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