1 files changed, 48 insertions, 0 deletions
diff --git a/src/include/base3.h b/src/include/base3.h
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+++ b/src/include/base3.h
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+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2014 Google Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef __SRC_INCLUDE_BASE3_H__
+#define __SRC_INCLUDE_BASE3_H__
+
+/* We translate a floating pin (Z) as the ternary digit 2. */
+#define Z 2
+
+/*
+ * This provides a variadic macro BASE3() that can be used to translate a set of
+ * pin states into its base-3 integer representation, even in the context of a
+ * static initializer. You can call it with any number of up to 6 arguments,
+ * e.g. BASE3(1, Z) -> 5 or BASE3(0, Z, 1, 0) -> 21. Just don't look too closely
+ * at how the sausage is made. (Pay extra attention to typos when expanding it!)
+ */
+#define _BASE3_IMPL_1(arg0, arg1, arg2, arg3, arg4, arg5) arg0
+#define _BASE3_IMPL_2(arg0, arg1, arg2, arg3, arg4, arg5) \
+	(arg1 + (3 * _BASE3_IMPL_1(arg0, arg1, arg2, arg3, arg4, arg5)))
+#define _BASE3_IMPL_3(arg0, arg1, arg2, arg3, arg4, arg5) \
+	(arg2 + (3 * _BASE3_IMPL_2(arg0, arg1, arg2, arg3, arg4, arg5)))
+#define _BASE3_IMPL_4(arg0, arg1, arg2, arg3, arg4, arg5) \
+	(arg3 + (3 * _BASE3_IMPL_3(arg0, arg1, arg2, arg3, arg4, arg5)))
+#define _BASE3_IMPL_5(arg0, arg1, arg2, arg3, arg4, arg5) \
+	(arg4 + (3 * _BASE3_IMPL_4(arg0, arg1, arg2, arg3, arg4, arg5)))
+#define _BASE3_IMPL_6(arg0, arg1, arg2, arg3, arg4, arg5) \
+	(arg5 + (3 * _BASE3_IMPL_5(arg0, arg1, arg2, arg3, arg4, arg5)))
+#define _BASE3_IMPL(arg0, arg1, arg2, arg3, arg4, arg5, NARGS, ...) \
+	_BASE3_IMPL##NARGS(arg0, arg1, arg2, arg3, arg4, arg5)
+#define BASE3(...) _BASE3_IMPL(__VA_ARGS__, _6, _5, _4, _3, _2, _1)
+
+#endif /* __SRC_INCLUDE_BASE3_H__ */