99 lines
1.7 KiB
C
99 lines
1.7 KiB
C
#include <c_timespec.h>
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#include <limits.h>
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/* ------------------------------------------------------------------------------------------------------------------ */
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/* */
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struct timespec c_timespec_mod(struct timespec ts1, struct timespec ts2)
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{
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int i = 0;
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bool neg1 = false;
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bool neg2 = false;
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/* Normalise inputs to prevent tv_nsec rollover if whole-second values
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* are packed in it.
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*/
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ts1 = c_timespec_normalise(ts1);
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ts2 = c_timespec_normalise(ts2);
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/* If ts2 is zero, just return ts1
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*/
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if (ts2.tv_sec == 0 && ts2.tv_nsec == 0)
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{
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return ts1;
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}
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/* If inputs are negative, flip and record sign
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*/
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if (ts1.tv_sec < 0 || ts1.tv_nsec < 0)
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{
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neg1 = true;
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ts1.tv_sec = -ts1.tv_sec;
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ts1.tv_nsec = -ts1.tv_nsec;
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}
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if (ts2.tv_sec < 0 || ts2.tv_nsec < 0)
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{
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neg2 = true;
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ts2.tv_sec = -ts2.tv_sec;
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ts2.tv_nsec = -ts2.tv_nsec;
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}
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/* Shift ts2 until it is larger than ts1 or is about to overflow
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*/
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while ((ts2.tv_sec < (LONG_MAX >> 1)) && c_timespec_ge(ts1, ts2))
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{
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i++;
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ts2.tv_nsec <<= 1;
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ts2.tv_sec <<= 1;
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if (ts2.tv_nsec > C_NSEC_PER_SEC)
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{
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ts2.tv_nsec -= C_NSEC_PER_SEC;
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ts2.tv_sec++;
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}
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}
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/* Division by repeated subtraction
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*/
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while (i >= 0)
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{
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if (c_timespec_ge(ts1, ts2))
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{
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ts1 = c_timespec_sub(ts1, ts2);
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}
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if (i == 0)
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{
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break;
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}
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i--;
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if (ts2.tv_sec & 1)
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{
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ts2.tv_nsec += C_NSEC_PER_SEC;
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}
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ts2.tv_nsec >>= 1;
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ts2.tv_sec >>= 1;
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}
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/* If signs differ and result is nonzero, subtract once more to cross zero
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*/
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if (neg1 ^ neg2 && (ts1.tv_sec != 0 || ts1.tv_nsec != 0))
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{
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ts1 = c_timespec_sub(ts1, ts2);
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}
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/* Restore sign
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*/
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if (neg1)
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{
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ts1.tv_sec = -ts1.tv_sec;
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ts1.tv_nsec = -ts1.tv_nsec;
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}
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return ts1;
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}
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