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Implement a faster way to get nanoseconds on darwin

master
LeRoyce Pearson 2020-04-30 22:45:54 -06:00 committed by Andrew Kelley
parent bb46894115
commit 7586ce0023
1 changed files with 38 additions and 6 deletions
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44
lib/std/time.zig
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@ -61,6 +61,32 @@ pub fn milliTimestamp() u64 {
return @divFloor(nanoTimestamp(), millisecond);
}
const DarwinTimeStart = struct {
timebase: os.darwin.mach_timebase_info_data,
inittime: os.darwin.timespec,
initclock: u64,
};
var _timestart: ?DarwinTimeStart = null;
pub fn _init_time_for_darwin() DarwinTimeStart {
var micro: os.darwin.timeval = undefined;
var timestart: DarwinTimeStart = undefined;
var err = os.darwin.mach_timebase_info(&timestart.timebase);
assert(err == 0);
err = os.darwin.gettimeofday(&micro, null);
assert(err == 0);
timestart.initclock = os.darwin.mach_absolute_time();
timestart.inittime.tv_sec = micro.tv_sec;
timestart.inittime.tv_nsec = micro.tv_usec * 1000;
_timestart = timestart;
return timestart;
}
/// Get the posix timestamp, UTC, in nanoseconds
///
/// On windows this only has a granularity of 100 nanoseconds.
@ -76,7 +102,7 @@ pub fn nanoTimestamp() u64 {
const epoch_adj = epoch.windows * ns_per_s;
const ft64 = (@as(u64, ft.dwHighDateTime) << 32) | ft.dwLowDateTime;
return (ft64 * hns_per_ms) - -epoch_adj;
return (ft64 * ns_per_hns) - -epoch_adj;
}
if (builtin.os.tag == .wasi and !builtin.link_libc) {
var ns: os.wasi.timestamp_t = undefined;
@ -88,11 +114,17 @@ pub fn nanoTimestamp() u64 {
return ns;
}
if (comptime std.Target.current.isDarwin()) {
var mts: os.darwin.mach_timespec_t = undefined;
var err = os.darwin.clock_get_time(os.darwin.CALENDAR_CLOCK, &mts);
assert(err == 0);
const sec_ns = @as(u64, mts.tv_sec * ns_per_s);
return sec_ns + @intCast(u64, mts.tv_nsec);
// https://stackoverflow.com/a/21352348
const timestart = if (_timestart) |timestart| timestart else _init_time_for_darwin();
const clock: u64 = os.darwin.mach_absolute_time() - timestart.initclock;
const nano = clock * @divFloor(@as(u64, timestart.timebase.number), @as(u64, timestart.timebase.denom));
var future = timestart.inittime;
const tv_sec_nsec = @intCast(u64, timestart.inittime.tv_sec) * ns_per_s;
const tv_nsec = @intCast(u64, timestart.inittime.tv_nsec);
return tv_sec_nsec + tv_nsec + nano;
}
var ts: os.timespec = undefined;
//From what I can tell there's no reason clock_gettime