Trait Allocator

pub unsafe trait Allocator: Send {
    // Required methods
    fn alloc(&self, size: usize) -> (*mut u8, usize, u32);
    fn remap(
        &self,
        ptr: *mut u8,
        oldsize: usize,
        newsize: usize,
        can_move: bool,
    ) -> *mut u8;
    fn free_part(&self, ptr: *mut u8, oldsize: usize, newsize: usize) -> bool;
    fn free(&self, ptr: *mut u8, size: usize) -> bool;
    fn can_release_part(&self, flags: u32) -> bool;
    fn allocates_zeros(&self) -> bool;
    fn page_size(&self) -> usize;
}

In order for this crate to efficiently manage memory, it needs a way to communicate with the underlying platform. This Allocator trait provides an interface for this communication.

Required Methods

fn alloc(&self, size: usize) -> (*mut u8, usize, u32)

Allocates system memory region of at least size bytes Returns a triple of (base, size, flags) where base is a pointer to the beginning of the allocated memory region. size is the actual size of the region while flags specifies properties of the allocated region. If EXTERN_BIT (bit 0) set in flags, then we did not allocate this segment and so should not try to deallocate or merge with others. This function can return a std::ptr::null_mut() when allocation fails (other values of the triple will be ignored).

fn remap( &self, ptr: *mut u8, oldsize: usize, newsize: usize, can_move: bool, ) -> *mut u8

Remaps system memory region at ptr with size oldsize to a potential new location with size newsize. can_move indicates if the location is allowed to move to a completely new location, or that it is only allowed to change in size. Returns a pointer to the new location in memory. This function can return a std::ptr::null_mut() to signal an error.

fn free_part(&self, ptr: *mut u8, oldsize: usize, newsize: usize) -> bool

Frees a part of a memory chunk. The original memory chunk starts at ptr with size oldsize and is turned into a memory region starting at the same address but with newsize bytes. Returns true iff the access memory region could be freed.

fn free(&self, ptr: *mut u8, size: usize) -> bool

Frees an entire memory region. Returns true iff the operation succeeded. When false is returned, the dlmalloc may re-use the location on future allocation requests

fn can_release_part(&self, flags: u32) -> bool

Indicates if the system can release a part of memory. For the flags argument, see Allocator::alloc

fn allocates_zeros(&self) -> bool

Indicates whether newly allocated regions contain zeros.

fn page_size(&self) -> usize

Returns the page size. Must be a power of two

Implementors