map packs: Fs.mount / Fs.unmount at run time, and a map's bakes under assets/baked/maps/<map>/

Maps ship outside the game, each one a content-addressed pack (.lmap: the .lpak format) downloaded to
the save root. The runtime already served reads from packs mounted at boot (packs.index); now one can
come and go while the game runs:

- Fs.mount(path) -> bool maps a pack over the ones mounted before it (searched first, as a later
  packs.index line is); Fs.unmount(path) -> bool gives the mapping back (munmap, UnmapViewOfFile on
  Windows) and closes the gap in the search order. Each slot keeps its length and path for it. A
  FILE* still open over one of its entries (a baked_open_range) is closed first. Still 8 packs at most.
- baked_path(map, file) is assets/baked/maps/<map>/<file> for a map's bake - what its .lmap carries
  and the game's own pack never does - and assets/baked/<file> for the rest.

The IR assembles for macOS and Windows (llvm-as). Compile-only: nothing mounted or run here.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/ludic.base/baked.ludic

@@ -10,10 +10,11 @@ export state BakeState {
   said: []string = new []string       # the keys a dev build has said it made at run time
 }
 
-# assets/baked/<map>/<file>, or assets/baked/<file> for no map
+# a map's bake: assets/baked/maps/<map>/<file>, which ships in that map's own pack (.lmap), never the
+# game's; anything else: assets/baked/<file>, in the game's pack
 export function baked_path(map: string, file: string) -> string {
   if len(map) == 0 { return "assets/baked/" + file }
-  return "assets/baked/" + map + "/" + file
+  return "assets/baked/maps/" + map + "/" + file
 }
 
 # the payload of a baked file that is this bake at this version, or null (missing, not a baked file,

selfhost/backend/stdlib/emit_fs.ludic

@@ -39,6 +39,7 @@ function is_fs_ns(meth: pointer) -> bool {
   if (meth == "exists") or (meth == "is_dir") or (meth == "read_text") { return true }
   if (meth == "write_text") or (meth == "append_text") or (meth == "remove") { return true }
   if (meth == "size") or (meth == "mkdir") or (meth == "copy") or (meth == "list") { return true }
+  if (meth == "mount") or (meth == "unmount") { return true }
   return false
 }
 function is_path_ns(meth: pointer) -> bool {
@@ -55,6 +56,9 @@ function emit_fs_ns(meth: pointer, e: Node) -> Val {
   use_pak()
   let a = emit_expr(e.kids[0])
   if (meth == "exists")      { return val(emit_bind(`call i32 @lp_fs_exists(ptr {a.code})`), "bool") }
+  # a pack (.lpak / .lmap) mounted at run time over the packs.index ones, searched first; and let go
+  if (meth == "mount")       { return val(emit_bind(`call i32 @lp_pak_mount(ptr {a.code})`), "bool") }
+  if (meth == "unmount")     { return val(emit_bind(`call i32 @lp_pak_unmount(ptr {a.code})`), "bool") }
   if (meth == "is_dir")      { return val(emit_bind(`call i32 @lp_fs_is_dir(ptr {a.code})`), "bool") }
   if (meth == "read_text")   { return val(emit_bind(`call ptr @lp_fs_read_text(ptr {a.code})`), "string") }
   if (meth == "remove")      { return val(emit_bind(`call i32 @lp_fs_remove(ptr {a.code})`), "bool") }

selfhost/backend/stdlib/emit_pak.ludic

@@ -96,6 +96,7 @@ function emit_pak_prelude() -> void {
     emith("declare i64 @lseek(i32, i64, i32)\n")
     if not g_mmap_declared { emith("declare ptr @mmap(ptr, i64, i32, i32, i32, i64)\n");  g_mmap_declared = true }
     emith("declare ptr @fmemopen(ptr, i64, ptr)\n")
+    emith("declare i32 @munmap(ptr, i64)\n")
     emith("declare i32 @chdir(ptr)\n")
     emith("declare i32 @_NSGetExecutablePath(ptr, ptr)\n")
   }
@@ -109,6 +110,8 @@ function emit_pak_prelude() -> void {
   # up to 8 packs may be mounted; the base pointer of each mapping, in mount order
   emith("@L_pak_base = internal global [8 x ptr] zeroinitializer\n")
   emith("@L_pak_n    = internal global i32 0\n")
+  emith("@L_pak_len  = internal global [8 x i64] zeroinitializer\n")   # each mapping's length, for unmount
+  emith("@L_pak_path = internal global [8 x ptr] zeroinitializer\n")   # and the path it was mounted from
   # the splash, named by packs.index and served out of the pack like any asset
   emith("@L_pak_splash   = internal global ptr null\n")
   emith("@L_pak_splashbg = internal global i32 0\n")
@@ -128,6 +131,7 @@ function emit_pak_prelude() -> void {
   }
 
   emit_pak_mount()
+  emit_pak_unmount()
   emit_pak_lookup()
   emit_pak_open()
   emit_pak_boot()
@@ -157,11 +161,36 @@ function emit_pak_mount() -> void {
   # "LPAK" read as a little-endian i32
   emith("chk:\n  %m = load i32, ptr %base\n  %okm = icmp eq i32 %m, 1262571596\n  br i1 %okm, label %keep, label %clo\n")
   emith("keep:\n  %slot = getelementptr [8 x ptr], ptr @L_pak_base, i32 0, i32 %n\n  store ptr %base, ptr %slot\n")
+  # its length and path too, so Fs.unmount can find it and give the mapping back
+  emith("  %lslot = getelementptr [8 x i64], ptr @L_pak_len, i32 0, i32 %n\n  store i64 %end, ptr %lslot\n")
+  emith("  %pcopy = call ptr @lp_fs_strdup(ptr %path)\n  %pslot = getelementptr [8 x ptr], ptr @L_pak_path, i32 0, i32 %n\n  store ptr %pcopy, ptr %pslot\n")
   emith("  %n1 = add i32 %n, 1\n  store i32 %n1, ptr @L_pak_n\n  %c1 = call i32 @close(i32 %fd)\n  ret i32 1\n")
   emith("clo:\n  %c2 = call i32 @close(i32 %fd)\n  ret i32 0\n")
   emith("no:\n  ret i32 0\n}\n")
 }
 
+# unmount(path): the pack mounted from exactly that path given back and taken out of the search, the
+# ones after it moving up a slot; 1 when it was mounted. A map pack downloaded at run time comes and
+# goes (Fs.mount / Fs.unmount); a FILE* still open over one of its entries must be closed first
+function emit_pak_unmount() -> void {
+  emith("define i32 @lp_pak_unmount(ptr %path) {\n")
+  emith("entry:\n  %n = load i32, ptr @L_pak_n\n  %ip = alloca i32\n  store i32 0, ptr %ip\n  br label %find\n")
+  emith("find:\n  %i = load i32, ptr %ip\n  %end = icmp sge i32 %i, %n\n  br i1 %end, label %no, label %cmp\n")
+  emith("cmp:\n  %pp = getelementptr [8 x ptr], ptr @L_pak_path, i32 0, i32 %i\n  %p = load ptr, ptr %pp\n  %isnull = icmp eq ptr %p, null\n  br i1 %isnull, label %next, label %str\n")
+  emith("str:\n  %c = call i32 @strcmp(ptr %p, ptr %path)\n  %same = icmp eq i32 %c, 0\n  br i1 %same, label %drop, label %next\n")
+  emith("next:\n  %i1 = add i32 %i, 1\n  store i32 %i1, ptr %ip\n  br label %find\n")
+  emith("drop:\n  %bp = getelementptr [8 x ptr], ptr @L_pak_base, i32 0, i32 %i\n  %base = load ptr, ptr %bp\n  %lp = getelementptr [8 x i64], ptr @L_pak_len, i32 0, i32 %i\n  %len = load i64, ptr %lp\n")
+  if g_target_win { emith("  %u = call i32 @UnmapViewOfFile(ptr %base)\n") } else { emith("  %u = call i32 @munmap(ptr %base, i64 %len)\n") }
+  emith("  call void @lp_free(ptr %p)\n  %jp = alloca i32\n  store i32 %i, ptr %jp\n  br label %shift\n")
+  emith("shift:\n  %j = load i32, ptr %jp\n  %j1 = add i32 %j, 1\n  %more = icmp slt i32 %j1, %n\n  br i1 %more, label %mv, label %done\n")
+  emith("mv:\n  %sb = getelementptr [8 x ptr], ptr @L_pak_base, i32 0, i32 %j1\n  %vb = load ptr, ptr %sb\n  %db = getelementptr [8 x ptr], ptr @L_pak_base, i32 0, i32 %j\n  store ptr %vb, ptr %db\n")
+  emith("  %sl = getelementptr [8 x i64], ptr @L_pak_len, i32 0, i32 %j1\n  %vl = load i64, ptr %sl\n  %dl = getelementptr [8 x i64], ptr @L_pak_len, i32 0, i32 %j\n  store i64 %vl, ptr %dl\n")
+  emith("  %sp = getelementptr [8 x ptr], ptr @L_pak_path, i32 0, i32 %j1\n  %vp = load ptr, ptr %sp\n  %dp = getelementptr [8 x ptr], ptr @L_pak_path, i32 0, i32 %j\n  store ptr %vp, ptr %dp\n")
+  emith("  store i32 %j1, ptr %jp\n  br label %shift\n")
+  emith("done:\n  %n1 = sub i32 %n, 1\n  store i32 %n1, ptr @L_pak_n\n  %last = getelementptr [8 x ptr], ptr @L_pak_path, i32 0, i32 %n1\n  store ptr null, ptr %last\n  ret i32 1\n")
+  emith("no:\n  ret i32 0\n}\n")
+}
+
 # ---- lookup -----------------------------------------------------------------
 
 function emit_pak_lookup() -> void {

selfhost/backend/stdlib/emit_win.ludic

@@ -62,6 +62,7 @@ function emit_win_prelude() -> void {
   emith("declare i32 @FindClose(ptr)\n")
   emith("declare ptr @CreateFileMappingA(ptr, ptr, i32, i32, i32, ptr)\n")
   emith("declare ptr @MapViewOfFile(ptr, i32, i32, i32, i64)\n")
+  emith("declare i32 @UnmapViewOfFile(ptr)\n")
   emith("declare i32 @CloseHandle(ptr)\n")
   emith("declare i32 @GetModuleFileNameA(ptr, ptr, i32)\n")
   emith("declare i32 @GetTempPathA(i32, ptr)\n")