From 78653b911c0ef23753d569bd63af3c755be2a37d Mon Sep 17 00:00:00 2001
From: Ilya Rezvov <ilya.rezvov@revjet.com>
Date: Sun, 18 Feb 2018 22:46:19 -0800
Subject: [PATCH] write import section

---
 src/Language/Wasm/Binary.hs | 80 +++++++++++++++++++++++++++++++++++++
 1 file changed, 80 insertions(+)

diff --git a/src/Language/Wasm/Binary.hs b/src/Language/Wasm/Binary.hs
index 1a4929f..7937f11 100644
--- a/src/Language/Wasm/Binary.hs
+++ b/src/Language/Wasm/Binary.hs
@@ -11,6 +11,9 @@ import Data.Bits
 import Data.Word (Word8)
 import Data.Serialize
 import qualified Data.ByteString as BS
+import qualified Data.ByteString.Lazy as LBS
+import qualified Data.Text.Lazy as TL
+import qualified Data.Text.Lazy.Encoding as TLEncoding
 
 putULEB128 :: Natural -> Put
 putULEB128 val =
@@ -54,6 +57,18 @@ putSection section content = do
     putULEB128 $ fromIntegral $ BS.length payload
     putByteString payload
 
+putName :: TL.Text -> Put
+putName txt = do
+    let bs = TLEncoding.encodeUtf8 txt
+    putULEB128 $ fromIntegral $ LBS.length bs
+    putLazyByteString bs
+
+getName :: Get TL.Text
+getName = do
+    len <- getULEB128
+    bytes <- getLazyByteString $ fromIntegral len
+    return $ TLEncoding.decodeUtf8 bytes
+
 data SectionType =
     CustomSection
     | TypeSection
@@ -103,6 +118,70 @@ instance Serialize FuncType where
         results <- getVec
         return $ FuncType { params, results }
 
+instance Serialize ElemType where
+    put AnyFunc = putWord8 0x70
+    get = byteGuard 0x70 >> return AnyFunc
+
+instance Serialize Limit where
+    put (Limit min Nothing) = putWord8 0x00 >> putULEB128 min
+    put (Limit min (Just max)) = putWord8 0x01 >> putULEB128 min >> putULEB128 max
+    get = do
+        op <- getWord8
+        case op of
+            0x00 -> do
+                min <- getULEB128
+                return $ Limit min Nothing
+            0x01 -> do
+                min <- getULEB128
+                max <- getULEB128
+                return $ Limit min (Just max)
+            _ -> fail "Unexpected byte in place of Limit opcode"
+
+instance Serialize TableType where
+    put (TableType limit elemType) = do
+        put elemType
+        put limit
+    get = do
+        elemType <- get
+        limit <- get
+        return $ TableType limit elemType
+
+instance Serialize GlobalType where
+    put (Const valType) = put valType >> putWord8 0x00
+    put (Mut valType) = put valType >> putWord8 0x01
+    get = do
+        valType <- get
+        op <- getWord8
+        case op of
+            0x00 -> return $ Const valType
+            0x01 -> return $ Mut valType
+            _ -> fail "Unexpected byte in place of Global type opcode"
+
+instance Serialize ImportDesc where
+    put (ImportFunc typeIdx) = putWord8 0x00 >> putULEB128 typeIdx
+    put (ImportTable tableType) = putWord8 0x01 >> put tableType
+    put (ImportMemory memType) = putWord8 0x02 >> put memType
+    put (ImportGlobal globalType) = putWord8 0x03 >> put globalType
+    get = do
+        op <- getWord8
+        case op of
+            0x00 -> ImportFunc <$> getULEB128
+            0x01 -> ImportTable <$> get
+            0x02 -> ImportMemory <$> get
+            0x03 -> ImportGlobal <$> get
+            _ -> fail "Unexpected byte in place of Import Declaration opcode"
+
+instance Serialize Import where
+    put (Import sourceModule name desc) = do
+        putName sourceModule
+        putName name
+        put desc
+    get = do
+        sourceModule <- getName
+        name <- getName
+        desc <- get
+        return $ Import sourceModule name desc
+
 instance Serialize Module where
     put mod = do
         -- magic
@@ -117,4 +196,5 @@ instance Serialize Module where
         putWord8 0x00
 
         putSection TypeSection $ types mod
+        putSection ImportSection $ imports mod
     get = undefined
\ No newline at end of file