chore: scoped public span params + CountLeadingZeros test/benchmark cleanup

src/Base58Encoding.Benchmarks/CountLeadingZerosBenchmark.cs

@@ -104,6 +104,19 @@ public int Combined()
         return totalCount;
     }
 
+    [Benchmark(Description = "IndexOfAnyExcept")]
+    public int IndexOfAnyExceptScan()
+    {
+        var totalCount = 0;
+        foreach (var data in TestData)
+        {
+            var index = data.AsSpan().IndexOfAnyExcept((byte)0);
+            totalCount += index < 0 ? data.Length : index;
+        }
+
+        return totalCount;
+    }
+
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     private static int CountLeadingZerosArray(ReadOnlySpan<byte> data)
     {

src/Base58Encoding.Tests/SimpleLeadingZerosTest.cs

@@ -1,11 +1,9 @@
-using System.Runtime.Intrinsics;
-
 namespace Base58Encoding.Tests;
 
 public class SimpleLeadingZerosTest
 {
     [Fact]
-    public void BitcoinAddress_CountLeadingZerosMultipleWays_SameResult()
+    public void BitcoinAddress_CountLeadingZeros_MatchesManualCount()
     {
         var address = "1111111111111111111114oLvT2";
         var decoded = Base58.Bitcoin.Decode(address);
@@ -18,16 +16,7 @@ public void BitcoinAddress_CountLeadingZerosMultipleWays_SameResult()
             manualCount++;
         }
 
-        // Test SIMD
-        int simdCount = Base58.CountLeadingZerosSimd(decoded, out int processed);
-        var simdScalarCount = 0;
-        if (simdCount >= processed)
-        {
-            int remaining = Base58.CountLeadingZerosScalar(decoded.AsSpan(simdCount));
-            simdScalarCount = simdCount + remaining;
-        }
-
-        Assert.Equal(simdScalarCount, manualCount);
+        Assert.Equal(manualCount, Base58.CountLeadingZeros(decoded));
     }
 
     [Theory]
@@ -38,33 +27,35 @@ public void BitcoinAddress_CountLeadingZerosMultipleWays_SameResult()
     [InlineData(31)]
     public void CountLeadingZeros_32Size_ReturnsCorrectNumber(int zerosCount)
     {
-        Assert.SkipUnless(Vector256.IsHardwareAccelerated, "Requires Vector256 hardware acceleration");
-
         // Arrange
         var data = new byte[32];
         data.AsSpan(0, zerosCount).Fill(0x00);
         Random.Shared.NextBytes(data.AsSpan(zerosCount));
+        data[zerosCount] = 1;
 
-        // Act
-        var result = Base58.CountLeadingZerosSimd(data, out var processed);
-
-        Assert.Equal(zerosCount, result);
-        Assert.Equal(data.Length, processed);
+        // Act / Assert
+        Assert.Equal(zerosCount, Base58.CountLeadingZeros(data));
     }
 
     [Fact]
     public void CountLeadingZeros_512Size_ReturnsCorrectNumber()
     {
-        Assert.SkipUnless(Vector256.IsHardwareAccelerated, "Requires Vector256 hardware acceleration");
-
         // Arrange
         var zerosCount = 123;
         var data = new byte[512];
         data.AsSpan(0, zerosCount).Fill(0x00);
         Random.Shared.NextBytes(data.AsSpan(zerosCount));
-        // Act
-        var result = Base58.CountLeadingZerosSimd(data, out var processed);
-        Assert.Equal(zerosCount, result);
-        Assert.Equal(Vector256<byte>.Count * 4, processed); // Vector256 used 4 times
+        data[zerosCount] = 1;
+
+        // Act / Assert
+        Assert.Equal(zerosCount, Base58.CountLeadingZeros(data));
+    }
+
+    [Fact]
+    public void CountLeadingZeros_AllZeros_ReturnsLength()
+    {
+        var data = new byte[40];
+
+        Assert.Equal(data.Length, Base58.CountLeadingZeros(data));
     }
 }

src/Base58Encoding/Base58.CountLeading.cs

@@ -71,6 +71,7 @@ internal static int CountLeadingZerosScalar(ReadOnlySpan<byte> data)
                 }
                 return count;
             }
+
             count += sizeof(ulong);
             length -= sizeof(ulong);
         }

src/Base58Encoding/Base58.Decode.cs

@@ -14,7 +14,7 @@ public sealed partial class Base58<TAlphabet>
     /// <param name="encoded">Base58 encoded input.</param>
     /// <returns>Decoded byte array.</returns>
     /// <exception cref="ArgumentException">Invalid Base58 character.</exception>
-    public byte[] Decode(ReadOnlySpan<char> encoded)
+    public byte[] Decode(scoped ReadOnlySpan<char> encoded)
     {
         if (encoded.IsEmpty)
         {
@@ -53,7 +53,7 @@ public byte[] Decode(ReadOnlySpan<char> encoded)
     /// <exception cref="ArgumentException">
     /// Thrown on invalid Base58 character or when <paramref name="destination"/> is too small.
     /// </exception>
-    public int Decode(ReadOnlySpan<char> encoded, Span<byte> destination)
+    public int Decode(scoped ReadOnlySpan<char> encoded, scoped Span<byte> destination)
     {
         if (encoded.IsEmpty)
         {
@@ -72,7 +72,7 @@ public int Decode(ReadOnlySpan<char> encoded, Span<byte> destination)
     /// <exception cref="ArgumentException">
     /// Thrown on invalid Base58 character or when <paramref name="destination"/> is too small.
     /// </exception>
-    public int Decode(ReadOnlySpan<byte> encoded, Span<byte> destination)
+    public int Decode(scoped ReadOnlySpan<byte> encoded, scoped Span<byte> destination)
     {
         if (encoded.IsEmpty)
         {

src/Base58Encoding/Base58.Encode.cs

@@ -14,7 +14,7 @@ public sealed partial class Base58<TAlphabet>
     /// </summary>
     /// <param name="data">Bytes to encode.</param>
     /// <returns>Base58 encoded string.</returns>
-    public string Encode(ReadOnlySpan<byte> data)
+    public string Encode(scoped ReadOnlySpan<byte> data)
     {
         if (data.IsEmpty)
         {
@@ -41,7 +41,7 @@ public string Encode(ReadOnlySpan<byte> data)
     /// <param name="destination">Destination buffer for ASCII-encoded Base58 characters.</param>
     /// <returns>Number of bytes written to <paramref name="destination"/>.</returns>
     /// <exception cref="ArgumentException">Thrown if <paramref name="destination"/> is too small.</exception>
-    public int Encode(ReadOnlySpan<byte> data, Span<byte> destination)
+    public int Encode(scoped ReadOnlySpan<byte> data, scoped Span<byte> destination)
     {
         if (data.IsEmpty)
         {