+REQUIRE

1 files changed, 60 insertions, 0 deletions

diff --git a/chad/experimental/require.h b/chad/experimental/require.h
new file mode 100644
index 0000000..e9a8ea8
--- /dev/null
+++ b/chad/experimental/require.h
@@ -0,0 +1,60 @@
+#ifndef REQUIRE_H
+#define REQUIRE_H
+
+#include <chad/experimental/bits.h>
+
+/* Require macros for easy uniform error handling.
+ * They can be used to replace repeated error handling logic
+ *  or some messier solutions.
+ *
+ * REQUIRE() and REQUIRE_EX() assert a statement,
+ *  on failure they invoke REQUIRE_TERMINATOR,
+ *  on success they return the resulting value.
+ *
+ * REQUIRE_EX() takes a custom error value as its first argument,
+ *  REQUIRE() assumes standard C truthliness.
+ *
+ * Example:
+ *     int extreme_example(int i) {
+ *         switch (i) {
+ *             case 1: return 4;
+ *             case 2: return 5;
+ *             default: return 0;
+ *         }
+ *     }
+ *     
+ *     signed main(void) {
+ *         FILE * f = REQUIRE(fopen("a.txt", "r"));
+ *     
+ *         REQUIRE(3 < 5);
+ *     
+ *         int i = REQUIRE(extreme_example(1));
+ *     
+ *         return 0;
+ *     }
+ * Possible (stderr) output:
+ *     Required operation 'fopen("a.txt", "r")' failed.
+ */
+
+thread_local long long require_v;
+
+#ifndef REQUIRE_TERMINATOR
+# define REQUIRE_TERMINATOR default_require_terminator
+#endif
+
+[[ noreturn ]]
+static inline
+void require_default_terminator(const char * const argv) {
+    fprintf(stderr, "Required operation '%s' failed.\n", argv);
+    exit(1);
+}
+
+#define REQUIRE_EX(errval, ...) (typeof(__VA_ARGS__))( \
+    (typeof(__VA_ARGS__))(require_v = (long long)(__VA_ARGS__)) != (typeof(__VA_ARGS__))errval \
+    ? require_v \
+    : (REQUIRE_TERMINATOR(STRINGIFY(__VA_ARGS__)), 0ll) \
+)
+
+#define REQUIRE(...) REQUIRE_EX(0ll, __VA_ARGS__)
+
+#endif