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Advanced Programming Techniques in D

Anonymous Unions and Dissecting Other Members

Explore how anonymous unions in D enable multiple members to share the same memory space, and learn techniques for dissecting complex data types. Understand practical uses such as breaking down IPv4 addresses into bytes, recognizing the impact of system endianness, and managing memory efficiently using unions. This lesson guides you through the safe and effective application of unions for advanced memory and data manipulation in D.

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Anonymous unions

Anonymous unions specify what members of a user-defined type share the same area:

D
import std.stdio;



struct S {

    int first;

    

    union {

        int second;

        int third; 

    }

}



void main () {

    writeln(S.sizeof);

}

The last two members of S share the same area. So, the size of the struct is a total of two ints: 4 bytes needed for first and another 4 bytes to be shared by second and third.

Dissecting other members

Unions can be used for accessing individual bytes of variables of other types. For example, they make it easy to access the 4 bytes of an IPv4 address individually.

The ...