## 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
Fix [add command failing with ambiguous type names + refactor for performance
### Problem
[add blight would fail with "No type with that name was found" because multiple types contain "blight" (e.g., Server.Items.Blight, Server.Ethics.Evil.Blight, Server.Items.BlightGrippedLongbow, Server.Items.QuiverOfBlight). The old code only succeeded when exactly one type matched the search regardless of constructability and inheriting Mobi les/Items.
### Solution
Exact match takes priority: If a type's name exactly equals the search string (case-insensitive), use it directly. Otherwise, show the AddGump with all partial matches.
- [add blight → Creates Blight (exact name match)
- [add bligh → Shows gump with Blight, BlightGrippedLongbow, etc.
### Refactoring
- CommandEventArgs context: Added GetContext<T>/SetContext<T> to pass resolved type through the command chain without method signature changes
- Removed TrySetupTarget duplication: Validation now happens only in ValidateArgs, eliminating redundant code paths
- Split type matching:
- ExactMatch(string) → Returns Type for exact name match (used by [add)
- MatchEmptyCtor(string) → Returns ConstructorInfo[] for gump display (empty-callable constructors only)
### Memory & Performance Improvements
| Optimization | Benefit |
|-------------------------------|----------------------------------------------------------------------------------------------|
| _mobileItemTypes cache | Filters Mobile/Item types once per assembly, reused on all subsequent searches |
| ReadOnlySpan<string> for args | Avoids string[] heap allocations when slicing arguments |
| ValueStringBuilder | Stack-allocated string building, avoids StringBuilder heap allocation |
| Single type resolution | Type resolved once in ValidateArgs, passed via context to Execute (was resolved 2-3x before) |
### Summary
* Adds `StaticNoticeGump<T>` and `StaticWarningGump<T>`
* Converts NoticeGump/WarningGump to use `DynamicGump`
* Changes various uses of notice gump and warning gump to their static counterpart.
> [!IMPORTANT]
> This code change includes important fixes for all spawners after they were converted to codegen!
> [!NOTE]
> **Developer Note**
> Usage/Description/Aliases attributes were moved to the core so they can be used by the command registration system.
### Summary
- **Fixes spawners not registering their spawns on world load**
- Changes `[GenerateSpawners` to `[ImportSpawners`
- Removes `ConvertPremiumSpawners`
- Adds Premium spawner import support to `[ImportSpawners`
- Adds RunUO XML import support: https://github.com/ruaduck/xmlspawner/blob/ServUOMaster/XmlSpawner/XmlSpawner%20Core/SpawnerExporter.cs
- Fixed an issue where not manually registering an alias meant it wasn't available as a command
### Summary
- Fixes `[AdvancedSearch` being accessible by players 😱
- Adds `[GenCommands` to generate the same commands html page on https://muo.gg/commands.
- Fixes `[helpinfo` so all commands properly show up!
> [!WARNING]
> ### Developer Warning:
> Commands must now be registered in the `Configure` bootup phase.
> If a command is not registered early enough, it may not be available to systems like [helpinfo
> that cache their information.
> [!NOTE]
> ### Developer Note:
> Various commands related to generating content have been changed to _Developer_ and above access level.
### Screenshots
<img width="673" alt="image" src="https://github.com/modernuo/ModernUO/assets/3953314/b105b5c9-5eb4-4ace-93ff-1bfb31e7132f">
<img width="547" alt="image" src="https://github.com/modernuo/ModernUO/assets/3953314/e97487e8-47a5-4aa7-89cc-9fe3deda584d">
## Breaking Changes
* The Firewall and IP Limiter have been rewritten. Please read the notes carefully!
* `TcpServer.Instances` moved back to `NetState.Instances` - sorry - it was stupid to move it to begin with.
> [!Note]
> Sockets that fail the IP Limiter or Firewall will be immediately and forcibly disconnected.
> This means they will be stuck at "Verifying account..." if it was a real client.
### Summary
- Removes firewall wildcard support.
- Removes `AccessRestrictions`.
- Moves Firewall/IPLimiter to the core.
- Moves `TcpServer` to its own thread.
- Removes the `SocketConnect` and `SocketDisconnect` event sinks.
- Moves `Instances` back to `NetState.Instances`.
- Fixes a long standing bug with bad handling of duplicate listener addresses.
#### Firewall
The firewall has been completely rewritten. There is now an "Admin Firewall" which saves to the config file. Secondarily, there is an internal firewall used exclusively by the TcpServer while processing sockets. The Admin firewall mirrors it's additions/deletions to the internal firewall by adding requests to a queue.
> [!IMPORTANT]
> **Wildcard firewall entries, such as `X`, `*`, `?` are not allowed.**
> **Ranges in between IP classes or sextets are not allowed.**
> **Please make sure to use one of the following:**
> * IP Address - `192.168.1.1`
> * CIDR - `192.168.1.0/24`
> * Range - `192.168.1.1-192.168.1.100`
#### IP Limiter
The IP Limiter has been completely rewritten. The available configurations are:
```json
"ipLimiter.enable": "True",
"ipLimiter.maxConnectionsPerIP": 10,
"ipLimiter.clearConnectionAttemptsDuration": "00:00:00:10",
"ipLimiter.clearThrottledDuration": "00:00:02:00",
```
The IP Limiter is set up to prevent spamming connections from the same IP. Every time an IP connects, it is added to a connection list. After 10 attempts, the IP is added to the throttle list. To keep the system fast, the connection list is entirely wiped every 10 seconds, and the throttle list is entirely wiped every 2 minutes.
## **MAJOR CHANGE**
* `Stabled` has been moved to `PlayerMobile`.
* New methods added, `PlayerMobile.AddStabled` and `PlayerMobile.RemoveStabled`.
* Added `PlayerMobile.AddFollower` and `PlayerMobile.RemoveFollower`.
* `Stabled`, `AutoStabled`, and `AllFollowers` are now `HashSet` and **_CAN BE NULL_**.
### Summary
* Fixes monster abilities causing harm to the monster through reflect
* Adds `CanTriggerAgainstSelf` to override this for healing or some other self-affecting ability
* Fixes a major memory leak where `UnsummonTimer` from animated dead spell lasts up-to 24hrs and therefore holds onto references of dead/deleted mobs.
* Fixes another minor leak where a mob is not unregistered from the animated dead spell list until the next spell cast.
## Adds Auto Archiving
Backups are archived once an hour, day, and month. Archives older than 60 days are pruned automatically.
_Note: Automatic pruning is off by default_
### Archive compression format
The following formats are supported:
* Zstd (The fastest with best compression ratio)
* GZip
* Zip
* None (Tar)
_Note: By default archives use [zstandard](http://facebook.github.io/zstd/) format.
The archive format can be changed in modernuo.json `autoArchive.compressionFormat`_
### Restoring world from archive
Move the archive to the Saves folder (tar.zst file). On startup the server will extract the file and restore the latest save. See pictures below.
### Manually extracting an archives
#### Windows
* Use the latest version of [7-zip w/ ZStandard](https://github.com/mcmilk/7-Zip-zstd/releases/latest)
1. Extract the `.tar.zst` file.
2. Extract the `.tar` file. (Yes you have to do it in two steps)
* On Windows 10 you can use the command line. `zstd.exe` is in the Assemblies folder after building ModernUO.
1. `tar --use-compress-program "Distribution\Assemblies\zstd.exe -d" -xvf "Archives\Hourly\archivefile.tar.zst" -C "path to where you want to extract it"`
#### Mac
* Install [Keka](https://www.keka.io)
1. Drop the .tar.zst onto the keka interface.
#### Linux
1. Install zstd from a package manager
2. Run `tar -I zstd -xvf "Archives\Hourly\archivefile.tar.zst" -C "path to where you want to extract it"`
### Other changes
* Changes Autosave to occur at the same time no matter when the server is booted.
* Adds `[SaveFrequency <delay> [warning]`command to set save frequency and warning frequency in-game.
* Adds support for time zones that are configurable. The system timezone can also be manually configured. Check `TimeZoneHandler.cs` for details.
<img width="257" alt="Screen Shot 2021-09-22 at 11 23 18 PM" src="https://user-images.githubusercontent.com/3953314/134464929-a5bf3cd8-2ef0-4476-a9ad-71d0816a19ac.png">
<img width="241" alt="Screen Shot 2021-09-22 at 11 23 39 PM" src="https://user-images.githubusercontent.com/3953314/134464945-5f6f96dc-3d1e-434d-8256-5c6b3705e786.png">
<img width="836" alt="Screen Shot 2021-09-22 at 11 34 39 PM" src="https://user-images.githubusercontent.com/3953314/134464957-625e57f2-ef47-4ca1-a0a7-cd40c9b6539c.png">
<img width="631" alt="Screen Shot 2021-09-22 at 11 34 50 PM" src="https://user-images.githubusercontent.com/3953314/134464969-b2d65c0d-f8f5-497a-a832-5d805e8e0b22.png">
- [X] Removes network pause/resume
- [X] Adds back packet profiler
- [X] Adds state machine to keep track and trace netstates
- [X] Changes NetState.Running back to using an interlock exchange
- [X] Adds preliminary packet throttling support
### Packet Throttling
- `[GetThrottle <packetId>` to get the delay in milliseconds for that packet
- `[SetThrottle <packetId> <delay>` to set the delay in milliseconds for that packet
The settings are saved to `Configuration/throttles.json`
- [X] Adds support for `SkipLocalsInitAttribute`. SkipLocalsInitAttribute skips initializing stack variables including `stackalloc`. I don't think it is wired/working yet but should be implemented soon.
- [X] Optimizes broadcasted packets by checking if the first byte (packet ID) is non-zero. If it is already set, it reuses the buffer.
- [X] Removes unnecessary refs to Spans. I don't think the Span struct itself is mutable, so a ref is not helpful.
- [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
- [X] Updates Movement packets
- [X] Adds OSI fastwalk packets. These aren't used on OSi anymore.
- [X] Adds new movement handling, but looks like the client doesn't use it. (Also leaving the 0x4000 Character List Flag off)
- [X] Adds time sync request handler, but also looks like the client doesn't use it.
- [X] Adds time sync response for time sync, just in case, but it isn't used, so not sure about the arguments.
- [X] Reimplements RunUO's fastwalk to use a circular array on the netstate instead of every mobile
- [X] Removes ClearFastwalkStack from RunUO implementation. This shouldn't be needed anymore
Changed fastwalk settings:
```cs
public static int WalkFootDelay { get; set; } = 440;
public static int RunFootDelay { get; set; } = 220;
public static int WalkMountDelay { get; set; } = 220;
public static int RunMountDelay { get; set; } = 110;
public static bool EnableFastwalkPrevention { get; set; } = true;
public static AccessLevel FastwalkExemptionLevel { get; set; } = AccessLevel.Counselor;
// If this is changed during runtime, then the steps array needs resizing.
public static int MaxSteps { get; private set; } = 4;
```
modernuo.json
```json
{
"settings": {
"movement.delay.runFoot": "220",
"movement.delay.runMount": "110",
"movement.delay.walkFoot": "440",
"movement.delay.walkMount": "220",
"movement.enableFastWalkPrevention": "True",
"movement.fastwalkExemptionLevel": "Counselor",
"movement.maxSteps": "4"
}
}
```
Notes about OSI fastwalk:
While it does work, I can't find a benefit in using it because of the variable speeds. If players moved at a single speed then we could refill the stack every X milliseconds with 6 keys and use a naive token bucket implementation.
Unfortunately variable speeds mount/run/walk/etc means we would have to use a leaky bucket algorithm.
If we are using a leaky bucket algorithm with a variable leak, then we don't need to send tokens because we are already tracking it on the server side.
ModernUO vs OSI Fastwalk:
When the fastwalk was implemented on OSI, it used up to 6 tokens. These tokens were probably distributed every 600-750 milliseconds. To get the same effect, the new fastwalk settings might need to be adjusted. I would tweak them and feel free to let me know what worked for you!
Bumps release version
- [X] Fixes several bugs
- [X] Updates more ordinal issues
- [X] Cleans up the code a bit
- [X] Turns classes static that should have been
- [X] Changes TcpServer.Instances to a HashSet
Bumps release version
- [X] Changes effect packets
- [X] Updates playing sounds
- [X] Updates Effects class to have more options so there are less direct calls to building the packets
- [X] Changes bonding status packet
- [X] Fixes bugs in the buffer writer
- [X] Removes background save commands
- [X] Avoids calling Serialize() on deserialization
- In a future optimization I will copy the entire object to a buffer, deserialize using a SpanReader, then use that buffer for the SaveBuffer
- [X] Fixes issue with decay queue.
Bumps release version
