C library macro - offsetof ()
C standard library - <stddef.h>
description
C library macrooffsetof (type, member-designator) will generate a constant integer type size_t,which is a structural member of the structure relative to the beginning byte offset. Member by member-designator given, in the name of the structure type is given.
statement
Here is offsetof () macro statement.
offsetof(type, member-designator)
parameter
- type - this is a class type, wherein, member-designator is a valid member of the indicator.
- member-designator - which is a member of a class type indicator.
return value
This macro returns a value of typesize_t, showing the offset type of members.
Examples
The following example demonstrates offsetof () macro usage.
#include <stddef.h>
#include <stdio.h>
struct address {
char name[50];
char street[50];
int phone;
};
int main()
{
printf("address 结构中的 name 偏移 = %d 字节。\n",
offsetof(struct address, name));
printf("address 结构中的 street 偏移 = %d 字节。\n",
offsetof(struct address, street));
printf("address 结构中的 phone 偏移 = %d 字节。\n",
offsetof(struct address, phone));
return(0);
}
Let's compile and run the above program, which will result in the following:
address 结构中的 name 偏移 = 0 字节。 address 结构中的 street 偏移 = 50 字节。 address 结构中的 phone 偏移 = 100 字节。