[−][src]Crate basic_allocator

A simple memory allocator, written for educational purposes.

This module was written primarily for the code to be read. The allocator enclosed can be used as a memory allocator in a rust program.

Usage

use basic_allocator::UnixAllocator;

#[global_allocator]
static ALLOCATOR: UnixAllocator = UnixAllocator::new();
fn main() {
    println!("It works!")
}

Major Components

This module has several parts.

`BlockList`

A BlockList is a linked list of freed memory not returned to the OS, which can be reused by the allocator.

The free block starts with a header, and then has unused memory after that. The header is 16 bytes, and consists of a pointer to the next block and the size of the block as a whole.

A RawAlloc is a single-threaded, non-thread-safe heap and freed memory manager, implementing core::alloc::GlobalAlloc. However, because it is not thread-safe, it canot be used as a global allocator.BlockList

`UnixAllocator`

A UnixAllocator wraps RawAlloc with a spin lock to make it thread-safe, allowing it to be used as the global allocator. It also combines RawAlloc with a unix-specific UnixHeapGrower to use virtual memory pages as its underlying basis for making those calls.

Lesser Components

HeapGrower is a simple trait interface meant to abstract over the calls to the OS to expand the heap.

Structs

BlockIter
BlockList	A `BlockList` is a linked list of "free" blocks in memory.
FreeBlock	A `FreeBlock` is a wrapper around a pointer to a freed block to be maintained in a `BlockList`.
FreeHeader	The header for our free blocks.
GenericAllocator	A thread-safe allocator, using a spin lock around a RawAlloc.
RawAlloc	A raw allocator, capable of growing the heap, returning pointers to new allocations, and tracking and reusing freed memory.
Stats
ToyHeap
UnixAllocator
UnixHeapGrower	UnixHeapGrower uses virtual memory to grow the heap upon request.
Validity	Validity contains a representation of all invalid states found in a BlockList.

Enums

ApplyState	State after a single "apply".
Relation	An enum for easy comparison of blocks and their order

Traits

HeapGrower