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App/util/StlExtra.h

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+/* Copyright 2003-2005 ROBLOX Corporation, All Rights Reserved */
+
+#pragma once
+
+#include "rbx/Debug.h"
+#include <vector>
+
+
+namespace RBX {
+
+	// only fast for very short vectors - should do no allocation
+	// returns index of the item removed
+
+	template<class T>
+	void fastRemoveIndex(std::vector<T>& vec, size_t index)
+	{
+		RBXASSERT(index >= 0);
+		RBXASSERT(index < vec.size());
+		RBXASSERT(!vec.empty());
+		RBXASSERT(vec.size() < 32);			// Note - possibly should be using some other container here - to find item requires N time
+#ifdef _DEBUG
+		size_t currentCapacity = vec.capacity();
+#endif
+		size_t newSize = vec.size() - 1;
+
+		if (index < newSize)
+		{
+			vec[index] = vec.back();
+		}
+		vec.resize(newSize);				// hopefully, don't do a memory realloc/shrink
+
+#ifdef _DEBUG
+		RBXASSERT(currentCapacity == vec.capacity());		// confirm no reallocation
+#endif
+	}
+
+
+	// only fast for very short vectors - should do no allocation
+	// returns index of the item removed
+	template<class T>
+	size_t fastRemoveShort(std::vector<T>& vec, const T& item)
+	{
+		typename std::vector<T>::iterator it = std::find(vec.begin(), vec.end(), item);
+
+		size_t answer = it - vec.begin();
+
+		RBXASSERT(vec[answer] == item);
+		RBXASSERT(it != vec.end());
+		RBXASSERT(vec.size() < 32);			// Note - possibly should be using some other container here - to find item requires N time
+#ifdef _DEBUG
+		size_t currentCapacity = vec.capacity();
+#endif
+
+		typename std::vector<T>::iterator lastOne(vec.end());
+		--lastOne;
+
+		RBXASSERT(*lastOne == vec.back());
+
+		if (it != lastOne) {
+			*it = *lastOne;					// move back item into the place once held by item
+		}
+		vec.resize(vec.size() - 1);				// hopefully, don't do a memory realloc/shrink
+
+#ifdef _DEBUG
+		RBXASSERT(currentCapacity == vec.capacity());		// confirm no reallocation
+#endif
+		return answer;
+	}
+
+
+
+}	// namespace RBX
+