OneDiff

Text diff and document comparison for .NET.

This project is unaffiliated with any other project named OneDiff, including the Python diffusion-model accelerator of that name.

OneDiff is a clean-room diff and comparison library for .NET, in two layers:

• A text diff core (RecursiveAI.OneDiff): Myers, patience and histogram diff over any sequence; line, word, character and grapheme tokenizers; semantic and efficiency cleanup; unified and diff-match-patch patches with fuzzy apply; three-way merge in git's conflict styles. It depends on nothing beyond the .NET base class library.
• Document comparison (RecursiveAI.OneDiff.Documents and the adapters): a compare model with source anchors, alignment that follows moves, splits and merges, typed changes with resolved values (30 days → 60 days), renumbering and renamed defined terms as single changes, combining reviewers' copies, and version chains. PDFs (digital, and scans through a local OCR engine) are read into the model; the changes are marked on the original pages with real annotations, written as a rendered redline PDF, as HTML (inline or side by side), or as a versioned JSON change list.

Every comparison is checked for completeness: old plus the changes gives new, and new minus the changes gives old. If a grouping cannot be inverted, the engine falls back to a coarser complete one and says so; strict mode throws instead. Differences that a setting hides (typography, page numbers, comments, …) are counted in a ledger, never dropped. Nothing needs a model: the deterministic engine keeps that promise on its own.

It targets net10.0, uses no native code, and is built to be NativeAOT-, trimming- and WebAssembly-friendly. The same inputs and settings give byte-identical output. Nothing touches the network.

Install

dotnet add package RecursiveAI.OneDiff            # the text core
dotnet add package RecursiveAI.OneDiff.Documents  # document comparison, HTML and JSON
dotnet add package RecursiveAI.OneDiff.Pdf        # PDF in, PDF out
dotnet add package RecursiveAI.OneDiff.Ocr        # scans
dotnet tool install --global RecursiveAI.OneDiff.Tool   # the `onediff` command

Coming in later releases: Word documents in and tracked-changes DOCX out (RecursiveAI.OneDiff.Word, in this repository and not in the first release), spreadsheets, slides, and the OneNLP value recognizer (RecursiveAI.OneDiff.Nlp). Until then a Word file is refused with a message that names the package.

The happy path

Each line below is a runnable sample in samples/OneDiff.Samples.

using OneDiff;
using OneDiff.Documents;
using OneDiff.Documents.Serialization;
using OneDiff.Merge;
using OneDiff.Pdf;
 
// Text: the words that changed, a unified patch, a three-way merge.
string marked  = Diff.ToMarkdownInline(Diff.Words(oldText, newText));
string patch   = Diff.Unified(oldText, newText);
TextMerge both = Diff.Merge(baseText, ours, theirs);      // both.Text, both.HasConflicts
 
// PDF: a redline on the new document's own pages (highlights, with the old text in the pop-ups).
PdfRedline.Register();                                    // once at startup
Redline.Create("v1.pdf", "v2.pdf", "markup.pdf");
 
// PDF: a rendered, tagged redline PDF; or an HTML page with the two documents side by side.
var cmp = Comparison.Of("v1.pdf", "v2.pdf");
cmp.SaveAs("redline.pdf", PdfRedline.Rendered);
cmp.SaveAs("side-by-side.html", RedlineForm.HtmlSideBySide);
 
// The change list: walk what changed in substance, or save it as JSON and read it back.
foreach (var c in cmp.Changes.Where(c => c.IsSubstantive))
    Console.WriteLine($"{c.Kind}: {c.Old.Text} -> {c.New.Text}");
Redline.Create("v1.pdf", "v2.pdf", "changes.json");
Comparison again = ComparisonJson.Read(File.ReadAllBytes("changes.json"));

Inputs are recognized by their content, and the output form follows the extension of the output path. The same from a shell: onediff compare v1.pdf v2.pdf -o markup.pdf. A PDF that has no text layer is refused with a message that names RecursiveAI.OneDiff.Ocr (call OcrRedline.Register() to read scans); it is never compared as an empty document. For streams that refuse synchronous I/O, such as an ASP.NET Core request body, use Redline.CreateAsync, Comparison.OfAsync, SaveAsync and ComparisonJson.ReadAsync.

The low level

Every layer is public: the comparison is five stages over immutable values, and the alignment between the two documents is a value you can correct and run again.

using OneDiff.Documents;
using OneDiff.Documents.Model;      // CompareDocument
using OneDiff.Documents.Pipeline;   // Alignment
 
CompareDocument a = CompareDocument.FromText(oldText, "old");
CompareDocument b = CompareDocument.FromText(newText, "new");
 
Alignment alignment = Stages.Align(a, b);
alignment = alignment.Pin(oldNodeId, newNodeId);          // a reviewer's correction
 
Comparison result = Stages.Verify(Stages.Classify(Stages.Group(Stages.DiffPairs(alignment))));

Documentation

Start at docs/index.md. The pages that matter first:

• Samples, every redline look, and how to choose a form: docs/samples/README.md
• Coming from DiffPlex: docs/migrating-from-diffplex.md; from WmlComparer or Docxodus: docs/migrating-from-wmlcomparer.md
• What a comparison is and how it is proved complete: docs/compare-model.md
• Measured results, including the rows that are pending or lose: docs/results.md. Nothing beyond that page is claimed. In short: Myers' edit length equals GNU diff's minimum on 9,483 corpus pairs, three-way merge equals git merge-file byte for byte on 2,599 real triples in all three conflict styles, and in the speed rows against DiffPlex and diff-match-patch every area's geometric-mean time ratio is below 1.0 (the worst single row is 1.13×, patch make on x64).

Building

dotnet build -c Release
dotnet test --solution OneDiff.slnx -c Release

Build output goes outside the checkout; set ONEDIFF_ARTIFACTS to choose where. See docs/building.md.

License

Dual-licensed under either of MIT or Apache-2.0, at your option. © Recursive AI, LLC.