Ryujinx/Ryujinx.Graphics.Gpu/Shader/HashTable/PartitionHashTable.cs
Nicholas Rodine 951700fdd8
Removed unused usings. (#3593)
* Removed unused usings.

* Added back using, now that it's used.

* Removed extra whitespace.
2022-08-18 18:04:54 +02:00

451 lines
16 KiB
C#

using System;
using System.Collections.Generic;
using System.Numerics;
namespace Ryujinx.Graphics.Gpu.Shader.HashTable
{
/// <summary>
/// Partitioned hash table.
/// </summary>
/// <typeparam name="T">Hash table entry type</typeparam>
class PartitionHashTable<T>
{
/// <summary>
/// Hash table entry.
/// </summary>
private struct Entry
{
/// <summary>
/// Hash <see cref="OwnSize"/> bytes of <see cref="Data"/>.
/// </summary>
public readonly uint Hash;
/// <summary>
/// If this entry is only a sub-region of <see cref="Data"/>, this indicates the size in bytes
/// of that region. Otherwise, it should be zero.
/// </summary>
public readonly int OwnSize;
/// <summary>
/// Data used to compute the hash for this entry.
/// </summary>
/// <remarks>
/// To avoid additional allocations, this might be a instance of the full entry data,
/// and only a sub-region of it might be actually used by this entry. Such sub-region
/// has its size indicated by <see cref="OwnSize"/> in this case.
/// </remarks>
public readonly byte[] Data;
/// <summary>
/// Item associated with this entry.
/// </summary>
public T Item;
/// <summary>
/// Indicates if the entry is partial, which means that this entry is only for a sub-region of the data.
/// </summary>
/// <remarks>
/// Partial entries have no items associated with them. They just indicates that the data might be present on
/// the table, and one must keep looking for the full entry on other tables of larger data size.
/// </remarks>
public bool IsPartial => OwnSize != 0;
/// <summary>
/// Creates a new partial hash table entry.
/// </summary>
/// <param name="hash">Hash of the data</param>
/// <param name="ownerData">Full data</param>
/// <param name="ownSize">Size of the sub-region of data that belongs to this entry</param>
public Entry(uint hash, byte[] ownerData, int ownSize)
{
Hash = hash;
OwnSize = ownSize;
Data = ownerData;
Item = default;
}
/// <summary>
/// Creates a new full hash table entry.
/// </summary>
/// <param name="hash">Hash of the data</param>
/// <param name="data">Data</param>
/// <param name="item">Item associated with this entry</param>
public Entry(uint hash, byte[] data, T item)
{
Hash = hash;
OwnSize = 0;
Data = data;
Item = item;
}
/// <summary>
/// Gets the data for this entry, either full or partial.
/// </summary>
/// <returns>Data sub-region</returns>
public ReadOnlySpan<byte> GetData()
{
if (OwnSize != 0)
{
return new ReadOnlySpan<byte>(Data).Slice(0, OwnSize);
}
return Data;
}
}
/// <summary>
/// Hash table bucket.
/// </summary>
private struct Bucket
{
/// <summary>
/// Inline entry, to avoid allocations for the common single entry case.
/// </summary>
public Entry InlineEntry;
/// <summary>
/// List of additional entries for the not-so-common multiple entries case.
/// </summary>
public List<Entry> MoreEntries;
}
private Bucket[] _buckets;
private int _count;
/// <summary>
/// Total amount of entries on the hash table.
/// </summary>
public int Count => _count;
/// <summary>
/// Creates a new instance of the partitioned hash table.
/// </summary>
public PartitionHashTable()
{
_buckets = Array.Empty<Bucket>();
}
/// <summary>
/// Gets an item on the table, or adds a new one if not present.
/// </summary>
/// <param name="data">Data</param>
/// <param name="dataHash">Hash of the data</param>
/// <param name="item">Item to be added if not found</param>
/// <returns>Existing item if found, or <paramref name="item"/> if not found</returns>
public T GetOrAdd(byte[] data, uint dataHash, T item)
{
if (TryFindItem(dataHash, data, out T existingItem))
{
return existingItem;
}
Entry entry = new Entry(dataHash, data, item);
AddToBucket(dataHash, ref entry);
return item;
}
/// <summary>
/// Adds an item to the hash table.
/// </summary>
/// <param name="data">Data</param>
/// <param name="dataHash">Hash of the data</param>
/// <param name="item">Item to be added</param>
/// <returns>True if the item was added, false due to an item associated with the data already being on the table</returns>
public bool Add(byte[] data, uint dataHash, T item)
{
if (TryFindItem(dataHash, data, out _))
{
return false;
}
Entry entry = new Entry(dataHash, data, item);
AddToBucket(dataHash, ref entry);
return true;
}
/// <summary>
/// Adds a partial entry to the hash table.
/// </summary>
/// <param name="ownerData">Full data</param>
/// <param name="ownSize">Size of the sub-region of <paramref name="ownerData"/> used by the partial entry</param>
/// <returns>True if added, false otherwise</returns>
public bool AddPartial(byte[] ownerData, int ownSize)
{
ReadOnlySpan<byte> data = new ReadOnlySpan<byte>(ownerData).Slice(0, ownSize);
return AddPartial(ownerData, HashState.CalcHash(data), ownSize);
}
/// <summary>
/// Adds a partial entry to the hash table.
/// </summary>
/// <param name="ownerData">Full data</param>
/// <param name="dataHash">Hash of the data sub-region</param>
/// <param name="ownSize">Size of the sub-region of <paramref name="ownerData"/> used by the partial entry</param>
/// <returns>True if added, false otherwise</returns>
public bool AddPartial(byte[] ownerData, uint dataHash, int ownSize)
{
ReadOnlySpan<byte> data = new ReadOnlySpan<byte>(ownerData).Slice(0, ownSize);
if (TryFindItem(dataHash, data, out _))
{
return false;
}
Entry entry = new Entry(dataHash, ownerData, ownSize);
AddToBucket(dataHash, ref entry);
return true;
}
/// <summary>
/// Adds entry with a given hash to the table.
/// </summary>
/// <param name="dataHash">Hash of the entry</param>
/// <param name="entry">Entry</param>
private void AddToBucket(uint dataHash, ref Entry entry)
{
int pow2Count = GetPow2Count(++_count);
if (pow2Count != _buckets.Length)
{
Rebuild(pow2Count);
}
ref Bucket bucket = ref GetBucketForHash(dataHash);
AddToBucket(ref bucket, ref entry);
}
/// <summary>
/// Adds an entry to a bucket.
/// </summary>
/// <param name="bucket">Bucket to add the entry into</param>
/// <param name="entry">Entry to be added</param>
private void AddToBucket(ref Bucket bucket, ref Entry entry)
{
if (bucket.InlineEntry.Data == null)
{
bucket.InlineEntry = entry;
}
else
{
(bucket.MoreEntries ??= new List<Entry>()).Add(entry);
}
}
/// <summary>
/// Creates partial entries on a new hash table for all existing full entries.
/// </summary>
/// <remarks>
/// This should be called every time a new hash table is created, and there are hash
/// tables with data sizes that are higher than that of the new table.
/// This will then fill the new hash table with "partial" entries of full entries
/// on the hash tables with higher size.
/// </remarks>
/// <param name="newTable">New hash table</param>
/// <param name="newEntrySize">Size of the data on the new hash table</param>
public void FillPartials(PartitionHashTable<T> newTable, int newEntrySize)
{
for (int i = 0; i < _buckets.Length; i++)
{
ref Bucket bucket = ref _buckets[i];
ref Entry inlineEntry = ref bucket.InlineEntry;
if (inlineEntry.Data != null)
{
if (!inlineEntry.IsPartial)
{
newTable.AddPartial(inlineEntry.Data, newEntrySize);
}
if (bucket.MoreEntries != null)
{
foreach (Entry entry in bucket.MoreEntries)
{
if (entry.IsPartial)
{
continue;
}
newTable.AddPartial(entry.Data, newEntrySize);
}
}
}
}
}
/// <summary>
/// Tries to find an item on the table.
/// </summary>
/// <param name="dataHash">Hash of <paramref name="data"/></param>
/// <param name="data">Data to find</param>
/// <param name="item">Item associated with the data</param>
/// <returns>True if an item was found, false otherwise</returns>
private bool TryFindItem(uint dataHash, ReadOnlySpan<byte> data, out T item)
{
if (_count == 0)
{
item = default;
return false;
}
ref Bucket bucket = ref GetBucketForHash(dataHash);
if (bucket.InlineEntry.Data != null)
{
if (bucket.InlineEntry.Hash == dataHash && bucket.InlineEntry.GetData().SequenceEqual(data))
{
item = bucket.InlineEntry.Item;
return true;
}
if (bucket.MoreEntries != null)
{
foreach (Entry entry in bucket.MoreEntries)
{
if (entry.Hash == dataHash && entry.GetData().SequenceEqual(data))
{
item = entry.Item;
return true;
}
}
}
}
item = default;
return false;
}
/// <summary>
/// Indicates the result of a hash table lookup.
/// </summary>
public enum SearchResult
{
/// <summary>
/// No entry was found, the search must continue on hash tables of lower size.
/// </summary>
NotFound,
/// <summary>
/// A partial entry was found, the search must continue on hash tables of higher size.
/// </summary>
FoundPartial,
/// <summary>
/// A full entry was found, the search was concluded and the item can be retrieved.
/// </summary>
FoundFull
}
/// <summary>
/// Tries to find an item on the table.
/// </summary>
/// <param name="dataAccessor">Data accessor</param>
/// <param name="size">Size of the hash table data</param>
/// <param name="item">The item on the table, if found, otherwise unmodified</param>
/// <param name="data">The data on the table, if found, otherwise unmodified</param>
/// <returns>Table lookup result</returns>
public SearchResult TryFindItem(ref SmartDataAccessor dataAccessor, int size, ref T item, ref byte[] data)
{
if (_count == 0)
{
return SearchResult.NotFound;
}
ReadOnlySpan<byte> dataSpan = dataAccessor.GetSpanAndHash(size, out uint dataHash);
if (dataSpan.Length != size)
{
return SearchResult.NotFound;
}
ref Bucket bucket = ref GetBucketForHash(dataHash);
if (bucket.InlineEntry.Data != null)
{
if (bucket.InlineEntry.Hash == dataHash && bucket.InlineEntry.GetData().SequenceEqual(dataSpan))
{
item = bucket.InlineEntry.Item;
data = bucket.InlineEntry.Data;
return bucket.InlineEntry.IsPartial ? SearchResult.FoundPartial : SearchResult.FoundFull;
}
if (bucket.MoreEntries != null)
{
foreach (Entry entry in bucket.MoreEntries)
{
if (entry.Hash == dataHash && entry.GetData().SequenceEqual(dataSpan))
{
item = entry.Item;
data = entry.Data;
return entry.IsPartial ? SearchResult.FoundPartial : SearchResult.FoundFull;
}
}
}
}
return SearchResult.NotFound;
}
/// <summary>
/// Rebuilds the table for a new count.
/// </summary>
/// <param name="newPow2Count">New power of two count of the table</param>
private void Rebuild(int newPow2Count)
{
Bucket[] newBuckets = new Bucket[newPow2Count];
uint mask = (uint)newPow2Count - 1;
for (int i = 0; i < _buckets.Length; i++)
{
ref Bucket bucket = ref _buckets[i];
if (bucket.InlineEntry.Data != null)
{
AddToBucket(ref newBuckets[(int)(bucket.InlineEntry.Hash & mask)], ref bucket.InlineEntry);
if (bucket.MoreEntries != null)
{
foreach (Entry entry in bucket.MoreEntries)
{
Entry entryCopy = entry;
AddToBucket(ref newBuckets[(int)(entry.Hash & mask)], ref entryCopy);
}
}
}
}
_buckets = newBuckets;
}
/// <summary>
/// Gets the bucket for a given hash.
/// </summary>
/// <param name="hash">Data hash</param>
/// <returns>Bucket for the hash</returns>
private ref Bucket GetBucketForHash(uint hash)
{
int index = (int)(hash & (_buckets.Length - 1));
return ref _buckets[index];
}
/// <summary>
/// Gets a power of two count from a regular count.
/// </summary>
/// <param name="count">Count</param>
/// <returns>Power of two count</returns>
private static int GetPow2Count(int count)
{
// This returns the nearest power of two that is lower than count.
// This was done to optimize memory usage rather than performance.
return 1 << BitOperations.Log2((uint)count);
}
}
}