Replace relevant Substring use with AsSpan

src/Humanizer/Humanizer.csproj

@@ -12,6 +12,7 @@
     <DebugType Condition=" '$(BuildingForLiveUnitTesting)' != 'true' ">embedded</DebugType>
     <NoWarn>CS1573;CS1591</NoWarn>
     <IsTrimmable>true</IsTrimmable>
+    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
   </PropertyGroup>
   <ItemGroup>
     <Using Remove="System.Net.Http" />

src/Humanizer/Inflections/Vocabulary.cs

@@ -1,4 +1,4 @@
-namespace Humanizer;
+namespace Humanizer;
 
 /// <summary>
 /// A container for exceptions to simple pluralization/singularization rules.
@@ -185,7 +185,7 @@ bool IsUncountable(string word) =>
 
     static string MatchUpperCase(string word, string replacement) =>
         char.IsUpper(word[0]) &&
-        char.IsLower(replacement[0]) ? char.ToUpper(replacement[0]) + replacement.Substring(1) : replacement;
+        char.IsLower(replacement[0]) ? StringHumanizeExtensions.Concat(char.ToUpper(replacement[0]), replacement.AsSpan(1)) : replacement;
 
     /// <summary>
     /// If the word is the letter s, singular or plural, return the letter s singular

src/Humanizer/InflectorExtensions.cs

@@ -1,4 +1,4 @@
-//The Inflector class was cloned from Inflector (https://github.com/srkirkland/Inflector)
+//The Inflector class was cloned from Inflector (https://github.com/srkirkland/Inflector)
 
 //The MIT License (MIT)
 
@@ -65,9 +65,9 @@ public static string Camelize(this string input)
     {
         var word = input.Pascalize();
         return word.Length > 0
-            ? word
-                .Substring(0, 1)
-                .ToLower() + word.Substring(1)
+            ? StringHumanizeExtensions.Concat(
+                char.ToLower(word[0]),
+                word.AsSpan(1))
             : word;
     }
 

src/Humanizer/Localisation/Formatters/LuxembourgishFormatter.cs

@@ -1,4 +1,4 @@
-namespace Humanizer;
+namespace Humanizer;
 
 class LuxembourgishFormatter(CultureInfo culture) :
     DefaultFormatter(culture)
@@ -18,12 +18,12 @@ public static string ApplyEifelerRule(string word)
         => word.TrimEnd(EifelerRuleSuffix);
 
     public static string CheckForAndApplyEifelerRule(string word, string nextWord)
-        => DoesEifelerRuleApply(nextWord)
+        => DoesEifelerRuleApply(nextWord.AsSpan())
             ? word.TrimEnd(EifelerRuleSuffix)
             : word;
 
-    public static bool DoesEifelerRuleApply(string nextWord)
-        => !string.IsNullOrWhiteSpace(nextWord)
+    public static bool DoesEifelerRuleApply(CharSpan nextWord)
+        => !nextWord.IsWhiteSpace()
            && !EifelerRuleCharacters.Contains(nextWord[0]);
 
     protected override string Format(TimeUnit unit, string resourceKey, int number, bool toWords = false)
@@ -33,7 +33,7 @@ protected override string Format(TimeUnit unit, string resourceKey, int number,
 
         return string.Format(resourceString,
             toWords ? numberAsWord : number,
-            DoesEifelerRuleApply(numberAsWord) ? "" : EifelerRuleSuffix);
+            DoesEifelerRuleApply(numberAsWord.AsSpan()) ? "" : EifelerRuleSuffix);
     }
 
     protected override string GetResourceKey(string resourceKey, int number)

src/Humanizer/Localisation/NumberToWords/ArabicNumberToWordsConverter.cs

@@ -1,4 +1,4 @@
-namespace Humanizer;
+namespace Humanizer;
 
 class ArabicNumberToWordsConverter :
     GenderedNumberToWordsConverter
@@ -268,7 +268,9 @@ static string ParseNumber(string word, int number, GrammaticalGender gender)
             foreach (var kv in ordinals.Where(kv => word.EndsWith(kv.Key)))
             {
                 // replace word with exception
-                return word.Substring(0, word.Length - kv.Key.Length) + kv.Value;
+                return StringHumanizeExtensions.Concat(
+                    word.AsSpan(0, word.Length - kv.Key.Length),
+                    kv.Value.AsSpan());
             }
         }
         else if (number is > 10 and < 100)
@@ -286,7 +288,9 @@ static string ParseNumber(string word, int number, GrammaticalGender gender)
                 foreach (var kv in ordinals.Where(kv => oldPart.EndsWith(kv.Key)))
                 {
                     // replace word with exception
-                    newPart = oldPart.Substring(0, oldPart.Length - kv.Key.Length) + kv.Value;
+                    newPart = StringHumanizeExtensions.Concat(
+                        oldPart.AsSpan(0, oldPart.Length - kv.Key.Length),
+                        kv.Value.AsSpan());
                 }
 
                 if (number > 19 && newPart == oldPart && oldPart.Length > 1)

src/Humanizer/Localisation/NumberToWords/AzerbaijaniNumberToWordsConverter.cs

@@ -1,4 +1,4 @@
-namespace Humanizer;
+namespace Humanizer;
 
 class AzerbaijaniNumberToWordsConverter :
     GenderlessNumberToWordsConverter
@@ -116,7 +116,7 @@ public override string ConvertToOrdinal(int number)
 
         if (word[^1] == 't')
         {
-            word = word.Substring(0, word.Length - 1) + 'd';
+            word = StringHumanizeExtensions.Concat(word.AsSpan(0, word.Length - 1), 'd');
         }
 
         if (suffixFoundOnLastVowel)

src/Humanizer/Localisation/NumberToWords/BrazilianPortugueseNumberToWordsConverter.cs

@@ -1,4 +1,4 @@
-namespace Humanizer;
+namespace Humanizer;
 
 class BrazilianPortugueseNumberToWordsConverter :
     GenderedNumberToWordsConverter
@@ -166,17 +166,17 @@ static string ApplyGender(string toWords, GrammaticalGender gender)
 
         if (toWords.EndsWith("os"))
         {
-            return toWords.Substring(0, toWords.Length - 2) + "as";
+            return StringHumanizeExtensions.Concat(toWords.AsSpan(0, toWords.Length - 2), "as".AsSpan());
         }
 
         if (toWords.EndsWith("um"))
         {
-            return toWords.Substring(0, toWords.Length - 2) + "uma";
+            return StringHumanizeExtensions.Concat(toWords.AsSpan(0, toWords.Length - 2), "uma".AsSpan());
         }
 
         if (toWords.EndsWith("dois"))
         {
-            return toWords.Substring(0, toWords.Length - 4) + "duas";
+            return StringHumanizeExtensions.Concat(toWords.AsSpan(0, toWords.Length - 4), "duas".AsSpan());
         }
 
         return toWords;
@@ -186,7 +186,9 @@ static string ApplyOrdinalGender(string toWords, GrammaticalGender gender)
     {
         if (gender == GrammaticalGender.Feminine)
         {
-            return toWords.TrimEnd('o') + 'a';
+            return StringHumanizeExtensions.Concat(
+                toWords.AsSpan().TrimEnd('o'),
+                'a');
         }
 
         return toWords;

src/Humanizer/Localisation/NumberToWords/DutchNumberToWordsConverter.cs

@@ -1,4 +1,4 @@
-namespace Humanizer;
+namespace Humanizer;
 
 /// <summary>
 /// Dutch spelling of numbers is not really officially regulated.
@@ -170,7 +170,7 @@ public override string ConvertToOrdinal(int number)
         foreach (var kv in OrdinalExceptions.Where(kv => word.EndsWith(kv.Key)))
         {
             // replace word with exception
-            return word.Substring(0, word.Length - kv.Key.Length) + kv.Value;
+            return StringHumanizeExtensions.Concat(word.AsSpan(0, word.Length - kv.Key.Length), kv.Value.AsSpan());
         }
 
         // achtste

src/Humanizer/Localisation/NumberToWords/LuxembourgishNumberToWordsConverter.cs

@@ -1,4 +1,4 @@
-namespace Humanizer;
+namespace Humanizer;
 
 class LuxembourgishNumberToWordsConverter : GenderedNumberToWordsConverter
 {
@@ -166,7 +166,7 @@ private static string GetEndingForGender(GrammaticalGender gender) =>
     private string GetPartWithEifelerRule(string pluralFormat, long number, GrammaticalGender gender)
     {
         var nextWord = pluralFormat
-            .Substring(3, pluralFormat.Length - 3)
+            .AsSpan(3, pluralFormat.Length - 3)
             .TrimStart();
         var wordForm = LuxembourgishFormatter.DoesEifelerRuleApply(nextWord)
             ? WordForm.Eifeler

src/Humanizer/Localisation/NumberToWords/PortugueseNumberToWordsConverter.cs

@@ -1,4 +1,4 @@
-namespace Humanizer;
+namespace Humanizer;
 
 class PortugueseNumberToWordsConverter : GenderedNumberToWordsConverter
 {
@@ -165,17 +165,17 @@ static string ApplyGender(string toWords, GrammaticalGender gender)
 
         if (toWords.EndsWith("os"))
         {
-            return toWords.Substring(0, toWords.Length - 2) + "as";
+            return StringHumanizeExtensions.Concat(toWords.AsSpan(0, toWords.Length - 2), "as".AsSpan());
         }
 
         if (toWords.EndsWith("um"))
         {
-            return toWords.Substring(0, toWords.Length - 2) + "uma";
+            return StringHumanizeExtensions.Concat(toWords.AsSpan(0, toWords.Length - 2), "uma".AsSpan());
         }
 
         if (toWords.EndsWith("dois"))
         {
-            return toWords.Substring(0, toWords.Length - 4) + "duas";
+            return StringHumanizeExtensions.Concat(toWords.AsSpan(0, toWords.Length - 4), "duas".AsSpan());
         }
 
         return toWords;

src/Humanizer/Localisation/NumberToWords/Romanian/RomanianOrdinalNumberConverter.cs

@@ -1,4 +1,4 @@
-namespace Humanizer;
+namespace Humanizer;
 
 class RomanianOrdinalNumberConverter
 {
@@ -72,7 +72,7 @@ public string Convert(int number, GrammaticalGender gender)
 
         if (gender == GrammaticalGender.Feminine && words.EndsWith("zeci"))
         {
-            words = words.Substring(0, words.Length - 4) + "zece";
+            words = StringHumanizeExtensions.Concat(words.AsSpan(0, words.Length - 4), "zece".AsSpan());
         }
         else if (gender == GrammaticalGender.Feminine && words.Contains("zeci") && (words.Contains("milioane") || words.Contains("miliarde")))
         {
@@ -82,15 +82,16 @@ public string Convert(int number, GrammaticalGender gender)
         if (gender == GrammaticalGender.Feminine && words.StartsWith("un "))
         {
             words = words
-                .Substring(2)
-                .TrimStart();
+                .AsSpan(2)
+                .TrimStart()
+                .ToString();
         }
 
         if (words.EndsWith("milioane"))
         {
             if (gender == GrammaticalGender.Feminine)
             {
-                words = words.Substring(0, words.Length - 8) + "milioana";
+                words = StringHumanizeExtensions.Concat(words.AsSpan(0, words.Length - 8), "milioana".AsSpan());
             }
         }
 
@@ -99,7 +100,7 @@ public string Convert(int number, GrammaticalGender gender)
         {
             if (gender == GrammaticalGender.Feminine)
             {
-                words = words.Substring(0, words.Length - 6) + "milioana";
+                words = StringHumanizeExtensions.Concat(words.AsSpan(0, words.Length - 6), "milioana".AsSpan());
             }
             else
             {

src/Humanizer/Localisation/NumberToWords/TurkishNumberToWordConverter.cs

@@ -1,4 +1,4 @@
-namespace Humanizer;
+namespace Humanizer;
 
 class TurkishNumberToWordConverter :
     GenderlessNumberToWordsConverter
@@ -154,7 +154,7 @@ public override string ConvertToOrdinal(int number)
 
         if (word[^1] == 't')
         {
-            word = word.Substring(0, word.Length - 1) + 'd';
+            word = StringHumanizeExtensions.Concat(word.AsSpan(0, word.Length - 1), 'd');
         }
 
         if (suffixFoundOnLastVowel)

src/Humanizer/StringHumanizeExtensions.cs

@@ -1,4 +1,8 @@
-namespace Humanizer;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+namespace Humanizer;
 
 /// <summary>
 /// Contains extension methods for humanizing string values.
@@ -49,8 +53,7 @@ static string FromPascalCase(string input)
         }
 
         return result.Length > 0
-            ? char.ToUpper(result[0]) +
-              result.Substring(1, result.Length - 1)
+            ? Concat(char.ToUpper(result[0]), result.AsSpan(1, result.Length - 1))
             : result;
     }
 
@@ -90,4 +93,32 @@ public static string Humanize(this string input, LetterCasing casing) =>
         input
             .Humanize()
             .ApplyCase(casing);
+
+#if NET
+    internal static string Concat(CharSpan left, CharSpan right) =>
+        string.Concat(left, right);
+
+    internal static string Concat(char left, CharSpan right) =>
+        string.Concat(MemoryMarshal.CreateReadOnlySpan(ref left, 1), right);
+
+    internal static string Concat(CharSpan left, char right) =>
+        string.Concat(left, MemoryMarshal.CreateReadOnlySpan(ref right, 1));
+#else
+    internal static unsafe string Concat(CharSpan left, CharSpan right)
+    {
+        var result = new string('\0', left.Length + right.Length);
+        fixed (char* pResult = result)
+        {
+            left.CopyTo(new Span<char>(pResult, left.Length));
+            right.CopyTo(new Span<char>(pResult + left.Length, right.Length));
+        }
+        return result;
+    }
+
+    internal static unsafe string Concat(char left, CharSpan right) =>
+        Concat(new CharSpan(&left, 1), right);
+
+    internal static unsafe string Concat(CharSpan left, char right) =>
+        Concat(left, new CharSpan(&right, 1));
+#endif
 }

src/Humanizer/Transformer/ToSentenceCase.cs

@@ -1,4 +1,4 @@
-namespace Humanizer;
+namespace Humanizer;
 
 class ToSentenceCase : ICulturedStringTransformer
 {
@@ -11,7 +11,12 @@ public string Transform(string input, CultureInfo? culture)
 
         if (input.Length >= 1)
         {
-            return culture.TextInfo.ToUpper(input[0]) + input.Substring(1);
+            if (char.IsUpper(input[0]))
+            {
+                return input;
+            }
+
+            return StringHumanizeExtensions.Concat(culture.TextInfo.ToUpper(input[0]), input.AsSpan(1));
         }
 
         return culture.TextInfo.ToUpper(input);

src/Humanizer/Truncation/FixedLengthTruncator.cs

@@ -1,4 +1,4 @@
-namespace Humanizer;
+namespace Humanizer;
 
 /// <summary>
 /// Truncate a string to a fixed length
@@ -28,12 +28,12 @@ class FixedLengthTruncator : ITruncator
         if (truncateFrom == TruncateFrom.Left)
         {
             return value.Length > length
-                ? truncationString + value.Substring(value.Length - length + truncationString.Length)
+                ? StringHumanizeExtensions.Concat(truncationString.AsSpan(), value.AsSpan(value.Length - length + truncationString.Length))
                 : value;
         }
 
         return value.Length > length
-            ? value.Substring(0, length - truncationString.Length) + truncationString
+            ? StringHumanizeExtensions.Concat(value.AsSpan(0, length - truncationString.Length), truncationString.AsSpan())
             : value;
     }
 }

src/Humanizer/Truncation/FixedNumberOfCharactersTruncator.cs

@@ -43,7 +43,7 @@ class FixedNumberOfCharactersTruncator : ITruncator
 
                 if (alphaNumericalCharactersProcessed + truncationString.Length == length)
                 {
-                    return truncationString + value.Substring(i);
+                    return StringHumanizeExtensions.Concat(truncationString.AsSpan(), value.AsSpan(i));
                 }
             }
         }
@@ -57,7 +57,7 @@ class FixedNumberOfCharactersTruncator : ITruncator
 
             if (alphaNumericalCharactersProcessed + truncationString.Length == length)
             {
-                return value.Substring(0, i + 1) + truncationString;
+                return StringHumanizeExtensions.Concat(value.AsSpan(0, i + 1), truncationString.AsSpan());
             }
         }