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// This file is part of context-allocator. It is subject to the license terms in the COPYRIGHT file found in the top-level directory of this distribution and at https://raw.githubusercontent.com/lemonrock/context-allocator/master/COPYRIGHT. No part of context-allocator, including this file, may be copied, modified, propagated, or distributed except according to the terms contained in the COPYRIGHT file.
// Copyright © 2019 The developers of context-allocator. See the COPYRIGHT file in the top-level directory of this distribution and at https://raw.githubusercontent.com/lemonrock/context-allocator/master/COPYRIGHT.


/// This NUMA-aware allocator allocates memory-mapped data, optionally using NUMA policy to allocate on a memory node closest to the current thread.
///
/// It is slow and uses system calls.
///
/// On non-Linux systems except for NetBSD, this allocator is extremely inefficient when reallocating.
///
/// On Android, DragonFlyBSD, FreeBSD, Linux and OpenBSD mappings are omitted from core dumps for data privacy.
///
/// When dropped, any memory allocated with this allocator is ***NOT*** freed.
#[derive(Debug, Clone, Ord, PartialOrd, Eq, PartialEq, Hash)]
pub struct MemoryMapAllocator(MemoryMapSource);

impl Allocator for MemoryMapAllocator
{
	#[inline(always)]
	fn allocate(&self, non_zero_size: NonZeroUsize, non_zero_power_of_two_alignment: NonZeroUsize) -> Result<MemoryAddress, AllocErr>
	{
		const AssumedPageSize: usize = 4096;

		if unlikely!(non_zero_power_of_two_alignment.get() > AssumedPageSize)
		{
			return Err(AllocErr)
		}

		self.0.mmap_memory(non_zero_size.get())
	}

	#[inline(always)]
	fn deallocate(&self, non_zero_size: NonZeroUsize, _non_zero_power_of_two_alignment: NonZeroUsize, current_memory: MemoryAddress)
	{
		MemoryMapSource::munmap_memory(current_memory, non_zero_size.get())
	}

	#[inline(always)]
	fn growing_reallocate(&self, non_zero_new_size: NonZeroUsize, _non_zero_power_of_two_alignment: NonZeroUsize, non_zero_current_size: NonZeroUsize, current_memory: MemoryAddress) -> Result<MemoryAddress, AllocErr>
	{
		self.0.mremap_memory(current_memory, non_zero_current_size.get(), non_zero_new_size.get())
	}

	#[inline(always)]
	fn shrinking_reallocate(&self, non_zero_new_size: NonZeroUsize, _non_zero_power_of_two_alignment: NonZeroUsize, non_zero_current_size: NonZeroUsize, current_memory: MemoryAddress) -> Result<MemoryAddress, AllocErr>
	{
		self.0.mremap_memory(current_memory, non_zero_current_size.get(), non_zero_new_size.get())
	}
}