enums.h: Combine related #defines into packed enums.
enums for BLOCK_SIZE, TX_SIZE and PREDICTION_MODE.
Note: These were converted to #defines earlier to save on memory:
https://chromium-review.googlesource.com/#/c/269854/
But we, instead, use attribute 'packed' (see here:
https://gcc.gnu.org/onlinedocs/gcc/Common-Type-Attributes.html#Common-Type-Attributes)
to ensure that these enums use the smallest possible integer type,
and so use smallest memory when used in structs/arrays etc.
Change-Id: If1fc136686b28847109c9f3a06f8728165e7e475
diff --git a/aom/aom_codec.h b/aom/aom_codec.h
index e1c4552..1d301d1 100644
--- a/aom/aom_codec.h
+++ b/aom/aom_codec.h
@@ -76,6 +76,17 @@
#define UNUSED
#endif
+/*!\brief Decorator indicating that given struct/union/enum is packed */
+#ifndef ATTRIBUTE_PACKED
+#if defined(__GNUC__) && __GNUC__
+#define ATTRIBUTE_PACKED __attribute__((packed))
+#elif defined(_MSC_VER)
+#define ATTRIBUTE_PACKED
+#else
+#define ATTRIBUTE_PACKED
+#endif
+#endif /* ATTRIBUTE_PACKED */
+
/*!\brief Current ABI version number
*
* \internal
