunkBuffer,
-      chunkByteLength,
-      chunkByteOffset);
+    readableByteStreamControllerEnqueue(this, chunk);
   }
 
   /**
@@ -1416,6 +1413,13 @@ function readableStreamPipeTo(
 }
 
 function readableStreamTee(stream, cloneForBranch2) {
+  if (isReadableByteStreamController(stream[kState].controller)) {
+    return readableByteStreamTee(stream);
+  }
+  return readableStreamDefaultTee(stream, cloneForBranch2);
+}
+
+function readableStreamDefaultTee(stream, cloneForBranch2) {
   const reader = new ReadableStreamDefaultReader(stream);
   let reading = false;
   let canceled1 = false;
@@ -1510,6 +1514,282 @@ function readableStreamTee(stream, cloneForBranch2) {
   return [branch1, branch2];
 }
 
+function readableByteStreamTee(stream) {
+  assert(isReadableStream(stream));
+  assert(isReadableByteStreamController(stream[kState].controller));
+
+  let reader = new ReadableStreamDefaultReader(stream);
+  let reading = false;
+  let readAgainForBranch1 = false;
+  let readAgainForBranch2 = false;
+  let canceled1 = false;
+  let canceled2 = false;
+  let reason1;
+  let reason2;
+  let branch1;
+  let branch2;
+  const cancelDeferred = createDeferredPromise();
+
+  function forwardReaderError(thisReader) {
+    PromisePrototypeThen(
+      thisReader[kState].close.promise,
+      undefined,
+      (error) => {
+        if (thisReader !== reader) {
+          return;
+        }
+        readableStreamDefaultControllerError(branch1[kState].controller, error);
+        readableStreamDefaultControllerError(branch2[kState].controller, error);
+        if (!canceled1 || !canceled2) {
+          cancelDeferred.resolve();
+        }
+      }
+    );
+  }
+
+  function pullWithDefaultReader() {
+    if (isReadableStreamBYOBReader(reader)) {
+      reader = new ReadableStreamDefaultReader(stream);
+      forwardReaderError(reader);
+    }
+
+    const readRequest = {
+      [kChunk](chunk) {
+        queueMicrotask(() => {
+          readAgainForBranch1 = false;
+          readAgainForBranch2 = false;
+          const chunk1 = chunk;
+          let chunk2 = chunk;
+
+          if (!canceled1 && !canceled2) {
+            try {
+              chunk2 = cloneAsUint8Array(chunk);
+            } catch (error) {
+              readableByteStreamControllerError(
+                branch1[kState].controller,
+                error
+              );
+              readableByteStreamControllerError(
+                branch2[kState].controller,
+                error
+              );
+              cancelDeferred.resolve(readableStreamCancel(stream, error));
+              return;
+            }
+          }
+          if (!canceled1) {
+            readableByteStreamControllerEnqueue(
+              branch1[kState].controller,
+              chunk1
+            );
+          }
+          if (!canceled2) {
+            readableByteStreamControllerEnqueue(
+              branch2[kState].controller,
+              chunk2
+            );
+          }
+          reading = false;
+
+          if (readAgainForBranch1) {
+            pull1Algorithm();
+          } else if (readAgainForBranch2) {
+            pull2Algorithm();
+          }
+        });
+      },
+      [kClose]() {
+        reading = false;
+
+        if (!canceled1) {
+          readableByteStreamControllerClose(branch1[kState].controller);
+        }
+        if (!canceled2) {
+          readableByteStreamControllerClose(branch2[kState].controller);
+        }
+        if (branch1[kState].controller[kState].pendingPullIntos.length > 0) {
+          readableByteStreamControllerRespond(branch1[kState].controller, 0);
+        }
+        if (branch2[kState].controller[kState].pendingPullIntos.length > 0) {
+          readableByteStreamControllerRespond(branch2[kState].controller, 0);
+        }
+        if (!canceled1 || !canceled2) {
+          cancelDeferred.resolve();
+        }
+      },
+      [kError]() {
+        reading = false;
+      },
+    };
+
+    readableStreamDefaultReaderRead(reader, readRequest);
+  }
+
+  function pullWithBYOBReader(view, forBranch2) {
+    if (isReadableStreamDefaultReader(reader)) {
+      reader = new ReadableStreamBYOBReader(stream);
+      forwardReaderError(reader);
+    }
+
+    const byobBranch = forBranch2 === true ? branch2 : branch1;
+    const otherBranch = forBranch2 === false ? branch2 : branch1;
+    const readIntoRequest = {
+      [kChunk](chunk) {
+        queueMicrotask(() => {
+          readAgainForBranch1 = false;
+          readAgainForBranch2 = false;
+          const byobCanceled = forBranch2 === true ? canceled2 : canceled1;
+          const otherCanceled = forBranch2 === false ? canceled2 : canceled1;
+
+          if (!otherCanceled) {
+            let clonedChunk;
+
+            try {
+              clonedChunk = cloneAsUint8Array(chunk);
+            } catch (error) {
+              readableByteStreamControllerError(
+                byobBranch[kState].controller,
+                error
+              );
+              readableByteStreamControllerError(
+                otherBranch[kState].controller,
+                error
+              );
+              cancelDeferred.resolve(readableStreamCancel(stream, error));
+              return;
+            }
+            if (!byobCanceled) {
+              readableByteStreamControllerRespondWithNewView(
+                byobBranch[kState].controller,
+                chunk
+              );
+            }
+
+            readableByteStreamControllerEnqueue(
+              otherBranch[kState].controller,
+              clonedChunk
+            );
+          } else if (!byobCanceled) {
+            readableByteStreamControllerRespondWithNewView(
+              byobBranch[kState].controller,
+              chunk
+            );
+          }
+          reading = false;
+
+          if (readAgainForBranch1) {
+            pull1Algorithm();
+          } else if (readAgainForBranch2) {
+            pull2Algorithm();
+          }
+        });
+      },
+      [kClose](chunk) {
+        reading = false;
+
+        const byobCanceled = forBranch2 === true ? canceled2 : canceled1;
+        const otherCanceled = forBranch2 === false ? canceled2 : canceled1;
+
+        if (!byobCanceled) {
+          readableByteStreamControllerClose(byobBranch[kState].controller);
+        }
+        if (!otherCanceled) {
+          readableByteStreamControllerClose(otherBranch[kState].controller);
+        }
+        if (chunk !== undefined) {
+          if (!byobCanceled) {
+            readableByteStreamControllerRespondWithNewView(
+              byobBranch[kState].controller,
+              chunk
+            );
+          }
+          if (
+            !otherCanceled &&
+            otherBranch[kState].controller[kState].pendingPullIntos.length > 0
+          ) {
+            readableByteStreamControllerRespond(
+              otherBranch[kState].controller,
+              0
+            );
+          }
+        }
+        if (!byobCanceled || !otherCanceled) {
+          cancelDeferred.resolve();
+        }
+      },
+      [kError]() {
+        reading = false;
+      },
+    };
+    readableStreamBYOBReaderRead(reader, view, readIntoRequest);
+  }
+
+  function pull1Algorithm() {
+    if (reading) {
+      readAgainForBranch1 = true;
+      return PromiseResolve();
+    }
+    reading = true;
+
+    const byobRequest = branch1[kState].controller.byobRequest;
+    if (byobRequest === null) {
+      pullWithDefaultReader();
+    } else {
+      pullWithBYOBReader(byobRequest[kState].view, false);
+    }
+    return PromiseResolve();
+  }
+
+  function pull2Algorithm() {
+    if (reading) {
+      readAgainForBranch2 = true;
+      return PromiseResolve();
+    }
+    reading = true;
+
+    const byobRequest = branch2[kState].controller.byobRequest;
+    if (byobRequest === null) {
+      pullWithDefaultReader();
+    } else {
+      pullWithBYOBReader(byobRequest[kState].view, true);
+    }
+    return PromiseResolve();
+  }
+
+  function cancel1Algorithm(reason) {
+    canceled1 = true;
+    reason1 = reason;
+    if (canceled2) {
+      cancelDeferred.resolve(readableStreamCancel(stream, [reason1, reason2]));
+    }
+    return cancelDeferred.promise;
+  }
+
+  function cancel2Algorithm(reason) {
+    canceled2 = true;
+    reason2 = reason;
+    if (canceled1) {
+      cancelDeferred.resolve(readableStreamCancel(stream, [reason1, reason2]));
+    }
+    return cancelDeferred.promise;
+  }
+
+  branch1 = new ReadableStream({
+    type: 'bytes',
+    pull: pull1Algorithm,
+    cancel: cancel1Algorithm,
+  });
+  branch2 = new ReadableStream({
+    type: 'bytes',
+    pull: pull2Algorithm,
+    cancel: cancel2Algorithm,
+  });
+
+  forwardReaderError(reader);
+
+  return [branch1, branch2];
+}
+
 function readableByteStreamControllerConvertPullIntoDescriptor(desc) {
   const {
     buffer,
@@ -2273,18 +2553,18 @@ function readableByteStreamControllerFillHeadPullIntoDescriptor(
   desc.bytesFilled += size;
 }
 
-function readableByteStreamControllerEnqueue(
-  controller,
-  buffer,
-  byteLength,
-  byteOffset) {
+function readableByteStreamControllerEnqueue(controller, chunk) {
   const {
     closeRequested,
     pendingPullIntos,
     queue,
     stream,
   } = controller[kState];
 
+  const buffer = ArrayBufferViewGetBuffer(chunk);
+  const byteOffset = ArrayBufferViewGetByteOffset(chunk);
+  const byteLength = ArrayBufferViewGetByteLength(chunk);
+
   if (closeRequested || stream[kState].state !== 'readable')
     return;