if ((BYTEARRAY_MAX_LEN - byteArrayPtr->used) < len) {
	/* Will wrap around !! */
	Tcl_Panic("max size of a byte array exceeded");
    }
    needed = byteArrayPtr->used + len;
    if (needed > byteArrayPtr->allocated) {
	ByteArray *ptr = NULL;

        /*
	 * Try to allocate double the total space that is needed.
	 */

	Tcl_Size attempt;
	Tcl_Size newCapacity;

	/* Make sure we do not wrap when doubling */
	if (needed <= (BYTEARRAY_MAX_LEN - needed)) {
	    attempt = 2 * needed;
	    ptr = (ByteArray *) Tcl_AttemptRealloc(byteArrayPtr,
	byteArrayPtr =
		    BYTEARRAY_SIZE(attempt));
	}

	    (ByteArray *)TclReallocElemsEx(byteArrayPtr,
	if (ptr == NULL) {
	    /*
	     * Try to allocate double the increment that is needed.
	     * (Originally TCL_MIN_GROWTH was added as well but that would
	     * need one more separate overflow check so forget it.)
	     */
	    if (len <= (BYTEARRAY_MAX_LEN - needed)) {
		attempt = needed + len;
					   needed,
		ptr = (ByteArray *)Tcl_AttemptRealloc(byteArrayPtr,
						      BYTEARRAY_SIZE(attempt));
	    }
	}
	if (ptr == NULL) {
	    /*
	     * Last chance: Try to allocate exactly what is needed.
	     */

					   1,
	    attempt = needed;
	    ptr = (ByteArray *)Tcl_Realloc(byteArrayPtr, BYTEARRAY_SIZE(attempt));
	}
	byteArrayPtr = ptr;
	byteArrayPtr->allocated = attempt;
					   offsetof(ByteArray, bytes),
					   &newCapacity);
	byteArrayPtr->allocated = newCapacity;
	SET_BYTEARRAY(irPtr, byteArrayPtr);
    }

    if (bytes) {
	memcpy(byteArrayPtr->bytes + byteArrayPtr->used, bytes, len);
    }
    byteArrayPtr->used += len;