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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
//
// ArrayStack: A stack, implemented as a growable array
template <class T>
class ArrayStack
{
static const int builtinSize = 8;
public:
ArrayStack(CompAllocator alloc, int initialCapacity = builtinSize) : m_alloc(alloc)
{
if (initialCapacity > builtinSize)
{
maxIndex = initialCapacity;
data = m_alloc.allocate<T>(initialCapacity);
}
else
{
maxIndex = builtinSize;
data = reinterpret_cast<T*>(builtinData);
}
tosIndex = 0;
}
void Push(T item)
{
if (tosIndex == maxIndex)
{
Realloc();
}
data[tosIndex] = item;
tosIndex++;
}
template <typename... Args>
void Emplace(Args&&... args)
{
if (tosIndex == maxIndex)
{
Realloc();
}
new (&data[tosIndex], jitstd::placement_t()) T(std::forward<Args>(args)...);
tosIndex++;
}
void Realloc()
{
// get a new chunk 2x the size of the old one
// and copy over
T* oldData = data;
noway_assert(maxIndex * 2 > maxIndex);
data = m_alloc.allocate<T>(maxIndex * 2);
for (int i = 0; i < maxIndex; i++)
{
data[i] = oldData[i];
}
maxIndex *= 2;
}
T Pop()
{
assert(tosIndex > 0);
tosIndex--;
return data[tosIndex];
}
// Pop `count` elements from the stack
void Pop(int count)
{
assert(tosIndex >= count);
tosIndex -= count;
}
// Return the i'th element from the top
T Top(int i = 0)
{
assert(tosIndex > i);
return data[tosIndex - 1 - i];
}
// Return a reference to the i'th element from the top
T& TopRef(int i = 0)
{
assert(tosIndex > i);
return data[tosIndex - 1 - i];
}
int Height()
{
return tosIndex;
}
bool Empty()
{
return tosIndex == 0;
}
// Return the i'th element from the bottom
T Bottom(int i = 0)
{
assert(tosIndex > i);
return data[i];
}
// Return a reference to the i'th element from the bottom
T& BottomRef(int i = 0)
{
assert(tosIndex > i);
return data[i];
}
void Reset()
{
tosIndex = 0;
}
private:
CompAllocator m_alloc;
int tosIndex; // first free location
int maxIndex;
T* data;
// initial allocation
char builtinData[builtinSize * sizeof(T)];
};
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