From 32919299ec541c1e6048338ed7486107c5a1f6d2 Mon Sep 17 00:00:00 2001
From: Alexander O'Mara <me@alexomara.com>
Date: Sat, 18 Jan 2025 22:00:48 -0500
Subject: [PATCH] Test open offset and length combinations

---
 macho/universal.test.ts | 45 +++++++++++++++++++++++++++++++++++------
 macho/universal.ts      | 18 +++++++++++++++++
 2 files changed, 57 insertions(+), 6 deletions(-)

diff --git a/macho/universal.test.ts b/macho/universal.test.ts
index 39b8e9b..209f1ce 100644
--- a/macho/universal.test.ts
+++ b/macho/universal.test.ts
@@ -5,22 +5,55 @@ import { Universal } from './universal.ts';
 
 const fixtures = fixtureMachos();
 
-for (const { kind, arch, file, archs } of fixtures) {
+for (const [index, { kind, arch, file, archs }] of fixtures.entries()) {
 	Deno.test(`${kind}: ${arch}: ${file}`, async () => {
 		const [macho] = await fixtureMacho(kind, arch, [file]);
-		const blob = new Blob([macho]);
 		const uni = new Universal();
 
-		await uni.open(blob);
+		switch (index % 4) {
+			case 0: {
+				const blob = new Blob([macho]);
+				await uni.open(blob);
+				assertEquals(uni.offset(), 0);
+				assertEquals(uni.length(), 0);
+				break;
+			}
+			case 1: {
+				const blob = new Blob([macho]);
+				await uni.open(blob, 0, blob.size);
+				assertEquals(uni.offset(), 0);
+				assertEquals(uni.length(), blob.size);
+				break;
+			}
+			case 2: {
+				const blob = new Blob([
+					new ArrayBuffer(3),
+					macho,
+					new ArrayBuffer(3),
+				]);
+				await uni.open(blob, 3);
+				assertEquals(uni.offset(), 3);
+				assertEquals(uni.length(), 0);
+				break;
+			}
+			case 3: {
+				const blob = new Blob([
+					new ArrayBuffer(3),
+					macho,
+					new ArrayBuffer(3),
+				]);
+				await uni.open(blob, 3, macho.byteLength);
+				assertEquals(uni.offset(), 3);
+				assertEquals(uni.length(), macho.byteLength);
+				break;
+			}
+		}
 		assertEquals(uni.isUniversal(), archs.size > 1);
 
 		const architectures = new Set<Architecture>();
 		uni.architectures(architectures);
-
 		assertEquals(architectures.size, archs.size);
-
 		uni.architectures(architectures);
-
 		assertEquals(architectures.size, archs.size);
 	});
 }
diff --git a/macho/universal.ts b/macho/universal.ts
index 4b75cff..9235885 100644
--- a/macho/universal.ts
+++ b/macho/universal.ts
@@ -255,4 +255,22 @@ export class Universal {
 	public isUniversal(): boolean {
 		return !!this.mArchList;
 	}
+
+	/**
+	 * Get offset in reader.
+	 *
+	 * @returns Byte offset in reader.
+	 */
+	public offset(): number {
+		return this.mBase;
+	}
+
+	/**
+	 * Get length in reader.
+	 *
+	 * @returns Byte length in reader.
+	 */
+	public length(): number {
+		return this.mLength;
+	}
 }