Views generated by each read stat 0, as acme's do: data, xdata, index, layout, recent and listeners; fs.md says which files have real lengths

A stat of index, layout, recent or listeners built the whole view to
count it, and data and xdata reported the body's length though a read
answers what addr selects. Those now stat 0, as screen and pane/new
already did, and fs.md lists the files whose length is real and says to
read the rest to the end.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

5 files changed, 23 insertions, 49 deletions

diff --git a/docs/fs.md b/docs/fs.md
index 6b73a124..d8324d47 100644
--- a/docs/fs.md
+++ b/docs/fs.md
@@ -194,8 +194,14 @@ reads at once; the next is refused `too many reads waiting: 128`. A mount
 keeps answering everything else beside them. Through a FUSE mount bash's
 `read -t` cannot time out: wrap the loop in `timeout N`.
 
-**Stats.** Lengths are real (for `event` and `pty/data` the next record's,
-zero when none waits; for `log` what an open would freeze). The qid
+**Stats.** A file whose text is kept has its real length: a pane's
+`body`, `tag`, `name`, `ctl`, `sel` and the range and flag files, the
+workspace's `tag`, the root `ctl`, `status`, `commands`, `README`, the
+`look`/`exec` answers, `focus`; `event` and `pty/data` the next record's,
+zero when none waits; `log` what an open would freeze. A view generated by
+each read stats 0, as acme's do: `screen`, `data`, `xdata`, `index`,
+`layout`, `recent`, `listeners`, `pane/new`. Read those to the end rather
+than trust a length (`cat` does). The qid
 version of `body`, `data` and `xdata` is the pane's revision, so a stat sees
 an edit land. Modes are 0644/0666, 0444 read-only, 0222 write-only.
 
diff --git a/src/ninep/cols.zig b/src/ninep/cols.zig
index 6828612c..b2e62d28 100644
--- a/src/ninep/cols.zig
+++ b/src/ninep/cols.zig
@@ -43,13 +43,6 @@ pub fn writeLayout(p: *Pardes, w: *std.Io.Writer) !void {
     if (p.activeColumn() orelse active) |c| try w.print("active {d}\n", .{layout.columnSerial(p, c)}) else try w.writeAll("active -\n");
 }
 
-pub fn layoutLen(p: *Pardes) u64 {
-    var buf: [256]u8 = undefined;
-    var counting: std.Io.Writer.Discarding = .init(&buf);
-    writeLayout(p, &counting.writer) catch return 0;
-    return counting.fullCount();
-}
-
 /// A header by its node: the workspace's (`serial` null) or the column's
 /// with that serial; null when that column has closed.
 const Header = struct { text: *Text, col: ?usize };
@@ -532,7 +525,8 @@ test "layout lists each column's place, panes and state, and the active one" {
     // Newcol gives the new, empty column's tag the keyboard.
     try testing.expect(std.mem.indexOf(u8, text, "current empty\n") != null);
     try testing.expect(std.mem.endsWith(u8, text, try std.fmt.bufPrint(&want, "active {d}\n", .{new_serial})));
-    try testing.expectEqual(@as(u64, text.len), th.call(p, .{ .tag = 1, .op = .getattr, .node = layout_node }).reply.attr.size);
+    try testing.expect(text.len > 0);
+    try testing.expectEqual(@as(u64, 0), th.call(p, .{ .tag = 1, .op = .getattr, .node = layout_node }).reply.attr.size); // generated by each read
     // /index says which column each pane is in, by its serial, last.
     try testing.expect(std.mem.endsWith(u8, th.rd(p, @intFromEnum(tree.TopFile.index), 0, 4096).bytes, try std.fmt.bufPrint(&want, " {d}\n", .{first_serial})));
     try testing.expect(th.logHas(p, try std.fmt.bufPrint(&want, "newcol {d}\n", .{new_serial})));
diff --git a/src/ninep/ctl.zig b/src/ninep/ctl.zig
index 63f89cdf..fc0558f5 100644
--- a/src/ninep/ctl.zig
+++ b/src/ninep/ctl.zig
@@ -2932,7 +2932,8 @@ test "/index shows a name as the log does: a newline in it is \\n, controls spac
     const index = rd(p, @intFromEnum(tree.TopFile.index), 0, 4096).bytes;
     try testing.expect(std.mem.indexOf(u8, index, "/tmp/two\\nlines \\xff ") != null);
     try testing.expectEqual(@as(usize, 1), std.mem.count(u8, index, "\n"));
-    try testing.expectEqual(@as(u64, index.len), call(p, .{ .tag = 1, .op = .getattr, .node = @intFromEnum(tree.TopFile.index) }).reply.attr.size);
+    try testing.expect(index.len > 0);
+    try testing.expectEqual(@as(u64, 0), call(p, .{ .tag = 1, .op = .getattr, .node = @intFromEnum(tree.TopFile.index) }).reply.attr.size);
     // Its tag never carries the raw newline either.
     const tag = rd(p, Node.of(serialOf(p), .tag), 0, 4096).bytes;
     try testing.expect(std.mem.indexOf(u8, tag, "/tmp/two\\nlines") != null);
diff --git a/src/ninep/pane.zig b/src/ninep/pane.zig
index 14877f0f..3b5f2e6c 100644
--- a/src/ninep/pane.zig
+++ b/src/ninep/pane.zig
@@ -398,7 +398,9 @@ pub fn fileSize(p: *Pardes, id: usize, f: PaneFile) u64 {
     return switch (f) {
         // A terminal's body reads its screen and history, as text.
         .body => if (pane.file == null and pane.isTerminal()) panes.terminal.screenTextLen(pane) else if (pdfText(p, pane)) |t| t.len else bodyOf(pane).len,
-        .data, .xdata => bodyOf(pane).len,
+        // What addr selects, generated by each read: no length, as acme's
+        // data and xdata have none.
+        .data, .xdata => 0,
         .tag => tagOf(p, pane).len,
         .name => nameOf(p, pane).len + 1,
         .ctl => ctl: {
@@ -437,23 +439,6 @@ pub fn columnOf(p: *Pardes, id: usize) u32 {
     return pardes.layout.columnSerial(p, at.col);
 }
 
-pub fn indexLen(p: *Pardes) u64 {
-    var n: u64 = 0;
-    var last: u32 = 0;
-    while (tree.nextSerialAfter(p, last)) |serial| {
-        last = serial;
-        const pane = p.panes[p.paneBySerial(serial).?].?;
-        var digits: [16]u8 = undefined;
-        // unreachable: a u32 serial is at most 10 digits
-        n += (std.fmt.bufPrint(&digits, "{d}", .{serial}) catch unreachable).len;
-        var name_buf: [4 * 4096]u8 = undefined;
-        n += 1 + kindOf(pane).len + 3 + events.shown(nameOf(p, pane), &name_buf).len + 1;
-        // unreachable: a column index is under 16 digits
-        n += 1 + (std.fmt.bufPrint(&digits, "{d}", .{columnOf(p, p.paneBySerial(serial).?)}) catch unreachable).len;
-    }
-    return n;
-}
-
 // ---- reads ----
 
 pub fn read(p: *Pardes, req: Req, id: usize, pane: *Pane, file: PaneFile) Reply {
@@ -1081,7 +1066,7 @@ const withFile = th.withFile;
 const serialOf = th.serialOf;
 const Status = tree.Status;
 
-test "index lists serial kind dirty flag and name and stat reports its length" {
+test "index lists serial kind dirty flag and name, and stats 0, a view generated by each read" {
     const gpa = testing.allocator;
     const p = try withFile(gpa, "hello\nthere\n");
     defer p.deinit();
@@ -1095,7 +1080,7 @@ test "index lists serial kind dirty flag and name and stat reports its length" {
     try testing.expect(std.mem.indexOf(u8, a.bytes, clean_row) != null);
     const at = std.mem.indexOf(u8, a.bytes, clean_row).?;
     const stat = call(p, .{ .tag = 1, .op = .getattr, .node = index });
-    try testing.expectEqual(@as(u64, a.bytes.len), stat.reply.attr.size);
+    try testing.expectEqual(@as(u64, 0), stat.reply.attr.size);
     try testing.expectEqual(@as(u16, 0o444), stat.reply.attr.mode);
 
     pane.file.?.saved_revision = pane.file.?.revision -% 1;
@@ -1107,7 +1092,6 @@ test "index lists serial kind dirty flag and name and stat reports its length" {
 
     const serial = try th.newPane(p);
     const both = rd(p, index, 0, 4096);
-    try testing.expectEqual(@as(u64, both.bytes.len), indexLen(p));
     var expected: [4200]u8 = undefined;
     const made = p.panes[p.paneBySerial(serial).?].?;
     try testing.expect(std.mem.endsWith(u8, both.bytes, try std.fmt.bufPrint(&expected, "\n{d} text 0 {s} {d}\n", .{ serial, nameOf(p, made), columnOf(p, p.paneBySerial(serial).?) })));
diff --git a/src/ninep/tree.zig b/src/ninep/tree.zig
index c0ace5be..a7f3f2a4 100644
--- a/src/ninep/tree.zig
+++ b/src/ninep/tree.zig
@@ -253,13 +253,6 @@ pub const TopFile = enum(u5) {
 
 pub const root: u64 = @intFromEnum(TopFile.root);
 
-fn recentLen(p: *Pardes) u64 {
-    var buf: [64]u8 = undefined;
-    var counting: std.Io.Writer.Discarding = .init(&buf);
-    pardes.panes.Output.recentText(p, &counting.writer, false) catch return 0;
-    return counting.fullCount();
-}
-
 /// Declaration order is readdir order.
 pub const PaneFile = enum(u5) {
     dir = 0,
@@ -643,23 +636,19 @@ fn attrOf(p: *Pardes, target: Target) ?Reply.Attr {
 
 fn topSize(p: *Pardes, f: TopFile) u64 {
     return switch (f) {
-        // ponytail: /screen has no length until an open renders its frame,
-        // and /pane/new none until an open has a pane to name.
-        .root, .pane, .col, .screen, .new => 0,
-        .layout => cols.layoutLen(p),
+        // Views generated whole by each read have no length, as acme's
+        // generated files have none: /screen until an open renders its
+        // frame, /pane/new until an open has a pane to name, and the index,
+        // layout, recent list and listeners, which a stat would otherwise
+        // have to build to count.
+        .root, .pane, .col, .screen, .new, .layout, .index, .recent, .listeners => 0,
         .tag => cols.headerText(p, null).?.len,
-        .index => pane.indexLen(p),
         .README => fs.help.len,
         .status => ctl.statusLen(p),
         .look, .exec, .tagexec => ctl.resultsLen(p),
         .log => events.logLen(&p.fs.log),
-        .listeners => listeners: {
-            var buf: [screen.listeners_cap]u8 = undefined;
-            break :listeners screen.listenersText(p, &buf).len;
-        },
         .ctl => ctl.rootLen(p),
         .commands => ctl.commandsLen(),
-        .recent => recentLen(p),
         .focus => focus: {
             if (p.header_focus) break :focus 0;
             const pn = p.panes[p.active] orelse break :focus 0;