1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132

use crate::lib::std::cell::Cell;
use crate::lib::std::marker::PhantomData;
use crate::lib::std::ops::Deref;
// use crate::lib::std::ops::{Bound, RangeBounds};
use crate::lib::std::slice;
use crate::lib::std::sync::atomic::{
    AtomicI16, AtomicI32, AtomicI64, AtomicI8, AtomicU16, AtomicU32, AtomicU64, AtomicU8,
};
use crate::native::ValueType;

pub trait Atomic {
    type Output;
}

macro_rules! atomic {
    ( $($for:ty => $output:ty),+ ) => {
        $(
            impl Atomic for $for {
                type Output = $output;
            }
        )+
    }
}

atomic!(
    i8 => AtomicI8,
    i16 => AtomicI16,
    i32 => AtomicI32,
    i64 => AtomicI64,
    u8 => AtomicU8,
    u16 => AtomicU16,
    u32 => AtomicU32,
    u64 => AtomicU64,
    f32 => AtomicU32,
    f64 => AtomicU64
);

/// A trait that represants an atomic type.
pub trait Atomicity {}

/// Atomically.
pub struct Atomically;
impl Atomicity for Atomically {}

/// Non-atomically.
pub struct NonAtomically;
impl Atomicity for NonAtomically {}

/// A view into a memory.
pub struct MemoryView<'a, T: 'a, A = NonAtomically> {
    ptr: *mut T,
    // Note: the length is in the terms of `size::<T>()`.
    // The total length in memory is `size::<T>() * length`.
    length: usize,
    _phantom: PhantomData<(&'a [Cell<T>], A)>,
}

impl<'a, T> MemoryView<'a, T, NonAtomically>
where
    T: ValueType,
{
    /// Creates a new MemoryView given a `pointer` and `length`.
    pub unsafe fn new(ptr: *mut T, length: u32) -> Self {
        Self {
            ptr,
            length: length as usize,
            _phantom: PhantomData,
        }
    }

    /// Creates a subarray view from this `MemoryView`.
    pub fn subarray(&self, start: u32, end: u32) -> Self {
        assert!(
            (start as usize) < self.length,
            "The range start is bigger than current length"
        );
        assert!(
            (end as usize) < self.length,
            "The range end is bigger than current length"
        );

        Self {
            ptr: unsafe { self.ptr.add(start as usize) },
            length: (end - start) as usize,
            _phantom: PhantomData,
        }
    }

    /// Copy the contents of the source slice into this `MemoryView`.
    ///
    /// This function will efficiently copy the memory from within the wasm
    /// module’s own linear memory to this typed array.
    ///
    /// # Safety
    ///
    /// This method is unsafe because the caller will need to make sure
    /// there are no data races when copying memory into the view.
    pub unsafe fn copy_from(&self, src: &[T]) {
        // We cap at a max length
        let sliced_src = &src[..self.length];
        for (i, byte) in sliced_src.iter().enumerate() {
            *self.ptr.offset(i as isize) = *byte;
        }
    }
}

impl<'a, T: Atomic> MemoryView<'a, T> {
    /// Get atomic access to a memory view.
    pub fn atomically(&self) -> MemoryView<'a, T::Output, Atomically> {
        MemoryView {
            ptr: self.ptr as *mut T::Output,
            length: self.length,
            _phantom: PhantomData,
        }
    }
}

impl<'a, T> Deref for MemoryView<'a, T, NonAtomically> {
    type Target = [Cell<T>];
    fn deref(&self) -> &[Cell<T>] {
        let mut_slice: &mut [T] = unsafe { slice::from_raw_parts_mut(self.ptr, self.length) };
        let cell_slice: &Cell<[T]> = Cell::from_mut(mut_slice);
        cell_slice.as_slice_of_cells()
    }
}

impl<'a, T> Deref for MemoryView<'a, T, Atomically> {
    type Target = [T];
    fn deref(&self) -> &[T] {
        unsafe { slice::from_raw_parts(self.ptr as *const T, self.length) }
    }
}