1 files changed, 15 insertions, 0 deletions
diff --git a/src/ninep/addr.zig b/src/ninep/addr.zig
index 9674a323..df2cfaf0 100644
--- a/src/ninep/addr.zig
+++ b/src/ninep/addr.zig
@@ -384,6 +384,21 @@ test "an address is evaluated from the current one, as acme's are" {
     try testing.expectEqualStrings(e_order, th.wr(q, qaddr, "/a/,/b/").reply.ename);
 }
 
+test "a backward search along one long line takes time in its length, not its square" {
+    const gpa = testing.allocator;
+    const line = try gpa.alloc(u8, 7 * 16800);
+    defer gpa.free(line);
+    for (0..16800) |i| @memcpy(line[i * 7 ..][0..7], "answer ");
+    const p = try th.withFile(gpa, line);
+    defer p.deinit();
+    const t0 = std.Io.Timestamp.now(testing.io, .awake);
+    try testing.expectEqual(Status.ok, th.wr(p, Node.of(th.serialOf(p), .addr), "?a?").reply.status);
+    // Quadratic, it took seconds (6.4 s through 9P in Debug); linear, a
+    // few milliseconds.
+    const took = t0.durationTo(std.Io.Timestamp.now(testing.io, .awake)).toNanoseconds();
+    try testing.expect(took < std.time.ns_per_s);
+}
+
 test "an alternation anchoring some branches and not others is refused with why, a $ not counting" {
     const p = try th.withFile(testing.allocator, "def\nfoo\n");
     defer p.deinit();