phoros 0.1.1

//! Zero-allocation ring buffer with XOR delta encoding and state rollback.
//!
//! `phoros` records state snapshots and byte-masked deltas into a
//! pre-allocated arena.
//!
//! # Quickstart
//!
//! ```
//! use phoros::bprb;
//!
//! let mut buf = bprb!(u64 => stack(1024)).unwrap();
//! buf.snapshot(&42u64).unwrap();
//! assert_eq!(buf.rollback_to(0).unwrap(), 42u64);
//! ```
//!
//! # Feature flags
//!
//! | Feature | Default | Enables |
//! |---------|---------|---------|
//! | `std` | Yes | `BoxedBPRB`, `std::error::Error` impls |
//! | `alloc` | Via `std` | `BoxedBPRB`, `bprb!()` boxed variant |
//! | `serde` | No | `Serialize`/`Deserialize` for `SlotType`, `SlotHeader`, `AnchorEntry`, error types |
//!
//! Bare `no_std` (no features) gives `StackBPRB` and `bprb!()` stack variant only.

#![cfg_attr(not(feature = "std"), no_std)]

extern crate alloc;

pub mod arena;
pub mod buffer;
pub mod codec;
pub mod error;
pub mod index;
pub mod slot;
pub mod storage;

pub use buffer::BPRB;
#[cfg(feature = "alloc")]
pub use buffer::BoxedBPRB;
pub use buffer::StackBPRB;
pub use buffer::{DEFAULT_ANCHOR_INTERVAL, DEFAULT_DELTA_THRESHOLD};
pub use error::{BufferError, CodecError, RollbackError};
pub use slot::SlotType;
pub use storage::ArenaStorage;

const _: () = assert!(
    core::mem::size_of::<arena::ArenaHeader>() == 32,
    "ArenaHeader must be exactly 32 bytes"
);

const _: () = assert!(
    core::mem::size_of::<slot::SlotHeader>() == 16,
    "SlotHeader must be exactly 16 bytes"
);

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn arena_header_size() {
        assert_eq!(core::mem::size_of::<arena::ArenaHeader>(), 32);
    }

    #[test]
    fn slot_header_size() {
        assert_eq!(core::mem::size_of::<slot::SlotHeader>(), 16);
    }

    #[test]
    fn anchor_entry_size() {
        assert_eq!(core::mem::size_of::<index::AnchorEntry>(), 16);
    }

    #[test]
    fn slot_kind_roundtrip() {
        assert_eq!(
            slot::SlotType::from_u8(0x01),
            Some(slot::SlotType::FullSnapshot)
        );
        assert_eq!(slot::SlotType::from_u8(0x02), Some(slot::SlotType::Delta));
        assert_eq!(slot::SlotType::from_u8(0x00), None);
        assert_eq!(slot::SlotType::from_u8(0xFF), None);
    }

    #[test]
    fn arena_header_magic() {
        let header = arena::ArenaHeader::new(1024);
        assert_eq!(header.magic, arena::ARENA_MAGIC);
        assert_eq!(header.version, arena::ARENA_VERSION);
        assert!(header.is_valid());
    }

    #[test]
    fn arena_header_roundtrip() {
        let header = arena::ArenaHeader::new(4096);
        let bytes = header.as_bytes();
        let restored = arena::ArenaHeader::from_bytes(bytes).unwrap();
        assert_eq!(restored.data_area_len, 4096);
        assert_eq!(restored.head_offset, 0);
        assert_eq!(restored.tail_offset, 0);
    }

    #[test]
    fn physical_offset_wrapping() {
        assert_eq!(arena::physical_offset(100, 50, 200), 150);
        assert_eq!(arena::physical_offset(150, 100, 200), 50);
        assert_eq!(arena::physical_offset(0, 0, 200), 0);
    }

    #[test]
    fn available_space_calculation() {
        assert_eq!(arena::available_space(50, 100, 200), 150);
        assert_eq!(arena::available_space(100, 50, 200), 50);
    }
}