Tcl_GetTime(3tcl)
Tcl_GetTime(3) Tcl Library Procedures Tcl_GetTime(3)
_________________________________________________________________
NAME
Tcl_GetTime, Tcl_SetTimeProc, Tcl_QueryTimeProc - get date
and time
SYNOPSIS
#include <tcl.h>
Tcl_GetTime(timePtr)
Tcl_SetTimeProc(getProc, scaleProc, clientData)
Tcl_QueryTimeProc(getProcPtr, scaleProcPtr, clientDataPtr)
ARGUMENTS
Tcl_Time * timePtr (out) Points to memory in which
to store the date and time
information.
Tcl_GetTimeProc * getProc (in) Pointer to handler
function replacing
Tcl_GetTime's access
to the OS.
Tcl_ScaleTimeProc * scaleProc (in) Pointer to
handler function
for the conver-
sion of time
delays in the
virtual domain
to real-time.
ClientData * clientData (in) Value passed through
to the two handler
functions.
Tcl_GetTimeProc ** getProcPtr (inout) Pointer to place
the currently
registered get
handler function
into.
Tcl_ScaleTimeProc ** scaleProcPtr (inout) Pointer to
place the
currently
registered
scale
handler
function
into.
Tcl Last change: 8.4 1
Tcl_GetTime(3) Tcl Library Procedures Tcl_GetTime(3)
ClientData ** clientDataPtr (inout) Pointer to place
the currently
registered pass-
through value
into.
_________________________________________________________________
DESCRIPTION
The Tcl_GetTime function retrieves the current time as a
Tcl_Time structure in memory the caller provides. This
structure has the following definition:
typedef struct Tcl_Time {
long sec;
long usec;
} Tcl_Time;
On return, the sec member of the structure is filled in with
the number of seconds that have elapsed since the epoch: the
epoch is the point in time of 00:00 UTC, 1 January 1970.
This number does not count leap seconds - an interval of one
day advances it by 86400 seconds regardless of whether a
leap second has been inserted.
The usec member of the structure is filled in with the
number of microseconds that have elapsed since the start of
the second designated by sec. The Tcl library makes every
effort to keep this number as precise as possible, subject
to the limitations of the computer system. On multiproces-
sor variants of Windows, this number may be limited to the
10- or 20-ms granularity of the system clock. (On single-
processor Windows systems, the usec field is derived from a
performance counter and is highly precise.)
The Tcl_SetTime function registers two related handler func-
tions with the core. The first handler function is a
replacement for Tcl_GetTime, or rather the OS access made by
Tcl_GetTime. The other handler function is used by the Tcl
notifier to convert wait/block times from the virtual domain
into real time.
The Tcl_QueryTime function returns the currently registered
handler functions. If no external handlers were set then
this will return the standard handlers accessing and pro-
cessing the native time of the OS. The arguments to the
function are allowed to be NULL; and any argument which is
NULL is ignored and not set.
Any handler pair specified has to return data which is con-
sistent between them. In other words, setting one handler of
the pair to something assuming a 10-times slowdown, and the
other handler of the pair to something assuming a two-times
slowdown is wrong and not allowed.
Tcl Last change: 8.4 2
Tcl_GetTime(3) Tcl Library Procedures Tcl_GetTime(3)
The set handler functions are allowed to run the delivered
time backwards, however this should be avoided. We have to
allow it as the native time can run backwards as the user
can fiddle with the system time one way or other. Note that
the insertion of the hooks will not change the behaviour of
the Tcl core with regard to this situation, i.e. the exist-
ing behaviour is retained.
SEE ALSO
clock
KEYWORDS
date, time
Tcl Last change: 8.4 3
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