ReadCode-001: memcpy memset bzero

最新推荐文章于 2020-04-29 21:04:30 发布

原创最新推荐文章于 2020-04-29 21:04:30 发布 · 808 阅读

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#struct #pthreads #file #variables #fp #logging

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本文介绍了一段使用C语言实现的结构体和指针操作的示例代码，展示了如何定义结构体类型、初始化结构体成员、通过指针访问结构体成员以及进行数据复制的方法。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

struct student{
	int age;
	char name[15];
};

typedef struct student student_t;

int main(void) {
	student_t stu1, *stu1_ptr;
	stu1.age = 12;
	strcpy(stu1.name, "amao");
	stu1_ptr = &stu1;

	student_t *stu2_ptr = (student_t *) malloc(sizeof(student_t));
	memset(stu2_ptr, 0, sizeof(student_t));
	printf("%d %s\n", stu1_ptr->age, stu1_ptr->name);
	printf("%d %s\n", stu2_ptr->age, stu2_ptr->name);

	memcpy(stu2_ptr, stu1_ptr, sizeof(student_t));
	printf("%d %s\n", stu2_ptr->age, stu2_ptr->name);
	return EXIT_SUCCESS;
}

/* static variables */
#ifdef WITH_PTHREADS
  static pthread_mutex_t  log_lock = PTHREAD_MUTEX_INITIALIZER;
#else
  static int              log_lock;
#endif /* WITH_PTHREADS */
//-----------------------------------
#  define slurm_mutex_lock(mutex)
#  define slurm_mutex_unlock(mutex)
//-----------------------------------
/* return the FILE * of the current logfile (stderr if logging to stderr)
 */
FILE *log_fp(void)
{
	FILE *fp;
	slurm_mutex_lock(&log_lock);
	if (log->logfp)
		fp = log->logfp;
	else
		fp = stderr;
	slurm_mutex_unlock(&log_lock);
	return fp;
}
//-----------------------------------
/*
 * "Safe" version of malloc().
 *   size (IN)	number of bytes to malloc
 *   RETURN	pointer to allocate heap space
 */
void *slurm_xmalloc(size_t size, const char *file, int line, const char *func)
{
	void *new;
	int *p;


	xmalloc_assert(size >= 0 && size <= INT_MAX);
	MALLOC_LOCK();
	p = (int *)malloc(size + 2*sizeof(int));
	MALLOC_UNLOCK();
	if (!p) {
		/* don't call log functions here, we're probably OOM
		 */
		fprintf(log_fp(), "%s:%d: %s: xmalloc(%d) failed\n",
				file, line, func, (int)size);
		exit(1);
	}
	p[0] = XMALLOC_MAGIC;	/* add "secret" magic cookie */
	p[1] = (int)size;	/* store size in buffer */

	new = &p[2];
	memset(new, 0, size);
	return new;
}
//-----------------------------------
#define xmalloc(__sz) \
	slurm_xmalloc (__sz, __FILE__, __LINE__, __CURRENT_FUNC__)
//-----------------------------------
extern int jobacct_common_init_struct(struct jobacctinfo *jobacct,
				      jobacct_id_t *jobacct_id)
{
	if (!jobacct_id) {
		jobacct_id_t temp_id;
		temp_id.taskid = (uint16_t)NO_VAL;
		temp_id.nodeid = (uint32_t)NO_VAL;
		jobacct_id = &temp_id;
	}
	memset(jobacct, 0, sizeof(struct jobacctinfo));
	jobacct->sys_cpu_sec = 0;
	jobacct->sys_cpu_usec = 0;
	jobacct->user_cpu_sec = 0;
	jobacct->user_cpu_usec = 0;

	jobacct->max_vsize = 0;
	memcpy(&jobacct->max_vsize_id, jobacct_id, sizeof(jobacct_id_t));
	jobacct->tot_vsize = 0;
	jobacct->max_rss = 0;
	memcpy(&jobacct->max_rss_id, jobacct_id, sizeof(jobacct_id_t));
	jobacct->tot_rss = 0;
	jobacct->max_pages = 0;
	memcpy(&jobacct->max_pages_id, jobacct_id, sizeof(jobacct_id_t));
	jobacct->tot_pages = 0;
	jobacct->min_cpu = (uint32_t)NO_VAL;
	memcpy(&jobacct->min_cpu_id, jobacct_id, sizeof(jobacct_id_t));
	jobacct->tot_cpu = 0;

	return SLURM_SUCCESS;
}

extern struct jobacctinfo *jobacct_common_alloc_jobacct(
	jobacct_id_t *jobacct_id)
{
	struct jobacctinfo *jobacct = xmalloc(sizeof(struct jobacctinfo));
	jobacct_common_init_struct(jobacct, jobacct_id);
	return jobacct;
}