timespecops.c revision 358659
1/* 2 * timespecops.c -- calculations on 'struct timespec' values 3 * 4 * Written by Juergen Perlinger (perlinger@ntp.org) for the NTP project. 5 * The contents of 'html/copyright.html' apply. 6 * 7 */ 8 9#include "config.h" 10 11#include <sys/types.h> 12#include <stdio.h> 13#include <math.h> 14 15#include "ntp.h" 16#include "timetoa.h" 17#include "timespecops.h" 18 19 20/* nanoseconds per second */ 21#define NANOSECONDS 1000000000 22 23/* conversion between l_fp fractions and nanoseconds */ 24#ifdef HAVE_U_INT64 25# define FTOTVN(tsf) \ 26 ((int32) \ 27 (((u_int64)(tsf) * NANOSECONDS + 0x80000000) >> 32)) 28# define TVNTOF(tvu) \ 29 ((u_int32) \ 30 ((((u_int64)(tvu) << 32) + NANOSECONDS / 2) / \ 31 NANOSECONDS)) 32#else 33# define NSECFRAC (FRAC / NANOSECONDS) 34# define FTOTVN(tsf) \ 35 ((int32)((tsf) / NSECFRAC + 0.5)) 36# define TVNTOF(tvu) \ 37 ((u_int32)((tvu) * NSECFRAC + 0.5)) 38#endif 39 40 41 42/* make sure nanoseconds are in nominal range */ 43struct timespec 44normalize_tspec( 45 struct timespec x 46 ) 47{ 48#if SIZEOF_LONG > 4 49 long z; 50 51 /* 52 * tv_nsec is of type 'long', and on a 64-bit machine using only 53 * loops becomes prohibitive once the upper 32 bits get 54 * involved. On the other hand, division by constant should be 55 * fast enough; so we do a division of the nanoseconds in that 56 * case. The floor adjustment step follows with the standard 57 * normalisation loops. And labs() is intentionally not used 58 * here: it has implementation-defined behaviour when applied 59 * to LONG_MIN. 60 */ 61 if (x.tv_nsec < -3l * NANOSECONDS || 62 x.tv_nsec > 3l * NANOSECONDS) { 63 z = x.tv_nsec / NANOSECONDS; 64 x.tv_nsec -= z * NANOSECONDS; 65 x.tv_sec += z; 66 } 67#endif 68 /* since 10**9 is close to 2**32, we don't divide but do a 69 * normalisation in a loop; this takes 3 steps max, and should 70 * outperform a division even if the mul-by-inverse trick is 71 * employed. */ 72 if (x.tv_nsec < 0) 73 do { 74 x.tv_nsec += NANOSECONDS; 75 x.tv_sec--; 76 } while (x.tv_nsec < 0); 77 else if (x.tv_nsec >= NANOSECONDS) 78 do { 79 x.tv_nsec -= NANOSECONDS; 80 x.tv_sec++; 81 } while (x.tv_nsec >= NANOSECONDS); 82 83 return x; 84} 85 86/* x = abs(a) */ 87struct timespec 88abs_tspec( 89 struct timespec a 90 ) 91{ 92 struct timespec c; 93 94 c = normalize_tspec(a); 95 if (c.tv_sec < 0) { 96 if (c.tv_nsec != 0) { 97 c.tv_sec = -c.tv_sec - 1; 98 c.tv_nsec = NANOSECONDS - c.tv_nsec; 99 } else { 100 c.tv_sec = -c.tv_sec; 101 } 102 } 103 104 return c; 105} 106 107/* 108 * compare previously-normalised a and b 109 * return 1 / 0 / -1 if a < / == / > b 110 */ 111int 112cmp_tspec( 113 struct timespec a, 114 struct timespec b 115 ) 116{ 117 int r; 118 119 r = (a.tv_sec > b.tv_sec) - (a.tv_sec < b.tv_sec); 120 if (0 == r) 121 r = (a.tv_nsec > b.tv_nsec) - 122 (a.tv_nsec < b.tv_nsec); 123 124 return r; 125} 126 127/* 128 * test previously-normalised a 129 * return 1 / 0 / -1 if a < / == / > 0 130 */ 131int 132test_tspec( 133 struct timespec a 134 ) 135{ 136 int r; 137 138 r = (a.tv_sec > 0) - (a.tv_sec < 0); 139 if (r == 0) 140 r = (a.tv_nsec > 0); 141 142 return r; 143} 144 145/* 146 * convert to l_fp type, relative and absolute 147 */ 148 149/* convert from timespec duration to l_fp duration */ 150l_fp 151tspec_intv_to_lfp( 152 struct timespec x 153 ) 154{ 155 struct timespec v; 156 l_fp y; 157 158 v = normalize_tspec(x); 159 y.l_uf = TVNTOF(v.tv_nsec); 160 y.l_i = (int32)v.tv_sec; 161 162 return y; 163} 164 165/* convert from l_fp type, relative signed/unsigned and absolute */ 166struct timespec 167lfp_intv_to_tspec( 168 l_fp x 169 ) 170{ 171 struct timespec out; 172 l_fp absx; 173 int neg; 174 175 neg = L_ISNEG(&x); 176 absx = x; 177 if (neg) { 178 L_NEG(&absx); 179 } 180 out.tv_nsec = FTOTVN(absx.l_uf); 181 out.tv_sec = absx.l_i; 182 if (neg) { 183 out.tv_sec = -out.tv_sec; 184 out.tv_nsec = -out.tv_nsec; 185 out = normalize_tspec(out); 186 } 187 188 return out; 189} 190 191struct timespec 192lfp_uintv_to_tspec( 193 l_fp x 194 ) 195{ 196 struct timespec out; 197 198 out.tv_nsec = FTOTVN(x.l_uf); 199 out.tv_sec = x.l_ui; 200 201 return out; 202} 203 204/* 205 * absolute (timestamp) conversion. Input is time in NTP epoch, output 206 * is in UN*X epoch. The NTP time stamp will be expanded around the 207 * pivot time *p or the current time, if p is NULL. 208 */ 209struct timespec 210lfp_stamp_to_tspec( 211 l_fp x, 212 const time_t * p 213 ) 214{ 215 struct timespec out; 216 vint64 sec; 217 218 sec = ntpcal_ntp_to_time(x.l_ui, p); 219 out.tv_nsec = FTOTVN(x.l_uf); 220 221 /* copying a vint64 to a time_t needs some care... */ 222#if SIZEOF_TIME_T <= 4 223 out.tv_sec = (time_t)sec.d_s.lo; 224#elif defined(HAVE_INT64) 225 out.tv_sec = (time_t)sec.q_s; 226#else 227 out.tv_sec = ((time_t)sec.d_s.hi << 32) | sec.d_s.lo; 228#endif 229 230 return out; 231} 232 233/* -*-EOF-*- */ 234