add WASM/nedondev.wat (#133)

* added WASM/nedondev.wat

* Change comment

WASM/nedondev.wat

@@ -0,0 +1,120 @@
+;; Used WASI
+;; Execute: wasmtime coffe2code.wat
+;; Only change "Coffee" to "Code"
+(module
+    ;; Import the required fd_write WASI function which will write the given io vectors to stdout
+    ;; The function signature for fd_write is:
+    ;; (File Descriptor, *iovs, iovs_len, nwritten) -> Returns number of bytes written
+    (import "wasi_unstable" "fd_write" (func $fd_write (param i32 i32 i32 i32) (result i32)))
+    (import "wasi_unstable" "fd_read" (func $fd_read (param i32 i32 i32 i32) (result i32)))
+
+    (memory 1)
+    (export "memory" (memory 0))
+    (data (i32.const 4) "Coffee\n") ;; 4-12
+    (data (i32.const 12) "Code\n") ;; 12-20
+
+    (func $check_char (param $offset i32) (param $expect_offset i32) (result i32)
+        (local $char i32)
+        (local $expect_char i32)
+
+        local.get $expect_offset
+        i32.load8_u 
+        local.set $expect_char
+
+        local.get $offset
+        i32.load8_u 
+        local.set $char
+
+
+        local.get $expect_char
+        local.get $char
+        i32.ne
+        return
+    )
+
+    (func $check_coffee (result i32)
+        (local $char_index i32)
+        (local $expect_index i32)
+        (local $limit i32)
+
+        i32.const 28
+        local.set $char_index
+
+        i32.const 4
+        local.set $expect_index
+
+        i32.const 6
+        local.set $limit
+
+        loop
+            ;; load and check
+            local.get $char_index
+            local.get $expect_index
+            call $check_char 
+            if 
+                i32.const 0
+                return
+            end         
+
+            local.get $limit
+            i32.const 1
+            i32.sub
+            local.set $limit
+
+            local.get $char_index
+            i32.const 1
+            i32.add
+            local.set $char_index
+
+            local.get $expect_index
+            i32.const 1
+            i32.add
+            local.set $expect_index
+
+            local.get $limit
+            i32.const 0
+            i32.gt_s
+            br_if 0
+
+        end
+
+        i32.const 1
+
+    )
+
+    (func $main (export "_start")
+        (local $cofee i32)
+        (i32.store (i32.const 20) (i32.const 28)) ;; 20 - 28
+        (i32.store (i32.const 24) (i32.const 100)) ;; Expect (28 - 128) to store buffer.
+        (i32.store (i32.const 128) (i32.const 12)) ;; 128 - 136
+        (i32.store (i32.const 132) (i32.const 8)) ;; Use declare space as string length.
+
+        (call $fd_read
+            (i32.const 0) ;; 0 for stdin
+            (i32.const 20) ;; *iovs
+            (i32.const 1) ;; iovs_len
+            (i32.const 24) ;; nread
+        )
+        drop
+
+        call $check_coffee
+
+        if
+            (call $fd_write
+                (i32.const 1) ;; file_descriptor - 1 for stdout
+                (i32.const 128) ;; *iovs
+                (i32.const 1) ;; iovs_len 
+                (i32.const 4) ;; nwritten 
+            )
+            drop ;; Discard the number of bytes written from the top of the stack
+        else
+            (call $fd_write
+                (i32.const 1) ;; file_descriptor - 1 for stdout
+                (i32.const 20) ;; *iovs
+                (i32.const 1) ;; iovs_len 
+                (i32.const 24) ;; nwritten 
+            )
+            drop ;; Discard the number of bytes written from the top of the stack
+        end
+    )
+)