diff options
Diffstat (limited to 'util/lamport.go')
| -rw-r--r-- | util/lamport.go | 85 |
1 files changed, 0 insertions, 85 deletions
diff --git a/util/lamport.go b/util/lamport.go deleted file mode 100644 index 4d5dcf5b..00000000 --- a/util/lamport.go +++ /dev/null @@ -1,85 +0,0 @@ -/* - - This Source Code Form is subject to the terms of the Mozilla Public - License, v. 2.0. If a copy of the MPL was not distributed with this file, - You can obtain one at http://mozilla.org/MPL/2.0/. - - Copyright (c) 2013, Armon Dadgar armon.dadgar@gmail.com - Copyright (c) 2013, Mitchell Hashimoto mitchell.hashimoto@gmail.com - - Alternatively, the contents of this file may be used under the terms - of the GNU General Public License Version 3 or later, as described below: - - This file is free software: you may copy, redistribute and/or modify - it under the terms of the GNU General Public License as published by the - Free Software Foundation, either version 3 of the License, or (at your - option) any later version. - - This file is distributed in the hope that it will be useful, but - WITHOUT ANY WARRANTY; without even the implied warranty of - MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General - Public License for more details. - - You should have received a copy of the GNU General Public License - along with this program. If not, see http://www.gnu.org/licenses/. - -*/ - -package util - -import ( - "sync/atomic" -) - -// LamportClock is a thread safe implementation of a lamport clock. It -// uses efficient atomic operations for all of its functions, falling back -// to a heavy lock only if there are enough CAS failures. -type LamportClock struct { - counter uint64 -} - -// LamportTime is the value of a LamportClock. -type LamportTime uint64 - -func NewLamportClock() LamportClock { - return LamportClock{ - counter: 1, - } -} - -func NewLamportClockWithTime(time uint64) LamportClock { - return LamportClock{ - counter: time, - } -} - -// Time is used to return the current value of the lamport clock -func (l *LamportClock) Time() LamportTime { - return LamportTime(atomic.LoadUint64(&l.counter)) -} - -// Increment is used to return the value of the lamport clock and increment it afterwards -func (l *LamportClock) Increment() LamportTime { - return LamportTime(atomic.AddUint64(&l.counter, 1) - 1) -} - -// Witness is called to update our local clock if necessary after -// witnessing a clock value received from another process -func (l *LamportClock) Witness(v LamportTime) { -WITNESS: - // If the other value is old, we do not need to do anything - cur := atomic.LoadUint64(&l.counter) - other := uint64(v) - if other < cur { - return - } - - // Ensure that our local clock is at least one ahead. - if !atomic.CompareAndSwapUint64(&l.counter, cur, other+1) { - // CAS: CompareAndSwap - // The CAS failed, so we just retry. Eventually our CAS should - // succeed or a future witness will pass us by and our witness - // will end. - goto WITNESS - } -} |