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。
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：
#include // 获取结构体成员大小#define GET_MEMBER_SIZE(type, member) sizeof(((type*)0)->member)// 获取结构体成员偏移量#define GET_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：
// 微信公众号：嵌入式大杂烩#include static 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：
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：
// 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, '\0', 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：
日志输出常常需要带一些格式。最简单的方式如：
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
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：
// 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！
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