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jedib0tjedib0t
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odometer
1 parent 337419c commit 422a86f

11 files changed

+668
-3
lines changed

‎Makefile

+1-1
Original file line numberDiff line numberDiff line change
@@ -3,7 +3,7 @@
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default: test
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bench:
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go test -bench=. -benchmem ./passphrase ./password ./password/sequencer
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go test -bench=. -benchmem ./odometer ./passphrase ./password ./password/sequencer
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cyclo:
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gocyclo -over 13 ./*/*.go

‎odometer/errors.go

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package odometer
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import "errors"
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var (
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ErrInvalidLocation = errors.New("invalid location")
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)

‎odometer/interface.go

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package odometer
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import (
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"math/big"
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)
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type Odometer interface {
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Decrement()
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DecrementN(n *big.Int)
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First()
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GetLocation() *big.Int
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Increment()
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IncrementN(n *big.Int)
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Last()
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SetLocation(n *big.Int) error
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String() string
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Value() []int
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}

‎odometer/odometer.go

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package odometer
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import (
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"math/big"
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"slices"
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"sync"
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"github.com/jedib0t/go-passwords/charset"
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)
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var (
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biZero = big.NewInt(0)
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biOne = big.NewInt(1)
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)
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type odometer struct {
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base int
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baseBigInt *big.Int
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charset []rune
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length int
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location *big.Int
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locationMax *big.Int
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mutex sync.RWMutex
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rollover bool
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value []int
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valueInCharset []rune
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}
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func New(cs charset.Charset, length int, opts ...Option) Odometer {
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base := len(cs)
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maxValues := numValues(base, length)
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o := &odometer{
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base: base,
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baseBigInt: big.NewInt(int64(base)),
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charset: []rune(cs),
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length: length,
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location: big.NewInt(1),
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locationMax: new(big.Int).Set(maxValues),
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value: make([]int, length),
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valueInCharset: make([]rune, length),
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}
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for _, opt := range opts {
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opt(o)
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}
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return o
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}
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func (o *odometer) Decrement() {
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o.mutex.Lock()
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defer o.mutex.Unlock()
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// set the location
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if o.location.Cmp(biOne) == 0 { // at first
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if o.rollover {
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o.last()
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}
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return
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}
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// decrement value
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o.location.Sub(o.location, biOne)
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for idx := o.length - 1; idx >= 0; idx-- {
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if o.decrementAtIndex(idx) {
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return
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}
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}
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}
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func (o *odometer) DecrementN(n *big.Int) {
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o.mutex.Lock()
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defer o.mutex.Unlock()
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o.location.Sub(o.location, n)
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if o.location.Cmp(biOne) < 0 { // less than min
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if !o.rollover {
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o.first()
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return
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}
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// move backwards from max; o.location is currently -ve --> so Add()
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for o.location.Cmp(biOne) < 0 {
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o.location.Add(o.locationMax, o.location)
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}
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}
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o.computeValue()
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}
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func (o *odometer) First() {
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o.mutex.Lock()
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defer o.mutex.Unlock()
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o.first()
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}
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func (o *odometer) GetLocation() *big.Int {
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o.mutex.RLock()
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defer o.mutex.RUnlock()
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return new(big.Int).Set(o.location)
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}
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func (o *odometer) Increment() {
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o.mutex.Lock()
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defer o.mutex.Unlock()
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// set the location
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if o.location.Cmp(o.locationMax) == 0 { // at max
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if o.rollover {
109+
o.first()
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}
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return
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}
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// increment value
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o.location.Add(o.location, biOne)
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for idx := o.length - 1; idx >= 0; idx-- {
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if o.incrementAtIndex(idx) {
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return
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}
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}
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}
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func (o *odometer) IncrementN(n *big.Int) {
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o.mutex.Lock()
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defer o.mutex.Unlock()
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o.location.Add(o.location, n)
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if o.location.Cmp(o.locationMax) > 0 { // more than max
129+
if !o.rollover {
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o.last()
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return
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}
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// move forwards from zero
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for o.location.Cmp(o.locationMax) > 0 {
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o.location.Sub(o.location, o.locationMax)
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}
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}
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o.computeValue()
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}
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func (o *odometer) Last() {
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o.mutex.Lock()
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defer o.mutex.Unlock()
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o.last()
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}
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func (o *odometer) SetLocation(n *big.Int) error {
149+
o.mutex.Lock()
150+
defer o.mutex.Unlock()
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if n.Cmp(biOne) < 0 || n.Cmp(o.locationMax) > 0 {
153+
return ErrInvalidLocation
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}
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o.location.Set(n)
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o.computeValue()
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return nil
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}
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func (o *odometer) String() string {
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o.mutex.Lock()
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defer o.mutex.Unlock()
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for idx := range o.valueInCharset {
165+
o.valueInCharset[idx] = o.charset[o.value[idx]]
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}
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return string(o.valueInCharset)
168+
}
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func (o *odometer) Value() []int {
171+
o.mutex.Lock()
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defer o.mutex.Unlock()
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return slices.Clone(o.value)
175+
}
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func (o *odometer) computeValue() {
178+
// base conversion: convert the value of location to a decimal with the
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// given base using continuous division and use all the remainders as the
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// values
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// prep the dividend, remainder and modulus
183+
dividend, remainder := new(big.Int).Sub(o.location, biOne), new(big.Int)
184+
// append values in reverse (from right to left)
185+
valIdx := o.length - 1
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// append every remainder until dividend becomes zero
187+
for ; dividend.Cmp(biZero) != 0; valIdx-- {
188+
dividend, remainder = dividend.QuoRem(dividend, o.baseBigInt, remainder)
189+
o.value[valIdx] = int(remainder.Int64())
190+
}
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// left-pad the remaining characters with 0 (==> 0th char in charset)
192+
for ; valIdx >= 0; valIdx-- {
193+
o.value[valIdx] = 0
194+
}
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}
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197+
func (o *odometer) decrementAtIndex(idx int) bool {
198+
if o.value[idx] > 0 {
199+
o.value[idx]--
200+
return true
201+
}
202+
if o.value[idx] == 0 && idx > 0 {
203+
o.value[idx] = o.base - 1
204+
o.decrementAtIndex(idx - 1)
205+
return true
206+
}
207+
return false
208+
}
209+
210+
func (o *odometer) first() {
211+
o.location.Set(biOne)
212+
for idx := range o.value {
213+
o.value[idx] = 0
214+
}
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}
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func (o *odometer) incrementAtIndex(idx int) bool {
218+
if o.value[idx] < o.base-1 {
219+
o.value[idx]++
220+
return true
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}
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if o.value[idx] == o.base-1 && idx > 0 {
223+
o.value[idx] = 0
224+
o.incrementAtIndex(idx - 1)
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return true
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}
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return false
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}
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func (o *odometer) last() {
231+
o.location.Set(o.locationMax)
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for idx := range o.value {
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o.value[idx] = o.base - 1
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}
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}

‎odometer/odometer_bench_test.go

+83
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@@ -0,0 +1,83 @@
1+
package odometer
2+
3+
import (
4+
"math"
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"math/big"
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"math/rand"
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"testing"
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"time"
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"github.com/jedib0t/go-passwords/charset"
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"github.com/stretchr/testify/assert"
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)
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func BenchmarkOdometer_Big_Decrement(b *testing.B) {
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o := New(charset.AllChars, 256)
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o.Last()
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for i := 0; i < b.N; i++ {
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o.Decrement()
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}
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}
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func BenchmarkOdometer_Big_Increment(b *testing.B) {
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o := New(charset.AllChars, 256)
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for i := 0; i < b.N; i++ {
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o.Increment()
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}
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}
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func BenchmarkOdometer_Decrement(b *testing.B) {
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o := New(charset.Numbers, 8, WithRolloverEnabled(true))
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for i := 0; i < b.N; i++ {
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o.Decrement()
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}
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}
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func BenchmarkOdometer_DecrementN(b *testing.B) {
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o := New(charset.Numbers, 8, WithRolloverEnabled(true))
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n := big.NewInt(5)
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for i := 0; i < b.N; i++ {
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o.DecrementN(n)
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}
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}
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func BenchmarkOdometer_Increment(b *testing.B) {
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o := New(charset.Numbers, 8, WithRolloverEnabled(true))
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for i := 0; i < b.N; i++ {
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o.Increment()
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}
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}
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func BenchmarkOdometer_IncrementN(b *testing.B) {
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o := New(charset.Numbers, 8, WithRolloverEnabled(true))
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n := big.NewInt(5)
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for i := 0; i < b.N; i++ {
61+
o.IncrementN(n)
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}
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}
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func BenchmarkOdometer_SetLocation(b *testing.B) {
66+
o := New(charset.Numbers, 8, WithRolloverEnabled(true))
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maxValues := int64(math.Pow(10, 8))
68+
rng := rand.New(rand.NewSource(time.Now().Unix()))
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for i := 0; i < b.N; i++ {
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n := big.NewInt(rng.Int63n(maxValues))
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err := o.SetLocation(n)
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assert.Nil(b, err)
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}
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}
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func BenchmarkOdometer_String(b *testing.B) {
78+
o := New(charset.Numbers, 12)
79+
80+
for i := 0; i < b.N; i++ {
81+
_ = o.String()
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}
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}

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