IPv4 Address to Integer

1. Background Knowledge

An IPv4 address is a 32-bit identifier composed of four 8-bit segments called octets, typically written in dotted-decimal notation (e.g., 192.168.1.1). Each octet ranges from 0 to 255. When stored or transmitted in network byte order, these four bytes are packed into a single 32-bit integer using big-endian representation, meaning the first octet occupies the most significant byte (bits 24–31), the second octet occupies bits 16–23, and so on.

The conversion from dotted-quad to integer is essentially a base-256 positional encoding. If the octets are $a, b, c, d$, the resulting integer is:

This mirrors how decimal digits work: the leftmost digit has the highest place value. In binary terms, you are concatenating four 8-bit chunks into one 32-bit word.

2. Algorithm Approach

The core pattern here is iterative base conversion or bit shifting. You can process the octets from left to right, accumulating the result by shifting the current value left by 8 bits and adding the next octet. This avoids explicitly computing powers of 256 and naturally handles the big-endian ordering.

Alternatively, you can compute the weighted sum directly using the formula above. Both approaches are valid; the shifting method is often preferred in systems programming because it maps directly to how hardware handles byte packing.

3. Step-by-Step Strategy