/**
* Checks if a value has exactly two bits set at pos1 and pos2, and no others.
* * Safe against:
* - 32-bit overflow (uses BigInt)
* - pos1 === pos2 (logic requires two distinct bits)
* - Out of bounds positions
* - Extra bits set elsewhere in the number
*/
function hasExactlyTwoBits(value: bigint, pos1: number, pos2: number): boolean {
// 1. Edge Case: Positions must be non-negative and distinct
if (pos1 < 0 || pos2 < 0 || pos1 === pos2) {
return false;
}
// 2. Create the target mask
// We shift 1n (BigInt 1) by the required positions
const mask = (1n << BigInt(pos1)) | (1n << BigInt(pos2));
// 3. Comparison
// If value matches the mask exactly, only those two bits are on.
return value === mask;
}
// --- Examples ---
const input = 0b1000100n; // Bits at index 2 and 6 are set
console.log(hasExactlyTwoBits(input, 2, 6)); // true
console.log(hasExactlyTwoBits(input, 2, 5)); // false (pos 5 is off)
console.log(0b1010100n === (1n<<2n | 1n<<6n)); // false (extra bit at pos 4)
/*
OUTPUT:
true
false
false
*/
