From 8e8a1a7541e33e2bd33905fd2fe3b407538f8683 Mon Sep 17 00:00:00 2001
From: Pierre Tachoire <pierre@lightpanda.io>
Date: Mon, 2 Mar 2026 17:51:33 +0100
Subject: [PATCH] use a pool arena with ReadableStream

---
 src/browser/webapi/streams/ReadableStream.zig      | 12 ++++++++++++
 .../streams/ReadableStreamDefaultController.zig    | 14 +++++++-------
 2 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/src/browser/webapi/streams/ReadableStream.zig b/src/browser/webapi/streams/ReadableStream.zig
index e4e5d0f9..6dd086fc 100644
--- a/src/browser/webapi/streams/ReadableStream.zig
+++ b/src/browser/webapi/streams/ReadableStream.zig
@@ -47,6 +47,8 @@ _page: *Page,
 _state: State,
 _reader: ?*ReadableStreamDefaultReader,
 _controller: *ReadableStreamDefaultController,
+// The arena is used by the builtin controller.
+_arena: std.mem.Allocator,
 _stored_error: ?[]const u8,
 _pull_fn: ?js.Function.Global = null,
 _pulling: bool = false,
@@ -68,9 +70,13 @@ const QueueingStrategy = struct {
 pub fn init(src_: ?UnderlyingSource, strategy_: ?QueueingStrategy, page: *Page) !*ReadableStream {
     const strategy: QueueingStrategy = strategy_ orelse .{};
 
+    const arena = try page.getArena(.{ .debug = "Animation" });
+    errdefer page.releaseArena(arena);
+
     const self = try page._factory.create(ReadableStream{
         ._page = page,
         ._state = .readable,
+        ._arena = arena,
         ._reader = null,
         ._controller = undefined,
         ._stored_error = null,
@@ -108,6 +114,10 @@ pub fn initWithData(data: []const u8, page: *Page) !*ReadableStream {
     return stream;
 }
 
+pub fn deinit(self: *ReadableStream, _: bool, page: *Page) void {
+    page.releaseArena(self._arena);
+}
+
 pub fn getReader(self: *ReadableStream, page: *Page) !*ReadableStreamDefaultReader {
     if (self.getLocked()) {
         return error.ReaderLocked;
@@ -367,6 +377,8 @@ pub const JsApi = struct {
         pub const name = "ReadableStream";
         pub const prototype_chain = bridge.prototypeChain();
         pub var class_id: bridge.ClassId = undefined;
+        pub const weak = true;
+        pub const finalizer = bridge.finalizer(ReadableStream.deinit);
     };
 
     pub const constructor = bridge.constructor(ReadableStream.init, .{});
diff --git a/src/browser/webapi/streams/ReadableStreamDefaultController.zig b/src/browser/webapi/streams/ReadableStreamDefaultController.zig
index 18228475..84cb14e7 100644
--- a/src/browser/webapi/streams/ReadableStreamDefaultController.zig
+++ b/src/browser/webapi/streams/ReadableStreamDefaultController.zig
@@ -27,6 +27,8 @@ const ReadableStreamDefaultReader = @import("ReadableStreamDefaultReader.zig");
 
 const IS_DEBUG = @import("builtin").mode == .Debug;
 
+/// ReadableStreamDefaultController uses ReadableStream's arena to make
+/// allocation. Indeed, the controller is owned by its ReadableStream.
 const ReadableStreamDefaultController = @This();
 
 pub const Chunk = union(enum) {
@@ -46,7 +48,6 @@ pub const Chunk = union(enum) {
 
 _page: *Page,
 _stream: *ReadableStream,
-_arena: std.mem.Allocator,
 _queue: std.ArrayList(Chunk),
 _pending_reads: std.ArrayList(js.PromiseResolver.Global),
 _high_water_mark: u32,
@@ -56,7 +57,6 @@ pub fn init(stream: *ReadableStream, high_water_mark: u32, page: *Page) !*Readab
         ._page = page,
         ._queue = .empty,
         ._stream = stream,
-        ._arena = page.arena,
         ._pending_reads = .empty,
         ._high_water_mark = high_water_mark,
     });
@@ -64,7 +64,7 @@ pub fn init(stream: *ReadableStream, high_water_mark: u32, page: *Page) !*Readab
 
 pub fn addPendingRead(self: *ReadableStreamDefaultController, page: *Page) !js.Promise {
     const resolver = page.js.local.?.createPromiseResolver();
-    try self._pending_reads.append(self._arena, try resolver.persist());
+    try self._pending_reads.append(self._stream._arena, try resolver.persist());
     return resolver.promise();
 }
 
@@ -74,8 +74,8 @@ pub fn enqueue(self: *ReadableStreamDefaultController, chunk: Chunk) !void {
     }
 
     if (self._pending_reads.items.len == 0) {
-        const chunk_copy = try chunk.dupe(self._page.arena);
-        return self._queue.append(self._arena, chunk_copy);
+        const chunk_copy = try chunk.dupe(self._stream._arena);
+        return self._queue.append(self._stream._arena, chunk_copy);
     }
 
     // I know, this is ouch! But we expect to have very few (if any)
@@ -109,7 +109,7 @@ pub fn enqueueValue(self: *ReadableStreamDefaultController, value: js.Value) !vo
 
     if (self._pending_reads.items.len == 0) {
         const persisted = try value.persist();
-        try self._queue.append(self._arena, .{ .js_value = persisted });
+        try self._queue.append(self._stream._arena, .{ .js_value = persisted });
         return;
     }
 
@@ -170,7 +170,7 @@ pub fn doError(self: *ReadableStreamDefaultController, err: []const u8) !void {
     }
 
     self._stream._state = .errored;
-    self._stream._stored_error = try self._page.arena.dupe(u8, err);
+    self._stream._stored_error = try self._stream._arena.dupe(u8, err);
 
     // Reject all pending reads
     for (self._pending_reads.items) |resolver| {