Base58 perfomance patch

src/Neo/Cryptography/Base58.cs

@@ -12,6 +12,7 @@
 using System;
 using System.Linq;
 using System.Numerics;
+using System.Runtime.CompilerServices;
 using System.Text;
 
 namespace Neo.Cryptography
@@ -25,6 +26,21 @@ public static class Base58
         /// Represents the alphabet of the base-58 encoder.
         /// </summary>
         public const string Alphabet = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
+        private const char ZeroChar = '1';
+        private static readonly BigInteger s_alphabetLength = Alphabet.Length;
+
+        #pragma warning disable format
+        private static readonly sbyte[] s_decodeMap =
+        [
+            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+            -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6,
+            7, 8, -1, -1, -1, -1, -1, -1, -1, 9, 10, 11, 12, 13, 14, 15, 16, -1, 17,
+            18, 19, 20, 21, -1, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, -1, -1,
+            -1, -1, -1, -1, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, -1, 44, 45,
+            46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57
+        ];
+        #pragma warning restore format
 
         /// <summary>
         /// Converts the specified <see cref="string"/>, which encodes binary data as base-58 digits, to an equivalent byte array. The encoded <see cref="string"/> contains the checksum of the binary data.
@@ -71,21 +87,30 @@ public static byte[] Decode(string input)
         {
             // Decode Base58 string to BigInteger
             var bi = BigInteger.Zero;
-            for (int i = 0; i < input.Length; i++)
+            sbyte digit;
+            for (var i = 0; i < input.Length; i++)
             {
-                int digit = Alphabet.IndexOf(input[i]);
-                if (digit < 0)
+                if (input[i] >= 123)
+                    throw new FormatException($"Invalid Base58 character '{input[i]}' at position {i}");
+                digit = s_decodeMap[input[i]];
+                if (digit == -1)
                     throw new FormatException($"Invalid Base58 character '{input[i]}' at position {i}");
-                bi = bi * Alphabet.Length + digit;
+                bi = bi * s_alphabetLength + digit;
             }
 
             // Encode BigInteger to byte[]
             // Leading zero bytes get encoded as leading `1` characters
-            int leadingZeroCount = input.TakeWhile(c => c == Alphabet[0]).Count();
-            var leadingZeros = new byte[leadingZeroCount];
-            if (bi.IsZero) return leadingZeros;
-            var bytesWithoutLeadingZeros = bi.ToByteArray(isUnsigned: true, isBigEndian: true);
-            return [.. leadingZeros, .. bytesWithoutLeadingZeros];
+
+            var leadingZeroCount = LeadingBase58Zeros(input);
+            if (bi.IsZero)
+            {
+                return new byte[leadingZeroCount];
+            }
+
+            var result = new byte[leadingZeroCount + bi.GetByteCount(true)];
+
+            _ = bi.TryWriteBytes(result.AsSpan(leadingZeroCount), out _, true, true);
+            return result;
         }
 
         /// <summary>
@@ -99,20 +124,35 @@ public static string Encode(ReadOnlySpan<byte> input)
             BigInteger value = new(input, isUnsigned: true, isBigEndian: true);
 
             // Encode BigInteger to Base58 string
-            var sb = new StringBuilder();
+            var sb = new StringBuilder(input.Length * 138 / 100 + 5);
 
             while (value > 0)
             {
-                value = BigInteger.DivRem(value, Alphabet.Length, out var remainder);
-                sb.Insert(0, Alphabet[(int)remainder]);
+                value = BigInteger.DivRem(value, s_alphabetLength, out var remainder);
+                sb.Append(Alphabet[(int)remainder]);
             }
 
             // Append `1` for each leading 0 byte
             for (int i = 0; i < input.Length && input[i] == 0; i++)
             {
-                sb.Insert(0, Alphabet[0]);
+                sb.Append(ZeroChar);
             }
-            return sb.ToString();
+
+            Span<char> copy = stackalloc char[sb.Length];
+            sb.CopyTo(0, copy, sb.Length);
+            copy.Reverse();
+
+            return copy.ToString();
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static int LeadingBase58Zeros(string collection)
+        {
+            var i = 0;
+            var len = collection.Length;
+            for (; i < len && collection[i] == ZeroChar; i++) { }
+
+            return i;
         }
     }
 }