chunkedReadEndless

    fn chunkedReadEndless(
        reader: *Reader,
        w: *Writer,
        limit: std.Io.Limit,
        chunk_len_ptr: *RemainingChunkLen,
    ) (BodyError || std.Io.Reader.StreamError)!usize {
        const in = reader.in;
        len: switch (chunk_len_ptr.*) {
            .head => {
                var cp: ChunkParser = .init;
                while (true) {
                    const i = cp.feed(in.buffered());
                    switch (cp.state) {
                        .invalid => return error.HttpChunkInvalid,
                        .data => {
                            in.toss(i);
                            break;
                        },
                        else => {
                            in.toss(i);
                            try in.fillMore();
                            continue;
                        },
                    }
                }
                if (cp.chunk_len == 0) return parseTrailers(reader, 0);
                const n = try in.stream(w, limit.min(.limited64(cp.chunk_len)));
                chunk_len_ptr.* = .init(cp.chunk_len + 2 - n);
                return n;
            },
            .n => {
                if ((try in.peekByte()) != '\n') return error.HttpChunkInvalid;
                in.toss(1);
                continue :len .head;
            },
            .rn => {
                const rn = try in.peekArray(2);
                if (rn[0] != '\r' or rn[1] != '\n') return error.HttpChunkInvalid;
                in.toss(2);
                continue :len .head;
            },
            else => |remaining_chunk_len| {
                const n = try in.stream(w, limit.min(.limited64(@backingInt(remaining_chunk_len) - 2)));
                chunk_len_ptr.* = .init(@backingInt(remaining_chunk_len) - n);
                return n;
            },
        }
    }