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Improve quality of our ANSI C clock() function

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It now works most excellently across all supported operating
sytsems (earlier it didn't work on NT and XNU). Demo code is
available in examples/clock.c and this change also adds some
of the newer ANSI C time functions like timespec_get(), plus
timespec_getres() which hasn't even come out yet as it's C23
This commit is contained in:
Justine Tunney 2022-09-05 21:43:49 -07:00
parent 7ff0ea8c13
commit 12d9e1e128
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GPG key ID: BE714B4575D6E328
24 changed files with 254 additions and 76 deletions
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57
libc/calls/clock.c
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@ -16,36 +16,51 @@
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/calls/struct/rusage.h"
#include "libc/calls/struct/timespec.h"
#include "libc/dce.h"
#include "libc/fmt/conv.h"
#include "libc/nt/accounting.h"
#include "libc/nt/runtime.h"
#include "libc/nt/synchronization.h"
#include "libc/calls/struct/timeval.h"
#include "libc/errno.h"
#include "libc/sysv/consts/clock.h"
#include "libc/sysv/consts/rusage.h"
#include "libc/time/time.h"
/**
* Returns how much CPU program has consumed on time-sharing system.
* Returns sum of CPU time consumed by current process since birth.
*
* @return value that can be divided by CLOCKS_PER_SEC, or -1 w/ errno
* @see clock_gettime()
* This function provides a basic idea of how computationally expensive
* your program is, in terms of both the userspace and kernel processor
* resources it's hitherto consumed. Here's an example of how you might
* display this information:
*
* printf("consumed %g seconds of cpu time\n",
* (double)clock() / CLOCKS_PER_SEC);
*
* This function offers at best microsecond accuracy on all supported
* platforms. Please note the reported values might be a bit chunkier
* depending on the kernel scheduler sampling interval see `CLK_TCK`.
*
* @return units of CPU time consumed, where each unit's time length
* should be `1./CLOCKS_PER_SEC` seconds; Cosmopolitan currently
* returns the unit count in microseconds, i.e. `CLOCKS_PER_SEC`
* is hard-coded as 1000000. On failure this returns -1 / errno.
* @raise ENOSYS should be returned currently if run on Bare Metal
* @see clock_gettime() which polyfills this on Linux and BSDs
* @see getrusage() which polyfills this on XNU and NT
*/
int64_t clock(void) {
int e;
struct rusage ru;
struct timespec ts;
struct NtFileTime creation_time, exit_time, kernel_time, user_time;
int64_t proc, total;
// polyfill on Windows where CLOCK_PROCESS_CPUTIME_ID may be not available
if (IsWindows() && CLOCK_PROCESS_CPUTIME_ID == -1) {
proc = GetCurrentProcess();
if (!GetProcessTimes(proc, &creation_time, &exit_time, &kernel_time,
&user_time))
e = errno;
if (clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &ts) == -1) {
errno = e;
if (getrusage(RUSAGE_SELF, &ru) != -1) {
ts = _timeval_totimespec(_timeval_add(ru.ru_utime, ru.ru_stime));
} else {
return -1;
total = ReadFileTime(kernel_time) + ReadFileTime(user_time);
ts = WindowsDurationToTimeSpec(total);
} else if (clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &ts) == -1) {
return -1;
}
}
return ts.tv_sec * CLOCKS_PER_SEC +
ts.tv_nsec / (1000000000 / CLOCKS_PER_SEC);
// convert nanoseconds to microseconds w/ ceil rounding
// this would need roughly ~7,019,309 years to overflow
return ts.tv_sec * 1000000 + (ts.tv_nsec + 999) / 1000;
}