大家好,我是杂烩君。
本次我们再来分享几个实用的代码小片段。
快速获取结构体成员大小
获取结构体成员大小及偏移量的方式有多种。最简便的方式:
代码:
左右滑动查看全部代码>>>
// 微信公众号:嵌入式大杂烩#include// 获取结构体成员大小#defineGET_MEMBER_SIZE(type, member) sizeof(((type*)0)->member)// 获取结构体成员偏移量#defineGET_MEMBER_OFFSET(type, member)((size_t)(&(((type*)0)->member)))typedef struct _test_struct0{ char x; char y;char z;}test_struct0;typedef struct _test_struct1{ char a; char c;short b;int d; test_struct0 e;}test_struct1;int main(int arc, char *argv[]){ printf(“GET_MEMBER_SIZE(test_struct1, a) = %ld”, GET_MEMBER_SIZE(test_struct1, a));printf(“GET_MEMBER_SIZE(test_struct1, c) = %ld”, GET_MEMBER_SIZE(test_struct1, c)); printf(“GET_MEMBER_SIZE(test_struct1, b) = %ld”, GET_MEMBER_SIZE(test_struct1, b)); printf(“GET_MEMBER_SIZE(test_struct1, d) = %ld”, GET_MEMBER_SIZE(test_struct1, d));printf(“GET_MEMBER_SIZE(test_struct1, e) = %ld”, GET_MEMBER_SIZE(test_struct1, e));printf(“test_struct1 size = %ld”, sizeof(test_struct1)); printf(“GET_MEMBER_OFFSET(a): %ld”, GET_MEMBER_OFFSET(test_struct1, a)); printf(“GET_MEMBER_OFFSET(c): %ld”, GET_MEMBER_OFFSET(test_struct1, c)); printf(“GET_MEMBER_OFFSET(b): %ld”, GET_MEMBER_OFFSET(test_struct1, b)); printf(“GET_MEMBER_OFFSET(d): %ld”, GET_MEMBER_OFFSET(test_struct1, d)); printf(“GET_MEMBER_OFFSET(e): %ld”, GET_MEMBER_OFFSET(test_struct1, e)); return 0;}
运行结果:
文件操作
文件操作平时用得很多,为了方便使用,可以自己根据实际需要再封装一层:
代码:
左右滑动查看全部代码>>>
// 微信公众号:嵌入式大杂烩#includestatic int file_opt_write(const char *filename, void *ptr, int size){ FILE *fp;size_t num;fp = fopen(filename, “wb”);if(NULL == fp){printf(“open %s file error!”, filename);return -1; }num = fwrite(ptr, 1, size, fp);if(num != size){fclose(fp);printf(“write %s file error!”, filename);return -1;} fclose(fp);return num;}static int file_opt_read(const char *filename, void *ptr, int size){FILE *fp;size_t num;fp = fopen(filename, “rb”);if(NULL == fp){printf(“open %s file error!”, filename);return -1;}num = fread(ptr, 1, size, fp);if(num != size){fclose(fp);printf(“write %s file error!”, filename);return -1;} fclose(fp);return num;}typedef struct _test_struct{ char a; char c;short b;int d;}test_struct;int main(int arc, char *argv[]){#define FILE_NAME”./test_file”test_struct write_data = {0};write_data.a = 1;write_data.b = 2;write_data.c = 3;write_data.d = 4;printf(“write_data.a = %d”, write_data.a);printf(“write_data.b = %d”, write_data.b);printf(“write_data.c = %d”, write_data.c);printf(“write_data.d = %d”, write_data.d);file_opt_write(FILE_NAME, (test_struct*)&write_data, sizeof(test_struct));test_struct read_data = {0};file_opt_read(FILE_NAME, (test_struct*)&read_data, sizeof(test_struct));printf(“read_data.a = %d”, read_data.a);printf(“read_data.b = %d”, read_data.b);printf(“read_data.c = %d”, read_data.c);printf(“read_data.d = %d”, read_data.d); return 0;}
运行结果:
嵌入式物联网需要学的东西真的非常多,千万不要学错了路线和内容,导致工资要不上去!
无偿分享大家一个资料包,差不多150多G。里面学习内容、面经、项目都比较新也比较全!某鱼上买估计至少要好几十。
点击这里找小助理0元领取:嵌入式物联网学习资料(头条)
进度条
有时候,加上进度条可以比较方便知道当前的下载进度、写入文件的进度等。
代码:
左右滑动查看全部代码>>>
// 微信公众号:嵌入式大杂烩#include #include #include typedef struct _progress{int cur_size;int sum_size;}progress_t;void progress_bar(progress_t *progress_data){int percentage = 0;int cnt = 0;char proc[102];memset(proc, ”, sizeof(proc));percentage = (int)(progress_data->cur_size * 100 / progress_data->sum_size);printf(“percentage = %d %%”, percentage);if (percentage <= 100){while (cnt <= percentage){printf("[%-100s] [%d%%]r", proc, cnt);fflush(stdout);proc[cnt] = '#';usleep(100000);cnt++;}}printf("");}int main(int arc, char *argv[]){progress_t progress_test = {0};progress_test.cur_size = 65;progress_test.sum_size = 100;progress_bar(&progress_test);return 0;}
运行结果:
日志输出
日志输出常常需要带一些格式。最简单的方式如:
代码:
左右滑动查看全部代码>>>
// 微信公众号:嵌入式大杂烩#include#define LOG_D(fmt, args…) do{printf(” “, __FILE__, __LINE__, __FUNCTION__);printf(fmt, ##args);}while(0)int main(int arc, char *argv[]){char ch = ‘a’;char str[10] = “ZhengN”;float float_val = 10.10;int num = 88;double double_val = 10.123456;LOG_D(“字符为 %c “, ch);LOG_D(“字符串为 %s ” , str);LOG_D(“浮点数为 %f “, float_val);LOG_D(“整数为 %d” , num);LOG_D(“双精度值为 %lf “, double_val);LOG_D(“八进制值为 %o “, num);LOG_D(“十六进制值为 %x “, num); return 0;}
运行结果:
可阅读往期文章:
C语言、嵌入式中几个非常实用的宏技巧
一个简单的日志模块
后台运行生成core文件
这个是我们上一篇文章分享一种你可能不知道的bug定位方法介绍的,方便大家使用,也汇总在这里。
代码:
左右滑动查看全部代码>>>
// 微信公众号:嵌入式大杂烩#include #include #include #include #define SHELL_CMD_CONF_CORE_FILE”echo /var/core-%e-%p-%t > /proc/sys/kernel/core_pattern”#define SHELL_CMD_DEL_CORE_FILE “rm -f /var/core*”static int enable_core_dump(void){int ret = -1;int resource = RLIMIT_CORE;struct rlimit rlim;rlim.rlim_cur = 1 ? RLIM_INFINITY : 0;rlim.rlim_max = 1 ? RLIM_INFINITY : 0;system(SHELL_CMD_DEL_CORE_FILE);if (0 != setrlimit(resource, &rlim)){printf(“setrlimit error!”);return -1;}else{system(SHELL_CMD_CONF_CORE_FILE);printf(“SHELL_CMD_CONF_CORE_FILE”);return 0;}return ret;}int main(int argc, char **argv){enable_core_dump();printf(“==================segmentation fault test==================”);int *p = NULL;*p = 1234;return 0;}
以上就是本次分享的几个小的代码片段。
期待你的三连支持!
原文作者:杂烩君
作品来源:嵌入式大杂烩
来源链接:https://mp.weixin.qq.com/s/_YIlvFdVYPLAUkyGsn3u3g