diff options
| -rw-r--r-- | newlib/libc/include/sys/time.h | 59 |
1 files changed, 52 insertions, 7 deletions
diff --git a/newlib/libc/include/sys/time.h b/newlib/libc/include/sys/time.h index 5182dc14e..081e0cf65 100644 --- a/newlib/libc/include/sys/time.h +++ b/newlib/libc/include/sys/time.h @@ -33,7 +33,7 @@ * SUCH DAMAGE. * * @(#)time.h 8.5 (Berkeley) 5/4/95 - * $FreeBSD$ + * $FreeBSD: head/sys/sys/time.h 340664 2018-11-20 07:11:23Z imp $ */ #ifndef _SYS_TIME_H_ @@ -172,9 +172,24 @@ sbttobt(sbintime_t _sbt) * large roundoff errors which sbttons() and nstosbt() avoid. Millisecond and * microsecond functions are also provided for completeness. * - * These functions return the smallest sbt larger or equal to the number of - * seconds requested so that sbttoX(Xtosbt(y)) == y. The 1 << 32 - 1 term added - * transforms the >> 32 from floor() to ceil(). + * These functions return the smallest sbt larger or equal to the + * number of seconds requested so that sbttoX(Xtosbt(y)) == y. Unlike + * top of second computations below, which require that we tick at the + * top of second, these need to be rounded up so we do whatever for at + * least as long as requested. + * + * The naive computation we'd do is this + * ((unit * 2^64 / SIFACTOR) + 2^32-1) >> 32 + * However, that overflows. Instead, we compute + * ((unit * 2^63 / SIFACTOR) + 2^31-1) >> 32 + * and use pre-computed constants that are the ceil of the 2^63 / SIFACTOR + * term to ensure we are using exactly the right constant. We use the lesser + * evil of ull rather than a uint64_t cast to ensure we have well defined + * right shift semantics. With these changes, we get all the ns, us and ms + * conversions back and forth right. + * Note: This file is used for both kernel and userland includes, so we can't + * rely on KASSERT being defined, nor can we pollute the namespace by including + * assert.h. */ static __inline int64_t sbttons(sbintime_t _sbt) @@ -186,8 +201,18 @@ sbttons(sbintime_t _sbt) static __inline sbintime_t nstosbt(int64_t _ns) { + sbintime_t sb = 0; - return ((_ns * (((uint64_t)1 << 63) / 500000000) + (1ull << 32) - 1) >> 32); +#ifdef KASSERT + KASSERT(_ns >= 0, ("Negative values illegal for nstosbt: %jd", _ns)); +#endif + if (_ns >= SBT_1S) { + sb = (_ns / 1000000000) * SBT_1S; + _ns = _ns % 1000000000; + } + /* 9223372037 = ceil(2^63 / 1000000000) */ + sb += ((_ns * 9223372037ull) + 0x7fffffff) >> 31; + return (sb); } static __inline int64_t @@ -200,8 +225,18 @@ sbttous(sbintime_t _sbt) static __inline sbintime_t ustosbt(int64_t _us) { + sbintime_t sb = 0; - return ((_us * (((uint64_t)1 << 63) / 500000) + (1ull << 32) - 1) >> 32); +#ifdef KASSERT + KASSERT(_us >= 0, ("Negative values illegal for ustosbt: %jd", _us)); +#endif + if (_us >= SBT_1S) { + sb = (_us / 1000000) * SBT_1S; + _us = _us % 1000000; + } + /* 9223372036855 = ceil(2^63 / 1000000) */ + sb += ((_us * 9223372036855ull) + 0x7fffffff) >> 31; + return (sb); } static __inline int64_t @@ -214,8 +249,18 @@ sbttoms(sbintime_t _sbt) static __inline sbintime_t mstosbt(int64_t _ms) { + sbintime_t sb = 0; - return ((_ms * (((uint64_t)1 << 63) / 500) + (1ull << 32) - 1) >> 32); +#ifdef KASSERT + KASSERT(_ms >= 0, ("Negative values illegal for mstosbt: %jd", _ms)); +#endif + if (_ms >= SBT_1S) { + sb = (_ms / 1000) * SBT_1S; + _ms = _ms % 1000; + } + /* 9223372036854776 = ceil(2^63 / 1000) */ + sb += ((_ms * 9223372036854776ull) + 0x7fffffff) >> 31; + return (sb); } /*- |