ccan: Add cppmagic

A couple of arguably useful C preprocessor abuses. License is BSD-MIT.

Signed-off-by: Alistair Popple <alistair@popple.id.au>

4 files changed, 314 insertions, 0 deletions

diff --git a/ccan/cppmagic/LICENSE b/ccan/cppmagic/LICENSE
new file mode 120000
index 0000000..2354d12
--- /dev/null
+++ b/ccan/cppmagic/LICENSE
@@ -0,0 +1 @@
+../../licenses/BSD-MIT
\ No newline at end of file
diff --git a/ccan/cppmagic/_info b/ccan/cppmagic/_info
new file mode 100644
index 0000000..aad394b
--- /dev/null
+++ b/ccan/cppmagic/_info
@@ -0,0 +1,30 @@
+#include "config.h"
+#include <stdio.h>
+#include <string.h>
+
+/**
+ * cppmagic - Abuse of the C preprocessor
+ *
+ * This contains a bunch of fancy macro techniques such as
+ * preprocessor-time evaluated conditionals and (quasi) recursion and
+ * iteration.
+ *
+ * It's based on these articles:
+ *  - http://jhnet.co.uk/articles/cpp_magic
+ *  - https://github.com/pfultz2/Cloak/wiki/C-Preprocessor-tricks,-tips,-and-idioms
+ * and code from the Boost C++ library.
+ *
+ * License: BSD-MIT
+ */
+int main(int argc, char *argv[])
+{
+	/* Expect exactly one argument */
+	if (argc != 2)
+		return 1;
+
+	if (strcmp(argv[1], "depends") == 0) {
+		return 0;
+	}
+
+	return 1;
+}
diff --git a/ccan/cppmagic/cppmagic.h b/ccan/cppmagic/cppmagic.h
new file mode 100644
index 0000000..f1f6868
--- /dev/null
+++ b/ccan/cppmagic/cppmagic.h
@@ -0,0 +1,191 @@
+/* MIT (BSD) license - see LICENSE file for details */
+#ifndef CCAN_CPPMAGIC_H
+#define CCAN_CPPMAGIC_H
+
+/**
+ * CPPMAGIC_NOTHING - expands to nothing
+ */
+#define CPPMAGIC_NOTHING()
+
+/**
+ * CPPMAGIC_STRINGIFY - convert arguments to a string literal
+ */
+#define _CPPMAGIC_STRINGIFY(...)	#__VA_ARGS__
+#define CPPMAGIC_STRINGIFY(...)		_CPPMAGIC_STRINGIFY(__VA_ARGS__)
+
+/**
+ * CPPMAGIC_GLUE2 - glue arguments together
+ *
+ * CPPMAGIC_GLUE2(@a_, @b_)
+ *	expands to the expansion of @a_ followed immediately
+ *	(combining tokens) by the expansion of @b_
+ */
+#define _CPPMAGIC_GLUE2(a_, b_)		a_##b_
+#define CPPMAGIC_GLUE2(a_, b_)		_CPPMAGIC_GLUE2(a_, b_)
+
+/**
+ * CPPMAGIC_1ST - return 1st argument
+ *
+ * CPPMAGIC_1ST(@a_, ...)
+ *	expands to the expansion of @a_
+ */
+#define CPPMAGIC_1ST(a_, ...)		a_
+
+/**
+ * CPPMAGIC_2ND - return 2nd argument
+ *
+ * CPPMAGIC_2ST(@a_, @b_, ...)
+ *	expands to the expansion of @b_
+ */
+#define CPPMAGIC_2ND(a_, b_, ...)	b_
+
+/**
+ * CPPMAGIC_ISZERO - is argument '0'
+ *
+ * CPPMAGIC_ISZERO(@a)
+ *	expands to '1' if @a is '0', otherwise expands to '0'.
+ */
+#define _CPPMAGIC_ISPROBE(...)		CPPMAGIC_2ND(__VA_ARGS__, 0)
+#define _CPPMAGIC_PROBE()		$, 1
+#define _CPPMAGIC_ISZERO_0		_CPPMAGIC_PROBE()
+#define CPPMAGIC_ISZERO(a_)		\
+	_CPPMAGIC_ISPROBE(CPPMAGIC_GLUE2(_CPPMAGIC_ISZERO_, a_))
+
+/**
+ * CPPMAGIC_NONZERO - is argument not '0'
+ *
+ * CPPMAGIC_NONZERO(@a)
+ *	expands to '0' if @a is '0', otherwise expands to '1'.
+ */
+#define CPPMAGIC_NONZERO(a_)		CPPMAGIC_ISZERO(CPPMAGIC_ISZERO(a_))
+
+/**
+ * CPPMAGIC_NONEMPTY - does the macro have any arguments?
+ *
+ * CPPMAGIC_NONEMPTY()
+ * 	expands to '0'
+ * CPPMAGIC_NONEMPTY(@a)
+ * CPPMAGIC_NONEMPTY(@a, ...)
+ * 	expand to '1'
+ */
+#define _CPPMAGIC_EOA()			0
+#define CPPMAGIC_NONEMPTY(...)		\
+	CPPMAGIC_NONZERO(CPPMAGIC_1ST(_CPPMAGIC_EOA __VA_ARGS__)())
+
+/**
+ * CPPMAGIC_ISEMPTY - does the macro have no arguments?
+ *
+ * CPPMAGIC_ISEMPTY()
+ * 	expands to '1'
+ * CPPMAGIC_ISEMPTY(@a)
+ * CPPMAGIC_ISEMPTY(@a, ...)
+ * 	expand to '0'
+ */
+#define CPPMAGIC_ISEMPTY(...)		\
+	CPPMAGIC_ISZERO(CPPMAGIC_NONEMPTY(__VA_ARGS__))
+
+/*
+ * CPPMAGIC_IFELSE - preprocessor conditional
+ *
+ * CPPMAGIC_IFELSE(@cond)(@if)(@else)
+ *	expands to @else if @cond is '0', otherwise expands to @if
+ */
+#define _CPPMAGIC_IF_0(...)		_CPPMAGIC_IF_0_ELSE
+#define _CPPMAGIC_IF_1(...)		__VA_ARGS__ _CPPMAGIC_IF_1_ELSE
+#define _CPPMAGIC_IF_0_ELSE(...)	__VA_ARGS__
+#define _CPPMAGIC_IF_1_ELSE(...)
+#define _CPPMAGIC_IFELSE(cond_)		CPPMAGIC_GLUE2(_CPPMAGIC_IF_, cond_)
+#define CPPMAGIC_IFELSE(cond_)		\
+	_CPPMAGIC_IFELSE(CPPMAGIC_NONZERO(cond_))
+
+/**
+ * CPPMAGIC_EVAL - force multiple expansion passes
+ *
+ * Forces macros in the arguments to be expanded repeatedly (up to
+ * 1024 times) even when CPP would usually stop expanding.
+ */
+#define CPPMAGIC_EVAL1(...)		__VA_ARGS__
+#define CPPMAGIC_EVAL2(...)		\
+	CPPMAGIC_EVAL1(CPPMAGIC_EVAL1(__VA_ARGS__))
+#define CPPMAGIC_EVAL4(...)		\
+	CPPMAGIC_EVAL2(CPPMAGIC_EVAL2(__VA_ARGS__))
+#define CPPMAGIC_EVAL8(...)		\
+	CPPMAGIC_EVAL4(CPPMAGIC_EVAL4(__VA_ARGS__))
+#define CPPMAGIC_EVAL16(...)		\
+	CPPMAGIC_EVAL8(CPPMAGIC_EVAL8(__VA_ARGS__))
+#define CPPMAGIC_EVAL32(...)		\
+	CPPMAGIC_EVAL16(CPPMAGIC_EVAL16(__VA_ARGS__))
+#define CPPMAGIC_EVAL64(...)		\
+	CPPMAGIC_EVAL32(CPPMAGIC_EVAL32(__VA_ARGS__))
+#define CPPMAGIC_EVAL128(...)		\
+	CPPMAGIC_EVAL64(CPPMAGIC_EVAL64(__VA_ARGS__))
+#define CPPMAGIC_EVAL256(...)		\
+	CPPMAGIC_EVAL128(CPPMAGIC_EVAL128(__VA_ARGS__))
+#define CPPMAGIC_EVAL512(...)		\
+	CPPMAGIC_EVAL256(CPPMAGIC_EVAL256(__VA_ARGS__))
+#define CPPMAGIC_EVAL1024(...)		\
+	CPPMAGIC_EVAL512(CPPMAGIC_EVAL512(__VA_ARGS__))
+#define CPPMAGIC_EVAL(...)		CPPMAGIC_EVAL1024(__VA_ARGS__)
+
+/**
+ * CPPMAGIC_DEFER1, CPPMAGIC_DEFER2 - defer expansion
+ */
+#define CPPMAGIC_DEFER1(a_)	a_ CPPMAGIC_NOTHING()
+#define CPPMAGIC_DEFER2(a_)	a_ CPPMAGIC_NOTHING CPPMAGIC_NOTHING()()
+
+/**
+ * CPPMAGIC_MAP - iterate another macro across arguments
+ * @m: name of a one argument macro
+ *
+ * CPPMAGIC_MAP(@m, @a1, @a2, ... @an)
+ *	expands to the expansion of @m(@a1) , @m(@a2) , ... , @m(@an)
+ */
+#define _CPPMAGIC_MAP_()		_CPPMAGIC_MAP
+#define _CPPMAGIC_MAP(m_, a_, ...)					\
+	m_(a_)								\
+	CPPMAGIC_IFELSE(CPPMAGIC_NONEMPTY(__VA_ARGS__))			\
+		(, CPPMAGIC_DEFER2(_CPPMAGIC_MAP_)()(m_, __VA_ARGS__))	\
+		()
+#define CPPMAGIC_MAP(m_, ...)						\
+	CPPMAGIC_IFELSE(CPPMAGIC_NONEMPTY(__VA_ARGS__))			\
+		(CPPMAGIC_EVAL(_CPPMAGIC_MAP(m_, __VA_ARGS__)))		\
+		()
+
+/**
+ * CPPMAGIC_2MAP - iterate another macro across pairs of arguments
+ * @m: name of a two argument macro
+ *
+ * CPPMAGIC_2MAP(@m, @a1, @b1, @a2, @b2, ..., @an, @bn)
+ *	expands to the expansion of
+ *		 @m(@a1, @b1) , @m(@a2, @b2) , ... , @m(@an, @bn)
+ */
+#define _CPPMAGIC_2MAP_()		_CPPMAGIC_2MAP
+#define _CPPMAGIC_2MAP(m_, a_, b_, ...)				\
+	m_(a_, b_)							\
+	CPPMAGIC_IFELSE(CPPMAGIC_NONEMPTY(__VA_ARGS__))			\
+		(, CPPMAGIC_DEFER2(_CPPMAGIC_2MAP_)()(m_, __VA_ARGS__)) \
+		()
+#define CPPMAGIC_2MAP(m_, ...)					\
+	CPPMAGIC_IFELSE(CPPMAGIC_NONEMPTY(__VA_ARGS__))			\
+		(CPPMAGIC_EVAL(_CPPMAGIC_2MAP(m_, __VA_ARGS__)))	\
+		()
+
+/**
+ * CPPMAGIC_JOIN - separate arguments with given delimiter
+ * @d: delimiter
+ *
+ * CPPMAGIC_JOIN(@d, @a1, @a2, ..., @an)
+ *	expands to the expansion of @a1 @d @a2 @d ... @d @an
+ */
+#define _CPPMAGIC_JOIN_()		_CPPMAGIC_JOIN
+#define _CPPMAGIC_JOIN(d_, a_, ...)					\
+	a_								\
+	CPPMAGIC_IFELSE(CPPMAGIC_NONEMPTY(__VA_ARGS__))			\
+		(d_ CPPMAGIC_DEFER2(_CPPMAGIC_JOIN_)()(d_, __VA_ARGS__)) \
+		()
+#define CPPMAGIC_JOIN(d_, ...)					\
+	CPPMAGIC_IFELSE(CPPMAGIC_NONEMPTY(__VA_ARGS__))			\
+		(CPPMAGIC_EVAL(_CPPMAGIC_JOIN(d_, __VA_ARGS__)))	\
+		()
+
+#endif /* CCAN_CPPMAGIC_H */
diff --git a/ccan/cppmagic/test/run.c b/ccan/cppmagic/test/run.c
new file mode 100644
index 0000000..7c0aa7f
--- /dev/null
+++ b/ccan/cppmagic/test/run.c
@@ -0,0 +1,92 @@
+#include "config.h"
+
+#include <string.h>
+
+#include <ccan/cppmagic/cppmagic.h>
+#include <ccan/tap/tap.h>
+
+static inline void check1(const char *orig, const char *expand,
+			  const char *match)
+{
+	ok(strcmp(expand, match) == 0,
+	   "%s => %s : %s", orig, expand, match);
+}
+
+#define CHECK1(orig, match) \
+	check1(#orig, CPPMAGIC_STRINGIFY(orig), match)
+
+#define TESTRECURSE()	R CPPMAGIC_DEFER1(_TESTRECURSE) ()()
+#define _TESTRECURSE()	TESTRECURSE
+
+#define TESTMAP1(x)	<<x>>
+
+#define TESTMAP2(x)		[[ x
+#define TESTMAP3(x)		x ]]
+
+#define TEST2MAP(x, y)	x ** y
+
+int main(void)
+{
+	plan_tests(42);
+
+	CHECK1(CPPMAGIC_NOTHING(), "");
+	CHECK1(CPPMAGIC_GLUE2(a, b), "ab");
+
+	CHECK1(CPPMAGIC_1ST(a), "a");
+	CHECK1(CPPMAGIC_1ST(a, b), "a");
+	CHECK1(CPPMAGIC_1ST(a, b, c), "a");
+
+	CHECK1(CPPMAGIC_2ND(a, b), "b");
+	CHECK1(CPPMAGIC_2ND(a, b, c), "b");
+
+	CHECK1(CPPMAGIC_ISZERO(0), "1");
+	CHECK1(CPPMAGIC_ISZERO(1), "0");
+	CHECK1(CPPMAGIC_ISZERO(123), "0");
+	CHECK1(CPPMAGIC_ISZERO(abc), "0");
+
+	CHECK1(CPPMAGIC_NONZERO(0), "0");
+	CHECK1(CPPMAGIC_NONZERO(1), "1");
+	CHECK1(CPPMAGIC_NONZERO(123), "1");
+	CHECK1(CPPMAGIC_NONZERO(abc), "1");
+
+	CHECK1(CPPMAGIC_NONEMPTY(), "0");
+	CHECK1(CPPMAGIC_NONEMPTY(0), "1");
+	CHECK1(CPPMAGIC_NONEMPTY(a, b, c), "1");
+
+	CHECK1(CPPMAGIC_ISEMPTY(), "1");
+	CHECK1(CPPMAGIC_ISEMPTY(0), "0");
+	CHECK1(CPPMAGIC_ISEMPTY(a, b, c), "0");
+	
+	CHECK1(CPPMAGIC_IFELSE(0)(abc)(def), "def");
+	CHECK1(CPPMAGIC_IFELSE(1)(abc)(def), "abc");
+	CHECK1(CPPMAGIC_IFELSE(not zero)(abc)(def), "abc");
+
+	CHECK1(TESTRECURSE(), "R R _TESTRECURSE ()()");
+	CHECK1(CPPMAGIC_EVAL1(TESTRECURSE()), "R R R _TESTRECURSE ()()");
+	CHECK1(CPPMAGIC_EVAL2(TESTRECURSE()), "R R R R R _TESTRECURSE ()()");
+
+	CHECK1(CPPMAGIC_MAP(TESTMAP1), "");
+	CHECK1(CPPMAGIC_MAP(TESTMAP1, a), "<<a>>");
+	CHECK1(CPPMAGIC_MAP(TESTMAP1, a, b), "<<a>> , <<b>>");
+	CHECK1(CPPMAGIC_MAP(TESTMAP1, a, b, c), "<<a>> , <<b>> , <<c>>");
+
+	CHECK1(CPPMAGIC_2MAP(TEST2MAP), "");
+	CHECK1(CPPMAGIC_2MAP(TEST2MAP, a, 1), "a ** 1");
+	CHECK1(CPPMAGIC_2MAP(TEST2MAP, a, 1, b, 2), "a ** 1 , b ** 2");
+	
+	CHECK1(CPPMAGIC_JOIN(;), "");
+	CHECK1(CPPMAGIC_JOIN(;, a), "a");
+	CHECK1(CPPMAGIC_JOIN(;, a, b), "a ; b");
+	CHECK1(CPPMAGIC_JOIN(;, a, b, c), "a ; b ; c");
+
+	/* Check chaining of MAPs */
+	CHECK1(CPPMAGIC_MAP(TESTMAP2, CPPMAGIC_MAP(TESTMAP3)), "");
+	CHECK1(CPPMAGIC_MAP(TESTMAP2, CPPMAGIC_MAP(TESTMAP3, a)), "[[ a ]]");
+	CHECK1(CPPMAGIC_MAP(TESTMAP2, CPPMAGIC_MAP(TESTMAP3, a, b)),
+	       "[[ a ]] , [[ b ]]");
+	CHECK1(CPPMAGIC_MAP(TESTMAP2, CPPMAGIC_MAP(TESTMAP3, a, b, c)),
+	       "[[ a ]] , [[ b ]] , [[ c ]]");
+						   
+	/* This exits depending on whether all tests passed */
+	return exit_status();
+}