waitset_wait - wait on (the entries of) a wait set
#include <magenta/syscalls.h>
mx_status_t mx_waitset_wait(mx_handle_t waitset_handle,
mx_time_t timeout,
mx_waitset_result_t* results,
uint32_t* count);
waitset_wait() waits until one of its entries has a result to report (waited for bits are pending or the handle was closed) or the specified timeout has elapsed.
waitset_handle must have the MX_RIGHT_READ right.
count is a required in-out parameter: its input value is the maximum number of results to write to the results buffer, while its output value is the number that was actually written. (results may be null only if the input value of count is zero.)
Each result (entry in the results buffer) is an mx_waitset_result_t:
typedef struct mx_waitset_result {
uint64_t cookie;
mx_status_t status;
mx_signals_t observed;
} mx_waitset_result_t;
cookie is set to the cookie for the entry with a result to report (as provided to waitset_add()); each entry yields at most one result. status is NO_ERROR if the watched signals provided to waitset_add() were satisfied, ERR_BAD_STATE if the watched signals became unsatisfiable, or ERR_HANDLE_CLOSED if the entry's handle was closed. observed is set to the entry's handle's observed signals at some point shortly before waitset_wait() returned.
waitset_wait() returns NO_ERROR if there was a result to report from one of the wait set's entries before the timeout elapsed. Only on success are count and results written to.
It is possible for count to be 0 on success if the condition that woke the waiter becomes untrue during a very small window.
On failure, an error value is returned. In particular, ERR_TIMED_OUT is returned if timeout elapses with no results to report.
ERR_NO_MEMORY (Temporary) Failure due to lack of memory.
ERR_BAD_HANDLE waitset_handle is not a valid handle.
ERR_HANDLE_CLOSED The waitset_handle was closed while waiting on it.
ERR_WRONG_TYPE waitset_handle is not a handle to a wait set.
ERR_INVALID_ARGS count or results are invalid pointers.
ERR_ACCESS_DENIED waitset_handle does not have the MX_RIGHT_READ right.
ERR_TIMED_OUT The specified timeout elapsed before any results were available.