1 files changed, 56 insertions, 0 deletions
diff --git a/wasm2c/examples/rot13/rot13.wat b/wasm2c/examples/rot13/rot13.wat
new file mode 100644
index 00000000..0a33d80e
--- /dev/null
+++ b/wasm2c/examples/rot13/rot13.wat
@@ -0,0 +1,56 @@
+(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 (get_local $c) (i32.const 65))
+    (return (get_local $c)))
+
+  ;; Clear 5th bit of c, to force uppercase. 0xdf = 0b11011111
+  (set_local $uc (i32.and (get_local $c) (i32.const 0xdf)))
+
+  ;; In range ['A', 'M'] return |c| + 13.
+  (if (i32.le_u (get_local $uc) (i32.const 77))
+    (return (i32.add (get_local $c) (i32.const 13))))
+
+  ;; In range ['N', 'Z'] return |c| - 13.
+  (if (i32.le_u (get_local $uc) (i32.const 90))
+    (return (i32.sub (get_local $c) (i32.const 13))))
+
+  ;; No change for everything else.
+  (return (get_local $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.
+  (set_local $size)
+
+  ;; Loop over all bytes and rot13 them.
+  (block $exit
+    (loop $top
+      ;; if (i >= size) break
+      (if (i32.ge_u (get_local $i) (get_local $size)) (br $exit))
+
+      ;; mem[i] = rot13c(mem[i])
+      (i32.store8
+        (get_local $i)
+        (call $rot13c
+          (i32.load8_u (get_local $i))))
+
+      ;; i++
+      (set_local $i (i32.add (get_local $i) (i32.const 1)))
+      (br $top)
+    )
+  )
+
+  (call $buf_done (i32.const 0) (get_local $size))
+)