APErebus · Mar 6, 2025 · Mar 7, 2025
diff --git a/LibGit2Sharp.Tests/DiffBufferToBufferFixture.cs b/LibGit2Sharp.Tests/DiffBufferToBufferFixture.cs
@@ -0,0 +1,332 @@
+using System;
+using System.IO;
+using System.Linq;
+using System.Text;
+using LibGit2Sharp.Tests.TestHelpers;
+using Xunit;
+
+namespace LibGit2Sharp.Tests
+{
+    public class DiffBufferToBufferFixture
+    {
+        [Fact]
+        public void ComparingTheSameBufferReturnsNoDifference()
+        {
+            const string text = @"
+1
+2
+3
+4
+5
+6";
+
+            var buffer = Encoding.UTF8.GetBytes(text);
+
+            var changes = Diff.Compare(buffer, buffer);
+
+            Assert.Equal(0, changes.LinesAdded);
+            Assert.Equal(0, changes.LinesDeleted);
+            Assert.Equal(string.Empty, changes.Patch);
+        }
+
+        [Fact]
+        public void CanCompareTwoBuffersWithADiffOfOneHunk()
+        {
+            var oldText = @"1
+2
+4
+5
+6
+8
+7".EnsureUnixLineEndings();
+
+            var newText = @"1
+2
+3
+4
+5
+6
+7
+8
+9".EnsureUnixLineEndings();
+
+            var oldBuffer = Encoding.UTF8.GetBytes(oldText);
+            var newBuffer = Encoding.UTF8.GetBytes(newText);
+
+            var changes = Diff.Compare(oldBuffer, newBuffer);
+
+            Assert.False(changes.IsBinaryComparison);
+
+            Assert.Equal(3, changes.LinesAdded);
+            Assert.Equal(1, changes.LinesDeleted);
+
+            var expected = new StringBuilder()
+                .Append("@@ -1,7 +1,9 @@\n")
+                .Append(" 1\n")
+                .Append(" 2\n")
+                .Append("+3\n")
+                .Append(" 4\n")
+                .Append(" 5\n")
+                .Append(" 6\n")
+                .Append("+7\n")
+                .Append(" 8\n")
+                .Append("-7\n")
+                .Append("\\ No newline at end of file\n")
+                .Append("+9\n")
+                .Append("\\ No newline at end of file\n");
+
+            Assert.Equal(expected.ToString(), changes.Patch);
+        }
+
+        [Fact]
+        public void CanCompareTwoBuffersWithADiffOfTwoHunks()
+        {
+            var oldText = @"1
+2
+3
+4
+5
+6
+8
+7
+9
+10
+11".EnsureUnixLineEndings();
+
+            var newText = @"2
+3
+4
+5
+6
+8
+7
+9
+10
+12".EnsureUnixLineEndings();
+
+            var oldBuffer = Encoding.UTF8.GetBytes(oldText);
+            var newBuffer = Encoding.UTF8.GetBytes(newText);
+
+            var changes = Diff.Compare(oldBuffer, newBuffer);
+
+            Assert.False(changes.IsBinaryComparison);
+
+            Assert.Equal(1, changes.LinesAdded);
+            Assert.Equal(2, changes.LinesDeleted);
+
+            var expected = new StringBuilder()
+                .Append("@@ -1,4 +1,3 @@\n")
+                .Append("-1\n")
+                .Append(" 2\n")
+                .Append(" 3\n")
+                .Append(" 4\n")
+                .Append("@@ -8,4 +7,4 @@\n")
+                .Append(" 7\n")
+                .Append(" 9\n")
+                .Append(" 10\n")
+                .Append("-11\n")
+                .Append("\\ No newline at end of file\n")
+                .Append("+12\n")
+                .Append("\\ No newline at end of file\n");
+
+            Assert.Equal(expected.ToString(), changes.Patch);
+        }
+
+        [Fact]
+        public void CanCompareATextualBufferAgainstABinaryBuffer()
+        {
+            var oldText = @"1
+2
+3
+4
+5".EnsureUnixLineEndings();
+
+            var binaryBuffer = new byte[] { 17, 16, 0, 4, 65 };
+
+
+            var oldBuffer = Encoding.UTF8.GetBytes(oldText);
+
+            var changes = Diff.Compare(oldBuffer, binaryBuffer);
+
+            Assert.True(changes.IsBinaryComparison);
+
+            Assert.Equal(0, changes.LinesAdded);
+            Assert.Equal(0, changes.LinesDeleted);
+        }
+
+        [Fact]
+        public void CanCompareABufferAgainstANullBuffer()
+        {
+            var oldText = @"1
+2
+3
+4
+5".EnsureUnixLineEndings();
+
+
+            var oldBuffer = Encoding.UTF8.GetBytes(oldText);
+
+            var changes = Diff.Compare(oldBuffer, null);
+
+            Assert.Equal(0, changes.LinesAdded);
+            Assert.NotEqual(0, changes.LinesDeleted);
+            Assert.NotEqual(string.Empty, changes.Patch);
+
+            changes = Diff.Compare(null, oldBuffer);
+
+            Assert.NotEqual(0, changes.LinesAdded);
+            Assert.Equal(0, changes.LinesDeleted);
+            Assert.NotEqual(string.Empty, changes.Patch);
+        }
+
+        [Fact]
+        public void CanCompareABufferAgainstAnEmptyBuffer()
+        {
+            var oldText = @"1
+2
+3
+4
+5".EnsureUnixLineEndings();
+
+
+            var oldBuffer = Encoding.UTF8.GetBytes(oldText);
+            var emptyBuffer = Array.Empty<byte>();
+
+            var changes = Diff.Compare(oldBuffer, emptyBuffer);
+
+            Assert.Equal(0, changes.LinesAdded);
+            Assert.NotEqual(0, changes.LinesDeleted);
+            Assert.NotEqual(string.Empty, changes.Patch);
+
+            changes = Diff.Compare(emptyBuffer, oldBuffer);
+
+            Assert.NotEqual(0, changes.LinesAdded);
+            Assert.Equal(0, changes.LinesDeleted);
+            Assert.NotEqual(string.Empty, changes.Patch);
+        }
+
+        [Fact]
+        public void ComparingTwoNullBlobsReturnsAnEmptyContentChanges()
+        {
+            var changes = Diff.Compare(null, null);
+            Assert.False(changes.IsBinaryComparison);
+
+            Assert.Equal(0, changes.LinesAdded);
+            Assert.Equal(0, changes.LinesDeleted);
+        }
+
+        [Fact]
+        public void ComparingBuffersWithNoSpacesAndIndentHeuristicOptionMakesADifference()
+        {
+                // Based on test diff indent heuristic from:
+                // https://github.com/git/git/blob/433860f3d0beb0c6f205290bd16cda413148f098/t/t4061-diff-indent.sh#L17
+                var oldContent =
+@"	1
+	2
+	a
+
+	b
+	3
+	4";
+                var newContent =
+@"	1
+	2
+	a
+
+	b
+	a
+
+	b
+	3
+	4";
+
+                var oldBuffer = Encoding.UTF8.GetBytes(oldContent);
+                var newBuffer = Encoding.UTF8.GetBytes(newContent);
+
+                var noIndentHeuristicOption = new CompareOptions { IndentHeuristic = false };
+                var indentHeuristicOption = new CompareOptions { IndentHeuristic = true };
+
+                var changes0 = Diff.Compare(oldBuffer, newBuffer, noIndentHeuristicOption);
+                var changes1 = Diff.Compare(oldBuffer, newBuffer, indentHeuristicOption);
+
+                Assert.NotEqual(changes0.Patch, changes1.Patch);
+                Assert.Equal(CanonicalChangedLines(changes0), CanonicalChangedLines(changes1));
+        }
+
+        [Fact]
+        public void ComparingBlobsWithNoSpacesIndentHeuristicOptionMakesNoDifference()
+        {
+                var oldContent =
+@"	1
+	2
+	a
+	b
+	3
+	4";
+                var newContent =
+@"	1
+	2
+	a
+	b
+	a
+	b
+	3
+	4";
+
+                var oldBuffer = Encoding.UTF8.GetBytes(oldContent);
+                var newBuffer = Encoding.UTF8.GetBytes(newContent);
+
+                var noIndentHeuristicOption = new CompareOptions { IndentHeuristic = false };
+                var indentHeuristicOption = new CompareOptions { IndentHeuristic = true };
+
+                var changes0 = Diff.Compare(oldBuffer, newBuffer, noIndentHeuristicOption);
+                var changes1 = Diff.Compare(oldBuffer, newBuffer, indentHeuristicOption);
+
+                Assert.Equal(changes0.Patch, changes1.Patch);
+
+        }
+
+        [Fact]
+        public void DiffSetsTheAddedAndDeletedLinesCorrectly()
+        {
+
+                var oldContent =
+                @"1
+2
+3
+4";
+
+                var newContent =
+                   @"1
+2
+3
+5";
+
+                var oldBuffer = Encoding.UTF8.GetBytes(oldContent);
+                var newBuffer = Encoding.UTF8.GetBytes(newContent);
+
+                ContentChanges changes = Diff.Compare(oldBuffer, newBuffer);
+
+                Assert.Single(changes.AddedLines);
+                Assert.Single(changes.DeletedLines);
+
+                Assert.Equal("4", changes.DeletedLines.First().Content);
+                Assert.Equal("5", changes.AddedLines.First().Content);
+
+                Assert.Equal(4, changes.DeletedLines.First().LineNumber);
+                Assert.Equal(4, changes.AddedLines.First().LineNumber);
+
+        }
+
+         static string CanonicalChangedLines(ContentChanges changes)
+         {
+             // Create an ordered representation of lines that have been added or removed
+             return string.Join("\n", changes.Patch.Split('\n').Where(l => l.StartsWith("+") || l.StartsWith("-")).OrderBy(l => l));
+         }
+    }
+
+    public static class StringExtensionMethods
+    {
+        public static string EnsureUnixLineEndings(this string str) => str.Replace("\r", "");
+    }
+}
diff --git a/LibGit2Sharp/ContentChanges.cs b/LibGit2Sharp/ContentChanges.cs
@@ -32,6 +32,16 @@ internal unsafe ContentChanges(Repository repo, Blob oldBlob, Blob newBlob, GitD
                                  LineCallback);
         }
 
+        internal unsafe ContentChanges(byte[] oldBuffer, byte[] newBuffer, GitDiffOptions options)
+        {
+            Proxy.git_diff_buffers(oldBuffer,
+                                   newBuffer,
+                                   options,
+                                   FileCallback,
+                                   HunkCallback,
+                                   LineCallback);
+        }
+
         internal ContentChanges(bool isBinaryComparison)
         {
             this.IsBinaryComparison = isBinaryComparison;

diff --git a/LibGit2Sharp/Core/NativeMethods.cs b/LibGit2Sharp/Core/NativeMethods.cs
@@ -712,6 +712,23 @@ internal static extern unsafe int git_diff_find_similar(
         [DllImport(libgit2, CallingConvention = CallingConvention.Cdecl)]
         internal static extern unsafe git_diff_delta* git_diff_get_delta(git_diff* diff, UIntPtr idx);
 
+        [DllImport(libgit2, CallingConvention = CallingConvention.Cdecl)]
+        internal static extern unsafe int git_diff_buffers(
+            IntPtr oldBuffer,
+            UIntPtr oldBufferLength,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(StrictUtf8Marshaler))]
+            string oldAsPath,
+            IntPtr newBuffer,
+            UIntPtr newBufferLength,
+            [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(StrictUtf8Marshaler))]
+            string newAsPath,
+            GitDiffOptions options,
+            git_diff_file_cb fileCallback,
+            git_diff_binary_cb binaryCallback,
+            git_diff_hunk_cb hunkCallback,
+            git_diff_line_cb lineCallback,
+            IntPtr payload);
+
         [DllImport(libgit2, CallingConvention = CallingConvention.Cdecl)]
         internal static extern int git_filter_register(
             [MarshalAs(UnmanagedType.CustomMarshaler, MarshalCookie = UniqueId.UniqueIdentifier, MarshalTypeRef = typeof(StrictUtf8Marshaler))] string name,