361 lines
10 KiB
C
361 lines
10 KiB
C
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/*****************************************************************************
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microclk.c
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Micro-ClockWork for MIDI subsystem
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Copyright (c) 1993-1999 Microsoft Corporation
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*****************************************************************************/
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#define INCL_WINMM
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#include "winmmi.h"
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#include "muldiv32.h"
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//#define STRICT
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//#include <windows.h>
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//#include <windowsx.h>
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//#include "mmsystem.h"
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//#include "mmddk.h"
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//#include "mmsysi.h"
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//#include "debug.h"
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//
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// This stuff needs to be do-able from inside a callback.
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//
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#ifndef WIN32
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#pragma alloc_text(FIXMIDI, clockSetRate)
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#pragma alloc_text(FIXMIDI, clockTime)
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#pragma alloc_text(FIXMIDI, clockOffsetTo)
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#endif
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/****************************************************************************
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* @doc INTERNAL CLOCK
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*
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* @func void | clockInit | This function initializes a clock for the first
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* time. It prepares the clock for use without actually starting it.
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*
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* @parm PCLOCK | pclock | The clock to initialize.
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*
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* @parm MILLISECS | msPrev | The number of milliseconds that have passed
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* up to the time when the clock is started. This option is provided so
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* that a clock may be initialized and started in the middle of a stream
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* without actually running to that point. Normally, this will be zero.
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*
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* @parm TICKS | tkPrev | The number of ticks that have elapsed up to the
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* next time the clock starts. This should specify the same instant in
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* time as msPrev.
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*
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* @comm The clock's numerator and divisor will be set to 1 indicating that
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* the clock will run in milliseconds. Use clockSetRate before starting the
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* clock for the first time if this is not the desired rate.
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*
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***************************************************************************/
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void FAR PASCAL clockInit
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(
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PCLOCK pclock,
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MILLISECS msPrev,
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TICKS tkPrev,
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CLK_TIMEBASE fnTimebase
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)
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{
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// dprintf1(( "clockInit(%04X) %lums %lutk", pclock, msPrev, tkPrev));
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pclock->msPrev = msPrev;
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pclock->tkPrev = tkPrev;
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pclock->dwNum = 1;
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pclock->dwDenom = 1;
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pclock->dwState = CLK_CS_PAUSED;
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pclock->msT0 = 0;
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pclock->fnTimebase = fnTimebase;
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}
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/****************************************************************************
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* @doc INTERNAL CLOCK
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*
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* @func void | clockSetRate | This functions sets a new rate for the clock.
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*
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* @parm PCLOCK | pclock | The clock to set the rate.
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*
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* @parm TICKS | tkWhen | This parameter specifies the absolute tick
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* time at which the rate change happened. This must be at or before the
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* current tick; you cannot schedule a pending rate change.
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* @flag CLK_TK_NOW | Specify this flag if you want the rate change to
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* happen now (this will be the time the clock was paused if it is paused
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* now).
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*
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* @parm DWORD | dwNum | Specifies the new numerator for converting
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* milliseconds to ticks.
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*
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* @parm DWORD | dwDenom | Specifies the new denominator for converting
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* milliseconds to ticks.
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*
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* @comm The clock's state will not be changed by this call; if it is
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* paused, it will stay paused.
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*
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***************************************************************************/
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void FAR PASCAL clockSetRate
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(
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PCLOCK pclock,
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TICKS tkWhen,
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DWORD dwNum,
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DWORD dwDenom
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)
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{
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MILLISECS msInPrevEpoch = pclock->fnTimebase(pclock) - pclock->msT0;
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TICKS tkInPrevEpoch;
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dprintf1(( "clockSetRate(%04X) %lutk Rate=%lu/%lu", pclock, tkWhen, dwNum, dwDenom));
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if (CLK_CS_PAUSED == pclock->dwState)
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{
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//
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// !!! Calling clockSetRate on a paused clock which has never been
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// started causes problems !!!
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//
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dprintf1(( "clockSetRate called when clock is paused."));
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}
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if (0 == dwNum || 0 == dwDenom)
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{
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dprintf1(( "Attempt to set 0 or infinite tick ratio!"));
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return;
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}
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if (CLK_TK_NOW == tkWhen)
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{
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tkInPrevEpoch = clockTime(pclock);
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}
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else
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{
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tkInPrevEpoch = tkWhen - pclock->tkPrev;
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msInPrevEpoch = muldiv32(tkInPrevEpoch, pclock->dwDenom, pclock->dwNum);
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}
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pclock->tkPrev += tkInPrevEpoch;
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pclock->msPrev += msInPrevEpoch;
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pclock->msT0 += msInPrevEpoch;
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pclock->dwNum = dwNum;
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pclock->dwDenom = dwDenom;
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}
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/****************************************************************************
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* @doc INTERNAL CLOCK
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*
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* @func void | clockPause | This functions pauses a clock.
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*
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* @parm PCLOCK | pclock | The clock to pause.
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*
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* @parm TICKS | tkWhen | The tick time to pause the clock.
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* @flag CLK_TK_NOW | Specify this flag if you want the rate change to
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* happen now (this will be the time the clock was paused if it is paused
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* now).
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*
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* @comm If the clock is already paused, this call will have no effect.
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*
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***************************************************************************/
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void FAR PASCAL clockPause
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(
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PCLOCK pclock,
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TICKS tkWhen
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)
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{
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MILLISECS msNow = pclock->fnTimebase(pclock) - pclock->msT0;
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TICKS tkNow;
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// dprintf1(( "clockPause(%04X) %lutk", pclock, tkWhen));
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if (CLK_CS_PAUSED == pclock->dwState)
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{
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dprintf1(( "Pause already paused clock!"));
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return;
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}
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//
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// Start a new epoch at the same rate. Then start will just have to
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// change the state and set a new T0.
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//
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if (CLK_TK_NOW == tkWhen)
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{
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tkNow = pclock->tkPrev +
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muldiv32(msNow, pclock->dwNum, pclock->dwDenom);
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}
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else
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{
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msNow = muldiv32(tkWhen - pclock->tkPrev, pclock->dwDenom, pclock->dwNum);
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tkNow = tkWhen;
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}
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pclock->dwState = CLK_CS_PAUSED;
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pclock->msPrev += msNow;
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pclock->tkPrev = tkNow;
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}
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/****************************************************************************
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* @doc INTERNAL CLOCK
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*
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* @func void | clockRestart | This functions starts a paused clock.
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*
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* @parm PCLOCK | pclock | The clock to start.
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*
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* @comm If the clock is already running, this call will have no effect.
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*
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***************************************************************************/
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void FAR PASCAL clockRestart
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(
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PCLOCK pclock,
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TICKS tkWhen, // What time it is now
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MILLISECS msWhen // Offset for fnTimebase()
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)
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{
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MILLISECS msDelta;
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// dprintf1(( "clockRestart(%04X)", pclock));
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if (CLK_CS_RUNNING == pclock->dwState)
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{
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dprintf1(( "Start already running clock!"));
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return;
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}
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// We've been given what tick time the clock SHOULD be at. Adjust the
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// clock to match this. We need to add the equivalent number of ms
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// into msPrev
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//
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msDelta = muldiv32(tkWhen - pclock->tkPrev, pclock->dwDenom, pclock->dwNum);
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dprintf1(( "clockRestart: Was tick %lu, now %lu, added %lu ms", pclock->tkPrev, tkWhen, msDelta));
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pclock->tkPrev = tkWhen;
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pclock->msPrev += msDelta;
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pclock->dwState = CLK_CS_RUNNING;
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pclock->msT0 = msWhen;
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}
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/****************************************************************************
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* @doc INTERNAL CLOCK
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*
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* @func DWORD | clockTime | This function returns the current absolute tick
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* time.
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*
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* @parm PCLOCK | pclock | The clock to read.
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*
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* @rdesc The current time.
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*
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* @comm If the clock is paused, the returned time will be the time the
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* clock was paused.
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*
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***************************************************************************/
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TICKS FAR PASCAL clockTime
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(
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PCLOCK pclock
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)
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{
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MILLISECS msNow;
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TICKS tkNow;
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TICKS tkDelta;
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msNow = pclock->fnTimebase(pclock) - pclock->msT0;
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tkNow = pclock->tkPrev;
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if (CLK_CS_RUNNING == pclock->dwState)
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{
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tkDelta = muldiv32(msNow, pclock->dwNum, pclock->dwDenom);
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tkNow += tkDelta;
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}
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// dprintf1(( "clockTime() timeGetTime() %lu msT0 %lu", (MILLISECS)pclock->fnTimebase(pclock), pclock->msT0));
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// dprintf1(( "clockTime() tkPrev %lutk msNow %lums dwNum %lu dwDenom %lu tkDelta %lutk", pclock->tkPrev, msNow, pclock->dwNum, pclock->dwDenom, tkDelta));
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// dprintf1(( "clockTime(%04X) -> %lutk", pclock, tkNow));
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return tkNow;
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}
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/****************************************************************************
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* @doc INTERNAL CLOCK
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*
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* @func DWORD | clockMsTime | This function returns the current absolute
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* millisecond time.
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*
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* @parm PCLOCK | pclock | The clock to read.
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*
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* @rdesc The current time.
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*
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* @comm If the clock is paused, the returned time will be the time the
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* clock was paused.
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*
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***************************************************************************/
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MILLISECS FAR PASCAL clockMsTime
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(
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PCLOCK pclock
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)
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{
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MILLISECS msNow = pclock->fnTimebase(pclock) - pclock->msT0;
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MILLISECS msRet;
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msRet = pclock->msPrev;
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if (CLK_CS_RUNNING == pclock->dwState)
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{
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msRet += msNow;
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}
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// dprintf1(( "clockMsTime(%04X) -> %lums", pclock, msRet));
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return msRet;
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}
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/****************************************************************************
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* @doc INTERNAL CLOCK
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*
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* @func DWORD | clockOffsetTo | This function determines the number
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* of milliseconds in the future that a given tick time will occur,
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* assuming the clock runs continously and monotonically until then.
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*
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* @parm PCLOCK | pclock | The clock to read.
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*
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* @parm TICKS | tkWhen | The tick value to calculate the offset to.
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*
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* @rdesc The number of milliseconds until the desired time. If the time
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* has already passed, 0 will be returned. If the clock is paused,
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* the largest possible value will be returned ((DWORD)-1L).
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*
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***************************************************************************/
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MILLISECS FAR PASCAL clockOffsetTo
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(
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PCLOCK pclock,
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TICKS tkWhen
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)
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{
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TICKS tkOffset;
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MILLISECS msOffset;
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if (CLK_CS_PAUSED == pclock->dwState)
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{
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msOffset = (MILLISECS)-1L;
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}
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else
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{
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tkOffset = clockTime(pclock);
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if (tkOffset >= tkWhen)
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{
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msOffset = 0;
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}
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else
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{
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msOffset = muldiv32(tkWhen-tkOffset, pclock->dwDenom, pclock->dwNum);
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}
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}
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// dprintf1(( "clockOffsetTo(%04X, %lutk)@%lutk -> %lums", pclock, tkWhen, tkOffset, msOffset));
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return msOffset;
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}
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