sd-id128: add convenience functions to compare multiple sd_id128_t

Similar to sd_bus_error_has_names() that was added in
2b07ec316a.

It is made inline in the hope that the compiler will be able to optimize
all the va_args boilerplate away, and do an efficient comparison when
the arguments are all constants.

src/systemd/sd-id128.h

@@ -18,6 +18,7 @@
 ***/
 
 #include <inttypes.h>
+#include <stdarg.h>
 #include <string.h>
 
 #include "_sd-common.h"
@@ -119,6 +120,32 @@ _sd_pure_ static __inline__ int sd_id128_is_allf(sd_id128_t a) {
 #define SD_ID128_NULL ((const sd_id128_t) { .qwords = { 0, 0 }})
 #define SD_ID128_ALLF ((const sd_id128_t) { .qwords = { UINT64_C(0xFFFFFFFFFFFFFFFF), UINT64_C(0xFFFFFFFFFFFFFFFF) }})
 
+_sd_pure_ static __inline__ int sd_id128_in_setv(sd_id128_t a, va_list ap) {
+        for (;;) {
+                sd_id128_t b = va_arg(ap, sd_id128_t);
+
+                if (sd_id128_is_null(b))
+                        return 0;
+
+                if (sd_id128_equal(a, b))
+                        return 1;
+        }
+}
+
+_sd_pure_ static __inline__ int sd_id128_in_set_sentinel(sd_id128_t a, ...) {
+        va_list ap;
+        int r;
+
+        va_start(ap, a);
+        r = sd_id128_in_setv(a, ap);
+        va_end(ap);
+
+        return r;
+}
+
+#define sd_id128_in_set(a, ...) \
+        sd_id128_in_set_sentinel(a, ##__VA_ARGS__, SD_ID128_NULL)
+
 _SD_END_DECLARATIONS;
 
 #endif

src/test/test-id128.c

@@ -31,6 +31,13 @@ int main(int argc, char *argv[]) {
 
         assert_se(sd_id128_from_string(t, &id2) == 0);
         assert_se(sd_id128_equal(id, id2));
+        assert_se(sd_id128_in_set(id, id));
+        assert_se(sd_id128_in_set(id, id2));
+        assert_se(sd_id128_in_set(id, id2, id));
+        assert_se(sd_id128_in_set(id, ID128_WALDI, id));
+        assert_se(!sd_id128_in_set(id));
+        assert_se(!sd_id128_in_set(id, ID128_WALDI));
+        assert_se(!sd_id128_in_set(id, ID128_WALDI, ID128_WALDI));
 
         if (sd_booted() > 0) {
                 assert_se(sd_id128_get_machine(&id) == 0);