// GetPreviousValue returns the value of key when the ledger's RootHash was previousHash, if it is still retained.
func (s smtLedger) GetPreviousValue(previousRootHash, key string) (result string, err error) {
	prevBytes, err := base64.StdEncoding.DecodeString(previousRootHash)
	if err != nil {
		return "", err
	}
	b, err := s.tree.GetPreviousValue(prevBytes, coerceKeyToHashLen(key))
	var i int
	// trim leading 0's from b
	for i = range b {

func decodeDockerConfigFieldAuth(field string) (username, password string, err error) {

	var decoded []byte

	// StdEncoding can only decode padded string
	// RawStdEncoding can only decode unpadded string
	if strings.HasSuffix(strings.TrimSpace(field), "=") {
		// decode padded data
		decoded, err = base64.StdEncoding.DecodeString(field)
	} else {
		// decode unpadded data
		decoded, err = base64.RawStdEncoding.DecodeString(field)

		} else {
			// Expires in 10 days.
			pp.SetExpires(UTCNow().AddDate(0, 0, 10))
		}

		formValues.Set("Policy", base64.StdEncoding.EncodeToString([]byte(pp.String())))
		formValues.Set("Success_action_status", tt.SuccessActionStatus)
		policyBytes, err := base64.StdEncoding.DecodeString(base64.StdEncoding.EncodeToString([]byte(pp.String())))
		if err != nil {
			t.Fatal(err)
		}

	credentials := `{
	"auths":{
		"%v":{
			"username": "%v",
			"password": "%v",
			"email": "******@****.***",
			"auth": "%v"
		}
	}
}`
	auth := base64.StdEncoding.EncodeToString([]byte(user + ":" + passwd))
	return fmt.Sprintf(credentials, registry, user, passwd, auth)

	// the chance of colliding hash P(N,X) approximates to 1-e^(-(N^2)/2^(8X+1)).
	// P(10,000, 8) ~= 2.7*10^(-12), which is low enough.
	// See https://en.wikipedia.org/wiki/Birthday_problem#Approximations.
	return base64.StdEncoding.EncodeToString(bytes[:8])

		if s, _ := getLine(restOfEndLine); len(s) != 0 {
			continue
		}

		base64Data := removeSpacesAndTabs(rest[:endIndex])
		p.Bytes = make([]byte, base64.StdEncoding.DecodedLen(len(base64Data)))
		n, err := base64.StdEncoding.Decode(p.Bytes, base64Data)
		if err != nil {
			continue
		}
		p.Bytes = p.Bytes[:n]

		// the -1 is because we might have only matched pemEnd without the

		}
		plainDER, err := base64.StdEncoding.DecodeString(data.plainDER)
		if err != nil {
			t.Fatal("cannot decode test DER data: ", err)
		}
		if !bytes.Equal(der, plainDER) {
			t.Error("data mismatch")
		}
	}
}

func TestEncrypt(t *testing.T) {
	for i, data := range testData {
		t.Logf("test %v. %v", i, data.kind)
		plainDER, err := base64.StdEncoding.DecodeString(data.plainDER)
		if err != nil {

		"X-Amz-Server-Side-Encryption-Context":        []string{base64.StdEncoding.EncodeToString([]byte("{}"))},
	}, ShouldFail: false}, // 3
	{Header: http.Header{
		"X-Amz-Server-Side-Encryption":                []string{"aws:kms"},
		"X-Amz-Server-Side-Encryption-Aws-Kms-Key-Id": []string{"s3-007-293847485-724784"},
		"X-Amz-Server-Side-Encryption-Context":        []string{base64.StdEncoding.EncodeToString([]byte(`{"bucket": "some-bucket"}`))},

			t.Fatalf("Test %d: ciphertext mismatch: got %x - want %x", i, key.Ciphertext, test.Key.Ciphertext)
		}
	}
}

func mustDecodeB64(s string) []byte {
	b, err := base64.StdEncoding.DecodeString(s)
	if err != nil {
		panic(err)
	}
	return b

	if err != nil {
		return nil, err
	}

	// Use base64 of encKey as the key into the cache because hashicorp/golang-lru
	// cannot hash []uint8.
	if t.cacheEnabled {
		t.transformers.Add(base64.StdEncoding.EncodeToString(encKey), transformer)
		metrics.RecordDekCacheFillPercent(float64(t.transformers.Len()) / float64(t.cacheSize))
	}
	return transformer, nil
}