1;; $$print_prestat_dirname is a WASI command which copies the first preopen dirname to stdout.
2(module $print_prestat_dirname
3 (import "wasi_snapshot_preview1" "fd_prestat_get"
4 (func $wasi.fd_prestat_get (param $fd i32) (param $result.prestat i32) (result (;errno;) i32)))
5
6 (import "wasi_snapshot_preview1" "fd_prestat_dir_name"
7 (func $wasi.fd_prestat_dir_name (param $fd i32) (param $result.path i32) (param $result.path_len i32) (result (;errno;) i32)))
8
9 (import "wasi_snapshot_preview1" "fd_write"
10 (func $wasi.fd_write (param $fd i32) (param $iovs i32) (param $iovs_len i32) (param $result.size i32) (result (;errno;) i32)))
11
12 (memory (export "memory") 1 1)
13
14 (func $main (export "_start")
15 ;; First, we need to know the size of the prestat dir name.
16 (call $wasi.fd_prestat_get
17 (i32.const 3) ;; preopen FD
18 (i32.const 0) ;; where to write prestat
19 )
20 drop ;; ignore the errno returned
21
22 ;; Next, write the dir name to offset 8 (past the prestat).
23 (call $wasi.fd_prestat_dir_name
24 (i32.const 3) ;; preopen FD
25 (i32.const 8) ;; where to write dir_name
26 (i32.load (i32.const 4)) ;; length is the last part of the prestat
27 )
28 drop ;; ignore the errno returned
29
30 ;; Now, convert the prestat to an iovec [offset, len] writing offset=8.
31 (i32.store (i32.const 0) (i32.const 8))
32
33 ;; Finally, write the dirname to stdout via its iovec [offset, len].
34 (call $wasi.fd_write
35 (i32.const 1) ;; stdout
36 (i32.const 0) ;; where's the iovec
37 (i32.const 1) ;; only one iovec
38 (i32.const 0) ;; overwrite the iovec with the ignored result.
39 )
40 drop ;; ignore the errno returned
41 )
42)
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