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
133
134
135
136
137

use crate::{CallbackRef, Owns};
use core::{
    alloc::{AllocErr, AllocInit, AllocRef, Layout, MemoryBlock, ReallocPlacement},
    ptr::NonNull,
};

/// Calls the provided callbacks when invoking methods on `AllocRef`.
///
/// A typical use case for a `Proxy` allocator is collecting statistics. `alloc-compose` provides
/// different implementations for [`CallbackRef`][].
///
/// # Examples
///
/// ```rust
/// #![feature(allocator_api)]
///
/// use alloc_compose::{stats, CallbackRef, Proxy};
/// use std::alloc::{AllocInit, AllocRef, Global, Layout};
///
/// let counter = stats::Counter::default();
/// let mut alloc = Proxy {
///     alloc: Global,
///     callbacks: counter.by_ref(),
/// };
///
/// unsafe {
///     let memory = alloc.alloc(Layout::new::<u32>(), AllocInit::Uninitialized)?;
///     alloc.dealloc(memory.ptr, Layout::new::<u32>());
/// }
///
/// assert_eq!(counter.num_allocs(), 1);
/// assert_eq!(counter.num_deallocs(), 1);
/// # Ok::<(), core::alloc::AllocErr>(())
/// ```
///
/// If more information is needed, one can either implement `CallbackRef` itself or use a more
/// fine-grained callback:
///
/// ```rust
/// # #![feature(allocator_api)]
/// # use alloc_compose::{stats, CallbackRef, Proxy};
/// # use std::alloc::{AllocInit, AllocRef, Layout};
/// use alloc_compose::{
///     stats::{AllocInitFilter, ResultFilter},
///     Region,
/// };
///
/// let counter = stats::FilteredCounter::default();
/// let mut data = [0; 32];
/// let mut alloc = Proxy {
///     alloc: Region::new(&mut data),
///     callbacks: counter.by_ref(),
/// };
///
/// unsafe {
///     let memory = alloc.alloc(Layout::new::<u32>(), AllocInit::Uninitialized)?;
///     alloc.dealloc(memory.ptr, Layout::new::<u32>());
///
///     alloc
///         .alloc(Layout::new::<[u32; 64]>(), AllocInit::Zeroed)
///         .unwrap_err();
/// }
///
/// assert_eq!(counter.num_allocs(), 2);
/// assert_eq!(
///     counter.num_allocs_filter(AllocInitFilter::None, ResultFilter::Ok),
///     1
/// );
/// assert_eq!(
///     counter.num_allocs_filter(AllocInit::Zeroed, ResultFilter::Err),
///     1
/// );
/// # Ok::<(), core::alloc::AllocErr>(())
/// ```
#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct Proxy<A, C> {
    pub alloc: A,
    pub callbacks: C,
}

unsafe impl<A: AllocRef, C: CallbackRef> AllocRef for Proxy<A, C> {
    fn alloc(&mut self, layout: Layout, init: AllocInit) -> Result<MemoryBlock, AllocErr> {
        self.callbacks.before_alloc(layout, init);
        let result = self.alloc.alloc(layout, init);
        self.callbacks.after_alloc(layout, init, result);
        result
    }

    #[track_caller]
    unsafe fn dealloc(&mut self, ptr: NonNull<u8>, layout: Layout) {
        self.callbacks.before_dealloc(ptr, layout);
        self.alloc.dealloc(ptr, layout);
        self.callbacks.after_dealloc(ptr, layout);
    }

    #[track_caller]
    unsafe fn grow(
        &mut self,
        ptr: NonNull<u8>,
        layout: Layout,
        new_size: usize,
        placement: ReallocPlacement,
        init: AllocInit,
    ) -> Result<MemoryBlock, AllocErr> {
        self.callbacks
            .before_grow(ptr, layout, new_size, placement, init);
        let result = self.alloc.grow(ptr, layout, new_size, placement, init);
        self.callbacks
            .after_grow(ptr, layout, new_size, placement, init, result);
        result
    }

    #[track_caller]
    unsafe fn shrink(
        &mut self,
        ptr: NonNull<u8>,
        layout: Layout,
        new_size: usize,
        placement: ReallocPlacement,
    ) -> Result<MemoryBlock, AllocErr> {
        self.callbacks
            .before_shrink(ptr, layout, new_size, placement);
        let result = self.alloc.shrink(ptr, layout, new_size, placement);
        self.callbacks
            .after_shrink(ptr, layout, new_size, placement, result);
        result
    }
}

impl<A: Owns, C: CallbackRef> Owns for Proxy<A, C> {
    fn owns(&self, memory: MemoryBlock) -> bool {
        self.callbacks.before_owns();
        let owns = self.alloc.owns(memory);
        self.callbacks.after_owns(owns);
        owns
    }
}