获取2字节整数的高8位和低8位

unsigned short port = 8888;
printf("high Byte：%u，low Byte：%u\n", port >> 8, port & 0xFF);

拷贝字符串

char buf[512] = {0};
snprintf(buf, sizeof(buf), "%s", "hello world"); // 需要格式化字符串
snprintf(buf, sizeof(buf), "hello world"); // 不需要格式化字符串，直接拷贝字符串的话，可直接使用这种方式

避免僵尸进程

在父进程中，通过忽略SIGCHLD即可避免僵尸进程：

signal(SIGCHLD, SIG_IGN);

封装perror与exit

#define ERR_EXIT(m) \
  do \
  { \
    perror(m); \
    exit(EXIT_FAILURE); \
  } while(0)

打开一个文件，并按行读取

C语言方式

FILE *fp = fopen("miniftpd.conf", "r");
if (NULL == fp)
{
  ERR_EXIT("fopen");
}

char setting_line[1024] = {0};
while (NULL != fgets(setting_line, sizeof(setting_line), fp))
{
  // TODO：使用setting_line
  bzero(setting_line, sizeof(setting_line));
}

fclose(fp);

C++方式

Java方式

计算较小/大值

#define MIN(a, b) ((a) > (b) ? (b) : (a))

#define MAX(a, b) ((a) > (b) ? (a) : (b))

将错误信息输出到标准错误中

fprintf(stderr, "error: %s", "404");

计算一段代码执行所需要的时间

time_t startTime = clock();
// TODO：添加需要执行的代码
time_t endTime = clock();

cout << "time : " << double(endTime - startTime) / CLOCKS_PER_SEC << " s" << endl;

计算数组大小的宏函数

#define ARRAY_SIZE(array) (sizeof(array) / sizeof(array[0]))

使用命令映射代替if-else和switch

typedef struct ftpcmd
{
    const char *cmd;
    void (*cmd_handler)(session_t *sess);
} ftpcmd_t;

ftpcmd_t ctrl_cmds[] = {
        {"USER", do_user},
        {"PASS", do_pass},
};

int main()
{
    int size = ARRAY_SIZE(ctrl_cmds);
    for (int i = 0; i < size; ++i)
    {
        if (0 == strcmp(ctrl_cmds[i].cmd, sess->cmd))
        {
            if (NULL != ctrl_cmds[i].cmd_handler)
            {
                ctrl_cmds[i].cmd_handler(sess);
            }
        }
    }
    
    return 0;
}

可读性以及可扩展性较好的结构体数组初始化方式

typedef struct person
{
    const char *name;
    int age;
    bool gender;
    double salary;
} person_t;

person_t students[] = {
        [0] = {
                .name = "A",
                .age = 20,
                .gender = true,
                .salary = 10000.0,
              },
        [1] = {
                .name = "B",
                .age = 20,
                .gender = true,
                .salary = 10000.0,
        },
};

int main()
{
    int size = ARRAY_SIZE(students);
    for (int i = 0; i < size; ++i)
    {
        printf("%s\n", students[i].name);
    }

    return 0;
}

从特定格式字符串中读取数据

const char *ip_str = "127,0,0,1";
unsigned char ip_int[4];
sscanf(ip_str, "%u,%u,%u,%u", (unsigned int *)ip_int, (unsigned int *)(ip_int + 1), (unsigned int *)(ip_int + 2), (unsigned int *)(ip_int + 3));

struct sockaddr_in addr;
bzero(&addr, sizeof(addr));
unsigned char *p = (unsigned char *)&addr.sin_addr.s_addr;
p[0] = ip_int[0];
p[1] = ip_int[1];
p[2] = ip_int[2];
p[3] = ip_int[3];

char ip[16] = {0};
inet_ntop(AF_INET, &addr.sin_addr.s_addr, ip, sizeof(ip));
printf("ip = %s\n", ip); // 127.0.0.1