feat(std/node): add buf.equals method (#6640)

std/node/buffer.ts

@@ -200,6 +200,26 @@ export default class Buffer extends Uint8Array {
     return sourceBuffer.length;
   }
 
+  /*
+   * Returns true if both buf and otherBuffer have exactly the same bytes, false otherwise.
+   */
+  equals(otherBuffer: Uint8Array | Buffer): boolean {
+    if (!(otherBuffer instanceof Uint8Array)) {
+      throw new TypeError(
+        `The "otherBuffer" argument must be an instance of Buffer or Uint8Array. Received type ${typeof otherBuffer}`
+      );
+    }
+
+    if (this === otherBuffer) return true;
+    if (this.byteLength !== otherBuffer.byteLength) return false;
+
+    for (let i = 0; i < this.length; i++) {
+      if (this[i] !== otherBuffer[i]) return false;
+    }
+
+    return true;
+  }
+
   readBigInt64BE(offset = 0): bigint {
     return new DataView(
       this.buffer,

std/node/buffer_test.ts

@@ -518,3 +518,33 @@ Deno.test({
     });
   },
 });
+
+// ported from:
+// https://github.com/nodejs/node/blob/56dbe466fdbc598baea3bfce289bf52b97b8b8f7/test/parallel/test-buffer-equals.js#L6
+Deno.test({
+  name: "buf.equals",
+  fn() {
+    const b = Buffer.from("abcdf");
+    const c = Buffer.from("abcdf");
+    const d = Buffer.from("abcde");
+    const e = Buffer.from("abcdef");
+
+    assertEquals(b.equals(c), true);
+    assertEquals(d.equals(d), true);
+    assertEquals(
+      d.equals(new Uint8Array([0x61, 0x62, 0x63, 0x64, 0x65])),
+      true
+    );
+
+    assertEquals(c.equals(d), false);
+    assertEquals(d.equals(e), false);
+
+    assertThrows(
+      // deno-lint-ignore ban-ts-comment
+      // @ts-ignore
+      () => Buffer.alloc(1).equals("abc"),
+      TypeError,
+      `The "otherBuffer" argument must be an instance of Buffer or Uint8Array. Received type string`
+    );
+  },
+});