blob: 605c89f9a5991c116f6db3fb2cdd0028c93d419d (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
|
(import "host" "mem" (memory $mem 1))
(import "host" "fill_buf" (func $fill_buf (param i32 i32) (result i32)))
(import "host" "buf_done" (func $buf_done (param i32 i32)))
(func $rot13c (param $c i32) (result i32)
(local $uc i32)
;; No change if < 'A'.
(if (i32.lt_u (local.get $c) (i32.const 65))
(then (return (local.get $c))))
;; Clear 5th bit of c, to force uppercase. 0xdf = 0b11011111
(local.set $uc (i32.and (local.get $c) (i32.const 0xdf)))
;; In range ['A', 'M'] return |c| + 13.
(if (i32.le_u (local.get $uc) (i32.const 77))
(then (return (i32.add (local.get $c) (i32.const 13)))))
;; In range ['N', 'Z'] return |c| - 13.
(if (i32.le_u (local.get $uc) (i32.const 90))
(then (return (i32.sub (local.get $c) (i32.const 13)))))
;; No change for everything else.
(return (local.get $c))
)
(func (export "rot13")
(local $size i32)
(local $i i32)
;; Ask host to fill memory [0, 1024) with data.
(call $fill_buf (i32.const 0) (i32.const 1024))
;; The host returns the size filled.
(local.set $size)
;; Loop over all bytes and rot13 them.
(block $exit
(loop $top
;; if (i >= size) break
(if (i32.ge_u (local.get $i) (local.get $size)) (then (br $exit)))
;; mem[i] = rot13c(mem[i])
(i32.store8
(local.get $i)
(call $rot13c
(i32.load8_u (local.get $i))))
;; i++
(local.set $i (i32.add (local.get $i) (i32.const 1)))
(br $top)
)
)
(call $buf_done (i32.const 0) (local.get $size))
)
|
