Wait for signals on an object.


#include <zircon/syscalls.h>

zx_status_t zx_object_wait_one(zx_handle_t handle,
                               zx_signals_t signals,
                               zx_time_t deadline,
                               zx_signals_t* observed);


zx_object_wait_one() is a blocking syscall which causes the caller to wait until either the deadline passes or the object to which handle refers asserts at least one of the specified signals. If the object is already asserting at least one of the specified signals, the wait ends immediately.

Upon return, if non-NULL, observed is a bitmap of all of the signals which were observed asserted on that object while waiting.

The observed signals may not reflect the actual state of the object's signals if the state of the object was modified by another thread or process. (For example, a Channel ceases asserting ZX_CHANNEL_READABLE once the last message in its queue is read).

The deadline parameter specifies a deadline with respect to ZX_CLOCK_MONOTONIC and will be automatically adjusted according to the job's [timer slack] policy. ZX_TIME_INFINITE is a special value meaning wait forever.


handle must have ZX_RIGHT_WAIT.


zx_object_wait_one() returns ZX_OK if any of signals were observed on the object before deadline passes.

In the event of ZX_ERR_TIMED_OUT, observed may reflect state changes that occurred after the deadline passed, but before the syscall returned.

In the event of ZX_ERR_CANCELED, handle has been closed, and observed will have the ZX_SIGNAL_HANDLE_CLOSED bit set.

For any other return value, observed is undefined.


ZX_ERR_INVALID_ARGS observed is an invalid pointer.

ZX_ERR_BAD_HANDLE handle is not a valid handle.

ZX_ERR_ACCESS_DENIED handle does not have ZX_RIGHT_WAIT and may not be waited upon.

ZX_ERR_CANCELED handle was invalidated (e.g., closed) during the wait.

ZX_ERR_TIMED_OUT The specified deadline passed before any of the specified signals are observed on handle.

ZX_ERR_NOT_SUPPORTED handle is a handle that cannot be waited on (for example, a Port handle).