From 6be7ed34017f754e540b9a21a9babb9cb6d4e869 Mon Sep 17 00:00:00 2001
From: David Smith <dsmith@datasync.com>
Date: Tue, 10 Jan 2017 19:45:24 -0600
Subject: [PATCH] Add default hash code function to use in unit tests.

---
 TallyCore/Utility/StringUtility.cs | 51 ++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)

diff --git a/TallyCore/Utility/StringUtility.cs b/TallyCore/Utility/StringUtility.cs
index 2e64f23c..dc11183a 100644
--- a/TallyCore/Utility/StringUtility.cs
+++ b/TallyCore/Utility/StringUtility.cs
@@ -159,4 +159,55 @@ public int Compare(string x, string y)
 
         int IEqualityComparer.GetHashCode(object obj) => GetHashCode(obj as string);
     }
+
+    public static class DefaultUnicodeHashFunction
+    {
+        /// <summary>
+        /// Hashes the provided string using the given CompareOptions.
+        /// Doing this allows all custom compare options to be applied in determining the hash value.
+        /// </summary>
+        /// <param name="str">The string.</param>
+        /// <param name="info">The CompareInfo object doing the unicode-aware comparison.</param>
+        /// <param name="options">The options to apply to the comparison.</param>
+        /// <returns>Returns the hash code for the string.</returns>
+        public static int HashFunction(string str, CompareInfo info, CompareOptions options)
+        {
+            if (info == null)
+                throw new ArgumentNullException(nameof(info));
+
+            if (string.IsNullOrEmpty(str))
+                return 0;
+
+            SortKey sortOrder = info.GetSortKey(str, options);
+
+            int hash = GetByteArrayHash(sortOrder.KeyData);
+
+            return hash;
+        }
+
+        /// <summary>
+        /// Generates a hash code for an array of bytes.
+        /// </summary>
+        /// <param name="keyData">The key data.</param>
+        /// <returns>Returns a hash code value.</returns>
+        private static int GetByteArrayHash(byte[] keyData)
+        {
+            unchecked
+            {
+                const int p = 16777619;
+                int hash = (int)2166136261;
+
+                for (int i = 0; i < keyData.Length; i++)
+                    hash = (hash ^ keyData[i]) * p;
+
+                hash += hash << 13;
+                hash ^= hash >> 7;
+                hash += hash << 3;
+                hash ^= hash >> 17;
+                hash += hash << 5;
+                return hash;
+            }
+        }
+    }
+
 }