add serial conv. functions and basic tests

core/util.go

@@ -18,6 +18,7 @@ import (
 	"encoding/base64"
 	"encoding/json"
 	"errors"
+	"fmt"
 	blog "github.com/letsencrypt/boulder/log"
 	"hash"
 	"io"
@@ -188,3 +189,16 @@ func VerifyCSR(csr *x509.CertificateRequest) error {
 
 	return errors.New("Unsupported CSR signing algorithm")
 }
+
+func SerialToString(serial *big.Int) string {
+	return fmt.Sprintf("%032x", serial)
+}
+
+func StringToSerial(serial string) (*big.Int, error)  {
+	var serialNum big.Int
+	if len(serial) != 32 {
+		return &serialNum, errors.New("Serial number should be 32 characters long")
+	}
+	_, err := fmt.Sscanf(serial, "%032x", &serialNum)
+	return &serialNum, err
+}

core/util_test.go

@@ -10,6 +10,7 @@ import (
 	"fmt"
 	"github.com/letsencrypt/boulder/test"
 	"math"
+	"math/big"
 )
 
 // challenges.go
@@ -34,3 +35,16 @@ func TestRandString(t *testing.T) {
   // This is covered by NewToken
   return
 }
+
+func TestSerialUtils(t *testing.T) {
+	serial := SerialToString(big.NewInt(100000000000000000))
+	test.AssertEquals(t, serial, "0000000000000000016345785d8a0000")
+
+	serialNum, err := StringToSerial("0000000000000000016345785d8a0000")
+	test.AssertNotError(t, err, "Couldn't convert serial number to *big.Int")
+	test.AssertBigIntEquals(t, serialNum, big.NewInt(100000000000000000))
+
+	badSerial, err := StringToSerial("doop!!!!000")
+	test.AssertEquals(t, fmt.Sprintf("%v", err), "Serial number should be 32 characters long")
+	fmt.Println(badSerial)
+}

test/test-tools.go

@@ -9,6 +9,7 @@ import (
 	"bytes"
 	"encoding/base64"
 	"fmt"
+	"math/big"
 	"runtime"
 	"strings"
 	"testing"
@@ -74,6 +75,12 @@ func AssertIntEquals(t *testing.T, one int, two int) {
 	}
 }
 
+func AssertBigIntEquals(t *testing.T, one *big.Int, two *big.Int) {
+	if one.Cmp(two) != 0 {
+		t.Errorf("%s Int [%d] != [%d]", caller(), one, two)
+	}
+}
+
 func AssertContains(t *testing.T, haystack string, needle string) {
 	if !strings.Contains(haystack, needle) {
 		t.Errorf("%s String [%s] does not contain [%s]", caller(), haystack, needle)