Trailing zero

Author: kzrnm

src/libraries/System.Runtime.Numerics/src/System/Number.BigInteger.cs

@@ -1069,7 +1069,7 @@ static ParsingStatus DivideAndConquer(ref NumberBuffer number, out BigInteger re
                     currentBuffer = buffer.Slice(0, currentBufferSize);
 
                     trailingZeroBuffer = trailingZeroBuffer.Slice(0, currentTrailingZeroBufferLength);
-                    if (trailingZeroBuffer.Length <= 1)
+                    if (trailingZeroBuffer.Length <= 1 && currentBufferSize < buffer.Length)
                     {
                         Debug.Assert(trailingZeroBuffer.Length == 1);
                         uint trailingZero = trailingZeroBuffer[0];

src/libraries/System.Runtime.Numerics/tests/BigInteger/parse.cs

@@ -207,6 +207,13 @@ private static void VerifyDefaultParse(Random random)
                 VerifyParseToString(GetDigitSequence(100, 1000, random));
             }
 
+            // Trailing Zero
+            VerifyParseToString("99000000000");
+            for (int i = 0; i < s_samples; i++)
+            {
+                VerifyParseToString(GetDigitSequence(1, 10, random) + "1000000000");
+            }
+
             // Leading White
             for (int i = 0; i < s_samples; i++)
             {
@@ -464,6 +471,13 @@ private static void VerifyNumberStyles(NumberStyles ns, Random random)
                 VerifyParseToString(GetDigitSequence(100, 1000, random), ns, true);
             }
 
+            // Trailing Zero
+            VerifyParseToString("99000000000", ns, true);
+            for (int i = 0; i < s_samples; i++)
+            {
+                VerifyParseToString(GetDigitSequence(1, 10, random) + "1000000000", ns, true);
+            }
+
             // Leading White
             for (int i = 0; i < s_samples; i++)
             {