From 73752bdd5989ff5a75b041f52cb3b6db4991689b Mon Sep 17 00:00:00 2001
From: Sean Grider <sean.grider@protonmail.com>
Date: Mon, 16 Sep 2024 14:28:39 -0400
Subject: [PATCH] Track inodes and use them for hard link comparisons on linux

---
 VDF.Core/FileEntry.cs  | 10 ++++++++++
 VDF.Core/ScanEngine.cs | 10 ++++++++++
 2 files changed, 20 insertions(+)

diff --git a/VDF.Core/FileEntry.cs b/VDF.Core/FileEntry.cs
index ba4de82f..64811ee9 100644
--- a/VDF.Core/FileEntry.cs
+++ b/VDF.Core/FileEntry.cs
@@ -38,6 +38,14 @@ public FileEntry(FileInfo fileInfo) {
 			DateCreated = fileInfo.CreationTimeUtc;
 			DateModified = fileInfo.LastWriteTimeUtc;
 			FileSize = fileInfo.Length;
+			if (CoreUtils.IsWindows) {
+				Inode = 0;
+			} else {
+				var ok = Mono.Unix.Native.Syscall.stat(_Path, out var stat);
+				if (ok == 0) {
+					Inode = stat.st_ino;
+				}
+			}
 		}
 
 		[ProtoMember(1)]
@@ -65,6 +73,8 @@ public string Path {
 		public DateTime DateModified;
 		[ProtoMember(8)]
 		public long FileSize;
+		[ProtoMember(9)]
+		public ulong Inode;
 
 		[ProtoIgnore]
 		internal bool invalid = true;
diff --git a/VDF.Core/ScanEngine.cs b/VDF.Core/ScanEngine.cs
index ec8e16e0..d930cccf 100644
--- a/VDF.Core/ScanEngine.cs
+++ b/VDF.Core/ScanEngine.cs
@@ -477,6 +477,16 @@ void ScanForDuplicates() {
 								continue;
 						}
 
+						// Shortcut for linux, if the inodes are known and they are the same
+						// these two files are by definition hard links of each other
+						// no further inspection necessary
+						if (Settings.ExcludeHardLinks &&
+							entry.Inode > 0 &&
+							entry.Inode == compItem.Inode) {
+							isDuplicate = false;
+							break;
+						}
+
 
 						flags = DuplicateFlags.None;
 						isDuplicate = CheckIfDuplicate(entry, null, compItem, out difference);