The stack_alloc buffer is now created using the maximum needed size for the input string (length of input string * maximum needed lenght for a single char)

Author: carlosirna

Unidecoder.Characters.cs

@@ -30,7 +30,6 @@ public static partial class Unidecoder
     {
         private static readonly string[][] characters;
         private static readonly int MaxDecodedCharLength;
-        private static readonly int MaxStringLengthForStackAlloc;
 
         static Unidecoder()
         {
@@ -549,7 +548,6 @@ static Unidecoder()
                         if (str.Length > MaxDecodedCharLength)
                             MaxDecodedCharLength = str.Length;
                 }
-                MaxStringLengthForStackAlloc = STACKALLOC_BUFFER_SIZE / MaxDecodedCharLength - 1;
             }
         }
     }

py2cs.py

@@ -36,7 +36,6 @@
     {
         private static readonly string[][] characters;
         private static readonly int MaxDecodedCharLength;
-        private static readonly int MaxStringLengthForStackAlloc;
 
         static Unidecoder()
         {
@@ -97,7 +96,6 @@ def formatch(ch, cc):
                         if (str.Length > MaxDecodedCharLength)
                             MaxDecodedCharLength = str.Length;
                 }
-                MaxStringLengthForStackAlloc = STACKALLOC_BUFFER_SIZE / MaxDecodedCharLength - 1;
             }
         }
     }

src/Unidecoder.Characters.cs

@@ -30,7 +30,6 @@ public static partial class Unidecoder
     {
         private static readonly string[][] characters;
         private static readonly int MaxDecodedCharLength;
-        private static readonly int MaxStringLengthForStackAlloc;
 
         static Unidecoder()
         {
@@ -549,8 +548,6 @@ static Unidecoder()
                         if (str.Length > MaxDecodedCharLength)
                             MaxDecodedCharLength = str.Length;
                 }
-                MaxStringLengthForStackAlloc = STACKALLOC_BUFFER_SIZE / MaxDecodedCharLength - 1;
             }
         }
     }
-    

src/Unidecoder.cs

@@ -20,7 +20,7 @@ public static partial class Unidecoder
   {
     // for short strings I use a buffer allocated in the stack instead of a stringbuilder.
     // (this is faster and gives less work to the garbage collector)
-    private const int STACKALLOC_BUFFER_SIZE = 8192;
+    private const int MAX_STACKALLOC_BUFFER_SIZE = 8192;
 
     [SkipLocalsInit] // this is to avoid the local raw buffer variable stackBuffer do be zeroed for every call: we don't need it and is very cpu intensive (this attribute needs unsafe compliation)
     /// <summary>
@@ -40,12 +40,12 @@ public static string Unidecode(this string input, int? tempStringBuilderCapacity
     {
       if (string.IsNullOrEmpty(input))
         return "";
-
-      if (input.Length >= MaxStringLengthForStackAlloc)
+      var neededBufferSize = input.Length * MaxDecodedCharLength + 1;
+      if (neededBufferSize >= MAX_STACKALLOC_BUFFER_SIZE)
         return SlowUnidecode(input, tempStringBuilderCapacity);
 
       bool noConversionNeeded = true;
-      Span<char> stackBuffer = stackalloc char[STACKALLOC_BUFFER_SIZE];
+      Span<char> stackBuffer = stackalloc char[neededBufferSize];
       int buffIdx = 0;
       foreach (char c in input)
       {