1 /* $OpenBSD: time.c,v 1.5 2005/08/08 08:05:34 espie Exp $ */ 2 /* 3 * Copyright (c) 1983, 1993 4 * The Regents of the University of California. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 3. Neither the name of the University nor the names of its contributors 15 * may be used to endorse or promote products derived from this software 16 * without specific prior written permission. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28 * SUCH DAMAGE. 29 */ 30 31 #include <time.h> 32 33 time_t 34 time(time_t *t) 35 { 36 struct timeval tt; 37 time_t ret; 38 39 if (gettimeofday(&tt, (struct timezone *)0) < 0) 40 ret = -1; 41 else 42 ret = tt.tv_sec; 43 if (t != NULL) 44 *t = ret; 45 return ret; 46 } 47 48 // return monotonically increasing CPU time in ticks relative to unspecified epoch 49 static inline clock_t clock_now(void) 50 { 51 struct timespec tm; 52 clock_gettime( CLOCK_MONOTONIC, &tm); 53 return tm.tv_sec * CLOCKS_PER_SEC + (tm.tv_nsec * (CLOCKS_PER_SEC/1e9)); 54 } 55 56 // initialized by the constructor below 57 static clock_t clock_start; 58 59 // called by dlopen when .so is loaded 60 __attribute__((constructor)) static void clock_crt0(void) 61 { 62 clock_start = clock_now(); 63 } 64 65 // return elapsed CPU time in clock ticks, since start of program execution 66 // (spec says epoch is undefined, but glibc uses crt0 as epoch) 67 clock_t 68 clock(void) 69 { 70 // note that if we are executing in a different thread than crt0, then the 71 // pthread_create that made us had a memory barrier so clock_start is defined 72 return clock_now() - clock_start; 73 } 74
