lbbs/src/user_list.c

/* SPDX-License-Identifier: GPL-3.0-or-later */
/*
 * user_list
 *   - data model and basic operations of (online) user list
 *
 * Copyright (C) 2004-2025  Leaflet <leaflet@leafok.com>
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "common.h"
#include "database.h"
#include "log.h"
#include "trie_dict.h"
#include "user_list.h"
#include "user_stat.h"
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <sys/mman.h>
#include <sys/param.h>
#include <sys/stat.h>

#ifdef HAVE_SYSTEM_V
#include <sys/sem.h>

#ifdef _SEM_SEMUN_UNDEFINED
union semun
{
        int val;                           /* Value for SETVAL */
        struct semid_ds *buf;  /* Buffer for IPC_STAT, IPC_SET */
        unsigned short *array; /* Array for GETALL, SETALL */
        struct seminfo *__buf; /* Buffer for IPC_INFO
                                                        (Linux-specific) */
};
#endif // #ifdef _SEM_SEMUN_UNDEFINED

#else
#include <semaphore.h>
#endif

enum _user_list_constant_t
{
        USER_LIST_TRY_LOCK_WAIT_TIME = 1, // second
        USER_LIST_TRY_LOCK_TIMES = 10,
        USER_LIST_DEAD_LOCK_TIMEOUT = 15, // second
};

struct user_list_pool_t
{
        size_t shm_size;
#ifndef HAVE_SYSTEM_V
        sem_t sem;
        uint16_t read_lock_count;
        uint16_t write_lock_count;
#else
        int semid;
#endif
        USER_LIST user_list[2];
        int user_list_index_current;
        int user_list_index_new;
        USER_ONLINE_LIST user_online_list[2];
        int user_online_list_index_current;
        int user_online_list_index_new;
        USER_STAT_MAP user_stat_map;
        int user_login_count;
};
typedef struct user_list_pool_t USER_LIST_POOL;

static char user_list_shm_name[FILE_NAME_LEN];
static USER_LIST_POOL *p_user_list_pool = NULL;
static TRIE_NODE *p_trie_action_dict = NULL;

typedef struct user_action_map_t
{
        char name[BBS_current_action_max_len + 1];
        char title[BBS_current_action_max_len + 1];
} USER_ACTION_MAP;

const USER_ACTION_MAP user_action_map[] =
        {
                {"ARTICLE_FAVOR", "浏览收藏"},
                {"BBS_NET", "站点穿梭"},
                {"CHICKEN", "电子小鸡"},
                {"EDIT_ARTICLE", "修改文章"},
                {"LOGIN", "进入大厅"},
                {"MENU", "菜单选择"},
                {"POST_ARTICLE", "撰写文章"},
                {"REPLY_ARTICLE", "回复文章"},
                {"TOP10_MENU", "十大热门"},
                {"USER_LIST", "查花名册"},
                {"USER_ONLINE", "环顾四周"},
                {"VIEW_ARTICLE", "阅读文章"},
                {"VIEW_FILE", "查看文档"},
                {"WWW", "Web浏览"}};

const int user_action_map_size = sizeof(user_action_map) / sizeof(USER_ACTION_MAP);

static int user_list_try_rd_lock(int wait_sec);
static int user_list_try_rw_lock(int wait_sec);
static int user_list_rd_unlock(void);
static int user_list_rw_unlock(void);
static int user_list_rd_lock(void);
static int user_list_rw_lock(void);
#ifndef HAVE_SYSTEM_V
static int user_list_reset_lock(void);
#endif

static int user_list_load(MYSQL *db, USER_LIST *p_list);
static int user_online_list_load(MYSQL *db, USER_ONLINE_LIST *p_online_list);
static int user_login_count_load(MYSQL *db);

static int user_info_index_uid_comp(const void *ptr1, const void *ptr2)
{
        const USER_INFO_INDEX_UID *p1 = ptr1;
        const USER_INFO_INDEX_UID *p2 = ptr2;

        if (p1->uid < p2->uid)
        {
                return -1;
        }
        else if (p1->uid > p2->uid)
        {
                return 1;
        }
        else if (p1->id < p2->id)
        {
                return -1;
        }
        else if (p1->id > p2->id)
        {
                return 1;
        }
        return 0;
}

int user_list_load(MYSQL *db, USER_LIST *p_list)
{
        MYSQL_RES *rs = NULL;
        MYSQL_ROW row;
        char sql[SQL_BUFFER_LEN];
        int ret = 0;
        int i;
        int j;
        int32_t last_uid;
        size_t intro_buf_offset;
        size_t intro_len;

        if (db == NULL || p_list == NULL)
        {
                log_error("NULL pointer error\n");
                return -1;
        }

        if (p_list->user_count > 0)
        {
                last_uid = p_list->users[p_list->user_count - 1].uid;
        }
        else
        {
                last_uid = -1;
        }

        snprintf(sql, sizeof(sql),
                         "SELECT user_list.UID AS UID, username, nickname, gender, gender_pub, life, exp, visit_count, "
                         "UNIX_TIMESTAMP(signup_dt), UNIX_TIMESTAMP(last_login_dt), UNIX_TIMESTAMP(last_logout_dt), "
                         "UNIX_TIMESTAMP(birthday), `introduction` "
                         "FROM user_list INNER JOIN user_pubinfo ON user_list.UID = user_pubinfo.UID "
                         "INNER JOIN user_reginfo ON user_list.UID = user_reginfo.UID "
                         "WHERE enable ORDER BY username");

        if (mysql_query(db, sql) != 0)
        {
                log_error("Query user info error: %s\n", mysql_error(db));
                ret = -1;
                goto cleanup;
        }

        if ((rs = mysql_use_result(db)) == NULL)
        {
                log_error("Get user info data failed\n");
                ret = -1;
                goto cleanup;
        }

        intro_buf_offset = 0;
        i = 0;
        while ((row = mysql_fetch_row(rs)))
        {
                // record
                p_list->users[i].id = i;
                p_list->users[i].uid = atoi(row[0]);
                strncpy(p_list->users[i].username, row[1], sizeof(p_list->users[i].username) - 1);
                p_list->users[i].username[sizeof(p_list->users[i].username) - 1] = '\0';
                strncpy(p_list->users[i].nickname, row[2], sizeof(p_list->users[i].nickname) - 1);
                p_list->users[i].nickname[sizeof(p_list->users[i].nickname) - 1] = '\0';
                p_list->users[i].gender = row[3][0];
                p_list->users[i].gender_pub = (int8_t)(row[4] == NULL ? 0 : atoi(row[4]));
                p_list->users[i].life = (row[5] == NULL ? 0 : atoi(row[5]));
                p_list->users[i].exp = (row[6] == NULL ? 0 : atoi(row[6]));
                p_list->users[i].visit_count = (row[7] == NULL ? 0 : atoi(row[7]));
                p_list->users[i].signup_dt = (row[8] == NULL ? 0 : atol(row[8]));
                p_list->users[i].last_login_dt = (row[9] == NULL ? 0 : atol(row[9]));
                p_list->users[i].last_logout_dt = (row[10] == NULL ? 0 : atol(row[10]));
                p_list->users[i].birthday = (row[11] == NULL ? 0 : atol(row[11]));
                intro_len = strlen((row[12] == NULL ? "" : row[12]));
                if (intro_len >= sizeof(p_list->user_intro_buf) - 1 - intro_buf_offset)
                {
                        log_error("OOM for user introduction: len=%d, i=%d\n", intro_len, i);
                        break;
                }
                memcpy(p_list->user_intro_buf + intro_buf_offset,
                           (row[12] == NULL ? "" : row[12]),
                           intro_len + 1);
                p_list->users[i].intro = p_list->user_intro_buf + intro_buf_offset;
                intro_buf_offset += (intro_len + 1);

                i++;
                if (i >= BBS_max_user_count)
                {
                        log_error("Too many users, exceed limit %d\n", BBS_max_user_count);
                        break;
                }
        }
        mysql_free_result(rs);
        rs = NULL;

        if (i != p_list->user_count || p_list->users[i - 1].uid != last_uid) // Count of users changed
        {
                // Rebuild index
                for (j = 0; j < i; j++)
                {
                        p_list->index_uid[j].uid = p_list->users[j].uid;
                        p_list->index_uid[j].id = j;
                }

                qsort(p_list->index_uid, (size_t)i, sizeof(USER_INFO_INDEX_UID), user_info_index_uid_comp);

#ifdef _DEBUG
                log_error("Rebuild index of %d users, last_uid=%d\n", i, p_list->users[i - 1].uid);
#endif
        }

        p_list->user_count = i;

#ifdef _DEBUG
        log_error("Loaded %d users\n", p_list->user_count);
#endif

cleanup:
        mysql_free_result(rs);

        return ret;
}

int user_online_list_load(MYSQL *db, USER_ONLINE_LIST *p_online_list)
{
        MYSQL_RES *rs = NULL;
        MYSQL_ROW row;
        char sql[SQL_BUFFER_LEN];
        int ret = 0;
        int i;
        int j;
        int user_cnt;
        int guest_cnt;

        if (db == NULL || p_online_list == NULL)
        {
                log_error("NULL pointer error\n");
                return -1;
        }

        snprintf(sql, sizeof(sql),
                         "SELECT SID, UID, ip, current_action, UNIX_TIMESTAMP(login_tm), "
                         "UNIX_TIMESTAMP(last_tm) FROM user_online "
                         "WHERE last_tm >= SUBDATE(NOW(), INTERVAL %d SECOND) "
                         "ORDER BY last_tm DESC",
                         BBS_user_off_line);

        if (mysql_query(db, sql) != 0)
        {
                log_error("Query user online error: %s\n", mysql_error(db));
                ret = -1;
                goto cleanup;
        }

        if ((rs = mysql_use_result(db)) == NULL)
        {
                log_error("Get user online data failed\n");
                ret = -1;
                goto cleanup;
        }

        i = 0;
        user_cnt = 0;
        guest_cnt = 0;
        while ((row = mysql_fetch_row(rs)))
        {
                if (atoi(row[1]) == 0) // guest
                {
                        guest_cnt++;
                        continue;
                }
                else
                {
                        user_cnt++;
                }

                p_online_list->users[i].id = i;
                strncpy(p_online_list->users[i].session_id, row[0], sizeof(p_online_list->users[i].session_id) - 1);
                p_online_list->users[i].session_id[sizeof(p_online_list->users[i].session_id) - 1] = '\0';

                if ((ret = query_user_info_by_uid(atoi(row[1]), &(p_online_list->users[i].user_info), NULL, 0)) <= 0)
                {
                        log_error("query_user_info_by_uid(%d) error\n", atoi(row[1]));
                        continue;
                }

                strncpy(p_online_list->users[i].ip, row[2], sizeof(p_online_list->users[i].ip) - 1);
                p_online_list->users[i].ip[sizeof(p_online_list->users[i].ip) - 1] = '\0';

                strncpy(p_online_list->users[i].current_action, row[3], sizeof(p_online_list->users[i].current_action) - 1);
                p_online_list->users[i].current_action[sizeof(p_online_list->users[i].current_action) - 1] = '\0';
                p_online_list->users[i].current_action_title = NULL;
                if (p_online_list->users[i].current_action[0] == '\0')
                {
                        p_online_list->users[i].current_action_title = "";
                }
                else if (trie_dict_get(p_trie_action_dict, p_online_list->users[i].current_action, (int64_t *)(&(p_online_list->users[i].current_action_title))) < 0)
                {
                        log_error("trie_dict_get(p_trie_action_dict, %s) error on session_id=%s\n",
                                          p_online_list->users[i].current_action, p_online_list->users[i].session_id);
                        continue;
                }

                p_online_list->users[i].login_tm = (row[4] == NULL ? 0 : atol(row[4]));
                p_online_list->users[i].last_tm = (row[5] == NULL ? 0 : atol(row[5]));

                i++;
                if (i >= BBS_max_user_online_count)
                {
                        log_error("Too many online users, exceed limit %d\n", BBS_max_user_online_count);
                        break;
                }
        }
        mysql_free_result(rs);
        rs = NULL;

        if (user_cnt > 0)
        {
                // Rebuild index
                for (j = 0; j < user_cnt; j++)
                {
                        p_online_list->index_uid[j].uid = p_online_list->users[j].user_info.uid;
                        p_online_list->index_uid[j].id = j;
                }

                qsort(p_online_list->index_uid, (size_t)user_cnt, sizeof(USER_INFO_INDEX_UID), user_info_index_uid_comp);
        }

        p_online_list->user_count = user_cnt;
        p_online_list->guest_count = guest_cnt;

cleanup:
        mysql_free_result(rs);

        return ret;
}

int user_login_count_load(MYSQL *db)
{
        MYSQL_RES *rs = NULL;
        MYSQL_ROW row;
        char sql[SQL_BUFFER_LEN];

        if (db == NULL)
        {
                log_error("NULL pointer error\n");
                return -1;
        }

        snprintf(sql, sizeof(sql),
                         "SELECT ID FROM user_login_log ORDER BY ID DESC LIMIT 1");
        if (mysql_query(db, sql) != 0)
        {
                log_error("Query user_login_log error: %s\n", mysql_error(db));
                return -2;
        }
        if ((rs = mysql_store_result(db)) == NULL)
        {
                log_error("Get user_login_log data failed\n");
                return -2;
        }
        if ((row = mysql_fetch_row(rs)))
        {
                p_user_list_pool->user_login_count = atoi(row[0]);
        }
        mysql_free_result(rs);

        return 0;
}

int user_list_pool_init(const char *filename)
{
        char filepath[FILE_PATH_LEN];
        int fd;
        size_t size;
        void *p_shm;
#ifdef HAVE_SYSTEM_V
        int proj_id;
        key_t key;
        int semid;
        union semun arg;
#endif
        int i;

        if (p_user_list_pool != NULL || p_trie_action_dict != NULL)
        {
                log_error("p_user_list_pool already initialized\n");
                return -1;
        }

        p_trie_action_dict = trie_dict_create();
        if (p_trie_action_dict == NULL)
        {
                log_error("trie_dict_create() error\n");
                return -1;
        }

        for (i = 0; i < user_action_map_size; i++)
        {
                if (trie_dict_set(p_trie_action_dict, user_action_map[i].name, (int64_t)(user_action_map[i].title)) < 0)
                {
                        log_error("trie_dict_set(p_trie_action_dict, %s) error\n", user_action_map[i].name);
                }
        }

        // Allocate shared memory
        size = sizeof(USER_LIST_POOL);

        strncpy(filepath, filename, sizeof(filepath) - 1);
        filepath[sizeof(filepath) - 1] = '\0';
        snprintf(user_list_shm_name, sizeof(user_list_shm_name), "/USER_LIST_SHM_%s", basename(filepath));

        if (shm_unlink(user_list_shm_name) == -1 && errno != ENOENT)
        {
                log_error("shm_unlink(%s) error (%d)\n", user_list_shm_name, errno);
                return -2;
        }

        if ((fd = shm_open(user_list_shm_name, O_CREAT | O_EXCL | O_RDWR, 0600)) == -1)
        {
                log_error("shm_open(%s) error (%d)\n", user_list_shm_name, errno);
                return -2;
        }
        if (ftruncate(fd, (off_t)size) == -1)
        {
                log_error("ftruncate(size=%d) error (%d)\n", size, errno);
                close(fd);
                return -2;
        }

        p_shm = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0L);
        if (p_shm == MAP_FAILED)
        {
                log_error("mmap() error (%d)\n", errno);
                close(fd);
                return -2;
        }

        if (close(fd) < 0)
        {
                log_error("close(fd) error (%d)\n", errno);
                return -1;
        }

        p_user_list_pool = p_shm;
        p_user_list_pool->shm_size = size;

        // Allocate semaphore as user list pool lock
#ifndef HAVE_SYSTEM_V
        if (sem_init(&(p_user_list_pool->sem), 1, 1) == -1)
        {
                log_error("sem_init() error (%d)\n", errno);
                return -3;
        }

        p_user_list_pool->read_lock_count = 0;
        p_user_list_pool->write_lock_count = 0;
#else
        proj_id = (int)(time(NULL) % getpid());
        key = ftok(filename, proj_id);
        if (key == -1)
        {
                log_error("ftok(%s %d) error (%d)\n", filename, proj_id, errno);
                return -2;
        }

        size = 2; // r_sem and w_sem
        semid = semget(key, (int)size, IPC_CREAT | IPC_EXCL | 0600);
        if (semid == -1)
        {
                log_error("semget(user_list_pool_sem, size = %d) error (%d)\n", size, errno);
                return -3;
        }

        // Initialize sem value to 0
        arg.val = 0;
        for (i = 0; i < size; i++)
        {
                if (semctl(semid, i, SETVAL, arg) == -1)
                {
                        log_error("semctl(user_list_pool_sem, SETVAL) error (%d)\n", errno);
                        return -3;
                }
        }

        p_user_list_pool->semid = semid;
#endif

        // Set user counts to 0
        p_user_list_pool->user_list[0].user_count = 0;
        p_user_list_pool->user_list[1].user_count = 0;

        p_user_list_pool->user_list_index_current = 0;
        p_user_list_pool->user_list_index_new = 1;

        p_user_list_pool->user_online_list_index_current = 0;
        p_user_list_pool->user_online_list_index_new = 1;

        user_stat_map_init(&(p_user_list_pool->user_stat_map));

        return 0;
}

void user_list_pool_cleanup(void)
{
        if (p_user_list_pool == NULL)
        {
                return;
        }

#ifdef HAVE_SYSTEM_V
        if (semctl(p_user_list_pool->semid, 0, IPC_RMID) == -1)
        {
                log_error("semctl(semid = %d, IPC_RMID) error (%d)\n", p_user_list_pool->semid, errno);
        }
#else
        if (sem_destroy(&(p_user_list_pool->sem)) == -1)
        {
                log_error("sem_destroy() error (%d)\n", errno);
        }
#endif

        detach_user_list_pool_shm();

        if (shm_unlink(user_list_shm_name) == -1 && errno != ENOENT)
        {
                log_error("shm_unlink(%s) error (%d)\n", user_list_shm_name, errno);
        }

        user_list_shm_name[0] = '\0';

        if (p_trie_action_dict != NULL)
        {
                trie_dict_destroy(p_trie_action_dict);

                p_trie_action_dict = NULL;
        }
}

int set_user_list_pool_shm_readonly(void)
{
        if (p_user_list_pool != NULL && mprotect(p_user_list_pool, p_user_list_pool->shm_size, PROT_READ) < 0)
        {
                log_error("mprotect() error (%d)\n", errno);
                return -1;
        }

        return 0;
}

int detach_user_list_pool_shm(void)
{
        if (p_user_list_pool != NULL && munmap(p_user_list_pool, p_user_list_pool->shm_size) < 0)
        {
                log_error("munmap() error (%d)\n", errno);
                return -1;
        }

        p_user_list_pool = NULL;

        return 0;
}

int user_list_pool_reload(int online_user)
{
        MYSQL *db = NULL;
        int tmp;
        int ret = 0;

        if (p_user_list_pool == NULL)
        {
                log_error("p_user_list_pool not initialized\n");
                return -1;
        }

        db = db_open();
        if (db == NULL)
        {
                log_error("db_open() error: %s\n", mysql_error(db));
                return -1;
        }

        if (online_user)
        {
                if (user_online_list_load(db, &(p_user_list_pool->user_online_list[p_user_list_pool->user_online_list_index_new])) < 0)
                {
                        log_error("user_online_list_load() error\n");
                        ret = -2;
                        goto cleanup;
                }

                if (user_login_count_load(db) < 0)
                {
                        log_error("user_login_count_load() error\n");
                        ret = -2;
                        goto cleanup;
                }
        }
        else
        {
                if (user_list_load(db, &(p_user_list_pool->user_list[p_user_list_pool->user_list_index_new])) < 0)
                {
                        log_error("user_list_load() error\n");
                        ret = -2;
                        goto cleanup;
                }
        }

        mysql_close(db);
        db = NULL;

        if (user_list_rw_lock() < 0)
        {
                log_error("user_list_rw_lock() error\n");
                ret = -3;
                goto cleanup;
        }

        if (online_user)
        {
                // Swap p_online_current and p_online_new
                tmp = p_user_list_pool->user_online_list_index_current;
                p_user_list_pool->user_online_list_index_current = p_user_list_pool->user_online_list_index_new;
                p_user_list_pool->user_online_list_index_new = tmp;
        }
        else
        {
                // Swap index_current and index_new
                tmp = p_user_list_pool->user_list_index_current;
                p_user_list_pool->user_list_index_current = p_user_list_pool->user_list_index_new;
                p_user_list_pool->user_list_index_new = tmp;
        }

        if (user_list_rw_unlock() < 0)
        {
                log_error("user_list_rw_unlock() error\n");
                ret = -3;
                goto cleanup;
        }

cleanup:
        mysql_close(db);

        return ret;
}

int user_list_try_rd_lock(int wait_sec)
{
#ifdef HAVE_SYSTEM_V
        struct sembuf sops[2];
#endif
        struct timespec timeout;
        int ret = 0;

        if (p_user_list_pool == NULL)
        {
                log_error("p_user_list_pool not initialized\n");
                return -1;
        }

        timeout.tv_sec = wait_sec;
        timeout.tv_nsec = 0;

#ifdef HAVE_SYSTEM_V
        sops[0].sem_num = 1; // w_sem
        sops[0].sem_op = 0;      // wait until unlocked
        sops[0].sem_flg = 0;

        sops[1].sem_num = 0;            // r_sem
        sops[1].sem_op = 1;                     // lock
        sops[1].sem_flg = SEM_UNDO; // undo on terminate

        ret = semtimedop(p_user_list_pool->semid, sops, 2, &timeout);
        if (ret == -1 && errno != EAGAIN && errno != EINTR)
        {
                log_error("semop(lock read) error %d\n", errno);
        }
#else
        if (sem_timedwait(&(p_user_list_pool->sem), &timeout) == -1)
        {
                if (errno != ETIMEDOUT && errno != EAGAIN && errno != EINTR)
                {
                        log_error("sem_timedwait() error %d\n", errno);
                }
                return -1;
        }

        if (p_user_list_pool->write_lock_count == 0)
        {
                p_user_list_pool->read_lock_count++;
        }
        else
        {
                errno = EAGAIN;
                ret = -1;
        }

        if (sem_post(&(p_user_list_pool->sem)) == -1)
        {
                log_error("sem_post() error %d\n", errno);
                return -1;
        }
#endif

        return ret;
}

int user_list_try_rw_lock(int wait_sec)
{
#ifdef HAVE_SYSTEM_V
        struct sembuf sops[3];
#endif
        struct timespec timeout;
        int ret = 0;

        if (p_user_list_pool == NULL)
        {
                log_error("p_user_list_pool not initialized\n");
                return -1;
        }

        timeout.tv_sec = wait_sec;
        timeout.tv_nsec = 0;

#ifdef HAVE_SYSTEM_V
        sops[0].sem_num = 1; // w_sem
        sops[0].sem_op = 0;      // wait until unlocked
        sops[0].sem_flg = 0;

        sops[1].sem_num = 1;            // w_sem
        sops[1].sem_op = 1;                     // lock
        sops[1].sem_flg = SEM_UNDO; // undo on terminate

        sops[2].sem_num = 0; // r_sem
        sops[2].sem_op = 0;      // wait until unlocked
        sops[2].sem_flg = 0;

        ret = semtimedop(p_user_list_pool->semid, sops, 3, &timeout);
        if (ret == -1 && errno != EAGAIN && errno != EINTR)
        {
                log_error("semop(lock write) error %d\n", errno);
        }
#else
        if (sem_timedwait(&(p_user_list_pool->sem), &timeout) == -1)
        {
                if (errno != ETIMEDOUT && errno != EAGAIN && errno != EINTR)
                {
                        log_error("sem_timedwait() error %d\n", errno);
                }
                return -1;
        }

        if (p_user_list_pool->read_lock_count == 0 && p_user_list_pool->write_lock_count == 0)
        {
                p_user_list_pool->write_lock_count++;
        }
        else
        {
                errno = EAGAIN;
                ret = -1;
        }

        if (sem_post(&(p_user_list_pool->sem)) == -1)
        {
                log_error("sem_post() error %d\n", errno);
                return -1;
        }
#endif

        return ret;
}

int user_list_rd_unlock(void)
{
#ifdef HAVE_SYSTEM_V
        struct sembuf sops[2];
#endif
        int ret = 0;

        if (p_user_list_pool == NULL)
        {
                log_error("p_user_list_pool not initialized\n");
                return -1;
        }

#ifdef HAVE_SYSTEM_V
        sops[0].sem_num = 0;                                     // r_sem
        sops[0].sem_op = -1;                                     // unlock
        sops[0].sem_flg = IPC_NOWAIT | SEM_UNDO; // no wait

        ret = semop(p_user_list_pool->semid, sops, 1);
        if (ret == -1 && errno != EAGAIN && errno != EINTR)
        {
                log_error("semop(unlock read) error %d\n", errno);
        }
#else
        if (sem_wait(&(p_user_list_pool->sem)) == -1)
        {
                if (errno != ETIMEDOUT && errno != EAGAIN && errno != EINTR)
                {
                        log_error("sem_wait() error %d\n", errno);
                }
                return -1;
        }

        if (p_user_list_pool->read_lock_count > 0)
        {
                p_user_list_pool->read_lock_count--;
        }
        else
        {
                log_error("read_lock_count already 0\n");
        }

        if (sem_post(&(p_user_list_pool->sem)) == -1)
        {
                log_error("sem_post() error %d\n", errno);
                return -1;
        }
#endif

        return ret;
}

int user_list_rw_unlock(void)
{
#ifdef HAVE_SYSTEM_V
        struct sembuf sops[1];
#endif
        int ret = 0;

        if (p_user_list_pool == NULL)
        {
                log_error("p_user_list_pool not initialized\n");
                return -1;
        }

#ifdef HAVE_SYSTEM_V
        sops[0].sem_num = 1;                                     // w_sem
        sops[0].sem_op = -1;                                     // unlock
        sops[0].sem_flg = IPC_NOWAIT | SEM_UNDO; // no wait

        ret = semop(p_user_list_pool->semid, sops, 1);
        if (ret == -1 && errno != EAGAIN && errno != EINTR)
        {
                log_error("semop(unlock write) error %d\n", errno);
        }
#else
        if (sem_wait(&(p_user_list_pool->sem)) == -1)
        {
                if (errno != ETIMEDOUT && errno != EAGAIN && errno != EINTR)
                {
                        log_error("sem_wait() error %d\n", errno);
                }
                return -1;
        }

        if (p_user_list_pool->write_lock_count > 0)
        {
                p_user_list_pool->write_lock_count--;
        }
        else
        {
                log_error("write_lock_count already 0\n");
        }

        if (sem_post(&(p_user_list_pool->sem)) == -1)
        {
                log_error("sem_post() error %d\n", errno);
                return -1;
        }
#endif

        return ret;
}

int user_list_rd_lock(void)
{
        int timer = 0;
        int ret = -1;
        time_t tm_first_failure = 0;

        if (p_user_list_pool == NULL)
        {
                log_error("p_user_list_pool not initialized\n");
                return -1;
        }

        while (!SYS_server_exit)
        {
                ret = user_list_try_rd_lock(USER_LIST_TRY_LOCK_WAIT_TIME);
                if (ret == 0) // success
                {
                        break;
                }
                else if (errno == EAGAIN || errno == EINTR) // retry
                {
                        timer++;
                        if (timer % USER_LIST_TRY_LOCK_TIMES == 0)
                        {
                                log_error("user_list_try_rd_lock() tried %d times\n", timer);

                                if (time(NULL) - tm_first_failure >= USER_LIST_DEAD_LOCK_TIMEOUT)
                                {
                                        log_error("Unable to acquire rw_lock for %d seconds\n", time(NULL) - tm_first_failure);
#ifndef HAVE_SYSTEM_V
                                        user_list_reset_lock();
                                        log_error("Reset POSIX semaphore to resolve dead lock\n");
#endif
                                        break;
                                }
                        }
                        usleep(100 * 1000); // 0.1 second
                }
                else // failed
                {
                        log_error("user_list_try_rd_lock() failed\n");
                        break;
                }
        }

        return ret;
}

int user_list_rw_lock(void)
{
        int timer = 0;
        int ret = -1;
        time_t tm_first_failure = 0;

        if (p_user_list_pool == NULL)
        {
                log_error("p_user_list_pool not initialized\n");
                return -1;
        }

        while (!SYS_server_exit)
        {
                ret = user_list_try_rw_lock(USER_LIST_TRY_LOCK_WAIT_TIME);
                if (ret == 0) // success
                {
                        break;
                }
                else if (errno == EAGAIN || errno == EINTR) // retry
                {
                        timer++;
                        if (timer % USER_LIST_TRY_LOCK_TIMES == 0)
                        {
                                log_error("user_list_try_rw_lock() tried %d times\n", timer);

                                if (time(NULL) - tm_first_failure >= USER_LIST_DEAD_LOCK_TIMEOUT)
                                {
                                        log_error("Unable to acquire rw_lock for %d seconds\n", time(NULL) - tm_first_failure);
#ifndef HAVE_SYSTEM_V
                                        user_list_reset_lock();
                                        log_error("Reset POSIX semaphore to resolve dead lock\n");
#endif
                                        break;
                                }
                        }
                        usleep(100 * 1000); // 0.1 second
                }
                else // failed
                {
                        log_error("user_list_try_rw_lock() failed\n");
                        break;
                }
        }

        return ret;
}

#ifndef HAVE_SYSTEM_V
int user_list_reset_lock(void)
{
        if (p_user_list_pool == NULL)
        {
                log_error("p_user_list_pool not initialized\n");
                return -1;
        }

        if (sem_destroy(&(p_user_list_pool->sem)) == -1)
        {
                log_error("sem_destroy() error (%d)\n", errno);
        }

        p_user_list_pool->read_lock_count = 0;
        p_user_list_pool->write_lock_count = 0;

        if (sem_init(&(p_user_list_pool->sem), 1, 1) == -1)
        {
                log_error("sem_init() error (%d)\n", errno);
        }

        return 0;
}
#endif

int query_user_list(int page_id, USER_INFO *p_users, int *p_user_count, int *p_page_count)
{
        int ret = 0;

        if (p_users == NULL || p_user_count == NULL || p_page_count == NULL)
        {
                log_error("NULL pointer error\n");
                return -1;
        }

        *p_user_count = 0;
        *p_page_count = 0;

        // acquire lock of user list
        if (user_list_rd_lock() < 0)
        {
                log_error("user_list_rd_lock() error\n");
                return -2;
        }

        if (p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].user_count == 0)
        {
                // empty list
                ret = 0;
                goto cleanup;
        }

        *p_page_count = (p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].user_count + BBS_user_limit_per_page - 1) /
                                        BBS_user_limit_per_page;

        if (page_id < 0 || page_id >= *p_page_count)
        {
                log_error("Invalid page_id = %d, not in range [0, %d)\n", page_id, *p_page_count);
                ret = -3;
                goto cleanup;
        }

        *p_user_count = MIN(BBS_user_limit_per_page,
                                                p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].user_count -
                                                        page_id * BBS_user_limit_per_page);

        memcpy(p_users,
                   p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].users + page_id * BBS_user_limit_per_page,
                   sizeof(USER_INFO) * (size_t)(*p_user_count));

cleanup:
        // release lock of user list
        if (user_list_rd_unlock() < 0)
        {
                log_error("user_list_rd_unlock() error\n");
                ret = -1;
        }

        return ret;
}

int query_user_online_list(int page_id, USER_ONLINE_INFO *p_online_users, int *p_user_count, int *p_page_count)
{
        int ret = 0;

        if (p_online_users == NULL || p_user_count == NULL || p_page_count == NULL)
        {
                log_error("NULL pointer error\n");
                return -1;
        }

        *p_user_count = 0;
        *p_page_count = 0;

        // acquire lock of user list
        if (user_list_rd_lock() < 0)
        {
                log_error("user_list_rd_lock() error\n");
                return -2;
        }

        if (p_user_list_pool->user_online_list[p_user_list_pool->user_online_list_index_current].user_count == 0)
        {
                // empty list
                ret = 0;
                goto cleanup;
        }

        *p_page_count = (p_user_list_pool->user_online_list[p_user_list_pool->user_online_list_index_current].user_count + BBS_user_limit_per_page - 1) / BBS_user_limit_per_page;

        if (page_id < 0 || page_id >= *p_page_count)
        {
                log_error("Invalid page_id = %d, not in range [0, %d)\n", page_id, *p_page_count);
                ret = -3;
                goto cleanup;
        }

        *p_user_count = MIN(BBS_user_limit_per_page,
                                                p_user_list_pool->user_online_list[p_user_list_pool->user_online_list_index_current].user_count -
                                                        page_id * BBS_user_limit_per_page);

        memcpy(p_online_users,
                   p_user_list_pool->user_online_list[p_user_list_pool->user_online_list_index_current].users + page_id * BBS_user_limit_per_page,
                   sizeof(USER_ONLINE_INFO) * (size_t)(*p_user_count));

cleanup:
        // release lock of user list
        if (user_list_rd_unlock() < 0)
        {
                log_error("user_list_rd_unlock() error\n");
                ret = -1;
        }

        return ret;
}

int get_user_list_count(int *p_user_cnt)
{
        if (p_user_cnt == NULL)
        {
                log_error("NULL pointer error\n");
                return -1;
        }

        // acquire lock of user list
        if (user_list_rd_lock() < 0)
        {
                log_error("user_list_rd_lock() error\n");
                return -2;
        }

        *p_user_cnt = p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].user_count;

        // release lock of user list
        if (user_list_rd_unlock() < 0)
        {
                log_error("user_list_rd_unlock() error\n");
                return -2;
        }

        return 0;
}

int get_user_online_list_count(int *p_user_cnt, int *p_guest_cnt)
{
        if (p_user_cnt == NULL || p_guest_cnt == NULL)
        {
                log_error("NULL pointer error\n");
                return -1;
        }

        // acquire lock of user list
        if (user_list_rd_lock() < 0)
        {
                log_error("user_list_rd_lock() error\n");
                return -2;
        }

        *p_user_cnt = p_user_list_pool->user_online_list[p_user_list_pool->user_online_list_index_current].user_count;
        *p_guest_cnt = p_user_list_pool->user_online_list[p_user_list_pool->user_online_list_index_current].guest_count;

        // release lock of user list
        if (user_list_rd_unlock() < 0)
        {
                log_error("user_list_rd_unlock() error\n");
                return -2;
        }

        return 0;
}

int get_user_login_count(int *p_login_cnt)
{
        if (p_login_cnt == NULL)
        {
                log_error("NULL pointer error\n");
                return -1;
        }

        *p_login_cnt = p_user_list_pool->user_login_count;

        return 0;
}

int query_user_info(int32_t id, USER_INFO *p_user)
{
        int ret = 0;

        if (p_user == NULL)
        {
                log_error("NULL pointer error\n");
                return -1;
        }

        // acquire lock of user list
        if (user_list_rd_lock() < 0)
        {
                log_error("user_list_rd_lock() error\n");
                return -2;
        }

        if (id >= 0 && id < p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].user_count) // Found
        {
                *p_user = p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].users[id];
                ret = 1;
        }

        // release lock of user list
        if (user_list_rd_unlock() < 0)
        {
                log_error("user_list_rd_unlock() error\n");
                ret = -1;
        }

        return ret;
}

int query_user_info_by_uid(int32_t uid, USER_INFO *p_user, char *p_intro_buf, size_t intro_buf_len)
{
        int left;
        int right;
        int mid;
        int32_t id;
        int ret = 0;

        if (p_user == NULL)
        {
                log_error("NULL pointer error\n");
                return -1;
        }

        // acquire lock of user list
        if (user_list_rd_lock() < 0)
        {
                log_error("user_list_rd_lock() error\n");
                return -2;
        }

        left = 0;
        right = p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].user_count - 1;

        while (left < right)
        {
                mid = (left + right) / 2;
                if (uid < p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].index_uid[mid].uid)
                {
                        right = mid - 1;
                }
                else if (uid > p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].index_uid[mid].uid)
                {
                        left = mid + 1;
                }
                else // if (uid == p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].index_uid[mid].uid)
                {
                        left = mid;
                        break;
                }
        }

        if (uid == p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].index_uid[left].uid) // Found
        {
                id = p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].index_uid[left].id;
                *p_user = p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].users[id];
                ret = 1;

                if (p_intro_buf != NULL)
                {
                        strncpy(p_intro_buf, p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].users[id].intro, intro_buf_len - 1);
                        p_intro_buf[intro_buf_len - 1] = '\0';
                        p_user->intro = p_intro_buf;
                }
        }

        // release lock of user list
        if (user_list_rd_unlock() < 0)
        {
                log_error("user_list_rd_unlock() error\n");
                ret = -1;
        }

        return ret;
}

int query_user_info_by_username(const char *username_prefix, int max_user_cnt,
                                                                int32_t uid_list[], char username_list[][BBS_username_max_len + 1])
{
        int left;
        int right;
        int mid;
        int left_save;
        int ret = 0;
        size_t prefix_len;
        int comp;
        int i;

        if (username_prefix == NULL || uid_list == NULL || username_list == NULL)
        {
                log_error("NULL pointer error\n");
                return -1;
        }

        prefix_len = strlen(username_prefix);

        // acquire lock of user list
        if (user_list_rd_lock() < 0)
        {
                log_error("user_list_rd_lock() error\n");
                return -2;
        }

        left = 0;
        right = p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].user_count - 1;

        while (left < right)
        {
                mid = (left + right) / 2;
                comp = strncasecmp(username_prefix, p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].users[mid].username, prefix_len);
                if (comp < 0)
                {
                        right = mid - 1;
                }
                else if (comp > 0)
                {
                        left = mid + 1;
                }
                else // if (comp == 0)
                {
                        left = mid;
                        break;
                }
        }

        if (strncasecmp(username_prefix, p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].users[left].username, prefix_len) == 0) // Found
        {
#ifdef _DEBUG
                log_error("Debug: match found, pos=%d\n", left);
#endif

                left_save = left;
                right = left;
                left = 0;

                while (left < right)
                {
                        mid = (left + right) / 2;
                        comp = strncasecmp(username_prefix, p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].users[mid].username, prefix_len);
                        if (comp > 0)
                        {
                                left = mid + 1;
                        }
                        else if (comp == 0)
                        {
                                right = mid;
                        }
                        else // if (comp < 0)
                        {
                                log_error("Bug: left=%d right=%d mid=%d");
                                ret = -2;
                                goto cleanup;
                        }
                }

#ifdef _DEBUG
                log_error("Debug: first match found, pos=%d\n", right);
#endif

                left = left_save;
                left_save = right;
                right = p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].user_count - 1;

                while (left < right)
                {
                        mid = (left + right) / 2 + (left + right) % 2;
                        comp = strncasecmp(username_prefix, p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].users[mid].username, prefix_len);
                        if (comp < 0)
                        {
                                right = mid - 1;
                        }
                        else if (comp == 0)
                        {
                                left = mid;
                        }
                        else // if (comp > 0)
                        {
                                log_error("Bug: left=%d right=%d mid=%d");
                                ret = -2;
                                goto cleanup;
                        }
                }

#ifdef _DEBUG
                log_error("Debug: last match found, pos=%d\n", left);
#endif

                right = left;
                left = left_save;

                for (i = 0; i < max_user_cnt && left + i <= right; i++)
                {
                        uid_list[i] = p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].users[left + i].uid;
                        strncpy(username_list[i], p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].users[left + i].username, sizeof(username_list[i]) - 1);
                        username_list[i][sizeof(username_list[i]) - 1] = '\0';
                }
                ret = i;
        }

cleanup:
        // release lock of user list
        if (user_list_rd_unlock() < 0)
        {
                log_error("user_list_rd_unlock() error\n");
                ret = -1;
        }

        return ret;
}

int query_user_online_info(int32_t id, USER_ONLINE_INFO *p_user)
{
        int ret = 0;

        if (p_user == NULL)
        {
                log_error("NULL pointer error\n");
                return -1;
        }

        // acquire lock of user list
        if (user_list_rd_lock() < 0)
        {
                log_error("user_list_rd_lock() error\n");
                return -2;
        }

        if (id >= 0 && id < p_user_list_pool->user_online_list[p_user_list_pool->user_online_list_index_current].user_count) // Found
        {
                *p_user = p_user_list_pool->user_online_list[p_user_list_pool->user_online_list_index_current].users[id];
                ret = 1;
        }

        // release lock of user list
        if (user_list_rd_unlock() < 0)
        {
                log_error("user_list_rd_unlock() error\n");
                ret = -1;
        }

        return ret;
}

int query_user_online_info_by_uid(int32_t uid, USER_ONLINE_INFO *p_users, int *p_user_cnt, int start_id)
{
        int left;
        int right;
        int mid;
        int32_t id;
        int ret = 0;
        int i;
        int user_cnt;

        if (p_users == NULL || p_user_cnt == NULL)
        {
                log_error("NULL pointer error\n");
                return -1;
        }

        user_cnt = *p_user_cnt;
        *p_user_cnt = 0;

        // acquire lock of user list
        if (user_list_rd_lock() < 0)
        {
                log_error("user_list_rd_lock() error\n");
                return -2;
        }

        left = start_id;
        right = p_user_list_pool->user_online_list[p_user_list_pool->user_online_list_index_current].user_count - 1;

        while (left < right)
        {
                mid = (left + right) / 2;
                if (uid < p_user_list_pool->user_online_list[p_user_list_pool->user_online_list_index_current].index_uid[mid].uid)
                {
                        right = mid - 1;
                }
                else if (uid > p_user_list_pool->user_online_list[p_user_list_pool->user_online_list_index_current].index_uid[mid].uid)
                {
                        left = mid + 1;
                }
                else // if (uid == p_user_list_pool->user_online_list[p_user_list_pool->user_online_list_index_current].index_uid[mid].uid)
                {
                        left = mid;
                        break;
                }
        }

        if (uid == p_user_list_pool->user_online_list[p_user_list_pool->user_online_list_index_current].index_uid[left].uid)
        {
                right = left;
                left = start_id;

                while (left < right)
                {
                        mid = (left + right) / 2;
                        if (uid - 1 < p_user_list_pool->user_online_list[p_user_list_pool->user_online_list_index_current].index_uid[mid].uid)
                        {
                                right = mid;
                        }
                        else // if (uid - 1 >= p_user_list_pool->user_online_list[p_user_list_pool->user_online_list_index_current].index_uid[mid].uid)
                        {
                                left = mid + 1;
                        }
                }

                for (i = 0;
                         left < p_user_list_pool->user_online_list[p_user_list_pool->user_online_list_index_current].user_count && i < user_cnt &&
                         uid == p_user_list_pool->user_online_list[p_user_list_pool->user_online_list_index_current].index_uid[left].uid;
                         left++, i++)
                {
                        id = p_user_list_pool->user_online_list[p_user_list_pool->user_online_list_index_current].index_uid[left].id;
                        p_users[i] = p_user_list_pool->user_online_list[p_user_list_pool->user_online_list_index_current].users[id];
                }

                if (i > 0)
                {
                        *p_user_cnt = i;
                        ret = 1;
                }
        }

        // release lock of user list
        if (user_list_rd_unlock() < 0)
        {
                log_error("user_list_rd_unlock() error\n");
                ret = -1;
        }

        return ret;
}

int get_user_id_list(int32_t *p_uid_list, int *p_user_cnt, int start_uid)
{
        int left;
        int right;
        int mid;
        int ret = 0;
        int i;

        if (p_uid_list == NULL || p_user_cnt == NULL)
        {
                log_error("NULL pointer error\n");
                return -1;
        }

        // acquire lock of user list
        if (user_list_rd_lock() < 0)
        {
                log_error("user_list_rd_lock() error\n");
                return -2;
        }

        left = 0;
        right = p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].user_count - 1;

        while (left < right)
        {
                mid = (left + right) / 2;
                if (start_uid < p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].index_uid[mid].uid)
                {
                        right = mid - 1;
                }
                else if (start_uid > p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].index_uid[mid].uid)
                {
                        left = mid + 1;
                }
                else // if (start_uid == p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].index_uid[mid].uid)
                {
                        left = mid;
                        break;
                }
        }

        for (i = 0; i < *p_user_cnt && left + i < p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].user_count; i++)
        {
                p_uid_list[i] = p_user_list_pool->user_list[p_user_list_pool->user_list_index_current].index_uid[left + i].uid;
        }
        *p_user_cnt = i;

        // release lock of user list
        if (user_list_rd_unlock() < 0)
        {
                log_error("user_list_rd_unlock() error\n");
                ret = -1;
        }

        return ret;
}

int user_stat_update(void)
{
        return user_stat_map_update(&(p_user_list_pool->user_stat_map));
}

int user_article_cnt_inc(int32_t uid, int n)
{
        return user_stat_article_cnt_inc(&(p_user_list_pool->user_stat_map), uid, n);
}

int get_user_article_cnt(int32_t uid)
{
        const USER_STAT *p_stat;
        int ret;

        ret = user_stat_get(&(p_user_list_pool->user_stat_map), uid, &p_stat);
        if (ret < 0)
        {
                log_error("user_stat_get(uid=%d) error: %d\n", uid, ret);
                return -1;
        }
        else if (ret == 0) // user not found
        {
                return -1;
        }

        return p_stat->article_count;
}
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