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 conversion of time  delays  in
                                              the virtual domain to real-time.

       ClientData clientData (in)             Value passed through to the two handler functions.

       Tcl_GetTimeProc *getProcPtr (out)      Pointer  to  place  the  currently registered get handler function
                                              into.

       Tcl_ScaleTimeProc *scaleProcPtr (out)  Pointer to place the currently registered scale  handler  function
                                              into.

       ClientData *clientDataPtr (out)        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 multiprocessor 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.)

   VIRTUALIZED TIME
       The Tcl_SetTimeProc function registers two related handler functions 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_QueryTimeProc  function  returns  the  currently  registered  handler  functions. If no external
       handlers were set then this will return the standard handlers accessing and processing 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.

       The signatures of the handler functions are as follows:

              typedef void Tcl_GetTimeProc(
                      Tcl_Time *timebuf,
                      ClientData clientData);
              typedef void Tcl_ScaleTimeProc(
                      Tcl_Time *timebuf,
                      ClientData clientData);

       The  timebuf  fields contain the time to manipulate, and the clientData fields contain a pointer supplied
       at the time the handler functions were registered.

       Any handler pair specified has to return data which is consistent 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.

       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 behavior of the Tcl  core
       with regard to this situation, i.e. the existing behavior is retained.

SEE ALSO

       clock(3tcl)

KEYWORDS

       date, time

Tcl                                                    8.4                                     Tcl_GetTime(3tcl)