Fix to/from array conversions for windows

uint is **at least** 32 bit integer, according to the standard.
on windows, the uint has 64 bits, as in linux, but:
C.sizeof_ulong is 0x4 on windows.
ASAN does not like that.
but even if the value is stored, the code can't read it properly,
because bytesToUlong checks
`if sliceSize > C.sizeof_ulong`

common.go

@@ -24,35 +24,38 @@ package crypto11
 import (
 	"C"
 	"encoding/asn1"
+	"encoding/binary"
+	"math"
 	"math/big"
-	"unsafe"
 
 	"github.com/miekg/pkcs11"
 	"github.com/pkg/errors"
 )
 
 func ulongToBytes(n uint) []byte {
-	return C.GoBytes(unsafe.Pointer(&n), C.sizeof_ulong) // ugh!
+	if n > math.MaxUint32 {
+		bytes := make([]byte, 8)
+		nn := uint64(n)
+		binary.LittleEndian.PutUint64(bytes, nn)
+		return bytes
+	}
+	bytes := make([]byte, 4)
+	nn := uint32(n)
+	binary.LittleEndian.PutUint32(bytes, nn)
+	return bytes
 }
 
 func bytesToUlong(bs []byte) (n uint) {
-	sliceSize := len(bs)
-	if sliceSize == 0 {
-		return 0
-	}
-
-	value := *(*uint)(unsafe.Pointer(&bs[0]))
-	if sliceSize > C.sizeof_ulong {
-		return value
-	}
-
-	// truncate the value to the # of bits present in the byte slice since
-	// the unsafe pointer will always grab/convert ULONG # of bytes
-	var mask uint
-	for i := 0; i < sliceSize; i++ {
-		mask |= 0xff << uint(i * 8)
+	const uint64Sz = 8
+	sz := len(bs)
+	if sz < uint64Sz {
+		placeholder := make([]byte, uint64Sz)
+		copy(placeholder, bs)
+		bs = placeholder
 	}
-	return value & mask
+	nn := binary.LittleEndian.Uint64(bs)
+	n = uint(nn)
+	return n
 }
 
 func concat(slices ...[]byte) []byte {

common_test.go

@@ -1,6 +1,7 @@
 package crypto11
 
 import (
+	"fmt"
 	"testing"
 )
 
@@ -10,6 +11,11 @@ func TestULongMasking(t *testing.T) {
 
 	// Build an slice that is longer than the size of a ulong
 	extraLongSlice := append(ulongSlice, ulongSlice...)
+	expected := "AABBCCDD00112233AABBCCDD00112233"
+	actual := fmt.Sprintf("%X", string(extraLongSlice))
+	if expected != actual {
+		t.Errorf("expected %s != %s", expected, actual)
+	}
 
 	tests := []struct {
 		slice    []uint8
@@ -30,7 +36,7 @@ func TestULongMasking(t *testing.T) {
 	for _, test := range tests {
 		got := bytesToUlong(test.slice)
 		if test.expected != got {
-			t.Errorf("conversion failed: 0x%X != 0x%X", test.expected, got)
+			t.Errorf("conversion failed: expected 0x%X != 0x%X", test.expected, got)
 		}
 	}
 }