101 lines
4.0 KiB
Groff
101 lines
4.0 KiB
Groff
'\"
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'\" Copyright (c) 2001 by Kevin B. Kenny <kennykb@acm.org>.
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'\"
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'\" See the file "license.terms" for information on usage and redistribution
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\"
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.so man.macros
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.TH Tcl_GetTime 3 8.4 Tcl "Tcl Library Procedures"
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.BS
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.SH NAME
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Tcl_GetTime, Tcl_SetTimeProc, Tcl_QueryTimeProc \- get date and time
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.SH SYNOPSIS
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.nf
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\fB#include <tcl.h>\fR
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.sp
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\fBTcl_GetTime\fR(\fItimePtr\fR)
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.sp
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\fBTcl_SetTimeProc\fR(\fIgetProc, scaleProc, clientData\fR)
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.sp
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\fBTcl_QueryTimeProc\fR(\fIgetProcPtr, scaleProcPtr, clientDataPtr\fR)
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.SH ARGUMENTS
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.AS "Tcl_Time *" timePtr out
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.AP "Tcl_Time *" timePtr out
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Points to memory in which to store the date and time information.
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.AS "Tcl_GetTimeProc *" getProc in
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.AP "Tcl_GetTimeProc *" getProc in
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Pointer to handler function replacing \fBTcl_GetTime\fR's access to the OS.
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.AS "Tcl_ScaleTimeProc *" scaleProc in
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.AP "Tcl_ScaleTimeProc *" scaleProc in
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Pointer to handler function for the conversion of time delays in the
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virtual domain to real-time.
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.AS "ClientData *" clientData in
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.AP "ClientData *" clientData in
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Value passed through to the two handler functions.
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.AS "Tcl_GetTimeProc **" getProcPtr inout
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.AP "Tcl_GetTimeProc **" getProcPtr inout
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Pointer to place the currently registered get handler function into.
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.AS "Tcl_ScaleTimeProc **" scaleProcPtr inout
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.AP "Tcl_ScaleTimeProc **" scaleProcPtr inout
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Pointer to place the currently registered scale handler function into.
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.AS "ClientData **" clientDataPtr inout
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.AP "ClientData **" clientDataPtr inout
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Pointer to place the currently registered pass-through value into.
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.BE
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.SH DESCRIPTION
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.PP
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The \fBTcl_GetTime\fR function retrieves the current time as a
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\fITcl_Time\fR structure in memory the caller provides. This
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structure has the following definition:
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.CS
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typedef struct Tcl_Time {
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long sec;
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long usec;
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} Tcl_Time;
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.CE
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.PP
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On return, the \fIsec\fR member of the structure is filled in with the
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number of seconds that have elapsed since the \fIepoch:\fR the epoch
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is the point in time of 00:00 UTC, 1 January 1970. This number does
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\fInot\fR count leap seconds \- an interval of one day advances it by
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86400 seconds regardless of whether a leap second has been inserted.
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.PP
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The \fIusec\fR member of the structure is filled in with the number of
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microseconds that have elapsed since the start of the second
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designated by \fIsec\fR. The Tcl library makes every effort to keep
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this number as precise as possible, subject to the limitations of the
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computer system. On multiprocessor variants of Windows, this number
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may be limited to the 10- or 20-ms granularity of the system clock.
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(On single-processor Windows systems, the \fIusec\fR field is derived
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from a performance counter and is highly precise.)
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.PP
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The \fBTcl_SetTime\fR function registers two related handler functions
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with the core. The first handler function is a replacement for
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\fBTcl_GetTime\fR, or rather the OS access made by
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\fBTcl_GetTime\fR. The other handler function is used by the Tcl
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notifier to convert wait/block times from the virtual domain into real
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time.
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.PP
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The \fBTcl_QueryTime\fR function returns the currently registered
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handler functions. If no external handlers were set then this will
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return the standard handlers accessing and processing the native time
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of the OS. The arguments to the function are allowed to be NULL; and
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any argument which is NULL is ignored and not set.
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.PP
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Any handler pair specified has to return data which is consistent
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between them. In other words, setting one handler of the pair to
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something assuming a 10-times slowdown, and the other handler of the
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pair to something assuming a two-times slowdown is wrong and not
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allowed.
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.PP
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The set handler functions are allowed to run the delivered time
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backwards, however this should be avoided. We have to allow it as the
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native time can run backwards as the user can fiddle with the system
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time one way or other. Note that the insertion of the hooks will not
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change the behaviour of the Tcl core with regard to this situation,
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i.e. the existing behaviour is retained.
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.SH "SEE ALSO"
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clock
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.SH KEYWORDS
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date, time
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