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package puddle
import (
"math"
"math/rand"
"testing"
"time"
"github.com/stretchr/testify/require"
)
func TestLog2Uint(t *testing.T) {
r := require.New(t)
r.Equal(uint8(0), log2Int(1))
r.Equal(uint8(0), log2Int[uint64](1))
r.Equal(uint8(1), log2Int[uint32](2))
r.Equal(uint8(7), log2Int[uint8](math.MaxUint8))
r.Equal(uint8(15), log2Int[uint16](math.MaxUint16))
r.Equal(uint8(31), log2Int[uint32](math.MaxUint32))
r.Equal(uint8(63), log2Int[uint64](math.MaxUint64))
r.Panics(func() { log2Int[uint64](0) })
r.Panics(func() { log2Int[int64](-1) })
}
func FuzzLog2Uint(f *testing.F) {
const cnt = 1000
rand := rand.New(rand.NewSource(time.Now().UnixNano()))
for i := 0; i < cnt; i++ {
val := uint64(rand.Int63())
// val + 1 not to test val == 0.
f.Add(val + 1)
}
f.Fuzz(func(t *testing.T, val uint64) {
var mx uint8
for i := 63; i >= 0; i-- {
mask := uint64(1) << i
if mask&val != 0 {
mx = uint8(i)
break
}
}
require.Equal(t, mx, log2Int(val))
})
}
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