func BenchmarkCrcHash(b *testing.B) {
	cases := []struct {
		key int
	}{
		{16},
		{64},
		{128},
		{256},
		{512},
		{1024},
	}
	for _, testCase := range cases {
		key := randString(testCase.key)
		b.Run("", func(b *testing.B) {
			b.SetBytes(1024)
			b.ReportAllocs()
			b.ResetTimer()
			for b.Loop() {
				crcHashMod(key, 16)
			}
		})
	}
}

		remain--
	}

	return *(*string)(unsafe.Pointer(&b))
}

// generate random object name.
func getRandomObjectName() string {
	return randString(16)
}

// generate random bucket name.
func getRandomBucketName() string {
	return randString(60)
}

// construct URL for http requests for bucket operations.

		// Upload objects which modtime as one week ago, supposed to be expired by ILM
		for range upload.expired {
			_, err := obj.PutObject(context.Background(), upload.bucket, randString(32),
				mustGetPutObjReader(t,
					bytes.NewBufferString(objContent),
					int64(len(objContent)),
					hex.EncodeToString(objMd5[:]),
					""),
				ObjectOptions{MTime: oneWeekAgo},
			)