Change static readonly fields to const fields. (#4211)

This will at least somewhat improve performance, as confirmed through microbenchmark testing.

const fields are replaced with literal values in the Assembly's IL code, while static readonly fields may be optimized by the JIT, and is not guaranteed to happen. const fields may also lend themselves to stronger optimizations at runtime.

Source/ACE.Common/DerethDateTime.cs

@@ -8,29 +8,29 @@ namespace ACE.Common
     public class DerethDateTime
     {
         // Changing the four variables below will result in the Date and Time reported in ACClient no longer matching
-        private static int hoursInADay      = 16;   // A Derethian day has 16 hours
-        private static int daysInAMonth     = 30;   // A Derethian month has 30 days and does not vary like Earth months.
-        private static int monthsInAYear    = 12;   // A Derethian year has 12 months
-        private static double dayTicks      = 7620; // A Derethain day has 7620 ticks per day
+        private const int hoursInADay      = 16;   // A Derethian day has 16 hours
+        private const int daysInAMonth     = 30;   // A Derethian month has 30 days and does not vary like Earth months.
+        private const int monthsInAYear    = 12;   // A Derethian year has 12 months
+        private const double dayTicks      = 7620; // A Derethain day has 7620 ticks per day
 
-        private static double hourTicks     = dayTicks / hoursInADay;
-        private static double minuteTicks   = hourTicks / 60;
-        private static double secondTicks   = minuteTicks / 60;
+        private const double hourTicks     = dayTicks / hoursInADay;
+        private const double minuteTicks   = hourTicks / 60;
+        private const double secondTicks   = minuteTicks / 60;
 
-        private static double monthTicks    = dayTicks * daysInAMonth;
-        private static double yearTicks     = monthTicks * monthsInAYear;
+        private const double monthTicks    = dayTicks * daysInAMonth;
+        private const double yearTicks     = monthTicks * monthsInAYear;
 
-        private static double dayZeroTicks  = 0; // Morningthaw 1, 10 P.Y. - Morntide-and-Half
-        private static double hourOneTicks  = 210; // Morningthaw 1, 10 P.Y. - Midsong
-        private static double dayOneTicks   = dayZeroTicks + hourOneTicks + (hourTicks * 8); // Morningthaw 2, 10 P.Y. - Darktide
-        private static double yearOneTicks  = dayOneTicks + (dayTicks * 359); // Morningthaw 1, 11 P.Y. - Darktide
-        private static double yearZeroTicks = dayOneTicks + (dayTicks * 269); // Snowreap 1, 10 P.Y. - Darktide
+        private const double dayZeroTicks  = 0; // Morningthaw 1, 10 P.Y. - Morntide-and-Half
+        private const double hourOneTicks  = 210; // Morningthaw 1, 10 P.Y. - Midsong
+        private const double dayOneTicks   = dayZeroTicks + hourOneTicks + (hourTicks * 8); // Morningthaw 2, 10 P.Y. - Darktide
+        private const double yearOneTicks  = dayOneTicks + (dayTicks * 359); // Morningthaw 1, 11 P.Y. - Darktide
+        private const double yearZeroTicks = dayOneTicks + (dayTicks * 269); // Snowreap 1, 10 P.Y. - Darktide
 
-        private static DateTime dayZero_RealWorld       = new DateTime(1999, 4, 1, 10, 30, 00);
-        private static DateTime dayOne_RealWorld        = new DateTime(1999, 4, 2, 00, 00, 00);
+        private static readonly DateTime dayZero_RealWorld       = new DateTime(1999, 4, 1, 10, 30, 00);
+        private static readonly DateTime dayOne_RealWorld        = new DateTime(1999, 4, 2, 00, 00, 00);
 
-        private static DateTime retailDayOne_RealWorld  = new DateTime(1999, 11, 2, 00, 00, 00);
-        private static DateTime retailDayLast_RealWorld = new DateTime(2017, 1, 31, 12, 00, 00); // Eastern Standard Time
+        private static readonly DateTime retailDayOne_RealWorld  = new DateTime(1999, 11, 2, 00, 00, 00);
+        private static readonly DateTime retailDayLast_RealWorld = new DateTime(2017, 1, 31, 12, 00, 00); // Eastern Standard Time
 
         /// <summary>
         /// <para>A <see cref="DerethDateTime"/> instance set to the Derethian Date, Portal Year and Time when the worlds first opened.</para>
@@ -55,13 +55,13 @@ public class DerethDateTime
         /// <summary>
         /// <para>Date: Morningthaw 1, 10 P.Y. | Time: Morntide-and-Half (0)</para>
         /// </summary>
-        public static readonly double MinValue = 0; // Morningthaw 1, 10 P.Y. - Morntide-and-Half
+        public const double MinValue = 0; // Morningthaw 1, 10 P.Y. - Morntide-and-Half
 
         /// <summary>
         /// <para>Any value higher than this results in acclient crashing upon connection to server.</para>
         /// <para>Date: Thistledown 2, 401 P.Y. | Time: Morntide-and-Half (1073741828)</para>
         /// </summary>
-        public static readonly double MaxValue = (yearTicks * 391) + (monthTicks * 5) + (dayTicks * 1) + 4; // Thistledown 2, 401 P.Y. - Morntide-and-Half (1073741828)
+        public const double MaxValue = (yearTicks * 391) + (monthTicks * 5) + (dayTicks * 1) + 4; // Thistledown 2, 401 P.Y. - Morntide-and-Half (1073741828)
 
         /// <summary>
         /// Months of the Portal Year

Source/ACE.Common/ThreadSafeRandom.cs

@@ -38,7 +38,7 @@ public static double NextInterval(float qualityMod)
         /// <summary>
         /// The maximum possible double < 1.0
         /// </summary>
-        private static readonly double maxExclusive = 0.9999999999999999;
+        private const double maxExclusive = 0.9999999999999999;
 
         public static double NextIntervalMax(float qualityMod)
         {

Source/ACE.DatLoader/DatDatabase.cs

@@ -13,7 +13,7 @@ public class DatDatabase
     {
         private static readonly ILog log = LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);
 
-        private static readonly uint DAT_HEADER_OFFSET = 0x140;
+        private const uint DAT_HEADER_OFFSET = 0x140;
 
         public string FilePath { get; }
 

Source/ACE.DatLoader/DatDirectoryHeader.cs

@@ -4,7 +4,7 @@ namespace ACE.DatLoader
 {
     public class DatDirectoryHeader : IUnpackable
     {
-        internal static readonly uint ObjectSize = ((sizeof(uint) * 0x3E) + sizeof(uint) + (DatFile.ObjectSize * 0x3D));
+        internal const uint ObjectSize = ((sizeof(uint) * 0x3E) + sizeof(uint) + (DatFile.ObjectSize * 0x3D));
 
         public uint[] Branches { get; } = new uint[0x3E];
         public uint EntryCount { get; private set; }

Source/ACE.DatLoader/DatFile.cs

@@ -7,7 +7,7 @@ namespace ACE.DatLoader
 {
     public class DatFile : IUnpackable
     {
-        internal static readonly uint ObjectSize = (sizeof(uint) * 6);
+        internal const uint ObjectSize = (sizeof(uint) * 6);
 
 
         //public uint BitFlags { get; private set; }

Source/ACE.Database/WorldDatabaseWithEntityCache.cs

@@ -863,7 +863,7 @@ public void CacheAllTreasureMaterialBase()
             }
         }
 
-        private static readonly float NormalizeEpsilon = 0.00001f;
+        private const float NormalizeEpsilon = 0.00001f;
 
         private void TreasureMaterialBase_Normalize(Dictionary<int, Dictionary<int, List<TreasureMaterialBase>>> materialBase)
         {

Source/ACE.Entity/Position.cs

@@ -503,9 +503,9 @@ public string ToLOCString()
             return $"0x{LandblockId.Raw:X8} [{PositionX:F6} {PositionY:F6} {PositionZ:F6}] {RotationW:F6} {RotationX:F6} {RotationY:F6} {RotationZ:F6}";
         }
 
-        public static readonly int BlockLength = 192;
-        public static readonly int CellSide = 8;
-        public static readonly int CellLength = 24;
+        public const int BlockLength = 192;
+        public const int CellSide = 8;
+        public const int CellLength = 24;
 
         public bool Equals(Position p)
         {

Source/ACE.Server/Command/Handlers/DeveloperFixCommands.cs

@@ -1333,10 +1333,10 @@ public static Dictionary<uint, int> GetImbuedEffect()
         }
 
         // head / hands / feet
-        public static readonly int MaxArmorLevel_Extremity = 345;
+        public const int MaxArmorLevel_Extremity = 345;
 
         // everything else
-        public static readonly int MaxArmorLevel_NonExtremity = 315;
+        public const int MaxArmorLevel_NonExtremity = 315;
 
         public static int GetArmorLevel(int armorLevel, EquipMask equipMask, TinkerLog tinkerLog, int numTinkers, int imbuedEffect)
         {

Source/ACE.Server/Entity/Chess/ChessMatch.cs

@@ -711,7 +711,7 @@ public void SendGameOver(Player player, int winner)
         /// <summary>
         /// How quickly the rankings will raise / lower
         /// </summary>
-        public static readonly int RankFactor = 50;
+        public const int RankFactor = 50;
 
         /// <summary>
         /// Adjusts the chess ranks for 2 players after a match

Source/ACE.Server/Entity/Cloak.cs

@@ -77,7 +77,7 @@ private static float MaxProcBase200
             }
         }
 
-        private static readonly float TwoThirds = 2.0f / 3.0f;
+        private const float TwoThirds = 2.0f / 3.0f;
 
         /// <summary>
         /// Rolls for a chance at procing a cloak spell
@@ -197,7 +197,7 @@ public static bool IsCloak(WorldObject wo)
         /// <summary>
         /// The amount of damage reduced by a cloak proced with PropertyInt.CloakWeaveProc=2
         /// </summary>
-        public static readonly int DamageReductionAmount = 200;
+        public const int DamageReductionAmount = 200;
 
         public static int GetDamageReductionAmount(WorldObject source)
         {

Source/ACE.Server/Entity/Fellowship.cs

@@ -630,7 +630,7 @@ internal double GetMemberSharePercent()
             return 1.0;
         }
 
-        public static readonly int MaxDistance = 600;
+        public const int MaxDistance = 600;
 
         /// <summary>
         /// Returns the amount to scale the XP for a fellow

Source/ACE.Server/Entity/LandblockMesh.cs

@@ -22,22 +22,22 @@ public class LandblockMesh: Mesh
         /// <summary>
         /// A landblock has this many cells squared
         /// </summary>
-        public static readonly int CellDim = 8;
+        public const int CellDim = 8;
 
         /// <summary>
         /// A landblock is this unit size squared
         /// </summary>
-        public static readonly int LandblockSize = 192;
+        public const int LandblockSize = 192;
 
         /// <summary>
         /// A landblock cell is this unit size squared
         /// </summary>
-        public static readonly int CellSize = LandblockSize / CellDim;
+        public const int CellSize = LandblockSize / CellDim;
 
         /// <summary>
         /// A landblock has this many vertices squared
         /// </summary>
-        public static readonly int VertexDim = CellDim + 1;
+        public const int VertexDim = CellDim + 1;
 
         /// <summary>
         /// LandHeightTable mapping non-linear heights

Source/ACE.Server/Entity/Mutations/MutationCache.cs

@@ -512,7 +512,7 @@ public static string GetSecondOperator(MutationEffectType effectType)
             return null;
         }
 
-        private static readonly string prefix = "ACE.Server.Entity.Mutations.";
+        private const string prefix = "ACE.Server.Entity.Mutations.";
 
         private static List<string> ReadScript(string filename)
         {

Source/ACE.Server/Factories/Entity/ChanceTable.cs

@@ -10,7 +10,7 @@ namespace ACE.Server.Factories.Entity
     public class ChanceTable<T> : List<(T result, float chance)>
     {
         private bool verified;
-        private static readonly decimal threshold = 0.0000001M;
+        private const decimal threshold = 0.0000001M;
 
         private static readonly ILog log = LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);
 

Source/ACE.Server/Factories/LootGenerationFactory.cs

@@ -736,8 +736,8 @@ public static MaterialType RollGemType(int tier)
             return gemResult.MaterialType;
         }
 
-        public static readonly float WeaponBulk = 0.50f;
-        public static readonly float ArmorBulk = 0.25f;
+        public const float WeaponBulk = 0.50f;
+        public const float ArmorBulk = 0.25f;
 
         private static bool MutateBurden(WorldObject wo, TreasureDeath treasureDeath, bool isWeapon)
         {
@@ -839,9 +839,9 @@ private static void MutateValue(WorldObject wo, int tier, TreasureRoll roll)
         }
 
         // increase for a wider variance in item value ranges
-        private static readonly float valueFactor = 1.0f / 3.0f;
+        private const float valueFactor = 1.0f / 3.0f;
 
-        private static readonly float valueNonFactor = 1.0f - valueFactor;
+        private const float valueNonFactor = 1.0f - valueFactor;
 
         private static void MutateValue_Generic(WorldObject wo, int tier)
         {

Source/ACE.Server/Factories/Tables/Cantrips/ArmorCantrips.cs

@@ -95,7 +95,7 @@ public static class ArmorCantrips
             SpellId.CANTRIPPIERCINGBANE1,
         };
 
-        private static readonly int NumLevels = 4;
+        private const int NumLevels = 4;
 
         // original api
         public static readonly SpellId[][] Table = new SpellId[spells.Count][];

Source/ACE.Server/Factories/Tables/Cantrips/JewelryCantrips.cs

@@ -73,7 +73,7 @@ public static class JewelryCantrips
             SpellId.CANTRIPPIERCINGWARD1,
         };
 
-        private static readonly int NumLevels = 4;
+        private const int NumLevels = 4;
 
         // original api
         public static readonly SpellId[][] Table = new SpellId[spells.Count][];

Source/ACE.Server/Factories/Tables/Cantrips/MeleeCantrips.cs

@@ -29,7 +29,7 @@ public static class MeleeCantrips
             SpellId.CantripSneakAttackProwess1,
         };
 
-        private static readonly int NumLevels = 4;
+        private const int NumLevels = 4;
 
         // original api
         public static readonly SpellId[][] Table = new SpellId[spells.Count][];

Source/ACE.Server/Factories/Tables/Cantrips/MissileCantrips.cs

@@ -28,7 +28,7 @@ public static class MissileCantrips
             SpellId.CantripSneakAttackProwess1,
         };
 
-        private static readonly int NumLevels = 4;
+        private const int NumLevels = 4;
 
         // original api
         public static readonly SpellId[][] Table = new SpellId[spells.Count][];

Source/ACE.Server/Factories/Tables/Cantrips/WandCantrips.cs

@@ -32,7 +32,7 @@ public static class WandCantrips
             SpellId.CantripSpiritThirst1,
         };
 
-        private static readonly int NumLevels = 4;
+        private const int NumLevels = 4;
 
         // original api
         public static readonly SpellId[][] Table = new SpellId[spells.Count][];

Source/ACE.Server/Factories/Tables/Spells/ArmorSpells.cs

@@ -103,7 +103,7 @@ public static class ArmorSpells
             SpellId.LightningBane1,
         };
 
-        private static readonly int NumTiers = 8;
+        private const int NumTiers = 8;
 
         // original api
         public static readonly SpellId[][] Table = new SpellId[spells.Count][];

Source/ACE.Server/Factories/Tables/Spells/GemSpells.cs

@@ -87,7 +87,7 @@ public static class GemSpells
             SpellId.LightningProtectionSelf1,
         };
 
-        private static readonly int NumTiers = 8;
+        private const int NumTiers = 8;
 
         // original api
         public static readonly SpellId[][] GemCreatureSpellMatrix = new SpellId[NumTiers][];

Source/ACE.Server/Factories/Tables/Spells/JewelrySpells.cs

@@ -85,7 +85,7 @@ public static class JewelrySpells
             SpellId.LightningProtectionSelf1,
         };
 
-        private static readonly int NumTiers = 8;
+        private const int NumTiers = 8;
 
         // original api
         public static readonly SpellId[][] Table = new SpellId[spells.Count][];

Source/ACE.Server/Factories/Tables/Spells/MeleeSpells.cs

@@ -30,7 +30,7 @@ public static class MeleeSpells
             SpellId.SneakAttackMasterySelf1,
         };
 
-        private static readonly int NumTiers = 8;
+        private const int NumTiers = 8;
 
         // original api
         public static readonly SpellId[][] Table = new SpellId[spells.Count][];

Source/ACE.Server/Factories/Tables/Spells/MissileSpells.cs

@@ -29,7 +29,7 @@ public static class MissileSpells
             SpellId.SneakAttackMasterySelf1,
         };
 
-        private static readonly int NumTiers = 8;
+        private const int NumTiers = 8;
 
         // original api
         public static readonly SpellId[][] Table = new SpellId[spells.Count][];

Source/ACE.Server/Factories/Tables/Spells/ScrollSpells.cs

@@ -346,9 +346,9 @@ public static class ScrollSpells
             SpellId.CurseWeakness1,
         };
 
-        private static readonly int NumLevels = 7;
+        private const int NumLevels = 7;
 
-        private static readonly int MaxLevels = 8;
+        private const int MaxLevels = 8;
 
         private static readonly int NumSpells = creatureSpells.Count + lifeSpells.Count + itemSpells.Count + warSpells.Count + voidSpells.Count;
 

Source/ACE.Server/Factories/Tables/Spells/WandSpells.cs

@@ -34,7 +34,7 @@ public static class WandSpells
             SpellId.SneakAttackMasterySelf1,
         };
 
-        private static readonly int NumTiers = 8;
+        private const int NumTiers = 8;
 
         // original api
         public static readonly SpellId[][] Table = new SpellId[spells.Count][];

Source/ACE.Server/Managers/RecipeManager.cs

@@ -1479,7 +1479,7 @@ public static void ModifyDataID(Player player, RecipeModsDID didMod, WorldObject
         /// <summary>
         /// flag to use c# logic instead of mutate script logic
         /// </summary>
-        private static readonly bool useMutateNative = false;
+        private const bool useMutateNative = false;
 
         public static bool TryMutate(Player player, WorldObject source, WorldObject target, Recipe recipe, uint dataId, HashSet<uint> modified)
         {

Source/ACE.Server/Network/GameAction/Actions/GameActionQueryAge.cs

@@ -17,19 +17,19 @@ public static void Handle(ClientMessage message, Session session)
             session.Network.EnqueueSend(new GameEventQueryAgeResponse(session, string.Empty, ageMsg));
         }
 
-        private static readonly int SecondsPerMinute = 60;
-        private static readonly int MinutesPerHour = 60;
-        private static readonly int HoursPerDay = 24;
-
-        private static readonly int DaysPerWeek = 7;
-        private static readonly int DaysPerMonth = 30;
-        private static readonly int DaysPerYear = 365;
-
-        private static readonly int SecondsPerHour = SecondsPerMinute * MinutesPerHour;     // 3600
-        private static readonly int SecondsPerDay = SecondsPerHour * HoursPerDay;           // 86400
-        private static readonly int SecondsPerWeek = SecondsPerDay * DaysPerWeek;           // 604800
-        private static readonly int SecondsPerMonth = SecondsPerDay * DaysPerMonth;         // 2592000
-        private static readonly int SecondsPerYear = SecondsPerDay * DaysPerYear;           // 31536000
+        private const int SecondsPerMinute = 60;
+        private const int MinutesPerHour = 60;
+        private const int HoursPerDay = 24;
+
+        private const int DaysPerWeek = 7;
+        private const int DaysPerMonth = 30;
+        private const int DaysPerYear = 365;
+
+        private const int SecondsPerHour = SecondsPerMinute * MinutesPerHour;     // 3600
+        private const int SecondsPerDay = SecondsPerHour * HoursPerDay;           // 86400
+        private const int SecondsPerWeek = SecondsPerDay * DaysPerWeek;           // 604800
+        private const int SecondsPerMonth = SecondsPerDay * DaysPerMonth;         // 2592000
+        private const int SecondsPerYear = SecondsPerDay * DaysPerYear;           // 31536000
 
         public static string CalculateAgeMessage(int ageSeconds)
         {