Remove another use of fmt.

internal/str/str.go

@@ -14,6 +14,26 @@ func Itod[T Int](n T) string {
 	return strconv.FormatInt(int64(n), 10)
 }
 
+// UToHex returns n formatted in hexidecimal.
+func UToHex[T Uint](n T) string {
+	return strconv.FormatUint(uint64(n), 16)
+}
+
+// ZeroPad pads value to the left with zeros, making the resulting string
+// count bytes long.
+func ZeroPad(count int, value string) string {
+	pad := count - len(value)
+	if pad < 0 {
+		panic("ZeroPad: count is less than len(value)")
+	}
+	buf := make([]byte, count)
+	for i := 0; i < pad; i++ {
+		buf[i] = '0'
+	}
+	copy(buf[:pad], value[:])
+	return string(buf)
+}
+
 type Uint interface {
 	~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uint
 }

rawpointer.go

@@ -1,8 +1,6 @@
 package capnp
 
 import (
-	"fmt"
-
 	"capnproto.org/go/capnp/v3/internal/str"
 )
 
@@ -250,7 +248,7 @@ func (p rawPointer) GoString() string {
 	default:
 		// other pointer
 		if p.otherPointerType() != 0 {
-			return fmt.Sprintf("rawPointer(%#016x)", uint64(p))
+			return "rawPointer(" + str.ZeroPad(16, str.UToHex(p)) + ")"
 		}
 		return "rawInterfacePointer(" + str.Utod(p.capabilityIndex()) + ")"
 	}