From 3d0d5e5de54611a88826600365bf0849d9ac4871 Mon Sep 17 00:00:00 2001 From: Gabriel Schneider Date: Wed, 30 Sep 2026 17:14:40 -0300 Subject: A tag rewrite counts its text without the newline it drops: echo of exactly 4096 bytes fits `echo <4096 bytes> > tag` wrote 4097 bytes and was refused "over 4096 bytes", although a rewrite drops that one trailing newline and would have held exactly 4096. The limit now counts a truncating write's text without the newline it drops, for a pane's, a column's and the workspace's tag. An append still counts its newline, which it keeps. Co-Authored-By: Claude Opus 5.5 --- src/ninep/cols.zig | 26 +++++++++++++++++++++++++- src/ninep/pane.zig | 6 +++++- 2 files changed, 30 insertions(+), 2 deletions(-) (limited to 'src') diff --git a/src/ninep/cols.zig b/src/ninep/cols.zig index c4ee83eb..4e497545 100644 --- a/src/ninep/cols.zig +++ b/src/ninep/cols.zig @@ -88,7 +88,11 @@ pub fn write(p: *Pardes, req: Req, serial: ?u32) Reply { return tree.failText(req.tag, E.INVAL, why); } const had = if (pending) 0 else headerText(p, serial).?.len; - if (req.data.len > limits.max_tag_tail -| had) { + // A rewrite drops its one trailing newline: `echo <4096 bytes> > tag` + // is 4096 bytes of tag, and fits. + const rewrite = pending or p.fs.header_rewrite == rewriteKey(serial); + const counted = req.data.len - @intFromBool(rewrite and req.data[req.data.len - 1] == '\n'); + if (counted > limits.max_tag_tail -| had) { if (pending) p.fs.header_trunc_pending = null; return tree.failText(req.tag, E.NOSPC, pardes.ctlfs.pane.e_tag_over); } @@ -249,6 +253,26 @@ test "pane/new takes rows from a pane in another column before refusing ENOSPC" try testing.expect(moved); } +test "exactly 4096 bytes written with echo's newline after a truncation fit every kind of tag" { + const p = try th.withFile(testing.allocator, "x\n"); + defer p.deinit(); + const serial = th.serialOf(p); + const text = "w" ** 4096 ++ "\n"; + for ([_]u64{ tree.Node.of(serial, .tag), tree.Node.ofCol(layout.columnSerial(p, 0), .tag), @intFromEnum(tree.TopFile.tag) }) |node| { + _ = th.call(p, .{ .tag = 1, .op = .setattr, .node = node, .truncate = true }); + const h = th.call(p, .{ .tag = 2, .op = .open, .node = node, .omode = 1 }).reply.handle; + const r = th.call(p, .{ .tag = 3, .op = .write, .node = node, .handle = h, .data = text }); + try testing.expectEqual(tree.Status.ok, r.reply.status); + _ = th.call(p, .{ .tag = 4, .op = .release, .node = node, .handle = h, .opened = true }); + try testing.expect(std.mem.endsWith(u8, th.rd(p, node, 0, 1 << 16).bytes, "w" ** 4096)); + // One more byte is over. + _ = th.call(p, .{ .tag = 5, .op = .setattr, .node = node, .truncate = true }); + const h2 = th.call(p, .{ .tag = 6, .op = .open, .node = node, .omode = 1 }).reply.handle; + try testing.expectEqual(E.NOSPC, th.call(p, .{ .tag = 7, .op = .write, .node = node, .handle = h2, .data = "w" ** 4097 ++ "\n" }).errno()); + _ = th.call(p, .{ .tag = 8, .op = .release, .node = node, .handle = h2, .opened = true }); + } +} + test "a Newcol refused because the tags would not fit logs its err alone and spends no column serial" { const p = try pardes.Pardes.init(testing.allocator, .{ .tty_only = true, .cols = 160, .rows = 14 }); defer p.deinit(); diff --git a/src/ninep/pane.zig b/src/ninep/pane.zig index fef0f85f..d5f2f20a 100644 --- a/src/ninep/pane.zig +++ b/src/ninep/pane.zig @@ -662,7 +662,11 @@ fn writeTag(p: *Pardes, req: Req, pane: *Pane) Reply { // is a text like any other (acme's tag file appends the same way). const had = if (pf.tag_trunc_pending) 0 else tagline.curTail(pane).len; const room = limits.max_tag_tail -| had -| @intFromBool(pf.tag_held_newline and !pf.tag_trunc_pending); - if (req.data.len > room) { + // A rewrite drops its one trailing newline: `echo <4096 bytes> > tag` + // is 4096 bytes of tag, and fits. + const rewrite = pf.tag_rewrite or pf.tag_trunc_pending; + const counted = req.data.len - @intFromBool(rewrite and req.data[req.data.len - 1] == '\n'); + if (counted > room) { pf.tag_trunc_pending = false; return tree.failText(req.tag, E.NOSPC, e_tag_over); } -- cgit v1.3