c: move c files into nostrdb in prep for switchover

nostrdb/structeq.h

@@ -0,0 +1,46 @@
+/* MIT (BSD) license - see LICENSE file for details */
+#ifndef CCAN_STRUCTEQ_H
+#define CCAN_STRUCTEQ_H
+#include "build_assert.h"
+#include "cppmagic.h"
+#include <string.h>
+#include <stdbool.h>
+
+/**
+ * STRUCTEQ_DEF - define an ..._eq function to compare two structures.
+ * @sname: name of the structure, and function (<sname>_eq) to define.
+ * @padbytes: number of bytes of expected padding, or negative "max".
+ * @...: name of every member of the structure.
+ *
+ * This generates a single memcmp() call in the common case where the
+ * structure contains no padding.  Since it can't tell the difference between
+ * padding and a missing member, @padbytes can be used to assert that
+ * there isn't any, or how many we expect.  A negative number means
+ * "up to or equal to that amount of padding", as padding can be
+ * platform dependent.
+ */
+#define STRUCTEQ_DEF(sname, padbytes, ...)                \
+static inline bool CPPMAGIC_GLUE2(sname, _eq)(const struct sname *_a, \
+                          const struct sname *_b) \
+{                                    \
+    BUILD_ASSERT(((padbytes) < 0 &&                    \
+              CPPMAGIC_JOIN(+, CPPMAGIC_MAP(STRUCTEQ_MEMBER_SIZE_, \
+                            __VA_ARGS__))    \
+              - (padbytes) >= sizeof(*_a))            \
+             || CPPMAGIC_JOIN(+, CPPMAGIC_MAP(STRUCTEQ_MEMBER_SIZE_, \
+                              __VA_ARGS__))    \
+             + (padbytes) == sizeof(*_a));            \
+    if (CPPMAGIC_JOIN(+, CPPMAGIC_MAP(STRUCTEQ_MEMBER_SIZE_, __VA_ARGS__)) \
+        == sizeof(*_a))                        \
+        return memcmp(_a, _b, sizeof(*_a)) == 0;        \
+    else                                \
+        return CPPMAGIC_JOIN(&&,                \
+                     CPPMAGIC_MAP(STRUCTEQ_MEMBER_CMP_, \
+                          __VA_ARGS__));    \
+}
+
+/* Helpers */
+#define STRUCTEQ_MEMBER_SIZE_(m) sizeof((_a)->m)
+#define STRUCTEQ_MEMBER_CMP_(m) memcmp(&_a->m, &_b->m, sizeof(_a->m)) == 0
+
+#endif /* CCAN_STRUCTEQ_H */