105 lines
4.0 KiB
C#
105 lines
4.0 KiB
C#
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// Grid2D from uMMORPG: get/set values of type T at any point
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// -> not named 'Grid' because Unity already has a Grid type. causes warnings.
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// -> struct to avoid memory indirection. it's accessed a lot.
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using System.Collections.Generic;
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using UnityEngine;
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namespace Mirror
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{
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// struct to avoid memory indirection. it's accessed a lot.
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public struct Grid2D<T>
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{
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// the grid
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// note that we never remove old keys.
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// => over time, HashSet<T>s will be allocated for every possible
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// grid position in the world
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// => Clear() doesn't clear them so we don't constantly reallocate the
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// entries when populating the grid in every Update() call
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// => makes the code a lot easier too
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// => this is FINE because in the worst case, every grid position in the
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// game world is filled with a player anyway!
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readonly Dictionary<Vector2Int, HashSet<T>> grid;
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// cache a 9 neighbor grid of vector2 offsets so we can use them more easily
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readonly Vector2Int[] neighbourOffsets;
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public Grid2D(int initialCapacity)
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{
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grid = new Dictionary<Vector2Int, HashSet<T>>(initialCapacity);
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neighbourOffsets = new[] {
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Vector2Int.up,
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Vector2Int.up + Vector2Int.left,
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Vector2Int.up + Vector2Int.right,
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Vector2Int.left,
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Vector2Int.zero,
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Vector2Int.right,
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Vector2Int.down,
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Vector2Int.down + Vector2Int.left,
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Vector2Int.down + Vector2Int.right
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};
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}
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// helper function so we can add an entry without worrying
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public void Add(Vector2Int position, T value)
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{
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// initialize set in grid if it's not in there yet
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if (!grid.TryGetValue(position, out HashSet<T> hashSet))
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{
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// each grid entry may hold hundreds of entities.
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// let's create the HashSet with a large initial capacity
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// in order to avoid resizing & allocations.
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#if !UNITY_2021_3_OR_NEWER
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// Unity 2019 doesn't have "new HashSet(capacity)" yet
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hashSet = new HashSet<T>();
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#else
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hashSet = new HashSet<T>(128);
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#endif
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grid[position] = hashSet;
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}
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// add to it
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hashSet.Add(value);
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}
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// helper function to get set at position without worrying
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// -> result is passed as parameter to avoid allocations
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// -> result is not cleared before. this allows us to pass the HashSet from
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// GetWithNeighbours and avoid .UnionWith which is very expensive.
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void GetAt(Vector2Int position, HashSet<T> result)
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{
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// return the set at position
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if (grid.TryGetValue(position, out HashSet<T> hashSet))
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{
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foreach (T entry in hashSet)
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result.Add(entry);
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}
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}
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// helper function to get at position and it's 8 neighbors without worrying
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// -> result is passed as parameter to avoid allocations
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public void GetWithNeighbours(Vector2Int position, HashSet<T> result)
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{
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// clear result first
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result.Clear();
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// add neighbours
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foreach (Vector2Int offset in neighbourOffsets)
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GetAt(position + offset, result);
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}
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// clear: clears the whole grid
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// IMPORTANT: we already allocated HashSet<T>s and don't want to do
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// reallocate every single update when we rebuild the grid.
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// => so simply remove each position's entries, but keep
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// every position in there
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// => see 'grid' comments above!
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// => named ClearNonAlloc to make it more obvious!
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public void ClearNonAlloc()
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{
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foreach (HashSet<T> hashSet in grid.Values)
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hashSet.Clear();
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}
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}
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}
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