Promote DBusBasicValue and DBus8ByteStruct to be API

In practice, D-Bus bindings end up reinventing DBusBasicValue anyway,
so it might as well be API.

Also stop claiming that all basic-typed values are guaranteed to fit in
8 bytes - this is not true if your platform has more than 8-byte pointers
(I'm not aware of any such platform now, but let's not rule it out).

Bug: https://bugs.freedesktop.org/show_bug.cgi?id=11191
Signed-off-by: Simon McVittie <simon.mcvittie@collabora.co.uk>
Reviewed-by: Will Thompson <will.thompson@collabora.co.uk>

dbus/dbus-marshal-basic.c

@@ -65,6 +65,13 @@ _DBUS_STATIC_ASSERT (sizeof (dbus_uint64_t) == 8);
 _DBUS_ASSERT_ALIGNMENT (dbus_uint64_t, <=, 8);
 #endif
 
+_DBUS_STATIC_ASSERT (sizeof (DBusBasicValue) >= 8);
+/* The alignment of a DBusBasicValue might conceivably be > 8 because of the
+ * pointer, so we don't assert about it */
+
+_DBUS_STATIC_ASSERT (sizeof (DBus8ByteStruct) == 8);
+_DBUS_ASSERT_ALIGNMENT (DBus8ByteStruct, <=, 8);
+
 /**
  * @defgroup DBusMarshal marshaling and unmarshaling
  * @ingroup  DBusInternals
@@ -119,7 +126,7 @@ pack_8_octets (DBusBasicValue     value,
   else
     *((dbus_uint64_t*)(data)) = DBUS_UINT64_TO_BE (value.u64);
 #else
-  *(DBus8ByteStruct*)data = value.u64;
+  *(DBus8ByteStruct*)data = value.eight;
   swap_8_octets ((DBusBasicValue*)data, byte_order);
 #endif
 }
@@ -169,7 +176,7 @@ swap_8_octets (DBusBasicValue    *value,
 #ifdef DBUS_HAVE_INT64
       value->u64 = DBUS_UINT64_SWAP_LE_BE (value->u64);
 #else
-      swap_bytes ((unsigned char *)value, 8);
+      swap_bytes (&value->bytes, 8);
 #endif
     }
 }
@@ -190,7 +197,7 @@ unpack_8_octets (int                  byte_order,
   else
     r.u64 = DBUS_UINT64_FROM_BE (*(dbus_uint64_t*)data);
 #else
-  r.u64 = *(DBus8ByteStruct*)data;
+  r.eight = *(DBus8ByteStruct*)data;
   swap_8_octets (&r, byte_order);
 #endif
 

dbus/dbus-marshal-basic.h

@@ -146,40 +146,6 @@
 #  define DBUS_UINT64_FROM_BE(val) (DBUS_UINT64_TO_BE (val))
 #endif /* DBUS_HAVE_INT64 */
 
-#ifndef DBUS_HAVE_INT64
-/**
- * An 8-byte struct you could use to access int64 without having
- * int64 support
- */
-typedef struct
-{
-  dbus_uint32_t first32;  /**< first 32 bits in the 8 bytes (beware endian issues) */
-  dbus_uint32_t second32; /**< second 32 bits in the 8 bytes (beware endian issues) */
-} DBus8ByteStruct;
-#endif /* DBUS_HAVE_INT64 */
-
-/**
- * A simple 8-byte value union that lets you access 8 bytes as if they
- * were various types; useful when dealing with basic types via
- * void pointers and varargs.
- */
-typedef union
-{
-  dbus_int16_t  i16;   /**< as int16 */
-  dbus_uint16_t u16;   /**< as int16 */
-  dbus_int32_t  i32;   /**< as int32 */
-  dbus_uint32_t u32;   /**< as int32 */
-#ifdef DBUS_HAVE_INT64
-  dbus_int64_t  i64;   /**< as int64 */
-  dbus_uint64_t u64;   /**< as int64 */
-#else
-  DBus8ByteStruct u64; /**< as 8-byte-struct */
-#endif
-  double dbl;          /**< as double */
-  unsigned char byt;   /**< as byte */
-  char *str;           /**< as char* */
-} DBusBasicValue;
-
 #ifdef DBUS_DISABLE_ASSERT
 #define _dbus_unpack_uint16(byte_order, data)           \
    (((byte_order) == DBUS_LITTLE_ENDIAN) ?              \

dbus/dbus-marshal-recursive-util.c

@@ -38,8 +38,8 @@ basic_value_zero (DBusBasicValue *value)
 #ifdef DBUS_HAVE_INT64
   value->u64 = 0;
 #else
-  value->u64.first32 = 0;
-  value->u64.second32 = 0;
+  value->eight.first32 = 0;
+  value->eight.second32 = 0;
 #endif
 }
 
@@ -59,8 +59,8 @@ basic_value_equal (int             type,
 #ifdef DBUS_HAVE_INT64
       return lhs->u64 == rhs->u64;
 #else
-      return lhs->u64.first32 == rhs->u64.first32 &&
-        lhs->u64.second32 == rhs->u64.second32;
+      return lhs->eight.first32 == rhs->eight.first32 &&
+        lhs->eight.second32 == rhs->eight.second32;
 #endif
     }
 }

dbus/dbus-message.c

@@ -2191,22 +2191,22 @@ dbus_message_iter_get_signature (DBusMessageIter *iter)
  * descriptors), you can get all the array elements at once with
  * dbus_message_iter_get_fixed_array(). Otherwise, you have to iterate
  * over the container's contents one value at a time.
- * 
- * All basic-typed values are guaranteed to fit in 8 bytes. So you can
- * write code like this:
+ *
+ * All basic-typed values are guaranteed to fit in a #DBusBasicValue,
+ * so in versions of libdbus that have that type, you can write code like this:
  *
  * @code
- * dbus_uint64_t value;
+ * DBusBasicValue value;
  * int type;
  * dbus_message_iter_get_basic (&read_iter, &value);
  * type = dbus_message_iter_get_arg_type (&read_iter);
  * dbus_message_iter_append_basic (&write_iter, type, &value);
  * @endcode
  *
- * On some really obscure platforms dbus_uint64_t might not exist, if
- * you need to worry about this you will know.  dbus_uint64_t is just
- * one example of a type that's large enough to hold any possible
- * value, you could use a struct or char[8] instead if you like.
+ * (All D-Bus basic types are either numeric and 8 bytes or smaller, or
+ * behave like a string; so in older versions of libdbus, DBusBasicValue
+ * can be replaced with union { char *string; unsigned char bytes[8]; },
+ * for instance.)
  *
  * @param iter the iterator
  * @param value location to store the value

dbus/dbus-types.h

@@ -134,6 +134,43 @@ typedef dbus_uint32_t  dbus_bool_t;
  * giving a literal such as "325145246765ULL"
  */
 
+/**
+ * An 8-byte struct you could use to access int64 without having
+ * int64 support
+ */
+typedef struct
+{
+  dbus_uint32_t first32;  /**< first 32 bits in the 8 bytes (beware endian issues) */
+  dbus_uint32_t second32; /**< second 32 bits in the 8 bytes (beware endian issues) */
+} DBus8ByteStruct;
+
+/**
+ * A simple value union that lets you access bytes as if they
+ * were various types; useful when dealing with basic types via
+ * void pointers and varargs.
+ *
+ * This union also contains a pointer member (which can be used
+ * to retrieve a string from dbus_message_iter_get_basic(), for
+ * instance), so on future platforms it could conceivably be larger
+ * than 8 bytes.
+ */
+typedef union
+{
+  unsigned char bytes[8]; /**< as 8 individual bytes */
+  dbus_int16_t  i16;   /**< as int16 */
+  dbus_uint16_t u16;   /**< as int16 */
+  dbus_int32_t  i32;   /**< as int32 */
+  dbus_uint32_t u32;   /**< as int32 */
+#ifdef DBUS_HAVE_INT64
+  dbus_int64_t  i64;   /**< as int64 */
+  dbus_uint64_t u64;   /**< as int64 */
+#endif
+  DBus8ByteStruct eight; /**< as 8-byte struct */
+  double dbl;          /**< as double */
+  unsigned char byt;   /**< as byte */
+  char *str;           /**< as char* */
+} DBusBasicValue;
+
 /** @} */
 
 #endif /* DBUS_TYPES_H */