Skip to content

Commit

Permalink
Rework IndexStableRingBuffer to speed up its indexing.
Browse files Browse the repository at this point in the history
  • Loading branch information
@TautvydasZilys
TautvydasZilys committed Mar 22, 2022
1 parent b8e29b1 commit 9c4f98d
Showing 1 changed file with 28 additions and 78 deletions.
106 changes: 28 additions & 78 deletions SearchEngine/Source/Utilities/IndexStableRingBuffer.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,7 @@ class IndexStableRingBuffer : NonCopyable
public:
IndexStableRingBuffer() :
m_Capacity(0),
m_NextIndex(0),
m_TailIndex(0),
m_Head(0),
m_Tail(0)
{
Expand All @@ -19,15 +19,15 @@ class IndexStableRingBuffer : NonCopyable
if (m_Tail >= m_Head)
{
for (TSize i = m_Head; i < m_Tail; i++)
GetElementPointer(i)->~Element();
GetPointer(i)->~T();
}
else
{
for (TSize i = m_Head; i < m_Capacity; i++)
GetElementPointer(i)->~Element();
GetPointer(i)->~T();

for (TSize i = 0; i < m_Tail; i++)
GetElementPointer(i)->~Element();
GetPointer(i)->~T();
}
}

Expand All @@ -39,36 +39,12 @@ class IndexStableRingBuffer : NonCopyable
T& operator[](TSize index)
{
Assert(Size() > 0);
Assert(GetElementPointer(m_Head)->index <= index);
Assert(GetElementPointer(m_Tail - 1)->index >= index);

Element* begin;
Element* end;
const auto indexFromEnd = m_TailIndex - index;
if (m_Tail >= m_Head || indexFromEnd <= m_Tail)
return *GetPointer(m_Tail - indexFromEnd);

if (m_Tail >= m_Head)
{
begin = GetElementPointer(m_Head);
end = GetElementPointer(m_Tail);
}
else if (GetElementPointer(0)->index > index)
{
begin = GetElementPointer(m_Head);
end = GetElementPointer(m_Capacity);
}
else
{
begin = GetElementPointer(0);
end = GetElementPointer(m_Tail);
}

auto result = std::lower_bound(begin, end, index, [](const Element& element, TSize index)
{
return element.index < index;
});

Assert(result != GetElementPointer(m_Tail));
Assert(result->index == index);
return result->item;
return *GetPointer(m_Capacity + m_Tail - indexFromEnd);
}

TSize Size() const
Expand All @@ -82,19 +58,19 @@ class IndexStableRingBuffer : NonCopyable
T& Front()
{
Assert(Size() > 0);
return GetElementPointer(m_Head)->item;
return *GetPointer(m_Head);
}

T& Back()
{
Assert(Size() > 0);
return GetElementPointer(m_Tail - 1)->item;
return *GetPointer(m_Tail - 1);
}

TSize BackIndex() const
{
Assert(Size() > 0);
return GetElementPointer(m_Tail - 1)->index;
return m_TailIndex - 1;
}

TSize PushBack(T&& item)
Expand All @@ -115,14 +91,13 @@ class IndexStableRingBuffer : NonCopyable
Grow();
}

auto index = m_NextIndex++;
new (GetElementPointer(m_Tail++)) Element(std::move(item), index);
return index;
new (GetPointer(m_Tail++)) T(std::move(item));
return m_TailIndex++;
}

void PopFront()
{
GetElementPointer(m_Head)->~Element();
GetPointer(m_Head)->~T();
m_Head++;

if (m_Head == m_Tail)
Expand All @@ -136,34 +111,34 @@ class IndexStableRingBuffer : NonCopyable
}

private:
inline static void TransferElement(uint8_t* srcBuffer, TSize srcIndex, uint8_t* dstBuffer, TSize dstIndex)
inline static void TransferT(uint8_t* srcBuffer, TSize srcIndex, uint8_t* dstBuffer, TSize dstIndex)
{
auto oldElement = reinterpret_cast<Element*>(&srcBuffer[srcIndex * sizeof(Element)]);
auto destination = &dstBuffer[dstIndex * sizeof(Element)];
new (destination) Element(std::move(*oldElement));
oldElement->~Element();
auto oldT = reinterpret_cast<T*>(&srcBuffer[srcIndex * sizeof(T)]);
auto destination = &dstBuffer[dstIndex * sizeof(T)];
new (destination) T(std::move(*oldT));
oldT->~T();
}

inline void Grow()
{
const auto newCapacity = m_Capacity > 0 ? m_Capacity * 2 : 4;
const auto size = Size();
std::unique_ptr<uint8_t[]> newBuffer(new uint8_t[newCapacity * sizeof(Element)]);
std::unique_ptr<uint8_t[]> newBuffer(new uint8_t[newCapacity * sizeof(T)]);

if (m_Tail >= m_Head)
{
TSize dstIndex = 0;
for (TSize i = m_Head; i < m_Tail; i++, dstIndex++)
TransferElement(m_Buffer.get(), i, newBuffer.get(), dstIndex);
TransferT(m_Buffer.get(), i, newBuffer.get(), dstIndex);
}
else
{
TSize dstIndex = 0;
for (TSize i = m_Head; i < m_Capacity; i++, dstIndex++)
TransferElement(m_Buffer.get(), i, newBuffer.get(), dstIndex);
TransferT(m_Buffer.get(), i, newBuffer.get(), dstIndex);

for (TSize i = 0; i < m_Tail; i++, dstIndex++)
TransferElement(m_Buffer.get(), i, newBuffer.get(), dstIndex);
TransferT(m_Buffer.get(), i, newBuffer.get(), dstIndex);
}

m_Buffer = std::move(newBuffer);
Expand All @@ -173,45 +148,20 @@ class IndexStableRingBuffer : NonCopyable
}

private:
struct Element : NonCopyable
{
T item;
TSize index;

Element(T item, TSize index) :
item(std::move(item)),
index(index)
{
}

Element(Element&& other) :
item(std::move(other.item)),
index(other.index)
{
}

Element& operator=(Element&& other)
{
item = std::move(other.item);
index = other.index;
return *this;
}
};

Element* GetElementPointer(TSize index)
T* GetPointer(TSize index)
{
return reinterpret_cast<Element*>(&m_Buffer[index * sizeof(Element)]);
return reinterpret_cast<T*>(&m_Buffer[index * sizeof(T)]);
}

const Element* GetElementPointer(TSize index) const
const T* GetPointer(TSize index) const
{
return reinterpret_cast<const Element*>(&m_Buffer[index * sizeof(Element)]);
return reinterpret_cast<const T*>(&m_Buffer[index * sizeof(T)]);
}

private:
std::unique_ptr<uint8_t[]> m_Buffer;
TSize m_Capacity;
TSize m_Head;
TSize m_Tail;
TSize m_NextIndex;
TSize m_TailIndex;
};

0 comments on commit 9c4f98d

Please sign in to comment.