add prestat struct

std/assembly/bindings/wasi_unstable.ts

@@ -164,7 +164,7 @@ export declare function fd_prestat_get(
   /** Input: The file descriptor about which to retrieve information. */
   fd: fd,
   /** Input: The buffer where the description is stored. */
-  buf: usize // TODO: struct<prestat>
+  buf: struct<prestat>
 ): errno;
 
 /** Return a description of the given preopened file descriptor. */
@@ -1085,6 +1085,23 @@ export namespace oflags {
 }
 export type oflags = u16;
 
+// TODO: undocumented
+export namespace preopentype {
+  @inline
+  export const DIR: preopentype = 0;
+}
+export type preopentype = u8;
+
+// TODO: undocumented
+export abstract class prestat {
+  type: preopentype;
+}
+
+// TODO: undocumented
+export class dirprestat extends prestat {
+  name_len: usize;
+}
+
 /** Flags provided to `sock_recv`. */
 export namespace riflags {
   /** Returns the message without removing it from the socket's receive queue. */

tests/compiler/wasi.ts

@@ -1,4 +1,4 @@
-import { dirent, rwevent, fdstat, filestat, iovec, clocksubscription, fdsubscription, signal } from "bindings/wasi";
+import { dirent, rwevent, fdstat, filestat, iovec, clocksubscription, fdsubscription, signal, dirprestat } from "bindings/wasi";
 
 // TODO: WASM64
 
@@ -49,6 +49,10 @@ assert(offsetof<fdsubscription>("type") == 8);
 assert(offsetof<fdsubscription>("fd") == 16);
 assert(offsetof<fdsubscription>() == 20);
 
+assert(offsetof<dirprestat>("type") == 0);
+assert(offsetof<dirprestat>("name_len") == 4);
+assert(offsetof<dirprestat>() == 8);
+
 // check assignability of mimicked typed enums
 var sig: signal = signal.HUP;
 sig = signal.KILL;

tests/compiler/wasi.untouched.wat

@@ -492,6 +492,42 @@
    call $~lib/env/abort
    unreachable
   end
+  i32.const 0
+  i32.const 0
+  i32.eq
+  i32.eqz
+  if
+   i32.const 0
+   i32.const 8
+   i32.const 52
+   i32.const 0
+   call $~lib/env/abort
+   unreachable
+  end
+  i32.const 4
+  i32.const 4
+  i32.eq
+  i32.eqz
+  if
+   i32.const 0
+   i32.const 8
+   i32.const 53
+   i32.const 0
+   call $~lib/env/abort
+   unreachable
+  end
+  i32.const 8
+  i32.const 8
+  i32.eq
+  i32.eqz
+  if
+   i32.const 0
+   i32.const 8
+   i32.const 54
+   i32.const 0
+   call $~lib/env/abort
+   unreachable
+  end
   i32.const 9
   global.set $wasi/sig
  )