From 394bacc1b5caeb2e27f24eb6a140956fd72343a9 Mon Sep 17 00:00:00 2001
From: Dongbo Wang <dongbow@microsoft.com>
Date: Mon, 23 Sep 2019 16:16:35 -0700
Subject: [PATCH] Make the history file mutext name unique across sessions
 (#1061)

---
 PSReadLine/Cmdlets.cs |  5 +----
 PSReadLine/History.cs | 36 +++++++++++++++++++++++++++++++++++-
 2 files changed, 36 insertions(+), 5 deletions(-)

diff --git a/PSReadLine/Cmdlets.cs b/PSReadLine/Cmdlets.cs
index ee747b22..b2ff9de6 100644
--- a/PSReadLine/Cmdlets.cs
+++ b/PSReadLine/Cmdlets.cs
@@ -8,7 +8,6 @@
 using System.Collections.ObjectModel;
 using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
-using System.IO;
 using System.Management.Automation;
 using System.Management.Automation.Language;
 using System.Reflection;
@@ -648,9 +647,7 @@ public string HistorySavePath
             get => _historySavePath;
             set
             {
-                // Normalize the path
-                var altPathChar = RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? '/' : '\\';
-                _historySavePath = value?.Replace(altPathChar, Path.DirectorySeparatorChar);
+                _historySavePath = GetUnresolvedProviderPathFromPSPath(value);
             }
         }
         private string _historySavePath;
diff --git a/PSReadLine/History.cs b/PSReadLine/History.cs
index 405c36af..e53f36c4 100644
--- a/PSReadLine/History.cs
+++ b/PSReadLine/History.cs
@@ -8,6 +8,7 @@
 using System.IO;
 using System.Linq;
 using System.Management.Automation;
+using System.Runtime.InteropServices;
 using System.Text;
 using System.Text.RegularExpressions;
 using System.Threading;
@@ -15,6 +16,34 @@
 
 namespace Microsoft.PowerShell
 {
+    /// <summary>
+    /// FNV-1a hashing algorithm: http://www.isthe.com/chongo/tech/comp/fnv/#FNV-1a
+    /// </summary>
+    internal class FNV1a32Hash
+    {
+        // FNV-1a algorithm parameters: http://www.isthe.com/chongo/tech/comp/fnv/#FNV-param
+        private const uint FNV32_PRIME = 16777619;
+        private const uint FNV32_OFFSETBASIS = 2166136261;
+
+        internal static uint ComputeHash(string input)
+        {
+            char ch;
+            uint hash = FNV32_OFFSETBASIS, lowByte, highByte;
+
+            for (int i = 0; i < input.Length; i++)
+            {
+                ch = input[i];
+                lowByte = (uint)(ch & 0x00FF);
+                hash = (hash ^ lowByte) * FNV32_PRIME;
+
+                highByte = (uint)(ch >> 8);
+                hash = (hash ^ highByte) * FNV32_PRIME;
+            }
+
+            return hash;
+        }
+    }
+
     public partial class PSConsoleReadLine
     {
         /// <summary>
@@ -182,7 +211,12 @@ private string GetHistorySaveFileMutexName()
         {
             // Return a reasonably unique name - it's not too important as there will rarely
             // be any contention.
-            return "PSReadLineHistoryFile_" + _options.HistorySavePath.GetHashCode();
+            uint hashFromPath = FNV1a32Hash.ComputeHash(
+                RuntimeInformation.IsOSPlatform(OSPlatform.Windows)
+                    ? _options.HistorySavePath.ToLower()
+                    : _options.HistorySavePath);
+
+            return "PSReadLineHistoryFile_" + hashFromPath.ToString();
         }
 
         private void IncrementalHistoryWrite()