ba852993e9
Pure-CPU slot allocator for the terrain modern dispatcher's global VBO/EBO. FIFO free-list + monotonic counter, mirroring WB's TerrainRenderManager pattern. Caller (TerrainModernRenderer) handles GPU buffer growth when Allocate sets needsGrow=true. 8 unit tests cover: fresh-allocator returns slot 0, sequential allocs, free+alloc reuse, FIFO ordering, needsGrow signaling on capacity overflow, GrowTo, LoadedCount tracking, and double-free detection. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
76 lines
2.6 KiB
C#
76 lines
2.6 KiB
C#
using System;
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using System.Collections.Generic;
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namespace AcDream.Core.Terrain;
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/// <summary>
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/// Pure-CPU slot allocator for the terrain modern dispatcher's global VBO/EBO.
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/// One slot = one landblock's worth of mesh data (384 verts + 384 indices).
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/// Uses a FIFO free-list for slot recycling and a monotonic counter for
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/// first-time growth, mirroring WorldBuilder's TerrainRenderManager pattern.
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/// All bookkeeping is CPU-side; the GPU buffer growth itself is performed
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/// by TerrainModernRenderer when <see cref="Allocate"/> sets needsGrow=true.
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/// </summary>
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public sealed class TerrainSlotAllocator
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{
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private readonly Queue<int> _freeSlots = new();
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private readonly HashSet<int> _liveSlots = new();
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private int _nextFreeSlot;
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private int _capacity;
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public TerrainSlotAllocator(int initialCapacity = 64)
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{
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if (initialCapacity <= 0)
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throw new ArgumentOutOfRangeException(nameof(initialCapacity), "must be > 0");
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_capacity = initialCapacity;
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}
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/// <summary>Current capacity in slots. Growable via <see cref="GrowTo"/>.</summary>
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public int Capacity => _capacity;
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/// <summary>Slots currently in use (allocated minus freed).</summary>
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public int LoadedCount => _liveSlots.Count;
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/// <summary>
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/// Allocate a slot index. Reuses a freed slot via FIFO if available,
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/// otherwise hands out the next monotonic index. Sets
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/// <paramref name="needsGrow"/> to true when the returned slot index is
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/// at or beyond current capacity — caller must <see cref="GrowTo"/>
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/// before using the slot.
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/// </summary>
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public int Allocate(out bool needsGrow)
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{
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int slot;
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if (_freeSlots.TryDequeue(out var freed))
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{
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slot = freed;
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}
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else
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{
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slot = _nextFreeSlot++;
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}
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_liveSlots.Add(slot);
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needsGrow = slot >= _capacity;
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return slot;
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}
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/// <summary>
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/// Return a slot to the free list. Throws if the slot wasn't currently
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/// allocated (catches double-free bugs).
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/// </summary>
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public void Free(int slot)
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{
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if (!_liveSlots.Remove(slot))
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throw new InvalidOperationException(
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$"Slot {slot} was not allocated (double-free or unknown slot).");
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_freeSlots.Enqueue(slot);
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}
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/// <summary>Update capacity counter after the caller has grown the GPU buffers.</summary>
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public void GrowTo(int newCapacity)
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{
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if (newCapacity < _capacity)
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throw new ArgumentException("Capacity can only grow", nameof(newCapacity));
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_capacity = newCapacity;
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}
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}
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