golden hour

/usr/include/mysql/server/mysql

File/Folder	Size	Actions
auth_dialog_client.h	2.01 KB
client_plugin.h	6.18 KB
plugin.h	28.69 KB
plugin_audit.h	5.41 KB
plugin_auth.h	5.27 KB
plugin_auth_common.h	4.4 KB
plugin_data_type.h	1.27 KB
plugin_encryption.h	4.33 KB
plugin_ftparser.h	7.65 KB
plugin_function.h	1.4 KB
plugin_password_validation.h	1.52 KB
psi	-
service_base64.h	2.86 KB
service_debug_sync.h	13.18 KB
service_encryption.h	5.52 KB
service_encryption_scheme.h	5.51 KB
service_json.h	4.44 KB
service_kill_statement.h	2.02 KB
service_logger.h	3.47 KB
service_md5.h	2.07 KB
service_my_crypt.h	4.07 KB
service_my_print_error.h	2.27 KB
service_my_snprintf.h	3.63 KB
service_print_check_msg.h	1.52 KB
service_progress_report.h	3.28 KB
service_sha1.h	2.11 KB
service_sha2.h	5.17 KB
service_sql.h	4.57 KB
service_thd_alloc.h	4.38 KB
service_thd_autoinc.h	1.65 KB
service_thd_error_context.h	3.34 KB
service_thd_mdl.h	1.25 KB
service_thd_rnd.h	1.86 KB
service_thd_specifics.h	3.6 KB
service_thd_timezone.h	2.24 KB
service_thd_wait.h	3.61 KB
service_wsrep.h	13.04 KB
services.h	1.72 KB

Edit: service_thd_rnd.h

#ifndef MYSQL_SERVICE_THD_RND_INCLUDED
/* Copyright (C) 2017 MariaDB Corporation

This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 of the License.

This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335  USA */

/**
  @file
  This service provides access to the thd-local random number generator.

It's preferable over the global one, because concurrent threads
  can generate random numbers without fighting each other over the access
  to the shared rnd state.
*/

#ifdef __cplusplus
extern "C" {
#endif

#ifndef MYSQL_ABI_CHECK
#include <stdlib.h>
#endif

extern struct thd_rnd_service_st {
  double (*thd_rnd_ptr)(MYSQL_THD thd);
  void   (*thd_c_r_p_ptr)(MYSQL_THD thd, char *to, size_t length);
} *thd_rnd_service;

#ifdef MYSQL_DYNAMIC_PLUGIN
#define thd_rnd(A) thd_rnd_service->thd_rnd_ptr(A)
#define thd_create_random_password(A,B,C) thd_rnd_service->thd_c_r_p_ptr(A,B,C)
#else

double thd_rnd(MYSQL_THD thd);

/**
  Generate string of printable random characters of requested length.

@param to[out]      Buffer for generation; must be at least length+1 bytes
                      long; result string is always null-terminated
  @param length[in]   How many random characters to put in buffer
*/
void thd_create_random_password(MYSQL_THD thd, char *to, size_t length);

#endif

#ifdef __cplusplus
}
#endif

#define MYSQL_SERVICE_THD_RND_INCLUDED
#endif