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// NOTE: Any change to CACHE_LINE_SIZE should also be made to CacheAligned<T>

// CACHE_LINE_SIZE is the size of a cache line on this specific architecture.
#[cfg(target_arch = "x86")]
pub const CACHE_LINE_SIZE: usize = 64;
#[cfg(target_arch = "x86_64")]
pub const CACHE_LINE_SIZE: usize = 64;
#[cfg(target_arch = "mips")]
pub const CACHE_LINE_SIZE: usize = 32;
#[cfg(target_arch = "powerpc")]
pub const CACHE_LINE_SIZE: usize = 64; // maybe 128?
#[cfg(target_arch = "powerpc64")]
pub const CACHE_LINE_SIZE: usize = 128;
#[cfg(target_arch = "arm")]
pub const CACHE_LINE_SIZE: usize = 32;
#[cfg(target_arch = "aarch64")]
pub const CACHE_LINE_SIZE: usize = 32; // aka arm64
#[cfg(target_arch = "s390x")]
pub const CACHE_LINE_SIZE: usize = 256;

// Use CacheAligned to align a struct to the size of this architectures cache line size.
#[cfg_attr(
    any(
        target_arch = "x86_64",
        target_arch = "x86",
        target_arch = "powerpc"
    ),
    repr(align(64))
)]
#[cfg_attr(
    any(
        target_arch = "mips",
        target_arch = "arm",
        target_arch = "aarch64"
    ),
    repr(align(32))
)]
#[cfg_attr(any(target_arch = "powerpc64"), repr(align(128)))]
#[cfg_attr(any(target_arch = "s390x"), repr(align(256)))]
pub struct CacheAligned<T: Sized>(pub T);

impl<T> CacheAligned<T> {
    pub fn new(v: T) -> CacheAligned<T> {
        CacheAligned { 0: v }
    }
}

#[cfg(test)]
mod tests {
    use super::{CacheAligned, CACHE_LINE_SIZE};
    use std::mem::size_of;

    #[test]
    fn it_works() {
        assert_eq!(size_of::<u8>(), 1);
        assert_eq!(size_of::<CacheAligned<u8>>(), CACHE_LINE_SIZE);
    }

    struct ThreeLineStruct {
      pub line_1: CacheAligned<u8>,
      pub line_2: CacheAligned<u8>,
      pub line_3: CacheAligned<u8>,
    }

    #[test]
    fn it_is_three_lines() {
        assert_eq!(size_of::<ThreeLineStruct>(), 3*CACHE_LINE_SIZE);
    }
}