55 lines
1.5 KiB
C
55 lines
1.5 KiB
C
#include "tick.h"
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#include <assert.h>
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#include <time.h>
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#ifdef _WIN32
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# include <windows.h>
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#endif
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sc_tick
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sc_tick_now(void) {
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#ifndef _WIN32
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// Maximum sc_tick precision (microsecond)
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struct timespec ts;
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int ret = clock_gettime(CLOCK_MONOTONIC, &ts);
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if (ret) {
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abort();
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}
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return SC_TICK_FROM_SEC(ts.tv_sec) + SC_TICK_FROM_NS(ts.tv_nsec);
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#else
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LARGE_INTEGER c;
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// On systems that run Windows XP or later, the function will always
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// succeed and will thus never return zero.
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// <https://docs.microsoft.com/en-us/windows/win32/api/profileapi/nf-profileapi-queryperformancecounter>
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// <https://docs.microsoft.com/en-us/windows/win32/api/profileapi/nf-profileapi-queryperformancefrequency>
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BOOL ok = QueryPerformanceCounter(&c);
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assert(ok);
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(void) ok;
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LONGLONG counter = c.QuadPart;
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static LONGLONG frequency;
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if (!frequency) {
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// Initialize on first call
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LARGE_INTEGER f;
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ok = QueryPerformanceFrequency(&f);
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assert(ok);
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frequency = f.QuadPart;
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assert(frequency);
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}
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if (frequency % SC_TICK_FREQ == 0) {
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// Expected case (typically frequency = 10000000, i.e. 100ns precision)
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sc_tick div = frequency / SC_TICK_FREQ;
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return SC_TICK_FROM_US(counter / div);
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}
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// Split the division to avoid overflow
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sc_tick secs = SC_TICK_FROM_SEC(counter / frequency);
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sc_tick subsec = SC_TICK_FREQ * (counter % frequency) / frequency;
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return secs + subsec;
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#endif
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}
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