Add simple code generator monad.

[hs-java.git] / JVM / Generator.hs

diff --git a/JVM/Generator.hs b/JVM/Generator.hs
new file mode 100644 (file)
index 0000000..d5db62c
--- /dev/null
+++ b/JVM/Generator.hs
@@ -0,0 +1,157 @@
+{-# LANGUAGE FlexibleContexts, TypeFamilies, OverloadedStrings #-}
+module JVM.Generator where
+
+import Control.Monad.State as St
+import Data.Array
+import Data.Word
+import Data.List
+import Data.Binary
+import qualified Data.Map as M
+import qualified Data.Set as S
+import qualified Data.ByteString.Lazy as B
+
+import JVM.Types
+import JVM.ClassFile
+import JVM.Assembler
+
+data GState = GState {
+  generated :: [Instruction],
+  currentPool :: Pool,
+  doneMethods :: [Method],
+  currentMethod :: Maybe Method}
+  deriving (Eq,Show)
+
+emptyGState = GState {
+  generated = [],
+  currentPool = listArray (0,0) [CInteger 0],
+  doneMethods = [],
+  currentMethod = Nothing }
+
+type Generate a = State GState a
+
+appendPool :: Constant -> Pool -> (Pool, Word16)
+appendPool c pool =
+  let list = assocs pool
+      size = fromIntegral (length list)
+      list' = list ++ [(size, c)]
+  in  (array (0, size) list',
+       size)
+
+addItem :: Constant -> Generate Word16
+addItem c = do
+  pool <- St.gets currentPool
+  case lookupPool c pool of
+    Just i -> return i
+    Nothing -> do
+      let (pool', i) = appendPool c pool
+      st <- St.get
+      St.put $ st {currentPool = pool'}
+      return i
+
+lookupPool :: Constant -> Pool -> Maybe Word16
+lookupPool c pool =
+  fromIntegral `fmap` findIndex (== c) (elems pool)
+
+addNT :: Binary (Signature a) => NameType a -> Generate Word16
+addNT (NameType name sig) = do
+  let bsig = encode sig
+  addItem (CUTF8 name)
+  addItem (CUTF8 bsig)
+  addItem (CNameType name bsig)
+
+addToPool :: Constant -> Generate Word16
+addToPool c@(CClass str) = do
+  addItem (CUTF8 str)
+  addItem c
+addToPool c@(CField cls name) = do
+  addToPool (CClass cls)
+  addNT name
+  addItem c
+addToPool c@(CMethod cls name) = do
+  addToPool (CClass cls)
+  addNT name
+  addItem c
+addToPool c@(CIfaceMethod cls name) = do
+  addToPool (CClass cls)
+  addNT name
+  addItem c
+addToPool c@(CString str) = do
+  addToPool (CUTF8 str)
+  addItem c
+addToPool c@(CNameType name sig) = do
+  addItem (CUTF8 name)
+  addItem (CUTF8 sig)
+  addItem c
+addToPool c = addItem c
+
+putInstruction :: Instruction -> Generate ()
+putInstruction instr = do
+  st <- St.get
+  let code = generated st
+  St.put $ st {generated = code ++ [instr]}
+
+i0 :: Instruction -> Generate ()
+i0 = putInstruction
+
+i1 :: (Word16 -> Instruction) -> Constant -> Generate ()
+i1 fn c = do
+  ix <- addToPool c
+  i0 (fn ix)
+
+startMethod :: B.ByteString -> MethodSignature -> Generate ()
+startMethod name sig = do
+  st <- St.get
+  let method = Method {
+    methodAccess = S.fromList [ACC_PUBLIC],
+    methodName = name,
+    methodSignature = sig,
+    methodAttrs = M.empty }
+  St.put $ st {generated = [],
+               currentMethod = Just method }
+
+endMethod :: Generate ()
+endMethod = do
+  m <- St.gets currentMethod
+  code <- St.gets genCode
+  case m of
+    Nothing -> fail "endMethod without startMethod!"
+    Just method -> do
+      let method' = method {methodAttrs = M.fromList [("Code", encodeMethod code)] }
+      st <- St.get
+      St.put $ st {generated = [],
+                   currentMethod = Nothing,
+                   doneMethods = doneMethods st ++ [method']}
+
+newMethod :: B.ByteString -> [ArgumentSignature] -> ReturnSignature -> Generate () -> Generate ()
+newMethod name args ret gen = do
+  startMethod name (MethodSignature args ret)
+  gen
+  endMethod
+
+genCode :: GState -> Code
+genCode st = Code {
+    codeStackSize = 4096,
+    codeMaxLocals = 100,
+    codeLength = len,
+    codeInstructions = generated st,
+    codeExceptionsN = 0,
+    codeExceptions = [],
+    codeAttrsN = 0,
+    codeAttributes = [] }
+  where
+    len = fromIntegral $ B.length $ encodeInstructions (generated st)
+
+generate :: B.ByteString -> Generate () -> Class
+generate name gen =
+  let res = execState gen emptyGState
+      code = genCode res
+  in  Class {
+        constantPool = currentPool res,
+        classAccess = S.fromList [ACC_PUBLIC],
+        this = name,
+        super = Nothing,
+        implements = [],
+        fields = [],
+        methods = doneMethods res,
+        classAttrs = M.empty }
+