Esempio n. 1
0
// This doesn't actually test anything, but prints probabilities to log
func TestBirthdayProblem(t *testing.T) {
	t.Log("Hash size is", dedup.HashSize*8, "bits")
	t.Log("1GiB, 1KiB blocks:")
	t.Log(dedup.BirthdayProblem((1 << 30) / (1 << 10)))
	w, _ := dedup.NewWriter(ioutil.Discard, ioutil.Discard, dedup.ModeFixed, 1<<10, 0)
	e, _ := w.MemUse(1 << 30)
	t.Logf("It will use %d MiB for encoder.", e>>20)

	t.Log("1TiB, 4KiB blocks:")
	t.Log(dedup.BirthdayProblem((1 << 40) / (4 << 10)))
	w, _ = dedup.NewWriter(ioutil.Discard, ioutil.Discard, dedup.ModeFixed, 4<<10, 0)
	e, _ = w.MemUse(1 << 40)
	t.Logf("It will use %d MiB for encoder.", e>>20)

	t.Log("1PiB, 4KiB blocks:")
	t.Log(dedup.BirthdayProblem((1 << 50) / (4 << 10)))
	e, _ = w.MemUse(1 << 50)
	t.Logf("It will use %d MiB for encoder.", e>>20)

	t.Log("1EiB, 64KiB blocks:")
	t.Log(dedup.BirthdayProblem((1 << 60) / (64 << 10)))
	w, _ = dedup.NewWriter(ioutil.Discard, ioutil.Discard, dedup.ModeFixed, 64<<10, 0)
	e, _ = w.MemUse(1 << 60)
	t.Logf("It will use %d MiB for encoder.", e>>20)

	t.Log("1EiB, 1KiB blocks:")
	t.Log(dedup.BirthdayProblem((1 << 60) / (1 << 10)))
	w, _ = dedup.NewWriter(ioutil.Discard, ioutil.Discard, dedup.ModeFixed, 1<<10, 0)
	e, _ = w.MemUse(1 << 60)
	t.Logf("It will use %d MiB for encoder.", e>>20)
}
Esempio n. 2
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// This shows an example of a birthday problem calculation.
// We calculate the probability of a collision of SHA1 hashes
// on 1 Terabyte data, using 1 Kilobyte blocks.
// With SHA-1, that gives a 1 in 2535301202817642046627252275200 chance
// of a collision occurring.
func ExampleBirthdayProblem() {
	fmt.Println("Hash size is", dedup.HashSize*8, "bits")
	fmt.Println("1TiB, 1KiB blocks:")
	fmt.Println(dedup.BirthdayProblem((1 << 40) / (1 << 10)))
	// Output: Hash size is 160 bits
	// 1TiB, 1KiB blocks:
	// Collision probability is ~ 1/2535301202817642046627252275200 ~ 3.944304522431639e-31
}
Esempio n. 3
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func TestFixedWriter(t *testing.T) {
	idx := bytes.Buffer{}
	data := bytes.Buffer{}

	const totalinput = 10 << 20
	input := getBufferSize(totalinput)

	const size = 64 << 10
	b := input.Bytes()
	// Create some duplicates
	for i := 0; i < 50; i++ {
		// Read from 10 first blocks
		src := b[(i%10)*size : (i%10)*size+size]
		// Write into the following ones
		dst := b[(10+i)*size : (i+10)*size+size]
		copy(dst, src)
	}
	input = bytes.NewBuffer(b)
	w, err := dedup.NewWriter(&idx, &data, dedup.ModeFixed, size, size*10)
	if err != nil {
		t.Fatal(err)
	}
	io.Copy(w, input)
	err = w.Close()
	if err != nil {
		t.Fatal(err)
	}
	removed := ((totalinput) - data.Len()) / size

	t.Log(dedup.BirthdayProblem(totalinput / size))
	t.Log("Index size:", idx.Len())
	t.Log("Data size:", data.Len())
	t.Log("Removed", removed, "blocks")
	// We should get at least 50 blocks
	if removed < 50 {
		t.Fatal("didn't remove at least 50 blocks")
	}
	if removed > 60 {
		t.Fatal("removed unreasonable high amount of blocks")
	}
}