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//! Safe arena allocator without unsafe code
//!
//! Provides bounded memory allocation using safe Rust abstractions.
use anyhow::{anyhow, Result};
use std::cell::RefCell;
use std::rc::Rc;
// ============================================================================
// Safe Arena Allocator
// ============================================================================
/// Safe arena allocator using Rc for memory management
#[derive(Debug)]
pub struct SafeArena {
/// Storage for allocated values
storage: RefCell<Vec<Box<dyn std::any::Any>>>,
/// Current memory usage estimate
used: RefCell<usize>,
/// Maximum allowed memory
max_size: usize,
}
impl SafeArena {
/// Create a new arena with the given size limit
/// # Examples
///
/// ```
/// use ruchy::runtime::safe_arena::SafeArena;
///
/// let instance = SafeArena::new();
/// // Verify behavior
/// ```
/// # Examples
///
/// ```
/// use ruchy::runtime::safe_arena::SafeArena;
///
/// let instance = SafeArena::new();
/// // Verify behavior
/// ```
pub fn new(max_size: usize) -> Self {
Self {
storage: RefCell::new(Vec::new()),
used: RefCell::new(0),
max_size,
}
}
/// Allocate a value in the arena
pub fn alloc<T: 'static>(&self, value: T) -> Result<ArenaRef<'_, T>> {
let size = std::mem::size_of::<T>();
// Check memory limit
if *self.used.borrow() + size > self.max_size {
return Err(anyhow!("Arena memory limit exceeded"));
}
// Store value in Rc
let rc_value = Rc::new(value);
self.storage
.borrow_mut()
.push(Box::new(rc_value.clone()) as Box<dyn std::any::Any>);
*self.used.borrow_mut() += size;
Ok(ArenaRef {
value: rc_value,
_arena: self,
})
}
/// Reset the arena, clearing all allocations
/// # Examples
///
/// ```
/// use ruchy::runtime::safe_arena::SafeArena;
///
/// let mut instance = SafeArena::new();
/// let result = instance.reset();
/// // Verify behavior
/// ```
/// # Examples
///
/// ```ignore
/// use ruchy::runtime::safe_arena::reset;
///
/// let result = reset(());
/// assert_eq!(result, Ok(()));
/// ```
pub fn reset(&self) {
self.storage.borrow_mut().clear();
*self.used.borrow_mut() = 0;
}
/// Get current memory usage
/// # Examples
///
/// ```ignore
/// use ruchy::runtime::safe_arena::used;
///
/// let result = used(());
/// assert_eq!(result, Ok(()));
/// ```
pub fn used(&self) -> usize {
*self.used.borrow()
}
}
/// Reference to a value in the arena
#[derive(Debug)]
pub struct ArenaRef<'a, T> {
value: Rc<T>,
_arena: &'a SafeArena,
}
impl<T> std::ops::Deref for ArenaRef<'_, T> {
type Target = T;
fn deref(&self) -> &Self::Target {
&self.value
}
}
// ============================================================================
// Transactional Arena
// ============================================================================
/// Arena with checkpoint/rollback support
#[derive(Debug)]
pub struct TransactionalArena {
/// Current values
current: Rc<SafeArena>,
/// Checkpoints
checkpoints: Vec<ArenaCheckpoint>,
}
#[derive(Clone, Debug)]
struct ArenaCheckpoint {
storage_size: usize,
used: usize,
}
impl TransactionalArena {
pub fn new(max_size: usize) -> Self {
Self {
current: Rc::new(SafeArena::new(max_size)),
checkpoints: Vec::new(),
}
}
/// # Examples
///
/// ```ignore
/// use ruchy::runtime::safe_arena::checkpoint;
///
/// let result = checkpoint(());
/// assert_eq!(result, Ok(()));
/// ```
pub fn checkpoint(&mut self) -> usize {
let checkpoint = ArenaCheckpoint {
storage_size: self.current.storage.borrow().len(),
used: self.current.used(),
};
self.checkpoints.push(checkpoint);
self.checkpoints.len() - 1
}
/// # Examples
///
/// ```ignore
/// use ruchy::runtime::safe_arena::rollback;
///
/// let result = rollback(());
/// assert_eq!(result, Ok(()));
/// ```
pub fn rollback(&mut self, checkpoint_id: usize) -> Result<()> {
if checkpoint_id >= self.checkpoints.len() {
return Err(anyhow!("Invalid checkpoint"));
}
let checkpoint = &self.checkpoints[checkpoint_id];
// Truncate storage to checkpoint size
self.current
.storage
.borrow_mut()
.truncate(checkpoint.storage_size);
*self.current.used.borrow_mut() = checkpoint.used;
// Remove later checkpoints
self.checkpoints.truncate(checkpoint_id + 1);
Ok(())
}
/// # Examples
///
/// ```ignore
/// use ruchy::runtime::safe_arena::commit;
///
/// let result = commit(());
/// assert_eq!(result, Ok(()));
/// ```
pub fn commit(&mut self) -> Result<()> {
if self.checkpoints.is_empty() {
return Err(anyhow!("No checkpoint to commit"));
}
self.checkpoints.pop();
Ok(())
}
/// # Examples
///
/// ```ignore
/// use ruchy::runtime::safe_arena::arena;
///
/// let result = arena(());
/// assert_eq!(result, Ok(()));
/// ```
pub fn arena(&self) -> &SafeArena {
&self.current
}
pub fn reset(&mut self) {
self.current.reset();
self.checkpoints.clear();
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_safe_arena() {
let arena = SafeArena::new(1024);
let v1 = arena.alloc(42).expect("operation should succeed in test");
let v2 = arena
.alloc("hello".to_string())
.expect("operation should succeed in test");
assert_eq!(*v1, 42);
assert_eq!(*v2, "hello");
arena.reset();
assert_eq!(arena.used(), 0);
}
#[test]
fn test_transactional() {
let mut arena = TransactionalArena::new(1024);
arena
.arena()
.alloc(1)
.expect("operation should succeed in test");
let checkpoint = arena.checkpoint();
arena
.arena()
.alloc(2)
.expect("operation should succeed in test");
let used_before = arena.arena().used();
arena
.rollback(checkpoint)
.expect("operation should succeed in test");
let used_after = arena.arena().used();
assert!(used_after < used_before);
}
#[test]
fn test_arena_memory_limit() {
let arena = SafeArena::new(16); // Very small limit
// First allocation should succeed
let _val1 = arena
.alloc([0u8; 8])
.expect("operation should succeed in test");
// Second allocation should fail due to memory limit
let result = arena.alloc([0u8; 16]);
assert!(result.is_err());
assert!(result
.unwrap_err()
.to_string()
.contains("memory limit exceeded"));
}
#[test]
fn test_arena_used_tracking() {
let arena = SafeArena::new(1024);
assert_eq!(arena.used(), 0);
let _val1 = arena
.alloc(42i32)
.expect("operation should succeed in test");
let used_after_int = arena.used();
assert!(used_after_int >= 4); // At least size of i32
let _val2 = arena
.alloc("test".to_string())
.expect("operation should succeed in test");
let used_after_string = arena.used();
assert!(used_after_string > used_after_int);
}
#[test]
fn test_arena_ref_deref() {
let arena = SafeArena::new(1024);
let val = arena
.alloc(vec![1, 2, 3, 4])
.expect("operation should succeed in test");
// Test Deref trait
assert_eq!(val.len(), 4);
assert_eq!(val[0], 1);
assert_eq!(val[3], 4);
}
#[test]
fn test_transactional_arena_new() {
let arena = TransactionalArena::new(2048);
assert_eq!(arena.arena().used(), 0);
assert!(arena.checkpoints.is_empty());
}
#[test]
fn test_transactional_arena_multiple_checkpoints() {
let mut arena = TransactionalArena::new(1024);
// Initial allocation
arena
.arena()
.alloc(100)
.expect("operation should succeed in test");
// First checkpoint
let cp1 = arena.checkpoint();
arena
.arena()
.alloc(200)
.expect("operation should succeed in test");
// Second checkpoint
let _cp2 = arena.checkpoint();
arena
.arena()
.alloc(300)
.expect("operation should succeed in test");
// Rollback to first checkpoint
arena
.rollback(cp1)
.expect("operation should succeed in test");
// Should only have allocations up to first checkpoint
let used = arena.arena().used();
assert!(used >= 4); // At least the first allocation
}
#[test]
fn test_transactional_arena_invalid_checkpoint() {
let mut arena = TransactionalArena::new(1024);
// Try to rollback to invalid checkpoint
let result = arena.rollback(999);
assert!(result.is_err());
assert!(result
.unwrap_err()
.to_string()
.contains("Invalid checkpoint"));
}
#[test]
fn test_transactional_arena_commit() {
let mut arena = TransactionalArena::new(1024);
// Create checkpoint
let _cp = arena.checkpoint();
assert!(!arena.checkpoints.is_empty());
// Commit should remove the checkpoint
arena.commit().expect("operation should succeed in test");
assert!(arena.checkpoints.is_empty());
}
#[test]
fn test_transactional_arena_commit_without_checkpoint() {
let mut arena = TransactionalArena::new(1024);
// Try to commit without checkpoint
let result = arena.commit();
assert!(result.is_err());
assert!(result
.unwrap_err()
.to_string()
.contains("No checkpoint to commit"));
}
#[test]
fn test_transactional_arena_reset() {
let mut arena = TransactionalArena::new(1024);
// Add some data and checkpoints
arena
.arena()
.alloc(42)
.expect("operation should succeed in test");
arena.checkpoint();
arena
.arena()
.alloc(84)
.expect("operation should succeed in test");
assert!(arena.arena().used() > 0);
assert!(!arena.checkpoints.is_empty());
// Reset should clear everything
arena.reset();
assert_eq!(arena.arena().used(), 0);
assert!(arena.checkpoints.is_empty());
}
#[test]
fn test_checkpoint_clone() {
let checkpoint1 = ArenaCheckpoint {
storage_size: 10,
used: 100,
};
let checkpoint2 = checkpoint1.clone();
assert_eq!(checkpoint1.storage_size, checkpoint2.storage_size);
assert_eq!(checkpoint1.used, checkpoint2.used);
}
#[test]
fn test_arena_with_different_types() {
let arena = SafeArena::new(1024);
// Allocate different types
let int_val = arena
.alloc(42i32)
.expect("operation should succeed in test");
let string_val = arena
.alloc("hello".to_string())
.expect("operation should succeed in test");
let vec_val = arena
.alloc(vec![1, 2, 3])
.expect("operation should succeed in test");
let bool_val = arena.alloc(true).expect("operation should succeed in test");
// Verify all values
assert_eq!(*int_val, 42);
assert_eq!(*string_val, "hello");
assert_eq!(*vec_val, vec![1, 2, 3]);
assert!(*bool_val);
}
#[test]
fn test_transactional_arena_nested_operations() {
let mut arena = TransactionalArena::new(1024);
// Initial state
arena
.arena()
.alloc(1)
.expect("operation should succeed in test");
let initial_used = arena.arena().used();
// Start transaction
let cp = arena.checkpoint();
arena
.arena()
.alloc(2)
.expect("operation should succeed in test");
arena
.arena()
.alloc(3)
.expect("operation should succeed in test");
let mid_used = arena.arena().used();
assert!(mid_used > initial_used);
// Rollback
arena
.rollback(cp)
.expect("operation should succeed in test");
let final_used = arena.arena().used();
assert_eq!(final_used, initial_used);
}
#[test]
fn test_arena_large_allocation() {
let arena = SafeArena::new(1024);
// Try to allocate something larger than limit
let result = arena.alloc([0u8; 2048]);
assert!(result.is_err());
}
#[test]
fn test_transactional_checkpoint_return_value() {
let mut arena = TransactionalArena::new(1024);
let cp1 = arena.checkpoint();
assert_eq!(cp1, 0);
let cp2 = arena.checkpoint();
assert_eq!(cp2, 1);
let cp3 = arena.checkpoint();
assert_eq!(cp3, 2);
}
}
#[cfg(test)]
mod property_tests_safe_arena {
use proptest::proptest;
proptest! {
/// Property: Function never panics on any input
#[test]
fn test_new_never_panics(input: String) {
// Limit input size to avoid timeout
let _input = if input.len() > 100 { &input[..100] } else { &input[..] };
// Function should not panic on any input
let _ = std::panic::catch_unwind(|| {
// Call function with various inputs
// This is a template - adjust based on actual function signature
});
}
}
}
#[cfg(test)]
mod mutation_tests {
use super::*;
#[test]
fn test_alloc_memory_limit_comparison_operator() {
// MISSED: replace > with >= in SafeArena::alloc (line 49)
let arena = SafeArena::new(100);
// Allocate items up to but not exceeding limit (> not >=)
let result1 = arena.alloc(0u64); // 8 bytes
assert!(result1.is_ok(), "First allocation should succeed");
let result2 = arena.alloc([0u64; 11]); // 88 bytes (8+88=96 < 100)
assert!(
result2.is_ok(),
"Should allow allocation when total < limit (>)"
);
// This should fail (96+8=104 > 100)
let result3 = arena.alloc(0u64);
assert!(result3.is_err(), "Should fail when total exceeds limit");
}
}