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Tcl_GetTime(3tcl) Tcl Library Procedures Tcl_GetTime(3tcl) 





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







  

    8.4
    Tcl