sd-json: add json_dispatch_const_path() helper

poettering · daandemeyer · commit 3866e9ce9d34 · 2025-01-03T16:38:56.000+01:00
The new json_dispatch_const_path() is to json_dispatch_path() what
sd_json_dispatch_const_string() is to sd_json_dispatch_ string(), i.e.
doesn't implicitly strdup() the string, but gives you the pointer into
the JSON structure, and thus requires you to keep it pinned.
diff --git a/src/libsystemd/sd-json/json-util.c b/src/libsystemd/sd-json/json-util.c
@@ -125,14 +125,13 @@ int json_dispatch_in_addr(const char *name, sd_json_variant *variant, sd_json_di
         return 0;
 }
 
-int json_dispatch_path(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata) {
-        char **p = ASSERT_PTR(userdata);
-        const char *path;
+int json_dispatch_const_path(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata) {
+        const char **p = ASSERT_PTR(userdata), *path;
 
         assert(variant);
 
         if (sd_json_variant_is_null(variant)) {
-                *p = mfree(*p);
+                *p = NULL;
                 return 0;
         }
 
@@ -145,6 +144,21 @@ int json_dispatch_path(const char *name, sd_json_variant *variant, sd_json_dispa
         if (!path_is_absolute(path))
                 return json_log(variant, flags, SYNTHETIC_ERRNO(EINVAL), "JSON field '%s' is not an absolute file system path.", strna(name));
 
+        *p = path;
+        return 0;
+}
+
+int json_dispatch_path(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata) {
+        char **p = ASSERT_PTR(userdata);
+        const char *path;
+        int r;
+
+        assert_return(variant, -EINVAL);
+
+        r = json_dispatch_const_path(name, variant, flags, &path);
+        if (r < 0)
+                return r;
+
         if (free_and_strdup(p, path) < 0)
                 return json_log_oom(variant, flags);
 
diff --git a/src/libsystemd/sd-json/json-util.h b/src/libsystemd/sd-json/json-util.h
@@ -113,6 +113,7 @@ int json_dispatch_user_group_name(const char *name, sd_json_variant *variant, sd
 int json_dispatch_const_user_group_name(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);
 int json_dispatch_in_addr(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);
 int json_dispatch_path(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);
+int json_dispatch_const_path(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);
 int json_dispatch_pidref(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);
 int json_dispatch_devnum(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);
 int json_dispatch_ifindex(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);
