Compact State via Bitwise TypedArrays

Snippet

Compact State via Bitwise TypedArrays

Using bitwise operators on TypedArrays allows storing multiple boolean flags within a single byte. This is crucial for high-performance Node.js applications handling millions of states, as it significantly reduces memory footprint and improves CPU cache locality.

snippet.js

javascript

const PERMS = { READ: 1 << 0, WRITE: 1 << 1, DELETE: 1 << 2 };
const userStates = new Uint8Array(1024);
 
// Grant READ and WRITE
userStates[42] |= (PERMS.READ | PERMS.WRITE);
 
// Check for DELETE permission
const canDelete = (userStates[42] & PERMS.DELETE) !== 0;
 
// Toggle WRITE
userStates[42] ^= PERMS.WRITE;

nodejs

Breakdown

userStates[42] |= (PERMS.READ | PERMS.WRITE);

Combines two flags using bitwise OR and assigns them to the index.

(userStates[42] & PERMS.DELETE) !== 0;

Uses a bitwise AND mask to check if a specific bit is set to 1.

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Compact State via Bitwise TypedArrays

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