initial commit

Identity.cs

@@ -0,0 +1,67 @@
+using System.Linq;
+using System.Runtime.CompilerServices;
+
+namespace Benchmark
+{
+    public readonly struct Identity
+    {
+        public Identity(string prefix, int index, int revision)
+        {
+            Prefix = prefix;
+            Index = index;
+            Revision = revision;
+        }
+
+        public string Prefix { get; }
+        public int Index { get; }
+        public int Revision { get; }
+
+        public static bool TryParse(string value, out Identity identity)
+        {
+            identity = default;
+            var position = value.Length;
+            if (!TryGetNumber(value, null, ref position, out var revision)) return false;
+            if (value[position] != '-') return false;
+            if (!TryGetNumber(value, 7, ref position, out var index)) return false;
+            if (!TryGetPrefix(value, ref position, out var prefix)) return false;
+            identity = new Identity(prefix, index, revision);
+            return true;
+        }
+
+        private static bool TryGetPrefix(in string identity, ref int lastPosition, out string prefix)
+        {
+            prefix = identity.Remove(lastPosition + 1);
+            if (prefix.Length <= 3) return false;
+            return !prefix.Any(character => character < 'A' || character > 'Z');
+        }
+
+        private static bool TryGetNumber(in string identity, int? exactLength, ref int currentPosition, out int revision)
+        {
+            revision = 0;
+            var start = currentPosition;
+            for (currentPosition = start - 1; currentPosition >= 0; currentPosition--)
+            {
+                var current = identity[currentPosition];
+                if(current == '0') continue;
+                if (current < '1' || current > '9') break;
+                revision += (current - '0') * IntegerPow(10, start - currentPosition - 1);
+            }
+
+            if (exactLength != null && start - (currentPosition + 1) != exactLength) return false;
+            return revision != default;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static int IntegerPow(int x, int y)
+        {
+            if (y == 0) return 1;
+            var result = x;
+            for (var i = 1; i < y; i++)
+            {
+                result *= x;
+            }
+
+            return result;
+        }
+    }
+}