## Summary
Hardens the **Advanced Search** engine (`Projects/UOContent/Engines/Advanced Search/`) — the GM entity finder that fans searches across background worker threads. A code review surfaced 14 defects (A–N), including a shard-crasher reachable from a single admin typo and a path that silently disables autosave for the rest of the shard's uptime. Each behavioral fix ships with a test.
Full `UOContent.Tests` suite: **530/530 green** (21 new AdvancedSearch tests).
## Fixes
### Crash / data-loss
- **A — Shard crash on a malformed Property Test.** `AdvancedSearchThreadWorker.Execute` had no `try/catch` and the worker `Thread` is foreground, so a parse throw (`Hits>abc`, `Layer=onehanded` — `Enum.Parse` was case-sensitive, `Hits>1@` — empty sub-expression indexing) terminated the process. Now: `ParseValue`/`CompareValues` use `TryParse`/`Enum.TryParse(ignoreCase)` and return no-match instead of throwing; the per-entity filter is wrapped in `try/catch` (logs + skips); empty expressions are guarded.
- **C — Overlapping searches corrupt state + brick autosave.** `_threadWorkers`/`_threadId` were `static` but `DoSearch` is an instance method; a second search (double-click / two admins) stomped shared worker state and could leave a drain waiting forever on the shared `AutoResetEvent`, so `AutoSave.SavesEnabled` was never restored. Now: an `Interlocked` re-entrancy guard rejects concurrent searches.
- **G — Autosave restore not guaranteed.** The restore lived only in the success callback. Now it's in a `finally` (plus an outer `catch` covering the synchronous setup and a `catch` on the drain body), so autosave + the guard are always released.
### Wrong results
- **D — `@`/`|` operator precedence.** `a@b|c` evaluated as `a && (b || c)` instead of `(a && b) || c`. OR now binds looser than AND (`AdvancedSearchUtilities.EvaluateBoolean`, unit-tested).
- **E — Descending sort, partial last page rendered blank** (the index decreased in descending mode and the `break` early-out killed the loop). Now a bounded `VisibleCount`-driven loop renders the last page in both directions.
- **F — Deleted entities** were not skipped (ghost rows). Now `DoEntitySearch` skips `entity.Deleted`.
- **N — Reference-type comparisons** threw (`Comparer<T>.Default.Compare` on non-`IComparable`) and compared references to a string. Now equality is by value and ordering is guarded to `IComparable` (no throw).
### Worker perf / hardening
- **H** busy-spin → `Thread.Yield()` in the drain; **I** `GetProperties()` cached per `Type`; **J** `HandleValidInternal` moved behind the cheap map/range/region filters; **K** worker threads are `IsBackground` + `Exit()` tolerates an already-terminated worker; **L** `_filter == null` guard; **M** consistent `Volatile` access on `_pause`/`_exit`.
### Documented
- **B** — the residual worker/event-loop read race is documented on `AdvancedSearchThreadWorker`: workers read live entity state concurrently with the loop, so value-type reads may be stale-but-safe and getter exceptions are swallowed; fully eliminating it would require snapshotting entity fields on the main thread (deferred).
## Notes
- New test-only seams (`TryBeginSearch`/`EndSearch`/`IsSearchInProgress`/`VisibleCount`/`TryParseValue`/`EvaluateBoolean`) are `internal` via the existing `InternalsVisibleTo("UOContent.Tests")`.
- Dead `public ParseValue<T>` removed.
- `ConcurrentDictionary` for the reflection cache is intentional — these workers are genuinely parallel.
## Summary
Adds a custom `:L` format specifier to `RawInterpolatedStringHandler`. When the format string is `"L"`, the handler lowercases the formatted value's chars in-place after the underlying `ISpanFormattable.TryFormat` / `IFormattable.ToString` path completes. Zero allocation, single-pass.
## Usage
```csharp
mob.SendMessage($"You earned a {rank:L} trophy!"); // "gold"
mob.SendMessage($"Welcome, {playerName:L}"); // lowercased
mob.SendMessage($"{count:L} kills"); // ints unchanged ("42")
```
## Motivation
Eliminates the `value.ToString().ToLowerInvariant()` two-allocation idiom that appears across the codebase for any type that goes through an interpolation handler. After this lands, content code can use the `:L` specifier directly instead of helper extensions or per-enum lookup tables.
## Coverage
- `AppendFormatted<T>(T value, string? format)` — generic path (covers IFormattable, ISpanFormattable, .ToString fallback)
- `AppendFormatted(ReadOnlySpan<char> value, int alignment, string? format)` — span path with alignment-aware lowercase range (only the value range is lowercased, not padding)
- `AppendFormatted<T>(T value, int alignment, string? format)` and `AppendFormatted(string? value, int alignment, string? format)` and `AppendFormatted(object? value, int alignment, string? format)` — inherit via delegation
The `format == "L"` comparison is case-sensitive — `:l` (lowercase L) is NOT recognized. `:L` matches the convention of e.g. `:N0` / `:F2` (numeric format specifiers traditionally use uppercase). `char.ToLowerInvariant` is used (not locale-dependent) for predictable game text.
## Future cleanup
Phase 3.3 (#2438) introduced a per-enum `TrophyRank.LowerName()` extension to eliminate `rank.ToString().ToLower()` allocations at 10 ConPVP sites. Once this PR lands, those sites can be simplified to `{rank:L}` and the `TrophyRankExtensions` helper can be removed. Tracked as a follow-up.
## Summary
- **Add a self-referencing `InterpolationHandler` to `ValueStringBuilder`** that writes directly into the builder's buffer — zero intermediate allocation, works with `stackalloc`-backed builders
- **Replace all `System.Text.StringBuilder` usage** across the codebase with `ValueStringBuilder`
- **Convert `ValueStringBuilder.Create()` to `stackalloc`** at 10 sites where output length is provably bounded
- **Convert manual `Dispose()` to `using var`** where possible, and hoist loop-scoped builders outside loops with `Reset()`
- **Convert verbose `Append()` chains to `Append($"...")`** interpolation for readability
- **Add comprehensive documentation** for string handling patterns
## InterpolationHandler Design
`ValueStringBuilder` is a `ref struct`, which creates challenges for C#'s interpolated string handler pattern:
- **`ref` fields to ref structs are not allowed** (CS9050)
- **`[InterpolatedStringHandlerArgument("")]` passes struct receivers by value**, not by ref
- **`ISelfInterpolatedStringHandler` requires boxing** ref structs into interface fields
**Solution: Copy-and-reconcile pattern.** The handler receives a value copy of the builder. The copy shares the same underlying `char` buffer (`Span` points to the same `stackalloc`/pooled memory), so writes go to the original buffer. `Append()` reconciles by `this = handler._builder`, updating `_length` and any buffer references changed by `Grow()`.
This is safe because:
- The game loop is single-threaded — no concurrent access between handler construction and reconciliation
- If `Grow()` occurs in the copy, the original's stale buffer isn't accessed until `Append()` replaces it
- `Dispose()` correctly returns the reconciled buffer to the pool
## Changes by Category
### ValueStringBuilder (`Projects/Server/Buffers/ValueStringBuilder.cs`)
- Added nested `InterpolationHandler` ref struct with copy-and-reconcile pattern
- Added `Append([InterpolatedStringHandlerArgument("")] scoped ref InterpolationHandler)` method
- Removed `RawInterpolatedStringHandler` overloads (new handler replaces them)
- All `AppendFormatted` overloads delegate to existing `Append` methods (no code duplication)
- Alignment support via direct private field access (nested type privilege)
### StringBuilder → ValueStringBuilder (15 files)
Replaced all `new StringBuilder()` with `ValueStringBuilder.Create()` or `stackalloc`:
- ConPVP games: KingOfTheHill, DoubleDom, CTF, BombingRun, TourneyMatch
- ConPVP infrastructure: Tournament, Participant, TourneyParticipant
- ConPVP gumps: ArenaGump, TournamentBracketGump, AcceptTeamGump, ConfirmSignupGump
- Commands: Handlers, Logging, Add
- Other: TownCrier, SpeechLogGump, TestCenter
Key patterns:
- `sb = new StringBuilder()` reassignment → `sb.Reset()`
- `sb.AppendFormat("{0:N0}", value)` → `sb.Append($"{value:N0}")`
- `sb.Append(x).Append(y)` chains → separate statements (VSB returns void)
### Create() → stackalloc (10 files)
Converted heap-allocated builders to stackalloc where output is bounded:
- ClientVersion (32), MapSelection (160), HouseRaffleStone (48)
- HolySense (96), UnholySense (96), ClientVerification (192)
- AcceptTeamGump (64), ConfirmSignupGump (64)
- BaseWeapon (160), BaseArmor (128)
### Loop optimizations (2 files)
Hoisted `ValueStringBuilder` creation outside loops with `Reset()` per iteration:
- TourneyMatch.cs: `using var` inside for loop → stackalloc before loop
- ArenaGump.cs: `Create()` + `Dispose()` per iteration → stackalloc before loop
### Append chain → interpolation (5 files)
Converted multi-line `Append()` chains to `Append($"...")`:
- BountyMessage.cs: title switch (6 cases), paragraph (15→1 Append), description lines, closing
- AcceptTeamGump, ConfirmSignupGump, TournamentBracketGump: tournament type strings
- AdminGump: comment/tag formatting in loops
### Documentation
- `dev-docs/string-handling.md`: Full reference — construction, interpolation, disposal, decision guide
- `dev-docs/claude-skills/modernuo-string-handling.md`: Claude skill with quick reference
- `CLAUDE.md`: Added rule 17 (no StringBuilder), dev-docs table entry, skills table entry
- `dev-docs/code-standards.md`: Updated memory management section
## Test Plan
- [x] `dotnet build` — 0 errors, 0 warnings
- [x] `dotnet test` — 940/940 tests pass
- [x] 28 ValueStringBuilder tests covering all reconciliation scenarios:
- Stackalloc no-grow, stackalloc with grow (→pool transition)
- Heap no-grow, heap with grow, heap double grow
- Pre-existing content with and without grow
- Sequential multiple `Append($"...")` calls
- Mixed plain + interpolated Append
- Empty interpolation, literal-only, format specifiers
- Null string holes, ISpanFormattable types
- Dispose after stackalloc→pool grow
## Summary
- Adds proper Latin1 encoding support, replacing CP1252 usage throughout the codebase
- Adds specialized, optimized string decoding methods with safe string filtering for each encoding type
- Filters invalid Unicode characters (C0/C1 control codes, non-characters) by removal rather than replacement since
the UO client renders nothing for these characters
- Fixes UTF-16 null terminator position handling to correctly advance by 2 bytes
## Changes
TextEncoding.cs
- Added SearchValues-based invalid byte/char detection for efficient filtering
- Added encoding-specific GetString methods: GetStringAscii, GetStringLatin1, GetStringUtf8, GetStringBigUni,
GetStringLittleUni
- Each method supports a safeString parameter for filtering invalid characters
- Little-endian UTF-16 uses direct memory cast for zero-copy decoding on LE systems
- Invalid characters are removed (not replaced with U+FFFD) since the client renders nothing for them
SpanReader.cs
- Added ReadLatin1() and ReadLatin1Safe() methods
- Rewrote encoding-specific read methods to use optimized TextEncoding.GetString* methods
- Fixed UTF-16 null terminator handling: position now correctly advances by byteLength (2) instead of 1
SpanWriter.cs
- Added WriteLatin1 and WriteLatin1Null methods
## Packet Updates
- Updated all packet code to use Latin1 encoding instead of CP1252
- Affected: account packets, equipment packets, menu packets, message packets, mobile packets, player packets, secure
trade packets, vendor packets, gump packets, book packets, mahjong packets
## Filtering Behavior
Invalid characters filtered in safe mode:
```
┌───────────────┬────────────────────────┐
│ Range │ Description │
├───────────────┼────────────────────────┤
│ 0x00-0x1F │ C0 control codes │
├───────────────┼────────────────────────┤
│ 0x7F │ DEL │
├───────────────┼────────────────────────┤
│ 0x80-0x9F │ C1 control codes │
├───────────────┼────────────────────────┤
│ 0xFFFE-0xFFFF │ Unicode non-characters │
└───────────────┴────────────────────────┘
```
Note: Surrogate pairs (0xD800-0xDFFF) are not filtered because proper validation requires context checking for paired
vs unpaired surrogates. The UO client renders nothing for these anyway.
## Test Plan
- All 631 Server.Tests pass
- Verified client rendering behavior using TestUnicodeGump command (pages 1-5)
- Confirmed U+FFFD, unpaired surrogates, and non-characters all render as blank in client
- Verified Latin1 characters (0xA0-0xFF) display correctly
- Verified C1 control codes (0x80-0x9F) are filtered and don't display
## Breaking Changes
Incoming packet registration signature has changed to:
```cs
delegate* void OnReceiveCallback(NetState state, SpanReader reader, int packetLength);
IncomingPackets.Register(int packetID, int length, bool ingame, OnReceiveCallback onReceive);
```
For example, an incoming packet handler signature would now look like this:
```cs
public static void SomeIncomingPacket(NetState state, SpanReader reader, int packetLength)
{
// Parse the data
}
```
## Summary
Updates the network Pipe class to use a mirrored memory technique. This technique involves mapping the same physical memory to two contiguous virtual memory spaces so the byte buffer appears duplicated. This allows writing to a double-sized array to wrap around without the need for the `CircularBuffer` classes.
In practice this allows us to use `Span<byte>` as if the buffer was a regular array.
### Bug Fixes
- [X] Fixes bad fixed length string parsing
## Added Feature
Adds a single threaded array pool that works exactly the same as `ArrayPool<T>.Shared`.
The `STArrayPool<T>.Shared` can only be used on a single thread, the main game thread of the server.
Note: Unlike the built-in array pool, there is no hook into the _GC Gen 2_. This means to relieve potentially high memory pressure, `ArrayPool<T>.Shared.Trim()` must be called. The pool will only release arrays _after two successive calls within 10 seconds or longer_. If the server is at less than 70% total memory usage, or the server is not going to use this pool for something egregious, then don't bother ever calling Trim().
## Changes
- [X] Fixes ArrayPool calls that should be cleared due to references.
- [X] Benchmarks against ArrayPool with 4+ rented arrays deep of the same length.
- [x] Unit tests
- [X] Cleans up gump packets
- [X] Adds event loop task synchronization
- [X] Moves timer pause and cleans up the delay task timer class
- [X] Cleans up the conserve cpu
- [X] Renames variables to make them consistent with the new style
- [X] Removes process delta recursion checking.
- [X] Properly diposes net states. This fixes edge cases that may cause hanging connections to stay open longer than they should.
- [X] Fixes an issue with gump items not compiling properly
Users can now utilize `Timer.Pause()` since the code will be executed on the proper thread.
```cs
public void async void Talk()
{
_canTalk = false;
await Timer.Pause(Utility.RandomMinMax(5000, 8000)); // Talk after 5-8 seconds
DoTalk();
await Timer.Pause(Utility.RandomMinMax(12000, 25000)); // Reset ability to talk after 12-25 seconds
_canTalk = true;
}
```
SpanWriter now has an argument that allows it to be resizable.
```cs
public SpanWriter(Span<byte> initialBuffer, bool resize = false)
public SpanWriter(int initialCapacity, bool resize = false)
```
If a SpanWriter is set to be resizable, or given an initial capacity instead of a buffer, it must be disposed:
```cs
public static void SomeMethod()
{
using var writer = new SpanWriter(stackalloc byte[512], true);
// stuff
// Automatic Dispose of writer
}
```
This is because the SpanWriter uses `ArrayPool<byte>.Shared` _rented buffers_ to resize. If the writer is not disposed, those buffers will never be reused resulting in a _memory leak_.
It is possible that the SpanWriter will outright ditch the initial buffer if resize is set to true and growing is needed. To check/account for that we can do the following:
```cs
public static void SomeMethod()
{
Span<byte> span = stackalloc byte[512];
using var writer = new SpanWriter(span, true);
// write some stuff that causes the span to grow
span = writer.RawBuffer;
// Do stuff with the span
}
```
Make sure you don't accidentally `Dispose()` the writer or use the `RawBuffer` outside of the `using` block. If you do, bad things will happen! (NullPointerException, or a fresh SpanWriter with no buffer, depending on the situation).
SpanWriter can also now be used with a fixed statement since it has a `PinnableReference()` function.
- [X] Removes some string allocations (e.g. split)
- [X] Optimizes some collections
- [X] Converts insensitive to extension methods of built-ins.
- [X] Adds ordinal (case sensitive) string helpers
- [X] Fixes conditionals for in-game commands so they use Ordinal comparisons.
- [X] Replaces ToLower.Contains with InsensitiveContains
- [X] Adds ValueStringBuilder
- [X] Implements ValueStringBuilder in a few places where it makes sense
- [X] Removes the redundant Wrap function and replaces it with an optimized version
- [X] Fixes list conversions in Utility
Closes#351
Bumps release version
