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Merged
myarichuk merged 5 commits into from
Apr 30, 2026
Merged

Chore/convenience functions utf8 string #75

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9f68905
fix: use EqualityComparer for POCO hashing to ignore padding
Apr 30, 2026
75f77e4
feat: add ReadOnlySpan<byte> overloads for ArenaUtf8String keys
Apr 30, 2026
7cb5d04
feat: support char span queries on Utf8 dictionaries via transcoding
Apr 30, 2026
8a6d190
feat: support byte span queries on Utf16 dictionaries via transcoding
Apr 30, 2026
e3cc13f
test: add stress tests for large string transcoding in ArenaDictionary
Apr 30, 2026
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271 changes: 238 additions & 33 deletions src/SharpArena/Collections/ArenaDictionary.cs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,6 @@
using System.Collections;
using System.Buffers;
using System.Text;
using System.Diagnostics.CodeAnalysis;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
Expand Down Expand Up @@ -242,29 +244,125 @@ public bool ContainsKey(TKey key)
}

/// <summary>
/// Specialized ContainsKey for ArenaUtf16String using ReadOnlySpan{char} to avoid allocations.
/// Specialized ContainsKey for string types using ReadOnlySpan{char} to avoid allocations.
/// Supports cross-encoding for ArenaUtf8String.
/// </summary>
/// <param name="key">The key to locate in the <see cref="ArenaDictionary{TKey, TValue}"/>.</param>
/// <returns><see langword="true"/> if the <see cref="ArenaDictionary{TKey, TValue}"/> contains an element with the key; otherwise, <see langword="false"/>.</returns>
public bool ContainsKey(ReadOnlySpan<char> key)
{
if (typeof(TKey) != typeof(ArenaUtf16String)) return false;
CheckAlive();
if (typeof(TKey) == typeof(ArenaUtf16String))
{
CheckAlive();

uint capacity = (uint)_header->Capacity;
int* buckets = _header->Buckets;
ArenaUtf16String* keys = (ArenaUtf16String*)_header->Keys;
uint mask = capacity - 1;
uint hash = Hashing.HashString(key);
uint index = hash & mask;

while (true)
{
int entryIdxPlusOne = buckets[index];
if (entryIdxPlusOne == 0) return false;
if (keys[entryIdxPlusOne - 1].Equals(key)) return true;
index = (index + 1) & mask;
}
}

uint capacity = (uint)_header->Capacity;
int* buckets = _header->Buckets;
ArenaUtf16String* keys = (ArenaUtf16String*)_header->Keys;
uint mask = capacity - 1;
uint hash = Hashing.HashString(key);
uint index = hash & mask;
if (typeof(TKey) == typeof(ArenaUtf8String))
{
CheckAlive();
int maxBytes = Encoding.UTF8.GetMaxByteCount(key.Length);
byte[]? rented = null;
Span<byte> buffer = maxBytes <= 512 ? stackalloc byte[512] : (rented = ArrayPool<byte>.Shared.Rent(maxBytes));
try
{
int written = Encoding.UTF8.GetBytes(key, buffer);
ReadOnlySpan<byte> byteKey = buffer.Slice(0, written);

uint capacity = (uint)_header->Capacity;
int* buckets = _header->Buckets;
ArenaUtf8String* keys = (ArenaUtf8String*)_header->Keys;
uint mask = capacity - 1;
uint hash = Hashing.HashUtf8(byteKey);
uint index = hash & mask;
while (true)
{
int entryIdxPlusOne = buckets[index];
if (entryIdxPlusOne == 0) return false;
if (keys[entryIdxPlusOne - 1].Equals(byteKey)) return true;
index = (index + 1) & mask;
}
}
finally
{
if (rented != null) ArrayPool<byte>.Shared.Return(rented);
}
}

while (true)
return false;
}

/// <summary>
/// Specialized ContainsKey for ArenaUtf8String using ReadOnlySpan{byte} to avoid allocations.
/// </summary>
/// <param name="key">The key to locate in the <see cref="ArenaDictionary{TKey, TValue}"/>.</param>
/// <returns><see langword="true"/> if the <see cref="ArenaDictionary{TKey, TValue}"/> contains an element with the key; otherwise, <see langword="false"/>.</returns>
public bool ContainsKey(ReadOnlySpan<byte> key)
{
if (typeof(TKey) == typeof(ArenaUtf8String))
{
int entryIdxPlusOne = buckets[index];
if (entryIdxPlusOne == 0) return false;
if (keys[entryIdxPlusOne - 1].Equals(key)) return true;
index = (index + 1) & mask;
CheckAlive();
uint capacity = (uint)_header->Capacity;
int* buckets = _header->Buckets;
ArenaUtf8String* keys = (ArenaUtf8String*)_header->Keys;
uint mask = capacity - 1;
uint hash = Hashing.HashUtf8(key);
uint index = hash & mask;
while (true)
{
int entryIdxPlusOne = buckets[index];
if (entryIdxPlusOne == 0) return false;
if (keys[entryIdxPlusOne - 1].Equals(key)) return true;
index = (index + 1) & mask;
}
}

if (typeof(TKey) == typeof(ArenaUtf16String))
{
CheckAlive();
int maxChars = Encoding.UTF8.GetMaxCharCount(key.Length);
char[]? rented = null;
Span<char> buffer = maxChars <= 512 ? stackalloc char[512] : (rented = ArrayPool<char>.Shared.Rent(maxChars));
try
{
int written = Encoding.UTF8.GetChars(key, buffer);
ReadOnlySpan<char> charKey = buffer.Slice(0, written);

uint capacity = (uint)_header->Capacity;
int* buckets = _header->Buckets;
ArenaUtf16String* keys = (ArenaUtf16String*)_header->Keys;
uint mask = capacity - 1;
uint hash = Hashing.HashString(charKey);
uint index = hash & mask;

while (true)
{
int entryIdxPlusOne = buckets[index];
if (entryIdxPlusOne == 0) return false;
if (keys[entryIdxPlusOne - 1].Equals(charKey)) return true;
index = (index + 1) & mask;
}
}
finally
{
if (rented != null) ArrayPool<char>.Shared.Return(rented);
}
}

return false;
}

/// <summary>
Expand All @@ -288,38 +386,145 @@ public bool TryGetValue(TKey key, out TValue value)
}

/// <summary>
/// Specialized TryGetValue for ArenaUtf16String using ReadOnlySpan{char} to avoid allocations.
/// Specialized TryGetValue for string types using ReadOnlySpan{char} to avoid allocations.
/// Supports cross-encoding for ArenaUtf8String.
/// </summary>
/// <param name="key">The key whose value to get.</param>
/// <param name="value">When this method returns, the value associated with the specified key, if the key is found; otherwise, the default value for the type of the <paramref name="value"/> parameter. This parameter is passed uninitialized.</param>
/// <returns><see langword="true"/> if the <see cref="ArenaDictionary{TKey, TValue}"/> contains an element with the specified key; otherwise, <see langword="false"/>.</returns>
public bool TryGetValue(ReadOnlySpan<char> key, out TValue value)
{
if (typeof(TKey) != typeof(ArenaUtf16String))
if (typeof(TKey) == typeof(ArenaUtf16String))
{
value = default;
return false;
CheckAlive();

uint capacity = (uint)_header->Capacity;
int* buckets = _header->Buckets;
ArenaUtf16String* keys = (ArenaUtf16String*)_header->Keys;
TValue* values = (TValue*)_header->Values;
uint mask = capacity - 1;
uint hash = Hashing.HashString(key);
uint index = hash & mask;

while (true)
{
int entryIdxPlusOne = buckets[index];
if (entryIdxPlusOne == 0) break;
if (keys[entryIdxPlusOne - 1].Equals(key))
{
value = values[entryIdxPlusOne - 1];
return true;
}
index = (index + 1) & mask;
}
}
CheckAlive();

uint capacity = (uint)_header->Capacity;
int* buckets = _header->Buckets;
ArenaUtf16String* keys = (ArenaUtf16String*)_header->Keys;
TValue* values = (TValue*)_header->Values;
uint mask = capacity - 1;
uint hash = Hashing.HashString(key);
uint index = hash & mask;
if (typeof(TKey) == typeof(ArenaUtf8String))
{
CheckAlive();
int maxBytes = Encoding.UTF8.GetMaxByteCount(key.Length);
byte[]? rented = null;
Span<byte> buffer = maxBytes <= 512 ? stackalloc byte[512] : (rented = ArrayPool<byte>.Shared.Rent(maxBytes));
try
{
int written = Encoding.UTF8.GetBytes(key, buffer);
ReadOnlySpan<byte> byteKey = buffer.Slice(0, written);

uint capacity = (uint)_header->Capacity;
int* buckets = _header->Buckets;
ArenaUtf8String* keys = (ArenaUtf8String*)_header->Keys;
TValue* values = (TValue*)_header->Values;
uint mask = capacity - 1;
uint hash = Hashing.HashUtf8(byteKey);
uint index = hash & mask;
while (true)
{
int entryIdxPlusOne = buckets[index];
if (entryIdxPlusOne == 0) break;
if (keys[entryIdxPlusOne - 1].Equals(byteKey))
{
value = values[entryIdxPlusOne - 1];
return true;
}
index = (index + 1) & mask;
}
}
finally
{
if (rented != null) ArrayPool<byte>.Shared.Return(rented);
}
}

while (true)
value = default;
return false;
}

/// <summary>
/// Specialized TryGetValue for ArenaUtf8String using ReadOnlySpan{byte} to avoid allocations.
/// </summary>
/// <param name="key">The key whose value to get.</param>
/// <param name="value">When this method returns, the value associated with the specified key, if the key is found; otherwise, the default value for the type of the <paramref name="value"/> parameter. This parameter is passed uninitialized.</param>
/// <returns><see langword="true"/> if the <see cref="ArenaDictionary{TKey, TValue}"/> contains an element with the specified key; otherwise, <see langword="false"/>.</returns>
public bool TryGetValue(ReadOnlySpan<byte> key, out TValue value)
{
if (typeof(TKey) == typeof(ArenaUtf8String))
{
int entryIdxPlusOne = buckets[index];
if (entryIdxPlusOne == 0) break;
if (keys[entryIdxPlusOne - 1].Equals(key))
CheckAlive();
uint capacity = (uint)_header->Capacity;
int* buckets = _header->Buckets;
ArenaUtf8String* keys = (ArenaUtf8String*)_header->Keys;
TValue* values = (TValue*)_header->Values;
uint mask = capacity - 1;
uint hash = Hashing.HashUtf8(key);
uint index = hash & mask;
while (true)
{
value = values[entryIdxPlusOne - 1];
return true;
int entryIdxPlusOne = buckets[index];
if (entryIdxPlusOne == 0) break;
if (keys[entryIdxPlusOne - 1].Equals(key))
{
value = values[entryIdxPlusOne - 1];
return true;
}
index = (index + 1) & mask;
}
}

if (typeof(TKey) == typeof(ArenaUtf16String))
{
CheckAlive();
int maxChars = Encoding.UTF8.GetMaxCharCount(key.Length);
char[]? rented = null;
Span<char> buffer = maxChars <= 512 ? stackalloc char[512] : (rented = ArrayPool<char>.Shared.Rent(maxChars));
try
{
int written = Encoding.UTF8.GetChars(key, buffer);
ReadOnlySpan<char> charKey = buffer.Slice(0, written);

uint capacity = (uint)_header->Capacity;
int* buckets = _header->Buckets;
ArenaUtf16String* keys = (ArenaUtf16String*)_header->Keys;
TValue* values = (TValue*)_header->Values;
uint mask = capacity - 1;
uint hash = Hashing.HashString(charKey);
uint index = hash & mask;

while (true)
{
int entryIdxPlusOne = buckets[index];
if (entryIdxPlusOne == 0) break;
if (keys[entryIdxPlusOne - 1].Equals(charKey))
{
value = values[entryIdxPlusOne - 1];
return true;
}
index = (index + 1) & mask;
}
}
finally
{
if (rented != null) ArrayPool<char>.Shared.Return(rented);
}
index = (index + 1) & mask;
}

value = default;
Expand Down
3 changes: 1 addition & 2 deletions src/SharpArena/Collections/Hashing.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -18,8 +18,7 @@ public static uint Hash<T>(T value) where T : unmanaged
return (uint)Unsafe.As<T, ArenaUtf8String>(ref value).GetHashCode();
}

var span = new ReadOnlySpan<byte>(&value, sizeof(T));
return (uint)XxHash3.HashToUInt64(span);
return (uint)EqualityComparer<T>.Default.GetHashCode(value);
}

[MethodImpl(MethodImplOptions.AggressiveInlining)]
Expand Down
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