From 9fd0c52d513ad363984c5cc5d3d60011320b17fa Mon Sep 17 00:00:00 2001
From: "Jeffrey C. Ollie" <jeff@ocjtech.us>
Date: Fri, 28 Aug 2026 21:05:49 -0500
Subject: [PATCH] Add README

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016uAPiLrcvxP4hyvSLokRrp
---
 README.md     | 79 +++++++++++++++++++++++++++++++++++++++++++++++++++
 build.zig.zon |  2 +-
 2 files changed, 80 insertions(+), 1 deletion(-)
 create mode 100644 README.md

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..abef0f6
--- /dev/null
+++ b/README.md
@@ -0,0 +1,79 @@
+<!--
+SPDX-FileCopyrightText: © 2026 Jeffrey C. Ollie
+SPDX-License-Identifier: MIT
+-->
+
+# isbn.zig
+
+A Zig library for parsing, validating, and converting International
+Standard Book Numbers (ISBNs) in both the 10-digit and 13-digit
+formats.
+
+## Features
+
+- Parse ISBNs from text, with or without `-` separators.
+- Validate check digits during parsing (including the `X` check digit
+  used by ISBN-10).
+- Compute check digits, optionally using SIMD vector operations.
+- Upgrade an ISBN-10 to its equivalent ISBN-13.
+- Compare ISBNs across formats: an ISBN-10 is equal to its 13-digit
+  equivalent.
+
+## Requirements
+
+- Zig 0.16.0 or later
+
+## Installation
+
+Add the dependency to your project:
+
+```sh
+zig fetch --save git+https://tangled.org/jcollie.dev/isbn.zig
+```
+
+Then wire it up in your `build.zig`:
+
+```zig
+const isbn = b.dependency("isbn", .{
+    .target = target,
+    .optimize = optimize,
+});
+exe.root_module.addImport("isbn", isbn.module("isbn"));
+```
+
+## Usage
+
+```zig
+const ISBN = @import("isbn").ISBN;
+
+// Parsing validates the check digit.
+const ten: ISBN = try .parse("0-306-40615-2");
+const thirteen: ISBN = try .parse("978-0-306-40615-7");
+
+// Upgrade an ISBN-10 to an ISBN-13.
+const upgraded = ten.upgrade();
+
+// Comparison works across formats.
+std.debug.assert(ten.eql(&thirteen));
+```
+
+`parse` returns `error.ParseError` for malformed input and
+`error.InvalidCheckDigit` when the check digit doesn't match.
+
+## Build options
+
+- `-Dsimd=[bool]` — use SIMD vector operations for computing check
+  digits (default: `true`).
+
+## Testing
+
+```sh
+zig build test
+```
+
+The test suite includes unit tests and a fuzz test.
+
+## License
+
+[MIT](LICENSES/MIT.txt). This project is compliant with the
+[REUSE Specification](https://reuse.software/).
diff --git a/build.zig.zon b/build.zig.zon
index e2258a7..e5cfa7c 100644
--- a/build.zig.zon
+++ b/build.zig.zon
@@ -12,6 +12,6 @@
         "build.zig.zon",
         "src",
         "LICENSES",
-        //"README.md",
+        "README.md",
     },
 }
-- 
2.51.2