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# Bitwise Operations
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Bitwise manipulation functions for IP addresses including NOT and OR operations with support for both IPv4 and IPv6 addresses and mixed-protocol operations.
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## Capabilities
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### Bitwise NOT Operation
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#### not
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Performs bitwise NOT (inversion) operation on an IP address, flipping all bits.
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```javascript { .api }
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/**
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 * Performs bitwise NOT operation on IP address
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 * @param {string} addr - IP address to invert
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 * @returns {string} Bitwise inverted IP address string
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 */
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function not(addr);
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```
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**Usage Examples:**
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```javascript
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const ip = require('ip');
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// IPv4 bitwise NOT
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console.log(ip.not('255.255.255.0')); // '0.0.0.255'
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console.log(ip.not('192.168.1.0')); // '63.87.254.255'
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console.log(ip.not('0.0.0.0')); // '255.255.255.255'
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// IPv6 bitwise NOT
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console.log(ip.not('ffff::')); // '::ffff:ffff:ffff:ffff'
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console.log(ip.not('::1')); // 'ffff:ffff:ffff:ffff:ffff:ffff:ffff:fffe'
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// Practical use case: Convert subnet mask to wildcard mask
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const subnetMask = '255.255.255.192';
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const wildcardMask = ip.not(subnetMask);
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console.log(wildcardMask); // '0.0.0.63'
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```
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### Bitwise OR Operation
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#### or
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Performs bitwise OR operation between two IP addresses, supporting same-protocol and mixed IPv4/IPv6 operations.
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```javascript { .api }
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/**
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 * Performs bitwise OR operation on two IP addresses
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 * @param {string} a - First IP address
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 * @param {string} b - Second IP address
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 * @returns {string} Result of bitwise OR operation
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 */
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function or(a, b);
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```
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**Usage Examples:**
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```javascript
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const ip = require('ip');
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// IPv4 bitwise OR
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console.log(ip.or('192.168.1.0', '0.0.0.255')); // '192.168.1.255'
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console.log(ip.or('10.0.0.0', '0.0.5.100')); // '10.0.5.100'
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console.log(ip.or('255.255.255.0', '0.0.0.63')); // '255.255.255.63'
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// IPv6 bitwise OR
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console.log(ip.or('::ff', '::abcd:dcba:abcd:dcba')); 
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// '::abcd:dcba:abcd:dcff'
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console.log(ip.or('ffff::', '::1')); 
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// 'ffff::1'
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// Mixed IPv4/IPv6 operations
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console.log(ip.or('0.0.0.255', '::abcd:dcba:abcd:dcba')); 
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// '::abcd:dcba:abcd:dcff'
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console.log(ip.or('192.168.1.100', '::ff')); 
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// '::c0a8:16ff'
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// Practical use case: Set specific bits in network address
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const networkAddr = '192.168.1.0';
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const hostBits = '0.0.0.100';
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const fullAddress = ip.or(networkAddr, hostBits);
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console.log(fullAddress); // '192.168.1.100'
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```
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## Advanced Usage Patterns
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### Subnet Calculation with Bitwise Operations
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```javascript
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const ip = require('ip');
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// Calculate broadcast address using OR operation
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const networkAddress = '192.168.1.128';  // /26 network
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const subnetMask = '255.255.255.192';    // /26 mask
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const wildcardMask = ip.not(subnetMask); // '0.0.0.63'
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const broadcastAddress = ip.or(networkAddress, wildcardMask);
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console.log(broadcastAddress); // '192.168.1.191'
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// Verify against subnet function
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const subnet = ip.subnet('192.168.1.128', subnetMask);
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console.log(subnet.broadcastAddress); // '192.168.1.191' (matches)
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```
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### Network Mask Manipulation
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```javascript
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const ip = require('ip');
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// Create custom network masks using bitwise operations
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const baseMask = '255.255.0.0';     // /16
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const additionalBits = '0.0.255.0'; // Additional /24 subnet bits
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const combinedMask = ip.or(baseMask, additionalBits);
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console.log(combinedMask); // '255.255.255.0' (/24)
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// Invert masks for wildcard operations
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const accessListMask = ip.not('255.255.255.240'); // /28 inverted
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console.log(accessListMask); // '0.0.0.15' (wildcard for /28)
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```