NAME
posix_trace_getnext_event, posix_trace_timedgetnext_event,
posix_trace_trygetnext_event - retrieve a trace event (TRACING)
SYNOPSIS
#include <sys/types.h>
#include <trace.h>
int posix_trace_getnext_event(trace_id_t trid,
struct posix_trace_event_info *restrict event,
void *restrict data, size_t num_bytes,
size_t *restrict data_len, int *restrict unavailable);
int posix_trace_timedgetnext_event(trace_id_t trid,
struct posix_trace_event_info *restrict event,
void *restrict data, size_t num_bytes,
size_t *restrict data_len, int *restrict unavailable,
const struct timespec *restrict abs_timeout);
int posix_trace_trygetnext_event(trace_id_t trid,
struct posix_trace_event_info *restrict event,
void *restrict data, size_t num_bytes,
size_t *restrict data_len, int *restrict unavailable);
DESCRIPTION
The posix_trace_getnext_event() function shall report a recorded trace
event either from an active trace stream without log or a pre-recorded
trace stream identified by the trid argument. The
posix_trace_trygetnext_event() function shall report a recorded trace
event from an active trace stream without log identified by the trid
argument.
The trace event information associated with the recorded trace event
shall be copied by the function into the structure pointed to by the
argument event and the data associated with the trace event shall be
copied into the buffer pointed to by the data argument.
The posix_trace_getnext_event() function shall block if the trid
argument identifies an active trace stream and there is currently no
trace event ready to be retrieved. When returning, if a recorded trace
event was reported, the variable pointed to by the unavailable argument
shall be set to zero. Otherwise, the variable pointed to by the
unavailable argument shall be set to a value different from zero.
The posix_trace_timedgetnext_event() function shall attempt to get
another trace event from an active trace stream without log, as in the
posix_trace_getnext_event() function. However, if no trace event is
available from the trace stream, the implied wait shall be terminated
when the timeout specified by the argument abs_timeout expires, and the
function shall return the error [ETIMEDOUT].
The timeout shall expire when the absolute time specified by
abs_timeout passes, as measured by the clock upon which timeouts are
based (that is, when the value of that clock equals or exceeds
abs_timeout), or if the absolute time specified by abs_timeout has
already passed at the time of the call.
If the Timers option is supported, the timeout shall be based on the
CLOCK_REALTIME clock; if the Timers option is not supported, the
timeout shall be based on the system clock as returned by the time()
function. The resolution of the timeout shall be the resolution of the
clock on which it is based. The timespec data type is defined in the
<time.h> header.
Under no circumstance shall the function fail with a timeout if a trace
event is immediately available from the trace stream. The validity of
the abs_timeout argument need not be checked if a trace event is
immediately available from the trace stream.
The behavior of this function for a pre-recorded trace stream is
unspecified.
The posix_trace_trygetnext_event() function shall not block. This
function shall return an error if the trid argument identifies a pre-
recorded trace stream. If a recorded trace event was reported, the
variable pointed to by the unavailable argument shall be set to zero.
Otherwise, if no trace event was reported, the variable pointed to by
the unavailable argument shall be set to a value different from zero.
The argument num_bytes shall be the size of the buffer pointed to by
the data argument. The argument data_len reports to the application the
length in bytes of the data record just transferred. If num_bytes is
greater than or equal to the size of the data associated with the trace
event pointed to by the event argument, all the recorded data shall be
transferred. In this case, the truncation-status member of the trace
event structure shall be either POSIX_TRACE_NOT_TRUNCATED, if the trace
event data was recorded without truncation while tracing, or
POSIX_TRACE_TRUNCATED_RECORD, if the trace event data was truncated
when it was recorded. If the num_bytes argument is less than the length
of recorded trace event data, the data transferred shall be truncated
to a length of num_bytes, the value stored in the variable pointed to
by data_len shall be equal to num_bytes, and the truncation-status
member of the event structure argument shall be set to
POSIX_TRACE_TRUNCATED_READ (see the posix_trace_event_info structure
defined in <trace.h>).
The report of a trace event shall be sequential starting from the
oldest recorded trace event. Trace events shall be reported in the
order in which they were generated, up to an implementation-defined
time resolution that causes the ordering of trace events occurring very
close to each other to be unknown. Once reported, a trace event cannot
be reported again from an active trace stream. Once a trace event is
reported from an active trace stream without log, the trace stream
shall make the resources associated with that trace event available to
record future generated trace events.
RETURN VALUE
Upon successful completion, these functions shall return a value of
zero. Otherwise, they shall return the corresponding error number.
If successful, these functions store:
* The recorded trace event in the object pointed to by event
* The trace event information associated with the recorded trace event
in the object pointed to by data
* The length of this trace event information in the object pointed to
by data_len
* The value of zero in the object pointed to by unavailable
ERRORS
These functions shall fail if:
EINVAL The trace stream identifier argument trid is invalid.
The posix_trace_getnext_event() and posix_trace_timedgetnext_event()
functions shall fail if:
EINTR The operation was interrupted by a signal, and so the call had
no effect.
The posix_trace_trygetnext_event() function shall fail if:
EINVAL The trace stream identifier argument trid does not correspond to
an active trace stream.
The posix_trace_timedgetnext_event() function shall fail if:
EINVAL There is no trace event immediately available from the trace
stream, and the timeout argument is invalid.
ETIMEDOUT
No trace event was available from the trace stream before the
specified timeout timeout expired.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
None.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
posix_trace_create() , posix_trace_open() , the Base Definitions volume
of IEEE Std 1003.1-2001, <sys/types.h>, <trace.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.opengroup.org/unix/online.html .