C语言中memcpy 函数的用法详解
C语言中memcpy 函数的用法详解
memcpy(内存拷贝函数)
c和c++使用的内存拷贝函数，memcpy函数的功能是从源src所指的内存地址的起始位置开始拷贝n个字节到目标dest所指的内存地址的起始位置中。
void* memcpy(void* destination, const void* source, size_t num);
void* dest 目标内存 const void* src 源内存 size_t num 字节个数
库中实现的memcpy函数
struct {
char name[40];
int age;
} person, person_copy;
int main()
{
char myname[] = "Pierre de Fermat";
/* using memcpy to copy string: */
memcpy(person.name, myname, strlen(myname) + 1);
person.age = 46;
/* using memcpy to copy structure: */
memcpy(&person_copy, &person, sizeof(person));
printf("person_copy: %s, %d \n", person_copy.name, person_copy.age);
system("pause");
return 0;
}
模拟实现memcpy函数
void* My_memcpy(void* dest, const void* src, size_t num)
{
assert(dest);
assert(src);
void* p = dest;
while (num--)
{
*(char*)dest = *(char*)src;
dest = (char*)dest + 1;
src = (char*)src + 1;
}
return p;
}
int main()
{
char dest[56];
char src[] = "abcb xxxx zzzzzzzzzzzzy";
printf("%s\n", My_memcpy(dest, src, strlen(src) + 1));
system("pause");
return 0;
}
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