[newlib-cygwin] When converting ns,us,ms to sbt, return the ceil()

[newlib-cygwin] When converting ns,us,ms to sbt, return the ceil()

[Sebastian Huber]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=7bf8fc0987838fc435e251183410ed16bfb36c95

commit 7bf8fc0987838fc435e251183410ed16bfb36c95
Author: imp <imp@FreeBSD.org>
Date:   Thu Nov 15 16:02:13 2018 +0000

    When converting ns,us,ms to sbt, return the ceil()
    
    of the result rather than the floor(). Returning the floor means that
    sbttoX(Xtosbt(y)) != y for almost all values of y. In practice, this
    results in a difference of at most 1 in the lsb of the sbintime_t. This
    difference is meaningless for all current users of these functions, but
    is important for the newly introduced sysctl conversion routines which
    implicitly rely on the transformation being idempotent.
    
    Sponsored by: Netflix, Inc

Diff:
---
 newlib/libc/include/sys/time.h | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/newlib/libc/include/sys/time.h b/newlib/libc/include/sys/time.h
index e5023ae..5182dc1 100644
--- a/newlib/libc/include/sys/time.h
+++ b/newlib/libc/include/sys/time.h
@@ -171,6 +171,10 @@ sbttobt(sbintime_t _sbt)
  * Decimal<->sbt conversions.  Multiplying or dividing by SBT_1NS results in
  * 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().
  */
 static __inline int64_t
 sbttons(sbintime_t _sbt)
@@ -183,7 +187,7 @@ static __inline sbintime_t
 nstosbt(int64_t _ns)
 {
 
-	return ((_ns * (((uint64_t)1 << 63) / 500000000)) >> 32);
+	return ((_ns * (((uint64_t)1 << 63) / 500000000) + (1ull << 32) - 1) >> 32);
 }
 
 static __inline int64_t
@@ -197,7 +201,7 @@ static __inline sbintime_t
 ustosbt(int64_t _us)
 {
 
-	return ((_us * (((uint64_t)1 << 63) / 500000)) >> 32);
+	return ((_us * (((uint64_t)1 << 63) / 500000) + (1ull << 32) - 1) >> 32);
 }
 
 static __inline int64_t
@@ -211,7 +215,7 @@ static __inline sbintime_t
 mstosbt(int64_t _ms)
 {
 
-	return ((_ms * (((uint64_t)1 << 63) / 500)) >> 32);
+	return ((_ms * (((uint64_t)1 << 63) / 500) + (1ull << 32) - 1) >> 32);
 }
 
 /*-