subms-arena-allocator 0.10.0

use super::*;

#[test]
fn alloc_and_read_back() {
    let mut a = Bump::with_capacity(256);
    let x = a.alloc_copy(42u32);
    assert_eq!(*x, 42);
    let y = a.alloc_copy(99u64);
    assert_eq!(*y, 99);
}

#[test]
fn reset_rewinds() {
    let mut a = Bump::with_capacity(128);
    for i in 0..16u32 {
        let _ = a.alloc_copy(i);
    }
    a.reset();
    // After reset we can fit a full new round in the same chunk.
    for i in 0..16u32 {
        let _ = a.alloc_copy(i);
    }
}

#[test]
fn fixed_capacity_refuses_when_full() {
    let mut a = Bump::with_capacity(64);
    // Fill it: 64 bytes / 8 = 8 u64s.
    for _ in 0..8u64 {
        let _ = a.alloc_copy(0u64);
    }
    // The 9th must fail via the fallible path.
    assert!(a.try_alloc_copy(0u64).is_none());
}

#[test]
fn alignment_is_respected() {
    let mut a = Bump::with_capacity(256);
    let _x = a.alloc_copy(1u8);
    let p = a.alloc_copy(0xdeadbeef_u64) as *mut u64 as usize;
    assert_eq!(p % 8, 0, "u64 must be 8-byte-aligned");
}

#[test]
fn many_resets_reuse_chunk() {
    let mut a = Bump::with_capacity(256);
    let cap = a.capacity();
    for _ in 0..1000 {
        for i in 0..30u8 {
            let _ = a.alloc_copy(i);
        }
        a.reset();
    }
    // Capacity is fixed - reset never reallocates.
    assert_eq!(a.capacity(), cap);
}

#[test]
fn alloc_default_constructor() {
    let mut a: Bump = Bump::default();
    let _x = a.alloc_copy(42u32);
    assert!(a.capacity() > 0);
}

#[test]
fn alloc_zero_size_allowed() {
    let mut a = Bump::with_capacity(64);
    #[derive(Copy, Clone)]
    struct Marker;
    let _ = a.alloc_copy(Marker);
}

#[test]
fn aligned_after_many_unaligned() {
    let mut a = Bump::with_capacity(1024);
    for _ in 0..10 {
        let _ = a.alloc_copy(1u8);
    }
    let p = a.alloc_copy(0xff_u32) as *mut u32 as usize;
    assert_eq!(
        p % 4,
        0,
        "u32 must be 4-byte aligned even after byte-stream"
    );
}

#[test]
fn read_back_matches_written() {
    let mut a = Bump::with_capacity(256);
    let v1 = *a.alloc_copy(123u32);
    let v2 = *a.alloc_copy(456u32);
    assert_eq!(v1, 123);
    assert_eq!(v2, 456);
}

#[test]
fn used_tracks_cursor() {
    let mut a = Bump::with_capacity(256);
    assert_eq!(a.used(), 0);
    let _ = a.alloc_copy(0u64);
    assert_eq!(a.used(), 8);
    a.reset();
    assert_eq!(a.used(), 0);
}

#[test]
fn alloc_raw_honours_layout_size_and_alignment() {
    let mut a = Bump::with_capacity(256);
    let one = a.alloc_raw(Layout::from_size_align(1, 1).unwrap());
    let wide = a.alloc_raw(Layout::from_size_align(32, 32).unwrap());
    assert_eq!(wide as usize % 32, 0);
    assert!(wide as usize > one as usize);
    // `one` sits at the arena base (cursor 0). Alignment is honoured on the
    // absolute address, so the padding to a 32-byte boundary depends on the
    // base's own alignment (the chunk is 16-aligned, not 32-aligned). Assert
    // the accounting relation - cursor = wide's offset plus its 32 bytes -
    // rather than a fixed byte count that only holds for a 32-aligned base.
    let wide_off = wide as usize - one as usize;
    assert_eq!(a.used(), wide_off + 32);
    assert!(a.used() == 48 || a.used() == 64);
}

#[test]
#[should_panic(expected = "out of capacity")]
fn alloc_copy_panics_when_full() {
    let mut a = Bump::with_capacity(64);
    // 64 bytes / 8 = 8 u64s fit; the 9th overflows and must panic.
    for _ in 0..8u64 {
        let _ = a.alloc_copy(0u64);
    }
    let _ = a.alloc_copy(0u64);
}

#[test]
#[should_panic(expected = "out of capacity")]
fn alloc_raw_panics_when_request_exceeds_capacity() {
    let mut a = Bump::with_capacity(64);
    let _ = a.alloc_raw(Layout::from_size_align(65, 1).unwrap());
}

#[test]
fn total_capacity_aliases_capacity() {
    let a = Bump::with_capacity(256);
    assert_eq!(a.total_capacity(), a.capacity());
}

#[test]
fn try_alloc_raw_returns_none_when_request_exceeds_capacity() {
    let mut a = Bump::with_capacity(64);
    assert!(
        a.try_alloc_raw(Layout::from_size_align(65, 1).unwrap())
            .is_none()
    );
    // A rejected request must not advance the cursor.
    assert_eq!(a.used(), 0);
    assert!(
        a.try_alloc_raw(Layout::from_size_align(64, 1).unwrap())
            .is_some()
    );
    assert_eq!(a.used(), 64);
}