Struct PrivacyBudget 

pub struct PrivacyBudget { /* private fields */ }

Thread-safe differential-privacy budget tracker.

Epsilon and delta consumption are tracked with AtomicU64 using the f64::to_bits / f64::from_bits trick, so that the struct can be shared across threads without a Mutex.

Implementations

impl PrivacyBudget

pub fn new(epsilon_total: f64, delta_total: f64) -> Result<Self, BudgetError>

Create a new budget.

Errors

Returns BudgetError::InvalidBudget if:

• epsilon_total ≤ 0
• delta_total ≤ 0
• delta_total ≥ 1

pub fn epsilon_total(&self) -> f64

Total epsilon budget (immutable).

pub fn delta_total(&self) -> f64

Total delta budget (immutable).

pub fn epsilon_remaining(&self) -> f64

Epsilon remaining (may be slightly negative under concurrent load).

pub fn delta_remaining(&self) -> f64

Delta remaining.

pub fn is_exhausted(&self) -> bool

Returns true if either epsilon or delta remaining is ≤ 0.

pub fn consume(&self, epsilon: f64, delta: f64) -> Result<(), BudgetError>

Atomically consume epsilon and delta from the budget.

Uses a spin-loop via fetch_update to ensure the combined check-then-add is linearisable. Both values are consumed together or not at all (epsilon is rolled back on delta failure).

Errors

• BudgetError::BudgetExceeded if epsilon would push spent past the total.
• BudgetError::DeltaExceeded if delta would push spent past the total.

pub fn increment_round(&self) -> u64

Increment the round counter and return the new count.

pub fn snapshot(&self) -> BudgetSnapshot

Take an immutable snapshot of the current budget state.

Trait Implementations

impl Debug for PrivacyBudget

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.