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// Copyright (C) 2019-2024 Algorand, Inc.
// This file is part of go-algorand
//
// go-algorand is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// go-algorand 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 Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with go-algorand. If not, see <https://www.gnu.org/licenses/>.
package basics
import (
"math/bits"
"golang.org/x/exp/constraints"
)
// OverflowTracker is used to track when an operation causes an overflow
type OverflowTracker struct {
Overflowed bool
}
// OAdd adds 2 values with overflow detection
func OAdd[T constraints.Unsigned](a, b T) (res T, overflowed bool) {
res = a + b
overflowed = res < a
return
}
// OSub subtracts b from a with overflow detection
func OSub[T constraints.Unsigned](a, b T) (res T, overflowed bool) {
res = a - b
overflowed = res > a
return
}
// OMul multiplies 2 values with overflow detection
func OMul[T constraints.Unsigned](a, b T) (res T, overflowed bool) {
if b == 0 {
return 0, false
}
c := a * b
if c/b != a {
return 0, true
}
return c, false
}
// MulSaturate multiplies 2 values with saturation on overflow
func MulSaturate[T constraints.Unsigned](a, b T) T {
res, overflowed := OMul(a, b)
if overflowed {
var defaultT T
return ^defaultT
}
return res
}
// AddSaturate adds 2 values with saturation on overflow
func AddSaturate[T constraints.Unsigned](a, b T) T {
res, overflowed := OAdd(a, b)
if overflowed {
var defaultT T
return ^defaultT
}
return res
}
// SubSaturate subtracts 2 values with saturation on underflow
func SubSaturate[T constraints.Unsigned](a, b T) T {
res, overflowed := OSub(a, b)
if overflowed {
return 0
}
return res
}
// Add adds 2 values with overflow detection
func (t *OverflowTracker) Add(a, b uint64) uint64 {
res, overflowed := OAdd(a, b)
if overflowed {
t.Overflowed = true
}
return res
}
// Sub subtracts b from a with overflow detection
func (t *OverflowTracker) Sub(a, b uint64) uint64 {
res, overflowed := OSub(a, b)
if overflowed {
t.Overflowed = true
}
return res
}
// Mul multiplies b by a with overflow detection
func (t *OverflowTracker) Mul(a, b uint64) uint64 {
res, overflowed := OMul(a, b)
if overflowed {
t.Overflowed = true
}
return res
}
// OAddA adds 2 MicroAlgos values with overflow tracking
func OAddA(a, b MicroAlgos) (res MicroAlgos, overflowed bool) {
res.Raw, overflowed = OAdd(a.Raw, b.Raw)
return
}
// OSubA subtracts b from a with overflow tracking
func OSubA(a, b MicroAlgos) (res MicroAlgos, overflowed bool) {
res.Raw, overflowed = OSub(a.Raw, b.Raw)
return
}
// MulAIntSaturate uses MulSaturate to multiply b (int) with a (MicroAlgos)
func MulAIntSaturate(a MicroAlgos, b int) MicroAlgos {
return MicroAlgos{Raw: MulSaturate(a.Raw, uint64(b))}
}
// AddA adds 2 MicroAlgos values with overflow tracking
func (t *OverflowTracker) AddA(a, b MicroAlgos) MicroAlgos {
return MicroAlgos{Raw: t.Add(a.Raw, b.Raw)}
}
// SubA subtracts b from a with overflow tracking
func (t *OverflowTracker) SubA(a, b MicroAlgos) MicroAlgos {
return MicroAlgos{Raw: t.Sub(a.Raw, b.Raw)}
}
// ScalarMulA multiplies an Algo amount by a scalar
func (t *OverflowTracker) ScalarMulA(a MicroAlgos, b uint64) MicroAlgos {
return MicroAlgos{Raw: t.Mul(a.Raw, b)}
}
// Muldiv computes a*b/c. The overflow flag indicates that
// the result was 2^64 or greater.
func Muldiv(a uint64, b uint64, c uint64) (res uint64, overflow bool) {
hi, lo := bits.Mul64(a, b)
if c <= hi {
return 0, true
}
quo, _ := bits.Div64(hi, lo, c)
return quo, false
}
// DivCeil provides `math.Ceil` semantics using integer division. The technique
// avoids slower floating point operations as suggested in https://stackoverflow.com/a/2745086.
//
// The method assumes both numbers are positive and does _not_ check for divide-by-zero.
func DivCeil[T constraints.Integer](numerator, denominator T) T {
return (numerator + denominator - 1) / denominator
}
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