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package tseq
import (
"encoding/hex"
"flag"
"testing"
)
var seed string
func init() {
flag.StringVar(&seed, "tseq.seed", seed, "")
}
func Run(t *testing.T, f func(tseq *TSeq)) {
tseq := TSeq{}
if seed == "" {
defer func() {
if t.Failed() {
t.Logf("rerun with --tseq.seed=%s", scriptToString(tseq.script))
}
}()
for {
f(&tseq)
if !tseq.next() {
break
}
}
} else {
var err error
tseq.script, err = scriptFromString(seed)
if err != nil {
t.Fatalf("invalid --tseq.seed %s: %s", seed, err)
}
f(&tseq)
}
}
type TSeq struct {
script []bool
i int
}
func scriptToString(script []bool) string {
b := make([]byte, (len(script)+7)/8)
for i := range script {
if script[i] {
idx := i / 8
off := i % 8
b[idx] |= 1 << off
}
}
return "00" + hex.EncodeToString(b)
}
func scriptFromString(s string) ([]bool, error) {
b, err := hex.DecodeString(s)
if err != nil {
return nil, err
}
b = b[1:]
script := make([]bool, len(b)*8)
for i := range script {
idx := i / 8
off := i % 8
script[i] = ((b[idx] >> off) & 1) == 1
}
return script, nil
}
func (tseq *TSeq) FlipCoin() bool {
if tseq.i == len(tseq.script) {
tseq.script = append(tseq.script, false)
}
outcome := tseq.script[tseq.i]
tseq.i++
return outcome
}
func (tseq *TSeq) Choose(n int) int {
if n == 0 {
panic("can't choose between 0 choices")
}
i := 0
j := n - 1
for i < j {
mid := (i + j) / 2
if tseq.FlipCoin() {
i = mid + 1
} else {
j = mid
}
}
return i
}
func (tseq *TSeq) next() bool {
for len(tseq.script) > 0 && tseq.script[len(tseq.script)-1] {
tseq.script = tseq.script[:len(tseq.script)-1]
}
if len(tseq.script) == 0 {
return false
}
tseq.script[len(tseq.script)-1] = true
tseq.i = 0
return true
}
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