fileWriteStreamingWindows

fn fileWriteStreamingWindows(file: File, buffer: []const u8) File.Writer.Error!usize {
    assert(buffer.len != 0);
    var iosb: windows.IO_STATUS_BLOCK = undefined;
    if (file.flags.nonblocking) {
        var done: bool = false;
        switch (windows.ntdll.NtWriteFile(
            file.handle,
            null, // event
            flagApc,
            &done, // APC context
            &iosb,
            buffer.ptr,
            @intCast(buffer.len),
            null, // byte offset
            null, // key
        )) {
            // We must wait for the APC routine.
            .PENDING, .SUCCESS => while (!done) {
                // Once we get here we must not return from the function until the
                // operation completes, thereby releasing reference to io_status_block.
                const alertable_syscall = AlertableSyscall.start() catch |err| switch (err) {
                    error.Canceled => |e| {
                        var cancel_iosb: windows.IO_STATUS_BLOCK = undefined;
                        _ = windows.ntdll.NtCancelIoFileEx(file.handle, &iosb, &cancel_iosb);
                        while (!done) waitForApcOrAlert();
                        return e;
                    },
                };
                waitForApcOrAlert();
                alertable_syscall.finish();
            },
            else => |status| iosb.u.Status = status,
        }
    } else {
        const syscall: Syscall = try .start();
        while (true) switch (windows.ntdll.NtWriteFile(
            file.handle,
            null, // event
            null, // APC routine
            null, // APC context
            &iosb,
            buffer.ptr,
            @intCast(buffer.len),
            null, // byte offset
            null, // key
        )) {
            .PENDING => unreachable, // unrecoverable: wrong File nonblocking flag
            .CANCELLED => try syscall.checkCancel(),
            else => |status| {
                syscall.finish();
                iosb.u.Status = status;
                break;
            },
        };
    }
    return ntWriteFileResult(&iosb);
}