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#pragma once
#include "../ds_core/ds_core.h"
#include "snmalloc/stl/atomic.h"
namespace snmalloc
{
/**
* Flags in a bitfield of optional features that a PAL may support. These
* should be set in the PAL's `pal_features` static constexpr field.
*/
enum PalFeatures : uint64_t
{
/**
* This PAL supports low memory notifications. It must implement a
* `register_for_low_memory_callback` method that allows callbacks to be
* registered when the platform detects low-memory and an
* `expensive_low_memory_check()` method that returns a `bool` indicating
* whether low memory conditions are still in effect.
*/
LowMemoryNotification = (1 << 0),
/**
* This PAL natively supports allocation with a guaranteed alignment. If
* this is not supported, then we will over-allocate and round the
* allocation.
*
* A PAL that does supports this must expose a `request()` method that takes
* a size and alignment. A PAL that does *not* support it must expose a
* `request()` method that takes only a size.
*/
AlignedAllocation = (1 << 1),
/**
* This PAL natively supports lazy commit of pages. This means have large
* allocations and not touching them does not increase memory usage. This is
* exposed in the Pal.
*/
LazyCommit = (1 << 2),
/**
* This Pal does not support allocation. All memory used with this Pal
* should be pre-allocated.
*/
NoAllocation = (1 << 3),
/**
* This Pal provides a source of Entropy
*/
Entropy = (1 << 4),
/**
* This Pal provides a millisecond time source
*/
Time = (1 << 5),
/**
* This Pal provides selective core dumps, so
* modify which parts get dumped.
*/
CoreDump = (1 << 6),
/**
* This Pal provides a way for parking threads at a specific address.
*/
WaitOnAddress = (1 << 7),
};
/**
* Flag indicating whether requested memory should be zeroed.
*/
enum ZeroMem
{
/**
* Memory should not be zeroed, contents are undefined.
*/
NoZero,
/**
* Memory must be zeroed. This can be lazily allocated via a copy-on-write
* mechanism as long as any load from the memory returns zero.
*/
YesZero
};
/**
* Default Tag ID for the Apple class
*/
static const int PALAnonDefaultID = 241;
/**
* Query whether the PAL supports a specific feature.
*/
template<PalFeatures F, typename PAL>
static constexpr bool pal_supports = (PAL::pal_features & F) == F;
} // namespace snmalloc