1// Copyright (c) 2020 Uber Technologies, Inc. 2// 3// Permission is hereby granted, free of charge, to any person obtaining a copy 4// of this software and associated documentation files (the "Software"), to deal 5// in the Software without restriction, including without limitation the rights 6// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 7// copies of the Software, and to permit persons to whom the Software is 8// furnished to do so, subject to the following conditions: 9// 10// The above copyright notice and this permission notice shall be included in 11// all copies or substantial portions of the Software. 12// 13// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 14// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 15// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 16// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 17// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 18// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN 19// THE SOFTWARE. 20 21package atomic 22 23import ( 24 "math" 25 "strconv" 26) 27 28//go:generate bin/gen-atomicwrapper -name=Float64 -type=float64 -wrapped=Uint64 -pack=math.Float64bits -unpack=math.Float64frombits -swap -json -imports math -file=float64.go 29 30// Add atomically adds to the wrapped float64 and returns the new value. 31func (f *Float64) Add(delta float64) float64 { 32 for { 33 old := f.Load() 34 new := old + delta 35 if f.CAS(old, new) { 36 return new 37 } 38 } 39} 40 41// Sub atomically subtracts from the wrapped float64 and returns the new value. 42func (f *Float64) Sub(delta float64) float64 { 43 return f.Add(-delta) 44} 45 46// CAS is an atomic compare-and-swap for float64 values. 47// 48// Note: CAS handles NaN incorrectly. NaN != NaN using Go's inbuilt operators 49// but CAS allows a stored NaN to compare equal to a passed in NaN. 50// This avoids typical CAS loops from blocking forever, e.g., 51// 52// for { 53// old := atom.Load() 54// new = f(old) 55// if atom.CAS(old, new) { 56// break 57// } 58// } 59// 60// If CAS did not match NaN to match, then the above would loop forever. 61func (f *Float64) CAS(old, new float64) (swapped bool) { 62 return f.v.CAS(math.Float64bits(old), math.Float64bits(new)) 63} 64 65// String encodes the wrapped value as a string. 66func (f *Float64) String() string { 67 // 'g' is the behavior for floats with %v. 68 return strconv.FormatFloat(f.Load(), 'g', -1, 64) 69} 70