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Fixes overflow trap when creating DispatchTime objects with large upt… #311

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Merged
merged 1 commit into from
Oct 16, 2017
Merged

Fixes overflow trap when creating DispatchTime objects with large upt… #311

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18 changes: 13 additions & 5 deletions src/swift/Time.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -59,9 +59,13 @@ public struct DispatchTime : Comparable {
public init(uptimeNanoseconds: UInt64) {
var rawValue = uptimeNanoseconds
#if HAVE_MACH
if (DispatchTime.timebaseInfo.numer != DispatchTime.timebaseInfo.denom) {
rawValue = (rawValue * UInt64(DispatchTime.timebaseInfo.denom)
+ UInt64(DispatchTime.timebaseInfo.numer - 1)) / UInt64(DispatchTime.timebaseInfo.numer)
// UInt64.max means distantFuture. Do not try to scale it.
if rawValue != UInt64.max && DispatchTime.timebaseInfo.numer != DispatchTime.timebaseInfo.denom {
var (result, overflow) = rawValue.multipliedReportingOverflow(by: UInt64(DispatchTime.timebaseInfo.denom))
if !overflow {
(result, overflow) = result.addingReportingOverflow(UInt64(DispatchTime.timebaseInfo.numer - 1))
}
rawValue = overflow ? UInt64.max : result / UInt64(DispatchTime.timebaseInfo.numer)
}
#endif
self.rawValue = dispatch_time_t(rawValue)
Expand All @@ -70,8 +74,12 @@ public struct DispatchTime : Comparable {
public var uptimeNanoseconds: UInt64 {
var result = self.rawValue
#if HAVE_MACH
if (DispatchTime.timebaseInfo.numer != DispatchTime.timebaseInfo.denom) {
result = result * UInt64(DispatchTime.timebaseInfo.numer) / UInt64(DispatchTime.timebaseInfo.denom)
var overflow: Bool

// UInt64.max means distantFuture. Do not try to scale it.
if rawValue != UInt64.max && DispatchTime.timebaseInfo.numer != DispatchTime.timebaseInfo.denom {
(result, overflow) = result.multipliedReportingOverflow(by: UInt64(DispatchTime.timebaseInfo.numer))
result = overflow ? UInt64.max : result / UInt64(DispatchTime.timebaseInfo.denom)
}
#endif
return result
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