#include
#include
#include
int main(int argc, char const *argv[])
{
struct K_DATA{
int a;
char b[10];
short c;
}t1;
t1.a = 666;
strcpy(t1.b,"FEFE");
t1.c = 101;
printf("t1.a = %d,t1.b = %s,t1.c = %d\n",t1.a,t1.b,t1.c);
struct K_DATA1{
int a;
char b[10];
short c;
}t2 = {888,"AUAU",102};
printf("t2.a = %d,t2.b = %s,t2.c = %d\n",t2.a,t2.b,t2.c);
typedef struct K_DATA2{
int a;
char b[10];
short c;
}t3;
t3 m;
m.a = 666;
strcpy(m.b,"FEFE");
m.c = 101;
printf("m.a = %d,m.b = %s,m.c = %d\n",m.a,m.b,m.c);
typedef struct K_DATA3{
int a;
char b[10];
short c;
}t4;
t4 n = {888,"AUAU",102};
printf("n.a = %d,n.b = %s,n.c = %d\n",n.a,n.b,n.c);
return 0;
}
t1.a = 666,t1.b = FEFE,t1.c = 101
t2.a = 888,t2.b = AUAU,t2.c = 102
m.a = 666,m.b = FEFE,m.c = 101
n.a = 888,n.b = AUAU,n.c = 102
#include
#include
#include
struct K_DATA{
int a;
char b[10];
short c;
};
int main(int argc, char const *argv[])
{
struct K_DATA k[3] = {{666,"zhang",101},
{667,"li",102},
{668,"wang",103}};
for(int i = 0; i < 3; i++){
printf("k[%d].a = %d,k[%d].b = %s,k[%d].c = %d\n",\
i, k[i].a,i,k[i].b,i,k[i].c);
}
puts("--------------------------------------------------");
typedef struct K_DATA2{
int a;
char b[10];
short c;
}t3;
t3 m[3];
m[0].a = 666;
strcpy(m[0].b,"zhang");
m[0].c = 101;
m[1].a = 667;
strcpy(m[1].b,"li");
m[1].c = 102;
m[2].a = 668;
strcpy(m[2].b,"wang");
m[2].c = 103;
for(int i = 0; i < 3; i++){
printf("m[%d].a = %d,m[%d].b = %s,m[%d].c = %d\n",\
i, m[i].a,i,m[i].b,i,m[i].c);
}
puts("--------------------------------------------------");
typedef struct K_DATA3{
int a;
char b[10];
short c;
}t4;
t4 n[3] = {{666,"zhang",101},
{667,"li",102},
{668,"wang",103}};
for(int i = 0; i < 3; i++){
printf("n[%d].a = %d,n[%d].b = %s,n[%d].c = %d\n",\
i, n[i].a,i,n[i].b,i,n[i].c);
}
return 0;
}
k[0].a = 666,k[0].b = zhang,k[0].c = 101
k[1].a = 667,k[1].b = li,k[1].c = 102
k[2].a = 668,k[2].b = wang,k[2].c = 103
--------------------------------------------------
m[0].a = 666,m[0].b = zhang,m[0].c = 101
m[1].a = 667,m[1].b = li,m[1].c = 102
m[2].a = 668,m[2].b = wang,m[2].c = 103
--------------------------------------------------
n[0].a = 666,n[0].b = zhang,n[0].c = 101
n[1].a = 667,n[1].b = li,n[1].c = 102
n[2].a = 668,n[2].b = wang,n[2].c = 103
- 结构体所有成员清0：
- 需要调用C语言的
库函数memset()；
- 该函数功能是：复制
字符c到指针str所指向地址的前n个字符；
void *memset(void *str, int c, size_t n)
#include
#include
#include
typedef struct K_DATA{
int a;
char b[10];
short c;
char *s;
}t1;
int main(int argc, char const *argv[])
{
t1 k[3] = {{666,"zhang",101},
{667,"li",102},
{668,"wang",103}};
for(int i = 0; i < 3; i++){
printf("k[%d].a = %d,k[%d].b = %s,k[%d].c = %d\n",\
i, k[i].a,i,k[i].b,i,k[i].c);
}
memset(k,0,sizeof(k));
puts("--------------------------------------------------");
for(int i = 0; i < 3; i++){
printf("k[%d].a = %d,k[%d].b = %s,k[%d].c = %d\n",\
i, k[i].a,i,k[i].b,i,k[i].c);
}
puts("--------------------------------------------------");
struct K_DATA *p = (struct K_DATA *)malloc(sizeof(struct K_DATA ));
printf("p = %p\n",p);
p->a = 666;
p->s = "li";
p->c = 101;
printf("%d %s %d\n", p->a, p->s,p->c);
memset(p,0,sizeof(t1));
printf("%d %s %d\n", p->a, p->s,p->c);
free(p);
p = NULL;
printf("p = %p\n",p);
return 0;
}
k[0].a = 666,k[0].b = zhang,k[0].c = 101
k[1].a = 667,k[1].b = li,k[1].c = 102
k[2].a = 668,k[2].b = wang,k[2].c = 103
--------------------------------------------------
k[0].a = 0,k[0].b = ,k[0].c = 0
k[1].a = 0,k[1].b = ,k[1].c = 0
k[2].a = 0,k[2].b = ,k[2].c = 0
--------------------------------------------------
p = 0x55ac015f3670
666 li 101
0 (null) 0
p = (nil)
- 结构体成员在内存中的对齐：
- PC为32位系统：
- 情况1：所有的成员都小于4个字节，按照最大的成员所占内存空间大小对齐；
- 情况2：有成员大于或者等于4个字节，按照4个字节大小对齐；
- 注意：
- char（占1个字节）和short（占2个字节）连续存储的情况；
- PC为64位系统：
- 在32位系统的基础上，按照最大的成员所占内存空间大小对齐；
- 结构体嵌套结构体对齐的情况：
- 示例代码：
#include
struct K1{
short a;
short b;
short c;
};
struct K2{
struct K1 d;
char e;
int f;
};
struct K3{
int a;
short b;
};
struct K4{
struct K3 d;
char e;
int f;
};
int main(int argc, const char *argv[])
{
printf("sizeof(struct K2) = %d\n", sizeof(struct K2));
struct K2 m;
printf("&m.d.a = %p\n", &m.d.a);
printf("&m.d.b = %p\n", &m.d.b);
printf("&m.d.c = %p\n", &m.d.c);
printf("&m.d = %p\n", &m.d);
printf("&m.e = %p\n", &m.e);
printf("&m.f = %p\n", &m.f);
puts("-----------------------------------------------");
printf("sizeof(struct K4) = %d\n", sizeof(struct K4));
struct K4 n;
printf("&n.d.a = %p\n", &n.d.a);
printf("&n.d.b = %p\n", &n.d.b);
printf("&n.d = %p\n", &n.d);
printf("&n.e = %p\n", &n.e);
printf("&n.f = %p\n", &n.f);
return 0;
}
sizeof(struct K2) = 12
&m.d.a = 0xffb61d80
&m.d.b = 0xffb61d82
&m.d.c = 0xffb61d84
&m.d = 0xffb61d80
&m.e = 0xffb61d86
&m.f = 0xffb61d88
-----------------------------------------------
sizeof(struct K4) = 16
&n.d.a = 0xffb61d8c
&n.d.b = 0xffb61d90
&n.d = 0xffb61d8c
&n.e = 0xffb61d94
&n.f = 0xffb61d98
- 结构体成员位域：
- 可以应用到压缩结构体，比如将一个字节拆成八个比特位使用；
- 示例代码：
#include
typedef struct Test
{
unsigned char k1:1;
unsigned char k2:1;
unsigned char k3:1;
unsigned char k4:1;
unsigned char k5:1;
unsigned char k6:1;
unsigned char k7:1;
unsigned char k8:1;
}t1;
int main(int argc, char const *argv[])
{
printf("sizeof(t1) = %ld\n",sizeof(t1));
return 0;
}
sizeof(t1) = 1
#include
int my_mul(int x,int y){
return x * y;
}
int my_div(int x,int y){
return x / y;
}
typedef struct K_DATA{
int(*p)(int,int);
}t1;
int main(int argc, char const *argv[])
{
t1 m;
m.p = my_mul;
t1 n;
n.p = my_div;
printf("my_mul = %d,my_div = %d\n",m.p(15,15),n.p(10,2));
return 0;
}
my_mul = 225,my_div = 5
