time.h

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#ifndef GRPC_SUPPORT_TIME_H
#define GRPC_SUPPORT_TIME_H
/* Time support.
   We use gpr_timespec, which is analogous to struct timespec.  On some
   machines, absolute times may be in local time.  */

#include <grpc/support/port_platform.h>
#include <stddef.h>
#include <time.h>

#ifdef __cplusplus
extern "C" {
#endif

/* The clocks we support. */
typedef enum {
  /* Monotonic clock. Epoch undefined. Always moves forwards. */
  GPR_CLOCK_MONOTONIC = 0,
  /* Realtime clock. May jump forwards or backwards. Settable by
     the system administrator. Has its epoch at 0:00:00 UTC 1 Jan 1970. */
  GPR_CLOCK_REALTIME,
  /* Unmeasurable clock type: no base, created by taking the difference
     between two times */
  GPR_TIMESPAN
} gpr_clock_type;

typedef struct gpr_timespec {
  time_t tv_sec;
  int tv_nsec;
  gpr_clock_type clock_type;
} gpr_timespec;

/* Time constants. */
gpr_timespec gpr_time_0(gpr_clock_type type);     /* The zero time interval. */
gpr_timespec gpr_inf_future(gpr_clock_type type); /* The far future */
gpr_timespec gpr_inf_past(gpr_clock_type type);   /* The far past. */

#define GPR_MS_PER_SEC 1000
#define GPR_US_PER_SEC 1000000
#define GPR_NS_PER_SEC 1000000000
#define GPR_NS_PER_MS 1000000
#define GPR_NS_PER_US 1000
#define GPR_US_PER_MS 1000

/* initialize time subsystem */
void gpr_time_init(void);

/* Return the current time measured from the given clocks epoch. */
gpr_timespec gpr_now(gpr_clock_type clock);

/* Convert a timespec from one clock to another */
gpr_timespec gpr_convert_clock_type(gpr_timespec t, gpr_clock_type target_clock);

/* Return -ve, 0, or +ve according to whether a < b, a == b, or a > b
   respectively.  */
int gpr_time_cmp(gpr_timespec a, gpr_timespec b);

gpr_timespec gpr_time_max(gpr_timespec a, gpr_timespec b);
gpr_timespec gpr_time_min(gpr_timespec a, gpr_timespec b);

/* Add and subtract times.  Calculations saturate at infinities. */
gpr_timespec gpr_time_add(gpr_timespec a, gpr_timespec b);
gpr_timespec gpr_time_sub(gpr_timespec a, gpr_timespec b);

/* Return a timespec representing a given number of time units. LONG_MIN is
   interpreted as gpr_inf_past, and LONG_MAX as gpr_inf_future.  */
gpr_timespec gpr_time_from_micros(long x, gpr_clock_type clock_type);
gpr_timespec gpr_time_from_nanos(long x, gpr_clock_type clock_type);
gpr_timespec gpr_time_from_millis(long x, gpr_clock_type clock_type);
gpr_timespec gpr_time_from_seconds(long x, gpr_clock_type clock_type);
gpr_timespec gpr_time_from_minutes(long x, gpr_clock_type clock_type);
gpr_timespec gpr_time_from_hours(long x, gpr_clock_type clock_type);

gpr_int32 gpr_time_to_millis(gpr_timespec timespec);

/* Return 1 if two times are equal or within threshold of each other,
   0 otherwise */
int gpr_time_similar(gpr_timespec a, gpr_timespec b, gpr_timespec threshold);

/* Sleep until at least 'until' - an absolute timeout */
void gpr_sleep_until(gpr_timespec until);

double gpr_timespec_to_micros(gpr_timespec t);

#ifdef __cplusplus
}
#endif

#endif /* GRPC_SUPPORT_TIME_H */