Set the timer's expiry time relative to now.

std::size_t expires_from_now(
    const duration_type & expiry_time,
    asio::error_code & ec);

This function sets the expiry time. Any pending asynchronous wait operations will be cancelled. The handler for each cancelled operation will be invoked with the asio::error::operation_aborted error code.

Parameters

Return Value

The number of asynchronous operations that were cancelled.

Remarks

If the timer has already expired when expires_from_now() is called, then the handlers for asynchronous wait operations will:

These handlers can no longer be cancelled, and therefore are passed an error code that indicates the successful completion of the wait operation.