From 17fa327ff69000a8174b274fda24de8da81c7a21 Mon Sep 17 00:00:00 2001
From: kzrnm <gengesa@gmail.com>
Date: Thu, 29 Feb 2024 02:56:29 +0900
Subject: [PATCH] Fix TryParseBigIntegerHexOrBinaryNumberStyle (#97995)

* Fix TryParseBigIntegerHexOrBinaryNumberStyle

* Fix typo

* Add hex test

---------

Co-authored-by: Tanner Gooding <tagoo@outlook.com>
---
 .../src/System/Number.BigInteger.cs                 |  6 +++---
 .../tests/BigInteger/parse.cs                       | 13 +++++++++++++
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/src/libraries/System.Runtime.Numerics/src/System/Number.BigInteger.cs b/src/libraries/System.Runtime.Numerics/src/System/Number.BigInteger.cs
index a5fc0e6f1f1d53..01db0ef3777e87 100644
--- a/src/libraries/System.Runtime.Numerics/src/System/Number.BigInteger.cs
+++ b/src/libraries/System.Runtime.Numerics/src/System/Number.BigInteger.cs
@@ -445,7 +445,7 @@ internal static ParsingStatus TryParseBigIntegerHexOrBinaryNumberStyle<TParser,
             int leadingBitsCount = value.Length % TParser.DigitsPerBlock;
 
             uint leading = signBits;
-            // First parse unanligned leading block if exists.
+            // First parse unaligned leading block if exists.
             if (leadingBitsCount != 0)
             {
                 if (!TParser.TryParseUnalignedBlock(value[0..leadingBitsCount], out leading))
@@ -484,8 +484,8 @@ internal static ParsingStatus TryParseBigIntegerHexOrBinaryNumberStyle<TParser,
                     // Require to store in _bits.
 
                     // Positive: sign=1, bits=[leading]
-                    // Negative: sign=-1, bits=[leading ^ -1 + 1]=[-leading]
-                    result = new BigInteger((int)signBits | 1, [leading ^ signBits - signBits]);
+                    // Negative: sign=-1, bits=[(leading ^ -1) + 1]=[-leading]
+                    result = new BigInteger((int)signBits | 1, [(leading ^ signBits) - signBits]);
                     return ParsingStatus.OK;
                 }
                 else
diff --git a/src/libraries/System.Runtime.Numerics/tests/BigInteger/parse.cs b/src/libraries/System.Runtime.Numerics/tests/BigInteger/parse.cs
index 86652ef6550a86..9852ea93bf1aa4 100644
--- a/src/libraries/System.Runtime.Numerics/tests/BigInteger/parse.cs
+++ b/src/libraries/System.Runtime.Numerics/tests/BigInteger/parse.cs
@@ -143,6 +143,18 @@ public void Parse_Hex32Bits()
             Assert.True(BigInteger.TryParse("080000001", NumberStyles.HexNumber, null, out result));
             Assert.Equal(0x80000001u, result);
 
+            Assert.True(BigInteger.TryParse("F0000001", NumberStyles.HexNumber, null, out result));
+            Assert.Equal(-0xFFFFFFFL, result);
+
+            Assert.True(BigInteger.TryParse("0F0000001", NumberStyles.HexNumber, null, out result));
+            Assert.Equal(0xF0000001u, result);
+            
+            Assert.True(BigInteger.TryParse("F00000001", NumberStyles.HexNumber, null, out result));
+            Assert.Equal(-0xFFFFFFFFL, result);
+
+            Assert.True(BigInteger.TryParse("0F00000001", NumberStyles.HexNumber, null, out result));
+            Assert.Equal(0xF00000001u, result);
+
             // Regression test for: https://github.com/dotnet/runtime/issues/74758
             Assert.True(BigInteger.TryParse("FFFFFFFFE", NumberStyles.HexNumber, null, out result));
             Assert.Equal(new BigInteger(-2), result);
@@ -175,6 +187,7 @@ public void Parse_Hex32Bits()
         [InlineData("10000000000000000000000000000000", (long)int.MinValue)]
         [InlineData("010000000000000000000000000000001", 0x080000001L)]
         [InlineData("111111111111111111111111111111110", -2L)]
+        [InlineData("100000000000000000000000000000001", -0xFFFFFFFFL)]
         [InlineData("0111111111111111111111111111111111", 0x1FFFFFFFFL)]
         public void Parse_BinSpecialCases(string input, long expectedValue)
         {