rpcs3/Utilities/lockless.h
2016-08-14 18:19:42 +03:00

148 lines
3.2 KiB
C++

#pragma once
#include "types.h"
#include "Atomic.h"
//! Simple sizeless array base for concurrent access. Cannot shrink, only growths automatically.
//! There is no way to know the current size. The smaller index is, the faster it's accessed.
//!
//! T is the type of elements. Currently, default constructor of T shall be constexpr.
//! N is initial element count, available without any memory allocation and only stored contiguously.
template<typename T, std::size_t N>
class lf_array
{
// Data (default-initialized)
T m_data[N]{};
// Next array block
atomic_t<lf_array*> m_next{};
public:
constexpr lf_array() = default;
~lf_array()
{
for (auto ptr = m_next.raw(); UNLIKELY(ptr);)
{
delete std::exchange(ptr, std::exchange(ptr->m_next.raw(), nullptr));
}
}
T& operator [](std::size_t index)
{
if (LIKELY(index < N))
{
return m_data[index];
}
else if (UNLIKELY(!m_next))
{
// Create new array block. It's not a full-fledged once-synchronization, unlikely needed.
for (auto _new = new lf_array, ptr = this; UNLIKELY(ptr);)
{
// Install the pointer. If failed, go deeper.
ptr = ptr->m_next.compare_and_swap(nullptr, _new);
}
}
// Access recursively
return (*m_next)[index - N];
}
};
//! Simple lock-free FIFO queue base. Based on lf_array<T, N> itself. Currently uses 32-bit counters.
//! There is no "push_end" or "pop_begin" provided, the queue element must signal its state on its own.
template<typename T, std::size_t N>
class lf_fifo : public lf_array<T, N>
{
struct alignas(8) ctrl_t
{
u32 push;
u32 pop;
};
atomic_t<ctrl_t> m_ctrl{};
public:
constexpr lf_fifo() = default;
// Get current "push" position
u32 size()
{
return reinterpret_cast<atomic_t<u32>&>(m_ctrl).load(); // Hack
}
// Acquire the place for one or more elements.
u32 push_begin(u32 count = 1)
{
return reinterpret_cast<atomic_t<u32>&>(m_ctrl).fetch_add(count); // Hack
}
// Get current "pop" position
u32 peek()
{
return m_ctrl.load().pop;
}
// Acknowledge processed element, return number of the next one.
// Perform clear if possible, zero is returned in this case.
u32 pop_end(u32 count = 1)
{
return m_ctrl.atomic_op([&](ctrl_t& ctrl)
{
ctrl.pop += count;
if (ctrl.pop == ctrl.push)
{
// Clean if possible
ctrl.push = 0;
ctrl.pop = 0;
}
return ctrl.pop;
});
}
};
//! Simple lock-free map. Based on lf_array<>. All elements are accessible, implicitly initialized.
template<typename K, typename T, typename Hash = value_hash<K>, std::size_t Size = 256>
class lf_hashmap
{
struct pair_t
{
// Default-constructed key means "no key"
atomic_t<K> key{};
T value{};
};
//
lf_array<pair_t, Size> m_data{};
// Value for default-constructed key
T m_default_key_data{};
public:
constexpr lf_hashmap() = default;
// Access element (added implicitly)
T& operator [](const K& key)
{
if (UNLIKELY(key == K{}))
{
return m_default_key_data;
}
// Calculate hash and array position
for (std::size_t pos = Hash{}(key) % Size;; pos += Size)
{
// Access the array
auto& pair = m_data[pos];
// Check the key value (optimistic)
if (LIKELY(pair.key == key) || pair.key.compare_and_swap_test(K{}, key))
{
return pair.value;
}
}
}
};