Use cloud9's file-server engine instead of the private copy

src/9p.zig shrinks to an 88-line alias: the engine and the backend contract
(Req, Reply/ReplyWith, Op, Status, Attr, E, error strings) now come from
cloud9.fs. The editor's limits become cloud9.fs.Options values; the ESP32-P4
board backend drops its own copies of the contract types. No behaviour
change; fs-bench still allocates nothing per request. cloud9 re-pinned to
the commit that carries the engine.

Co-Authored-By: Claude Fable 5.1 <[email protected]>

1 files changed, 27 insertions, 73 deletions

diff --git a/src/ninep/tree.zig b/src/ninep/tree.zig
index f716bf5f..56c3112d 100644
--- a/src/ninep/tree.zig
+++ b/src/ninep/tree.zig
@@ -1,11 +1,14 @@
 //! The control tree served over 9P: its nodes, lookup, readdir and the
-//! dispatch that answers the engine in src/9p.zig. The backend contract
-//! (Req, Reply, Op, Status, E) lives here; fs.zig keeps host access and mounts.
+//! dispatch that answers the engine (cloud9.fs.Server, configured in
+//! src/9p.zig). The backend contract (Req, Reply, Op, Status, E) is cloud9's,
+//! extended here with the editor's reply payload; fs.zig keeps host access
+//! and mounts.
 //!
 //!   /README /index /ctl /new /log /screen /listeners
 //!   /pane/<serial>/{name,body,tag,ctl,addr,data,xdata,sel,errors,event,pty/}
 //!   /os/...  the host filesystem      /src/...  embedded sources (opt-in)
 const std = @import("std");
+const cloud9 = @import("cloud9");
 const pardes = @import("../pardes.zig");
 const fs = @import("../fs.zig");
 pub const events = @import("events.zig");
@@ -22,84 +25,35 @@ const MAX_PANES = pardes.MAX_PANES;
 
 pub const name_capacity: usize = 255;
 
-// ---- the backend contract ----
-
-pub const Op = enum(u8) {
-    lookup,
-    getattr,
-    setattr,
-    open,
-    read,
-    write,
-    release,
-    readdir,
-};
+comptime {
+    // The editor's engine (src/9p.zig) remembers names this long.
+    std.debug.assert(@import("../9p.zig").editor.name_capacity == name_capacity);
+}
 
-pub const Status = enum(u8) {
-    ok,
-    again,
-    err,
-};
+// ---- the backend contract: cloud9.fs, with the editor's payload locator ----
 
-pub const Req = struct {
-    tag: u64,
-    op: Op,
-    node: u64,
-    handle: u32 = 0,
-    off: u64 = 0,
-    size: u32 = 0,
-    data: []const u8 = &.{},
-    truncate: bool = false,
+pub const Op = cloud9.fs.Op;
+pub const Status = cloud9.fs.Status;
+pub const Req = cloud9.fs.Req;
+pub const E = cloud9.fs.E;
 
-    pub fn changesPane(req: Req) bool {
-        return switch (req.op) {
-            .write, .setattr => true,
-            .open => req.node == @intFromEnum(TopFile.new),
-            .lookup, .getattr, .read, .release, .readdir => false,
-        };
-    }
+/// Where a reply's bytes live. The engine ignores it; `Pardes.fsPayload`
+/// resolves it into the slice that travels beside the reply.
+pub const Payload = union(enum) {
+    none,
+    staged: u32,
+    region: struct { pane: u8, serial: u32, off: u32, len: u32 },
 };
 
-pub const Reply = struct {
-    tag: u64,
-    status: Status = .ok,
-    errno: u16 = 0,
-    attr: Attr = .{},
-    handle: u32 = 0,
-    payload: Payload = .none,
-    written: u32 = 0,
-
-    pub const Attr = struct {
-        name: []const u8 = "",
-        node: u64 = 0,
-        dir: bool = false,
-        size: u64 = 0,
-        mode: u16 = 0o644,
-        mtime: u32 = 0,
-    };
+pub const Reply = cloud9.fs.ReplyWith(Payload);
 
-    pub const Payload = union(enum) {
-        none,
-        staged: u32,
-        region: struct { pane: u8, serial: u32, off: u32, len: u32 },
+pub fn changesPane(req: Req) bool {
+    return switch (req.op) {
+        .write, .setattr => true,
+        .open => req.node == @intFromEnum(TopFile.new),
+        .lookup, .getattr, .read, .release, .readdir => false,
     };
-
-    pub fn fail(tag: u64, e: u16) Reply {
-        return .{ .tag = tag, .status = .err, .errno = e };
-    }
-};
-
-pub const E = struct {
-    pub const PERM: u16 = 1;
-    pub const NOENT: u16 = 2;
-    pub const IO: u16 = 5;
-    pub const NOMEM: u16 = 12;
-    pub const NOTDIR: u16 = 20;
-    pub const INVAL: u16 = 22;
-    pub const NFILE: u16 = 23;
-    pub const NOSPC: u16 = 28;
-    pub const NOSYS: u16 = 38;
-};
+}
 
 pub const out_reserve = 4 * 1024;