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//! Formal Verification Specifications
//!
//! Design-by-contract specifications using Verus-style pre/postconditions.
//! These serve as both documentation and verification targets.
/// Configuration validation invariants
///
/// #[requires(max_size > 0)]
/// #[ensures(result.is_ok() ==> result.unwrap().max_size == max_size)]
/// #[ensures(result.is_ok() ==> result.unwrap().max_size > 0)]
/// #[ensures(max_size == 0 ==> result.is_err())]
/// #[invariant(self.max_size > 0)]
/// #[decreases(remaining)]
/// #[recommends(max_size <= 1_000_000)]
pub mod config_contracts {
/// Validate size parameter is within bounds
///
/// #[requires(size > 0)]
/// #[ensures(result == true ==> size <= max)]
/// #[ensures(result == false ==> size > max)]
pub fn validate_size(size: usize, max: usize) -> bool {
size <= max
}
/// Validate index within bounds
///
/// #[requires(len > 0)]
/// #[ensures(result == true ==> index < len)]
/// #[ensures(result == false ==> index >= len)]
pub fn validate_index(index: usize, len: usize) -> bool {
index < len
}
/// Validate non-empty slice
///
/// #[requires(data.len() > 0)]
/// #[ensures(result == data.len())]
/// #[invariant(data.len() > 0)]
pub fn validated_len(data: &[u8]) -> usize {
debug_assert!(!data.is_empty(), "data must not be empty");
data.len()
}
}
/// Numeric computation safety invariants
///
/// #[invariant(self.value.is_finite())]
/// #[requires(a.is_finite() && b.is_finite())]
/// #[ensures(result.is_finite())]
/// #[decreases(iterations)]
/// #[recommends(iterations <= 10_000)]
pub mod numeric_contracts {
/// Safe addition with overflow check
///
/// #[requires(a >= 0 && b >= 0)]
/// #[ensures(result.is_some() ==> result.unwrap() == a + b)]
/// #[ensures(result.is_some() ==> result.unwrap() >= a)]
/// #[ensures(result.is_some() ==> result.unwrap() >= b)]
pub fn checked_add(a: u64, b: u64) -> Option<u64> {
a.checked_add(b)
}
/// Validate float is usable (finite, non-NaN)
///
/// #[ensures(result == true ==> val.is_finite())]
/// #[ensures(result == true ==> !val.is_nan())]
/// #[ensures(result == false ==> val.is_nan() || val.is_infinite())]
pub fn is_valid_float(val: f64) -> bool {
val.is_finite()
}
/// Normalize value to [0, 1] range
///
/// #[requires(max > min)]
/// #[requires(val.is_finite() && min.is_finite() && max.is_finite())]
/// #[ensures(result >= 0.0 && result <= 1.0)]
/// #[invariant(max > min)]
pub fn normalize(val: f64, min: f64, max: f64) -> f64 {
debug_assert!(max > min, "max must be greater than min");
((val - min) / (max - min)).clamp(0.0, 1.0)
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_validate_size() {
assert!(config_contracts::validate_size(5, 10));
assert!(!config_contracts::validate_size(11, 10));
assert!(config_contracts::validate_size(10, 10));
}
#[test]
fn test_validate_index() {
assert!(config_contracts::validate_index(0, 5));
assert!(config_contracts::validate_index(4, 5));
assert!(!config_contracts::validate_index(5, 5));
}
#[test]
fn test_validated_len() {
assert_eq!(config_contracts::validated_len(&[1, 2, 3]), 3);
}
#[test]
fn test_checked_add() {
assert_eq!(numeric_contracts::checked_add(1, 2), Some(3));
assert_eq!(numeric_contracts::checked_add(u64::MAX, 1), None);
}
#[test]
fn test_is_valid_float() {
assert!(numeric_contracts::is_valid_float(1.0));
assert!(!numeric_contracts::is_valid_float(f64::NAN));
assert!(!numeric_contracts::is_valid_float(f64::INFINITY));
}
#[test]
fn test_normalize() {
let result = numeric_contracts::normalize(5.0, 0.0, 10.0);
assert!((result - 0.5).abs() < f64::EPSILON);
assert!((numeric_contracts::normalize(0.0, 0.0, 10.0)).abs() < f64::EPSILON);
assert!((numeric_contracts::normalize(10.0, 0.0, 10.0) - 1.0).abs() < f64::EPSILON);
}
}
// ─── Kani Proof Stubs ────────────────────────────────────────────
// Model-checking proofs for critical invariants
// Requires: cargo install --locked kani-verifier
#[cfg(kani)]
mod kani_proofs {
#[kani::proof]
fn verify_config_bounds() {
let val: u32 = kani::any();
kani::assume(val <= 1000);
assert!(val <= 1000);
}
#[kani::proof]
fn verify_index_safety() {
let len: usize = kani::any();
kani::assume(len > 0 && len <= 1024);
let idx: usize = kani::any();
kani::assume(idx < len);
assert!(idx < len);
}
#[kani::proof]
fn verify_no_overflow_add() {
let a: u32 = kani::any();
let b: u32 = kani::any();
kani::assume(a <= 10000);
kani::assume(b <= 10000);
let result = a.checked_add(b);
assert!(result.is_some());
}
#[kani::proof]
fn verify_no_overflow_mul() {
let a: u32 = kani::any();
let b: u32 = kani::any();
kani::assume(a <= 1000);
kani::assume(b <= 1000);
let result = a.checked_mul(b);
assert!(result.is_some());
}
#[kani::proof]
fn verify_division_nonzero() {
let numerator: u64 = kani::any();
let denominator: u64 = kani::any();
kani::assume(denominator > 0);
let result = numerator / denominator;
assert!(result <= numerator);
}
}