heap.rs.html -- source
Description: Source to the Rust file `src/liballoc/heap.rs`.
Keywords: rust, rustlang, rust-lang

      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
    138
    139
    140
    141
    142
    143
    144
    145
    146
    147
    148
    149
    150
    151
    152
    153
    154
    155
    156
    157
    158
    159
    160
    161
    162
    163
    164
    165
    166
    167
    168
    169
    170
    171
    172
    173
    174
    175
    176
    177
    178
    179
    180
    181
    182
    183
    184
    185
    186
    187
    188
    189
    190

    // Copyright 2014-2015 The Rust Project Developers. See the COPYRIGHT
    // file at the top-level directory of this distribution and at
    // http://rust-lang.org/COPYRIGHT.
    //
    // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
    // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
    // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
    // option. This file may not be copied, modified, or distributed
    // except according to those terms.

    #![unstable(feature = "heap_api",
                reason = "the precise API and guarantees it provides may be tweaked \
                          slightly, especially to possibly take into account the \
                          types being stored to make room for a future \
                          tracing garbage collector",
                issue = "27700")]

    use core::{isize, usize};
    #[cfg(not(test))]
    use core::intrinsics::{min_align_of, size_of};

    #[allow(improper_ctypes)]
    extern "C" {
        #[allocator]
        fn __rust_allocate(size: usize, align: usize) -> *mut u8;
        fn __rust_deallocate(ptr: *mut u8, old_size: usize, align: usize);
        fn __rust_reallocate(ptr: *mut u8, old_size: usize, size: usize, align: usize) -> *mut u8;
        fn __rust_reallocate_inplace(ptr: *mut u8,
                                     old_size: usize,
                                     size: usize,
                                     align: usize)
                                     -> usize;
        fn __rust_usable_size(size: usize, align: usize) -> usize;
    }

    #[inline(always)]
    fn check_size_and_alignment(size: usize, align: usize) {
        debug_assert!(size != 0);
        debug_assert!(size <= isize::MAX as usize,
                      "Tried to allocate too much: {} bytes",
                      size);
        debug_assert!(usize::is_power_of_two(align),
                      "Invalid alignment of allocation: {}",
                      align);
    }

    // FIXME: #13996: mark the `allocate` and `reallocate` return value as `noalias`

    /// Return a pointer to `size` bytes of memory aligned to `align`.
    ///
    /// On failure, return a null pointer.
    ///
    /// Behavior is undefined if the requested size is 0 or the alignment is not a
    /// power of 2. The alignment must be no larger than the largest supported page
    /// size on the platform.
    #[inline]
    pub unsafe fn allocate(size: usize, align: usize) -> *mut u8 {
        check_size_and_alignment(size, align);
        __rust_allocate(size, align)
    }

    /// Resize the allocation referenced by `ptr` to `size` bytes.
    ///
    /// On failure, return a null pointer and leave the original allocation intact.
    ///
    /// If the allocation was relocated, the memory at the passed-in pointer is
    /// undefined after the call.
    ///
    /// Behavior is undefined if the requested size is 0 or the alignment is not a
    /// power of 2. The alignment must be no larger than the largest supported page
    /// size on the platform.
    ///
    /// The `old_size` and `align` parameters are the parameters that were used to
    /// create the allocation referenced by `ptr`. The `old_size` parameter may be
    /// any value in range_inclusive(requested_size, usable_size).
    #[inline]
    pub unsafe fn reallocate(ptr: *mut u8, old_size: usize, size: usize, align: usize) -> *mut u8 {
        check_size_and_alignment(size, align);
        __rust_reallocate(ptr, old_size, size, align)
    }

    /// Resize the allocation referenced by `ptr` to `size` bytes.
    ///
    /// If the operation succeeds, it returns `usable_size(size, align)` and if it
    /// fails (or is a no-op) it returns `usable_size(old_size, align)`.
    ///
    /// Behavior is undefined if the requested size is 0 or the alignment is not a
    /// power of 2. The alignment must be no larger than the largest supported page
    /// size on the platform.
    ///
    /// The `old_size` and `align` parameters are the parameters that were used to
    /// create the allocation referenced by `ptr`. The `old_size` parameter may be
    /// any value in range_inclusive(requested_size, usable_size).
    #[inline]
    pub unsafe fn reallocate_inplace(ptr: *mut u8,
                                     old_size: usize,
                                     size: usize,
                                     align: usize)
                                     -> usize {
        check_size_and_alignment(size, align);
        __rust_reallocate_inplace(ptr, old_size, size, align)
    }

    /// Deallocates the memory referenced by `ptr`.
    ///
    /// The `ptr` parameter must not be null.
    ///
    /// The `old_size` and `align` parameters are the parameters that were used to
    /// create the allocation referenced by `ptr`. The `old_size` parameter may be
    /// any value in range_inclusive(requested_size, usable_size).
    #[inline]
    pub unsafe fn deallocate(ptr: *mut u8, old_size: usize, align: usize) {
        __rust_deallocate(ptr, old_size, align)
    }

    /// Returns the usable size of an allocation created with the specified the
    /// `size` and `align`.
    #[inline]
    pub fn usable_size(size: usize, align: usize) -> usize {
        unsafe { __rust_usable_size(size, align) }
    }

    /// An arbitrary non-null address to represent zero-size allocations.
    ///
    /// This preserves the non-null invariant for types like `Box<T>`. The address
    /// may overlap with non-zero-size memory allocations.
    pub const EMPTY: *mut () = 0x1 as *mut ();

    /// The allocator for unique pointers.
    #[cfg(not(test))]
    #[lang = "exchange_malloc"]
    #[inline]
    unsafe fn exchange_malloc(size: usize, align: usize) -> *mut u8 {
        if size == 0 {
            EMPTY as *mut u8
        } else {
            let ptr = allocate(size, align);
            if ptr.is_null() {
                ::oom()
            }
            ptr
        }
    }

    #[cfg(not(test))]
    #[lang = "exchange_free"]
    #[inline]
    unsafe fn exchange_free(ptr: *mut u8, old_size: usize, align: usize) {
        deallocate(ptr, old_size, align);
    }

    #[cfg(not(test))]
    #[lang = "box_free"]
    #[inline]
    unsafe fn box_free<T>(ptr: *mut T) {
        let size = size_of::<T>();
        // We do not allocate for Box<T> when T is ZST, so deallocation is also not necessary.
        if size != 0 {
            deallocate(ptr as *mut u8, size, min_align_of::<T>());
        }
    }

    #[cfg(test)]
    mod tests {
        extern crate test;
        use self::test::Bencher;
        use boxed::Box;
        use heap;

        #[test]
        fn basic_reallocate_inplace_noop() {
            unsafe {
                let size = 4000;
                let ptr = heap::allocate(size, 8);
                if ptr.is_null() {
                    ::oom()
                }
                let ret = heap::reallocate_inplace(ptr, size, size, 8);
                heap::deallocate(ptr, size, 8);
                assert_eq!(ret, heap::usable_size(size, 8));
            }
        }

        #[bench]
        fn alloc_owned_small(b: &mut Bencher) {
            b.iter(|| {
                let _: Box<_> = box 10;
            })
        }
    }

# Help

## Keyboard Shortcuts

?
  Show this help dialog
S
  Focus the search field
⇤
  Move up in search results
⇥
  Move down in search results
⏎
  Go to active search result
+
  Collapse/expand all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g. `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g. `vec -> usize` or `* -> vec`)