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163
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1 /*
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2 * NAME:
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3 * usleep -- This is the precision timer for Test Set
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4 * Automation. It uses the select(2) system
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5 * call to delay for the desired number of
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6 * micro-seconds. This call returns ZERO
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7 * (which is usually ignored) on successful
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167
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8 * completion, -1 otherwise.
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163
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9 *
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10 * ALGORITHM:
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11 * 1) We range check the passed in microseconds and log a
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12 * warning message if appropriate. We then return without
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167
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13 * delay, flagging an error.
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163
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14 * 2) Load the Seconds and micro-seconds portion of the
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15 * interval timer structure.
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16 * 3) Call select(2) with no file descriptors set, just the
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17 * timer, this results in either delaying the proper
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18 * ammount of time or being interupted early by a signal.
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19 *
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20 * HISTORY:
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21 * Added when the need for a subsecond timer was evident.
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22 *
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23 * AUTHOR:
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24 * Michael J. Dyer <mike@sherlock.med.ge.com>
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25 */
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26
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27 #include <unistd.h>
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28 #include <stdlib.h>
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29 #include <stdio.h>
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30 #include <errno.h>
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31 #include <time.h>
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32 #include <sys/time.h>
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33 #include <sys/param.h>
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34 #include <sys/types.h>
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35
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167
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36 int
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37 usleep (unsigned long microSeconds)
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163
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38 {
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167
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39 unsigned int Seconds, uSec;
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40 int nfds = 0;
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41 fd_set readfds, writefds, exceptfds;
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42 struct timeval Timer;
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163
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43
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167
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44 if( (microSeconds == (unsigned long) 0) ||
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45 microSeconds > (unsigned long) 4000000 )
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46 {
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47 errno = ERANGE; /* value out of range */
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48 perror( "usleep time out of range ( 0 -> 4000000 ) " );
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49 return -1;
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50 }
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163
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51
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167
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52 Seconds = microSeconds / (unsigned long) 1000000;
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53 uSec = microSeconds % (unsigned long) 1000000;
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163
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54
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167
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55 Timer.tv_sec = Seconds;
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56 Timer.tv_usec = uSec;
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163
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57
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167
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58 if( select( nfds, &readfds, &writefds, &exceptfds, &Timer ) < 0 )
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59 {
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60 perror( "usleep (select) failed" );
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61 return -1;
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62 }
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63
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64 return 0;
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163
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65 }
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