fix Utf8Formatter always assume invariant culture when formatting a floating-point whole number

Author: adienakhmad

Hexa.NET.Utilities.Tests/Utf8FormatterTests.cs

@@ -49,4 +49,40 @@ public unsafe void FormatDoubleTest(double value, int digit, string expected)
         // Assert
         Assert.That(Encoding.UTF8.GetString(utf8Span), Is.EqualTo(expected));
     }
+
+    [TestCase(10, 0, "en-US","10")]
+    [TestCase(10, 0, "de-DE","10")]
+    [TestCase(0.75f, 2, "en-US","0.75")]
+    [TestCase(0.75f, 2, "de-DE","0,75")]
+    public unsafe void FormatFloatCultureTest(float value, int digit, string cultureName, string expected)
+    {
+        // Arrange
+        byte* buffer = stackalloc byte[128];
+        CultureInfo culture = new CultureInfo(cultureName, false);
+
+        // Act
+        int len = Utf8Formatter.Format(value, buffer, 128, culture, digit);
+        ReadOnlySpan<byte> utf8Span = new ReadOnlySpan<byte>(buffer, len);
+
+        // Assert
+        Assert.That(Encoding.UTF8.GetString(utf8Span), Is.EqualTo(expected));
+    }
+
+    [TestCase(10, 0, "en-US","10")]
+    [TestCase(10, 0, "de-DE","10")]
+    [TestCase(0.75f, 2, "en-US","0.75")]
+    [TestCase(0.75f, 2, "de-DE","0,75")]
+    public unsafe void FormatDoubleCultureTest(double value, int digit, string cultureName, string expected)
+    {
+        // Arrange
+        byte* buffer = stackalloc byte[128];
+        CultureInfo culture = new CultureInfo(cultureName, false); // uses comma as decimal operator
+
+        // Act
+        int len = Utf8Formatter.Format(value, buffer, 128, culture, digit);
+        ReadOnlySpan<byte> utf8Span = new ReadOnlySpan<byte>(buffer, len);
+
+        // Assert
+        Assert.That(Encoding.UTF8.GetString(utf8Span), Is.EqualTo(expected));
+    }
 }

Hexa.NET.Utilities/Text/Utf8Formatter.cs

@@ -327,6 +327,7 @@ public static unsafe int Format(float value, byte* buffer, int bufSize, CultureI
             }
 
             buffer += ConvertUtf16ToUtf8(format.CurrencyDecimalSeparator, buffer, (int)(end - buffer));
+            byte separator = *(buffer - 1);
 
             digits = digits >= 0 ? digits : 7;
 
@@ -345,7 +346,7 @@ public static unsafe int Format(float value, byte* buffer, int bufSize, CultureI
                 buffer--;
             }
 
-            while (*(buffer - 1) == '.')
+            while (*(buffer - 1) == separator)
             {
                 buffer--;
             }
@@ -410,6 +411,7 @@ public static unsafe int Format(double value, byte* buffer, int bufSize, Culture
             }
 
             buffer += ConvertUtf16ToUtf8(format.CurrencyDecimalSeparator, buffer, (int)(end - buffer));
+            byte separator = *(buffer - 1);
 
             digits = digits >= 0 ? digits : 7;
 
@@ -428,7 +430,7 @@ public static unsafe int Format(double value, byte* buffer, int bufSize, Culture
                 buffer--;
             }
 
-            while (*(buffer - 1) == '.')
+            while (*(buffer - 1) == separator)
             {
                 buffer--;
             }