45 lines
1.5 KiB
C
45 lines
1.5 KiB
C
#include "utils.h"
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/*===========================================================================*
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* tick_delay *
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*===========================================================================*/
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PUBLIC int tick_delay(ticks)
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long ticks; /* number of ticks to wait */
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{
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/* This function uses the synchronous alarm to delay for a while. This works
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* even if a previous synchronous alarm was scheduled, because the remaining
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* tick of the previous alarm are returned so that it can be rescheduled.
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* Note however that a long tick_delay (longer than the remaining time of the
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* previous) alarm will also delay the previous alarm.
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*/
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message m, m_alarm;
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clock_t time_left;
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int s;
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if (ticks <= 0) return; /* check for robustness */
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m.m_type = SYS_SYNCALRM; /* request a synchronous alarm */
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m.ALRM_PROC_NR = SELF; /* SELF means this process nr */
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m.ALRM_EXP_TIME = ticks; /* request message after ticks */
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m.ALRM_ABS_TIME = 0; /* ticks are relative to now */
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s = _taskcall(SYSTASK, SYS_SYNCALRM, &m);
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if (s != OK) return(s);
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receive(HARDWARE,&m_alarm); /* await synchronous alarm */
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/* Check if we must reschedule the current alarm. */
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if (m.ALRM_TIME_LEFT > 0) {
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printf("tick_delay: reschedule alarm\n");
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m.ALRM_EXP_TIME = m.ALRM_TIME_LEFT - ticks;
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if (m.ALRM_EXP_TIME <= 0)
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m.ALRM_EXP_TIME = 1;
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s = _taskcall(SYSTASK, SYS_SYNCALRM, &m);
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}
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return(s);
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}
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