test-hostname-pick-word: add a simple test to check word selection

This is useful to check if how fast the code is (painfully slow) and whether
worlds indeed are selected with a flat distribution probability (they are).

The code is slow because the hashing and because chaseat is exteremely
inefficient :(

src/shared/hostname-setup.c

@@ -369,7 +369,7 @@ static int pick_word_linear_scan(FILE *f, off_t offset, char **ret) {
         }
 }
 
-static int hostname_pick_word(sd_id128_t mid, size_t pos, char **ret) {
+int hostname_pick_word(sd_id128_t mid, size_t pos, char **ret) {
         static const sd_id128_t word_key = SD_ID128_MAKE(2d,9f,1c,7a,4b,8e,43,11,9a,6d,5f,02,c8,77,e3,14);
         _cleanup_fclose_ FILE *f = NULL;
         struct stat st;

src/shared/hostname-setup.h

@@ -22,6 +22,7 @@ int read_etc_hostname(const char *path, bool substitute_wildcards, char **ret);
 void hostname_update_source_hint(const char *hostname, HostnameSource source);
 int hostname_setup(bool really);
 
+int hostname_pick_word(sd_id128_t mid, size_t pos, char **ret);
 int hostname_substitute_wildcards(const char *name, char **ret);
 
 char* get_default_hostname(void);

src/test/meson.build

@@ -395,6 +395,10 @@ executables += [
                 ],
                 'timeout' : 180,
         },
+        test_template + {
+                'sources': files('test-hostname-pick-word.c'),
+                'type' : 'manual',
+        },
         test_template + {
                 'sources' : files('test-ipcrm.c'),
                 'type' : 'unsafe',

src/test/test-hostname-pick-word.c

@@ -0,0 +1,47 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "sd-id128.h"
+
+#include "alloc-util.h"
+#include "hostname-setup.h"
+#include "log.h"
+#include "main-func.h"
+#include "parse-util.h"
+#include "tests.h"
+
+static int run(int argc, char **argv) {
+        int r;
+
+        log_parse_environment();
+
+        unsigned c = 100, pos = 1;
+
+        if (argc > 1) {
+                r = safe_atou(argv[1], &pos);
+                if (r < 0)
+                        return log_error_errno(r, "Cannot parse uint %s: %m", argv[1]);
+        }
+
+        if (argc > 2) {
+                r = safe_atou(argv[2], &c);
+                if (r < 0)
+                        return log_error_errno(r, "Cannot parse uint %s: %m", argv[2]);
+        }
+
+        sd_id128_t mid = SD_ID128_ARRAY(aa,bb,cc,ee,33,21,42,31,89,ba,a4,91,33,22,11,00);
+
+        while (c-- > 0) {
+                _cleanup_free_ char *w = NULL;
+
+                ASSERT_OK(hostname_pick_word(mid, pos, &w));
+                ASSERT_PTR(w);
+
+                printf("%s\n", w);
+
+                mid.qwords[0] += 3;
+        }
+
+        return 0;
+}
+
+DEFINE_MAIN_FUNCTION(run);