restructured bytecode code

project.cabal

@@ -12,18 +12,23 @@ executable compiler
                         utf8-string,
                         bytestring
     default-language:   Haskell2010
-    hs-source-dirs:     src,
+    hs-source-dirs:     src
-                        src/ByteCode,
-                        src/ByteCode/ClassFile
     build-tool-depends: alex:alex, happy:happy
     other-modules:      Parser.Lexer,
-                        Parser.JavaParser
+                        Parser.JavaParser,
                         Ast,
                         Example,
                         Typecheck,
                         ByteCode.ByteUtil,
                         ByteCode.ClassFile,
-                        ByteCode.ClassFile.Generator,
+                        ByteCode.Generation.Generator,
+                        ByteCode.Generation.Assembler.Expression,
+                        ByteCode.Generation.Assembler.Method,
+                        ByteCode.Generation.Assembler.Statement,
+                        ByteCode.Generation.Assembler.StatementExpression,
+                        ByteCode.Generation.Builder.Class,
+                        ByteCode.Generation.Builder.Field,
+                        ByteCode.Generation.Builder.Method,
                         ByteCode.Constants
 
 test-suite tests

src/ByteCode/ClassFile/Generator.hs

@@ -1,340 +0,0 @@
-module ByteCode.ClassFile.Generator(
-    classBuilder,
-    datatypeDescriptor,
-    methodParameterDescriptor,
-    methodDescriptor,
-    memberInfoIsMethod,
-    memberInfoName,
-    memberInfoDescriptor,
-    findMethodIndex
-) where
-
-import ByteCode.Constants
-import ByteCode.ClassFile (ClassFile (..), ConstantInfo (..), MemberInfo(..), Operation(..), Attribute(..), opcodeEncodingLength)
-import Ast
-import Data.Char
-import Data.List
-import Data.Word
-
-
-type ClassFileBuilder a = a -> ClassFile -> ClassFile
-
-
-datatypeDescriptor :: String -> String
-datatypeDescriptor "void" = "V"
-datatypeDescriptor "int" = "I"
-datatypeDescriptor "char" = "C"
-datatypeDescriptor "boolean" = "B"
-datatypeDescriptor x = "L" ++ x
-
-methodParameterDescriptor :: String -> String
-methodParameterDescriptor "void" = "V"
-methodParameterDescriptor "int" = "I"
-methodParameterDescriptor "char" = "C"
-methodParameterDescriptor "boolean" = "B"
-methodParameterDescriptor x = "L" ++ x ++ ";"
-
-memberInfoIsMethod :: [ConstantInfo] -> MemberInfo -> Bool
-memberInfoIsMethod constants info = elem '(' (memberInfoDescriptor constants info)
-
-findFieldIndex :: [ConstantInfo] -> String -> Maybe Int
-findFieldIndex constants name = let
-        fieldRefNameInfos = [
-                -- we only skip one entry to get the name since the Java constant pool
-                -- is 1-indexed (why)
-                (index, constants!!(fromIntegral index + 1))
-                | (index, FieldRefInfo _ _) <- (zip [1..] constants)
-            ]
-        fieldRefNames = map (\(index, nameInfo) -> case nameInfo of
-            Utf8Info fieldName -> (index, fieldName)
-            something_else -> error ("Expected UTF8Info but got" ++ show something_else))
-                fieldRefNameInfos
-        fieldIndex = find (\(index, fieldName) -> fieldName == name) fieldRefNames
-    in case fieldIndex of
-        Just (index, _) -> Just index
-        Nothing -> Nothing
-    
-
-findMethodIndex :: ClassFile -> String -> Maybe Int
-findMethodIndex classFile name = let
-        constants = constantPool classFile
-    in
-        findIndex (\method -> ((memberInfoIsMethod constants method) && (memberInfoName constants method) == name)) (methods classFile)
-
-memberInfoDescriptor :: [ConstantInfo] -> MemberInfo -> String
-memberInfoDescriptor constants MemberInfo {
-    memberAccessFlags = _,
-    memberNameIndex = _,
-    memberDescriptorIndex = descriptorIndex,
-    memberAttributes = _ } = let
-            descriptor = constants!!((fromIntegral descriptorIndex) - 1)
-        in case descriptor of
-            Utf8Info descriptorText -> descriptorText
-            _ -> ("Invalid Item at Constant pool index " ++ show descriptorIndex)
-
-
-memberInfoName :: [ConstantInfo] -> MemberInfo -> String
-memberInfoName constants MemberInfo {
-    memberAccessFlags = _,
-    memberNameIndex = nameIndex,
-    memberDescriptorIndex = _,
-    memberAttributes = _ } = let
-            name = constants!!((fromIntegral nameIndex) - 1)
-        in case name of
-            Utf8Info nameText -> nameText
-            _ -> ("Invalid Item at Constant pool index " ++ show nameIndex)
-
-
-methodDescriptor :: MethodDeclaration -> String
-methodDescriptor (MethodDeclaration returntype _ parameters _) = let
-        parameter_types = [datatype | ParameterDeclaration datatype _ <- parameters]
-    in
-        "("
-        ++ (concat (map methodParameterDescriptor parameter_types))
-        ++ ")"
-        ++ methodParameterDescriptor returntype
-
-injectDefaultConstructor :: [MethodDeclaration] -> [MethodDeclaration]
-injectDefaultConstructor pre
-    | any (\(MethodDeclaration _ name _ _) -> name == "<init>") pre = pre
-    | otherwise = pre ++ [MethodDeclaration "void" "<init>" [] (TypedStatement "void" (Block []))]
-
-
-classBuilder :: ClassFileBuilder Class
-classBuilder (Class name methods fields) _ = let
-        baseConstants = [
-            ClassInfo 4,
-            MethodRefInfo 1 3,
-            NameAndTypeInfo 5 6,
-            Utf8Info "java/lang/Object",
-            Utf8Info "<init>",
-            Utf8Info "()V",
-            Utf8Info "Code"
-            ]
-        nameConstants = [ClassInfo 9, Utf8Info name]
-        nakedClassFile = ClassFile {
-            constantPool = baseConstants ++ nameConstants,
-            accessFlags = accessPublic,
-            thisClass = 8,
-            superClass = 1,
-            fields = [],
-            methods = [],
-            attributes = []
-        }
-
-        methodsWithInjectedConstructor = injectDefaultConstructor methods
-
-        classFileWithFields = foldr fieldBuilder nakedClassFile fields
-        classFileWithMethods = foldr methodBuilder classFileWithFields methodsWithInjectedConstructor
-        classFileWithAssembledMethods = foldr methodAssembler classFileWithMethods methodsWithInjectedConstructor
-    in
-        classFileWithAssembledMethods
-
-
-
-fieldBuilder :: ClassFileBuilder VariableDeclaration
-fieldBuilder (VariableDeclaration datatype name _) input = let
-        baseIndex = 1 + length (constantPool input)
-        constants = [
-                FieldRefInfo (fromIntegral (thisClass input)) (fromIntegral (baseIndex + 1)),
-                NameAndTypeInfo (fromIntegral (baseIndex + 2)) (fromIntegral (baseIndex + 3)),
-                Utf8Info name,
-                Utf8Info (datatypeDescriptor datatype)
-            ]
-        field = MemberInfo {
-            memberAccessFlags = accessPublic,
-            memberNameIndex = (fromIntegral (baseIndex + 2)),
-            memberDescriptorIndex = (fromIntegral (baseIndex + 3)),
-            memberAttributes = []
-            }
-    in
-        input {
-            constantPool = (constantPool input) ++ constants,
-            fields = (fields input) ++ [field]
-        }
-
-methodBuilder :: ClassFileBuilder MethodDeclaration
-methodBuilder (MethodDeclaration returntype name parameters statement) input = let
-        baseIndex = 1 + length (constantPool input)
-        constants = [
-                Utf8Info name,
-                Utf8Info (methodDescriptor (MethodDeclaration returntype name parameters (Block [])))
-            ]
-
-        method = MemberInfo {
-            memberAccessFlags = accessPublic,
-            memberNameIndex = (fromIntegral baseIndex),
-            memberDescriptorIndex = (fromIntegral (baseIndex + 1)),
-            memberAttributes = []
-            }
-    in 
-        input {
-            constantPool = (constantPool input) ++ constants,
-            methods = (methods input) ++ [method]
-        }
-        
-
-
-methodAssembler :: ClassFileBuilder MethodDeclaration
-methodAssembler (MethodDeclaration returntype name parameters statement) input = let
-        methodConstantIndex = findMethodIndex input name
-    in case methodConstantIndex of
-        Nothing -> error ("Cannot find method entry in method pool for method: " ++ name)
-        Just index -> let
-                declaration = MethodDeclaration returntype name parameters statement
-                paramNames = "this" : [name | ParameterDeclaration _ name <- parameters]
-                (pre, method : post) = splitAt index (methods input)
-                (_, bytecode, _) = assembleMethod (constantPool input, [], paramNames) declaration
-                assembledMethod = method {
-                    memberAttributes = [
-                        CodeAttribute {
-                            attributeMaxStack = 420,
-                            attributeMaxLocals = 420,
-                            attributeCode = bytecode
-                        }
-                    ]
-                }
-            in
-                input {
-                    methods = pre ++ (assembledMethod : post)
-                }
-
-
-
-
-type Assembler a = ([ConstantInfo], [Operation], [String]) -> a -> ([ConstantInfo], [Operation], [String])
-
-returnOperation :: DataType -> Operation
-returnOperation dtype
-    | elem dtype ["int", "char", "boolean"] = Opireturn
-    | otherwise                             = Opareturn
-
-binaryOperation :: BinaryOperator -> Operation
-binaryOperation Addition       = Opiadd
-binaryOperation Subtraction    = Opisub
-binaryOperation Multiplication = Opimul
-binaryOperation Division       = Opidiv
-binaryOperation BitwiseAnd     = Opiand
-binaryOperation BitwiseOr      = Opior
-binaryOperation BitwiseXor     = Opixor
-
-comparisonOperation :: BinaryOperator -> Word16 -> Operation
-comparisonOperation CompareEqual          branchLocation = Opif_icmpeq branchLocation
-comparisonOperation CompareNotEqual       branchLocation = Opif_icmpne branchLocation
-comparisonOperation CompareLessThan       branchLocation = Opif_icmplt branchLocation
-comparisonOperation CompareLessOrEqual    branchLocation = Opif_icmple branchLocation
-comparisonOperation CompareGreaterThan    branchLocation = Opif_icmpgt branchLocation
-comparisonOperation CompareGreaterOrEqual branchLocation = Opif_icmpge branchLocation
-
-
-assembleMethod :: Assembler MethodDeclaration
-assembleMethod (constants, ops, lvars) (MethodDeclaration _ name _ (TypedStatement _ (Block statements)))
-    | name == "<init>" = let
-            (constants_a, ops_a, lvars_a) = foldl assembleStatement (constants, ops, lvars) statements
-            init_ops = [Opaload 0, Opinvokespecial 2]
-        in
-            (constants_a, init_ops ++ ops_a ++ [Opreturn], lvars_a)
-    | otherwise = let
-            (constants_a, ops_a, lvars_a) = foldl assembleStatement (constants, ops, lvars) statements
-            init_ops = [Opaload 0]
-        in
-            (constants_a, init_ops ++ ops_a, lvars_a)
-assembleMethod _ (MethodDeclaration _ _ _ stmt) = error ("Block expected for method body, got: " ++ show stmt) 
-
-assembleStatement :: Assembler Statement
-assembleStatement (constants, ops, lvars) (TypedStatement stype (Return expr)) = case expr of
-    Nothing -> (constants, ops ++ [Opreturn], lvars)
-    Just expr -> let
-            (expr_constants, expr_ops, _) = assembleExpression (constants, ops, lvars) expr
-        in
-            (expr_constants, expr_ops ++ [returnOperation stype], lvars)
-assembleStatement (constants, ops, lvars) (TypedStatement _ (Block statements)) =
-    foldl assembleStatement (constants, ops, lvars) statements
-assembleStatement (constants, ops, lvars) (TypedStatement _ (If expr if_stmt else_stmt)) = let
-        (constants_cmp, ops_cmp, _) = assembleExpression (constants, [], lvars) expr
-        (constants_ifa, ops_ifa, _) = assembleStatement (constants_cmp, [], lvars) if_stmt
-        (constants_elsea, ops_elsea, _) = case else_stmt of
-            Nothing -> (constants_ifa, [], lvars)
-            Just stmt -> assembleStatement (constants_ifa, [], lvars) stmt
-        -- +6 because we insert 2 gotos, one for if, one for else
-        if_length = sum (map opcodeEncodingLength ops_ifa) + 6
-        -- +3 because we need to account for the goto in the if statement.
-        else_length = sum (map opcodeEncodingLength ops_elsea) + 3
-    in
-        (constants_ifa, ops ++ ops_cmp ++ [Opsipush 0, Opif_icmpeq if_length] ++ ops_ifa ++ [Opgoto else_length] ++ ops_elsea, lvars)
-assembleStatement (constants, ops, lvars) (TypedStatement _ (While expr stmt)) = let
-        (constants_cmp, ops_cmp, _) = assembleExpression (constants, [], lvars) expr
-        (constants_stmta, ops_stmta, _) = assembleStatement (constants_cmp, [], lvars) stmt
-        -- +3 because we insert 2 gotos, one for the comparison, one for the goto back to the comparison
-        stmt_length = sum (map opcodeEncodingLength ops_stmta) + 6
-        entire_length = stmt_length + sum (map opcodeEncodingLength ops_cmp)
-    in
-        (constants_stmta, ops ++ ops_cmp ++ [Opsipush 0, Opif_icmpeq stmt_length] ++ ops_stmta ++ [Opgoto (-entire_length)], lvars)
-assembleStatement (constants, ops, lvars) (TypedStatement _ (LocalVariableDeclaration (VariableDeclaration dtype name expr))) = let
-        isPrimitive = elem dtype ["char", "boolean", "int"]
-        (constants_init, ops_init, _) = case expr of
-            Just exp -> assembleExpression (constants, ops, lvars) exp
-            Nothing -> (constants, ops ++ if isPrimitive then [Opsipush 0] else [Opaconst_null], lvars)
-        localIndex = fromIntegral (length lvars)
-        storeLocal = if isPrimitive then [Opistore localIndex] else [Opastore localIndex]
-    in
-        (constants_init, ops_init ++ storeLocal, lvars ++ [name])
-assembleStatement _ stmt = error ("Not yet implemented: " ++ show stmt)
-
-assembleExpression :: Assembler Expression
-assembleExpression (constants, ops, lvars) (TypedExpression _ (BinaryOperation op a b))
-    | elem op [Addition, Subtraction, Multiplication, Division, BitwiseAnd, BitwiseOr, BitwiseXor] = let
-            (aConstants, aOps, _) = assembleExpression (constants, ops, lvars) a
-            (bConstants, bOps, _) = assembleExpression (aConstants, aOps, lvars) b
-        in
-            (bConstants, bOps ++ [binaryOperation op], lvars)
-    | elem op [CompareEqual, CompareNotEqual, CompareLessThan, CompareLessOrEqual, CompareGreaterThan, CompareGreaterOrEqual] = let
-            (aConstants, aOps, _) = assembleExpression (constants, ops, lvars) a
-            (bConstants, bOps, _) = assembleExpression (aConstants, aOps, lvars) b
-            cmp_op = comparisonOperation op 9
-            cmp_ops = [cmp_op, Opsipush 0, Opgoto 6, Opsipush 1]
-        in
-            (bConstants, bOps ++ cmp_ops, lvars)
-assembleExpression (constants, ops, lvars) (TypedExpression _ (CharacterLiteral literal)) =
-    (constants, ops ++ [Opsipush (fromIntegral (ord literal))], lvars)
-assembleExpression (constants, ops, lvars) (TypedExpression _ (BooleanLiteral literal)) =
-    (constants, ops ++ [Opsipush (if literal then 1 else 0)], lvars)
-assembleExpression (constants, ops, lvars) (TypedExpression _ (IntegerLiteral literal))
-    | literal <= 32767 && literal >= -32768 = (constants, ops ++ [Opsipush (fromIntegral literal)], lvars)
-    | otherwise = (constants ++ [IntegerInfo (fromIntegral literal)], ops ++ [Opldc_w (fromIntegral (1 + length constants))], lvars)
-assembleExpression (constants, ops, lvars) (TypedExpression _ NullLiteral) =
-    (constants, ops ++ [Opaconst_null], lvars)
-assembleExpression (constants, ops, lvars) (TypedExpression etype (UnaryOperation Not expr)) = let
-        (exprConstants, exprOps, _) = assembleExpression (constants, ops, lvars) expr
-        newConstant = fromIntegral (1 + length exprConstants)
-    in case etype of
-        "int" -> (exprConstants ++ [IntegerInfo 0x7FFFFFFF], exprOps ++ [Opldc_w newConstant, Opixor], lvars)
-        "char" -> (exprConstants, exprOps ++ [Opsipush 0xFFFF, Opixor], lvars)
-        "boolean" -> (exprConstants, exprOps ++ [Opsipush 0x01, Opixor], lvars)
-assembleExpression (constants, ops, lvars) (TypedExpression _ (UnaryOperation Minus expr)) = let
-        (exprConstants, exprOps, _) = assembleExpression (constants, ops, lvars) expr
-    in
-        (exprConstants, exprOps ++ [Opineg], lvars)
-assembleExpression (constants, ops, lvars) (TypedExpression _ (FieldVariable name)) = let
-        fieldIndex = findFieldIndex constants name
-    in case fieldIndex of
-        Just index -> (constants, ops ++ [Opaload 0, Opgetfield (fromIntegral index)], lvars)
-        Nothing -> error ("No such field found in constant pool: " ++ name)
-assembleExpression (constants, ops, lvars) (TypedExpression dtype (LocalVariable name)) = let
-        localIndex = findIndex ((==) name) lvars
-        isPrimitive = elem dtype ["char", "boolean", "int"]
-    in case localIndex of
-        Just index -> (constants, ops ++ if isPrimitive then [Opiload (fromIntegral index)] else [Opaload (fromIntegral index)], lvars)
-        Nothing -> error ("No such local variable found in local variable pool: " ++ name)
-assembleExpression _ expr = error ("unimplemented: " ++ show expr)
-
-assembleStatementExpression :: Assembler StatementExpression
-assembleStatementExpression
-    (constants, ops, lvars)
-    (TypedStatementExpression _ (Assignment (TypedExpression dtype (LocalVariable name)) expr)) = let
-        localIndex = findIndex ((==) name) lvars
-        (constants_a, ops_a, _) = assembleExpression (constants, ops, lvars) expr
-        isPrimitive = elem dtype ["char", "boolean", "int"]
-    in case localIndex of
-        Just index -> (constants_a, ops_a ++ if isPrimitive then [Opistore (fromIntegral index)] else [Opastore (fromIntegral index)], lvars)
-        Nothing -> error ("No such local variable found in local variable pool: " ++ name)

src/ByteCode/Generation/Assembler/Expression.hs

@@ -0,0 +1,55 @@
+module ByteCode.Generation.Assembler.Expression where
+
+import Ast
+import ByteCode.ClassFile(ClassFile (..), ConstantInfo (..), MemberInfo(..), Operation(..), Attribute(..), opcodeEncodingLength)
+import ByteCode.Generation.Generator
+import Data.List
+import Data.Char
+import ByteCode.Generation.Builder.Field
+
+assembleExpression :: Assembler Expression
+assembleExpression (constants, ops, lvars) (TypedExpression _ (BinaryOperation op a b))
+    | elem op [Addition, Subtraction, Multiplication, Division, BitwiseAnd, BitwiseOr, BitwiseXor] = let
+            (aConstants, aOps, _) = assembleExpression (constants, ops, lvars) a
+            (bConstants, bOps, _) = assembleExpression (aConstants, aOps, lvars) b
+        in
+            (bConstants, bOps ++ [binaryOperation op], lvars)
+    | elem op [CompareEqual, CompareNotEqual, CompareLessThan, CompareLessOrEqual, CompareGreaterThan, CompareGreaterOrEqual] = let
+            (aConstants, aOps, _) = assembleExpression (constants, ops, lvars) a
+            (bConstants, bOps, _) = assembleExpression (aConstants, aOps, lvars) b
+            cmp_op = comparisonOperation op 9
+            cmp_ops = [cmp_op, Opsipush 0, Opgoto 6, Opsipush 1]
+        in
+            (bConstants, bOps ++ cmp_ops, lvars)
+assembleExpression (constants, ops, lvars) (TypedExpression _ (CharacterLiteral literal)) =
+    (constants, ops ++ [Opsipush (fromIntegral (ord literal))], lvars)
+assembleExpression (constants, ops, lvars) (TypedExpression _ (BooleanLiteral literal)) =
+    (constants, ops ++ [Opsipush (if literal then 1 else 0)], lvars)
+assembleExpression (constants, ops, lvars) (TypedExpression _ (IntegerLiteral literal))
+    | literal <= 32767 && literal >= -32768 = (constants, ops ++ [Opsipush (fromIntegral literal)], lvars)
+    | otherwise = (constants ++ [IntegerInfo (fromIntegral literal)], ops ++ [Opldc_w (fromIntegral (1 + length constants))], lvars)
+assembleExpression (constants, ops, lvars) (TypedExpression _ NullLiteral) =
+    (constants, ops ++ [Opaconst_null], lvars)
+assembleExpression (constants, ops, lvars) (TypedExpression etype (UnaryOperation Not expr)) = let
+        (exprConstants, exprOps, _) = assembleExpression (constants, ops, lvars) expr
+        newConstant = fromIntegral (1 + length exprConstants)
+    in case etype of
+        "int" -> (exprConstants ++ [IntegerInfo 0x7FFFFFFF], exprOps ++ [Opldc_w newConstant, Opixor], lvars)
+        "char" -> (exprConstants, exprOps ++ [Opsipush 0xFFFF, Opixor], lvars)
+        "boolean" -> (exprConstants, exprOps ++ [Opsipush 0x01, Opixor], lvars)
+assembleExpression (constants, ops, lvars) (TypedExpression _ (UnaryOperation Minus expr)) = let
+        (exprConstants, exprOps, _) = assembleExpression (constants, ops, lvars) expr
+    in
+        (exprConstants, exprOps ++ [Opineg], lvars)
+assembleExpression (constants, ops, lvars) (TypedExpression _ (FieldVariable name)) = let
+        fieldIndex = findFieldIndex constants name
+    in case fieldIndex of
+        Just index -> (constants, ops ++ [Opaload 0, Opgetfield (fromIntegral index)], lvars)
+        Nothing -> error ("No such field found in constant pool: " ++ name)
+assembleExpression (constants, ops, lvars) (TypedExpression dtype (LocalVariable name)) = let
+        localIndex = findIndex ((==) name) lvars
+        isPrimitive = elem dtype ["char", "boolean", "int"]
+    in case localIndex of
+        Just index -> (constants, ops ++ if isPrimitive then [Opiload (fromIntegral index)] else [Opaload (fromIntegral index)], lvars)
+        Nothing -> error ("No such local variable found in local variable pool: " ++ name)
+assembleExpression _ expr = error ("unimplemented: " ++ show expr)

src/ByteCode/Generation/Assembler/Method.hs

@@ -0,0 +1,20 @@
+module ByteCode.Generation.Assembler.Method where
+
+import Ast
+import ByteCode.ClassFile(ClassFile (..), ConstantInfo (..), MemberInfo(..), Operation(..), Attribute(..), opcodeEncodingLength)
+import ByteCode.Generation.Generator
+import ByteCode.Generation.Assembler.Statement
+
+assembleMethod :: Assembler MethodDeclaration
+assembleMethod (constants, ops, lvars) (MethodDeclaration _ name _ (TypedStatement _ (Block statements)))
+    | name == "<init>" = let
+            (constants_a, ops_a, lvars_a) = foldl assembleStatement (constants, ops, lvars) statements
+            init_ops = [Opaload 0, Opinvokespecial 2]
+        in
+            (constants_a, init_ops ++ ops_a ++ [Opreturn], lvars_a)
+    | otherwise = let
+            (constants_a, ops_a, lvars_a) = foldl assembleStatement (constants, ops, lvars) statements
+            init_ops = [Opaload 0]
+        in
+            (constants_a, init_ops ++ ops_a, lvars_a)
+assembleMethod _ (MethodDeclaration _ _ _ stmt) = error ("Block expected for method body, got: " ++ show stmt) 

src/ByteCode/Generation/Assembler/Statement.hs

@@ -0,0 +1,46 @@
+module ByteCode.Generation.Assembler.Statement where
+
+import Ast
+import ByteCode.ClassFile(ClassFile (..), ConstantInfo (..), MemberInfo(..), Operation(..), Attribute(..), opcodeEncodingLength)
+import ByteCode.Generation.Generator
+import ByteCode.Generation.Assembler.Expression
+
+assembleStatement :: Assembler Statement
+assembleStatement (constants, ops, lvars) (TypedStatement stype (Return expr)) = case expr of
+    Nothing -> (constants, ops ++ [Opreturn], lvars)
+    Just expr -> let
+            (expr_constants, expr_ops, _) = assembleExpression (constants, ops, lvars) expr
+        in
+            (expr_constants, expr_ops ++ [returnOperation stype], lvars)
+assembleStatement (constants, ops, lvars) (TypedStatement _ (Block statements)) =
+    foldl assembleStatement (constants, ops, lvars) statements
+assembleStatement (constants, ops, lvars) (TypedStatement _ (If expr if_stmt else_stmt)) = let
+        (constants_cmp, ops_cmp, _) = assembleExpression (constants, [], lvars) expr
+        (constants_ifa, ops_ifa, _) = assembleStatement (constants_cmp, [], lvars) if_stmt
+        (constants_elsea, ops_elsea, _) = case else_stmt of
+            Nothing -> (constants_ifa, [], lvars)
+            Just stmt -> assembleStatement (constants_ifa, [], lvars) stmt
+        -- +6 because we insert 2 gotos, one for if, one for else
+        if_length = sum (map opcodeEncodingLength ops_ifa) + 6
+        -- +3 because we need to account for the goto in the if statement.
+        else_length = sum (map opcodeEncodingLength ops_elsea) + 3
+    in
+        (constants_ifa, ops ++ ops_cmp ++ [Opsipush 0, Opif_icmpeq if_length] ++ ops_ifa ++ [Opgoto else_length] ++ ops_elsea, lvars)
+assembleStatement (constants, ops, lvars) (TypedStatement _ (While expr stmt)) = let
+        (constants_cmp, ops_cmp, _) = assembleExpression (constants, [], lvars) expr
+        (constants_stmta, ops_stmta, _) = assembleStatement (constants_cmp, [], lvars) stmt
+        -- +3 because we insert 2 gotos, one for the comparison, one for the goto back to the comparison
+        stmt_length = sum (map opcodeEncodingLength ops_stmta) + 6
+        entire_length = stmt_length + sum (map opcodeEncodingLength ops_cmp)
+    in
+        (constants_stmta, ops ++ ops_cmp ++ [Opsipush 0, Opif_icmpeq stmt_length] ++ ops_stmta ++ [Opgoto (-entire_length)], lvars)
+assembleStatement (constants, ops, lvars) (TypedStatement _ (LocalVariableDeclaration (VariableDeclaration dtype name expr))) = let
+        isPrimitive = elem dtype ["char", "boolean", "int"]
+        (constants_init, ops_init, _) = case expr of
+            Just exp -> assembleExpression (constants, ops, lvars) exp
+            Nothing -> (constants, ops ++ if isPrimitive then [Opsipush 0] else [Opaconst_null], lvars)
+        localIndex = fromIntegral (length lvars)
+        storeLocal = if isPrimitive then [Opistore localIndex] else [Opastore localIndex]
+    in
+        (constants_init, ops_init ++ storeLocal, lvars ++ [name])
+assembleStatement _ stmt = error ("Not yet implemented: " ++ show stmt)

src/ByteCode/Generation/Assembler/StatementExpression.hs

@@ -0,0 +1,18 @@
+module ByteCode.Generation.Assembler.StatementExpression where
+
+import Ast
+import ByteCode.ClassFile(ClassFile (..), ConstantInfo (..), MemberInfo(..), Operation(..), Attribute(..), opcodeEncodingLength)
+import ByteCode.Generation.Generator
+import Data.List
+import ByteCode.Generation.Assembler.Expression
+
+assembleStatementExpression :: Assembler StatementExpression
+assembleStatementExpression
+    (constants, ops, lvars)
+    (TypedStatementExpression _ (Assignment (TypedExpression dtype (LocalVariable name)) expr)) = let
+        localIndex = findIndex ((==) name) lvars
+        (constants_a, ops_a, _) = assembleExpression (constants, ops, lvars) expr
+        isPrimitive = elem dtype ["char", "boolean", "int"]
+    in case localIndex of
+        Just index -> (constants_a, ops_a ++ if isPrimitive then [Opistore (fromIntegral index)] else [Opastore (fromIntegral index)], lvars)
+        Nothing -> error ("No such local variable found in local variable pool: " ++ name)

src/ByteCode/Generation/Builder/Class.hs

@@ -0,0 +1,44 @@
+module ByteCode.Generation.Builder.Class where
+
+import ByteCode.Generation.Builder.Field
+import ByteCode.Generation.Builder.Method
+import ByteCode.Generation.Generator
+import Ast
+import ByteCode.ClassFile(ClassFile (..), ConstantInfo (..), MemberInfo(..), Operation(..), Attribute(..), opcodeEncodingLength)
+import ByteCode.Constants
+
+injectDefaultConstructor :: [MethodDeclaration] -> [MethodDeclaration]
+injectDefaultConstructor pre
+    | any (\(MethodDeclaration _ name _ _) -> name == "<init>") pre = pre
+    | otherwise = pre ++ [MethodDeclaration "void" "<init>" [] (TypedStatement "void" (Block []))]
+
+
+classBuilder :: ClassFileBuilder Class
+classBuilder (Class name methods fields) _ = let
+        baseConstants = [
+            ClassInfo 4,
+            MethodRefInfo 1 3,
+            NameAndTypeInfo 5 6,
+            Utf8Info "java/lang/Object",
+            Utf8Info "<init>",
+            Utf8Info "()V",
+            Utf8Info "Code"
+            ]
+        nameConstants = [ClassInfo 9, Utf8Info name]
+        nakedClassFile = ClassFile {
+            constantPool = baseConstants ++ nameConstants,
+            accessFlags = accessPublic,
+            thisClass = 8,
+            superClass = 1,
+            fields = [],
+            methods = [],
+            attributes = []
+        }
+
+        methodsWithInjectedConstructor = injectDefaultConstructor methods
+
+        classFileWithFields = foldr fieldBuilder nakedClassFile fields
+        classFileWithMethods = foldr methodBuilder classFileWithFields methodsWithInjectedConstructor
+        classFileWithAssembledMethods = foldr methodAssembler classFileWithMethods methodsWithInjectedConstructor
+    in
+        classFileWithAssembledMethods

src/ByteCode/Generation/Builder/Field.hs

@@ -0,0 +1,46 @@
+module ByteCode.Generation.Builder.Field where
+
+import Ast
+import ByteCode.ClassFile(ClassFile (..), ConstantInfo (..), MemberInfo(..), Operation(..), Attribute(..), opcodeEncodingLength)
+import ByteCode.Generation.Generator
+import ByteCode.Constants
+import Data.List
+
+findFieldIndex :: [ConstantInfo] -> String -> Maybe Int
+findFieldIndex constants name = let
+        fieldRefNameInfos = [
+                -- we only skip one entry to get the name since the Java constant pool
+                -- is 1-indexed (why)
+                (index, constants!!(fromIntegral index + 1))
+                | (index, FieldRefInfo _ _) <- (zip [1..] constants)
+            ]
+        fieldRefNames = map (\(index, nameInfo) -> case nameInfo of
+            Utf8Info fieldName -> (index, fieldName)
+            something_else -> error ("Expected UTF8Info but got" ++ show something_else))
+                fieldRefNameInfos
+        fieldIndex = find (\(index, fieldName) -> fieldName == name) fieldRefNames
+    in case fieldIndex of
+        Just (index, _) -> Just index
+        Nothing -> Nothing
+
+
+fieldBuilder :: ClassFileBuilder VariableDeclaration
+fieldBuilder (VariableDeclaration datatype name _) input = let
+        baseIndex = 1 + length (constantPool input)
+        constants = [
+                FieldRefInfo (fromIntegral (thisClass input)) (fromIntegral (baseIndex + 1)),
+                NameAndTypeInfo (fromIntegral (baseIndex + 2)) (fromIntegral (baseIndex + 3)),
+                Utf8Info name,
+                Utf8Info (datatypeDescriptor datatype)
+            ]
+        field = MemberInfo {
+            memberAccessFlags = accessPublic,
+            memberNameIndex = (fromIntegral (baseIndex + 2)),
+            memberDescriptorIndex = (fromIntegral (baseIndex + 3)),
+            memberAttributes = []
+            }
+    in
+        input {
+            constantPool = (constantPool input) ++ constants,
+            fields = (fields input) ++ [field]
+        }

src/ByteCode/Generation/Builder/Method.hs

@@ -0,0 +1,80 @@
+module ByteCode.Generation.Builder.Method where
+
+import Ast
+import ByteCode.ClassFile(ClassFile (..), ConstantInfo (..), MemberInfo(..), Operation(..), Attribute(..), opcodeEncodingLength)
+import ByteCode.Generation.Generator
+import ByteCode.Generation.Assembler.Method
+import ByteCode.Constants
+import Data.List
+
+methodDescriptor :: MethodDeclaration -> String
+methodDescriptor (MethodDeclaration returntype _ parameters _) = let
+        parameter_types = [datatype | ParameterDeclaration datatype _ <- parameters]
+    in
+        "("
+        ++ (concat (map methodParameterDescriptor parameter_types))
+        ++ ")"
+        ++ methodParameterDescriptor returntype
+
+methodParameterDescriptor :: String -> String
+methodParameterDescriptor "void" = "V"
+methodParameterDescriptor "int" = "I"
+methodParameterDescriptor "char" = "C"
+methodParameterDescriptor "boolean" = "B"
+methodParameterDescriptor x = "L" ++ x ++ ";"
+
+memberInfoIsMethod :: [ConstantInfo] -> MemberInfo -> Bool
+memberInfoIsMethod constants info = elem '(' (memberInfoDescriptor constants info)
+
+findMethodIndex :: ClassFile -> String -> Maybe Int
+findMethodIndex classFile name = let
+        constants = constantPool classFile
+    in
+        findIndex (\method -> ((memberInfoIsMethod constants method) && (memberInfoName constants method) == name)) (methods classFile)
+
+
+methodBuilder :: ClassFileBuilder MethodDeclaration
+methodBuilder (MethodDeclaration returntype name parameters statement) input = let
+        baseIndex = 1 + length (constantPool input)
+        constants = [
+                Utf8Info name,
+                Utf8Info (methodDescriptor (MethodDeclaration returntype name parameters (Block [])))
+            ]
+
+        method = MemberInfo {
+            memberAccessFlags = accessPublic,
+            memberNameIndex = (fromIntegral baseIndex),
+            memberDescriptorIndex = (fromIntegral (baseIndex + 1)),
+            memberAttributes = []
+            }
+    in 
+        input {
+            constantPool = (constantPool input) ++ constants,
+            methods = (methods input) ++ [method]
+        }
+        
+
+
+methodAssembler :: ClassFileBuilder MethodDeclaration
+methodAssembler (MethodDeclaration returntype name parameters statement) input = let
+        methodConstantIndex = findMethodIndex input name
+    in case methodConstantIndex of
+        Nothing -> error ("Cannot find method entry in method pool for method: " ++ name)
+        Just index -> let
+                declaration = MethodDeclaration returntype name parameters statement
+                paramNames = "this" : [name | ParameterDeclaration _ name <- parameters]
+                (pre, method : post) = splitAt index (methods input)
+                (_, bytecode, _) = assembleMethod (constantPool input, [], paramNames) declaration
+                assembledMethod = method {
+                    memberAttributes = [
+                        CodeAttribute {
+                            attributeMaxStack = 420,
+                            attributeMaxLocals = 420,
+                            attributeCode = bytecode
+                        }
+                    ]
+                }
+            in
+                input {
+                    methods = pre ++ (assembledMethod : post)
+                }

src/ByteCode/Generation/Generator.hs

@@ -0,0 +1,73 @@
+module ByteCode.Generation.Generator(
+    datatypeDescriptor,
+    memberInfoName,
+    memberInfoDescriptor,
+    returnOperation,
+    binaryOperation,
+    comparisonOperation,
+    ClassFileBuilder,
+    Assembler
+) where
+
+import ByteCode.Constants
+import ByteCode.ClassFile (ClassFile (..), ConstantInfo (..), MemberInfo(..), Operation(..), Attribute(..), opcodeEncodingLength)
+import Ast
+import Data.Char
+import Data.List
+import Data.Word
+
+type ClassFileBuilder a = a -> ClassFile -> ClassFile
+type Assembler a = ([ConstantInfo], [Operation], [String]) -> a -> ([ConstantInfo], [Operation], [String])
+
+datatypeDescriptor :: String -> String
+datatypeDescriptor "void" = "V"
+datatypeDescriptor "int" = "I"
+datatypeDescriptor "char" = "C"
+datatypeDescriptor "boolean" = "B"
+datatypeDescriptor x = "L" ++ x
+
+memberInfoDescriptor :: [ConstantInfo] -> MemberInfo -> String
+memberInfoDescriptor constants MemberInfo {
+    memberAccessFlags = _,
+    memberNameIndex = _,
+    memberDescriptorIndex = descriptorIndex,
+    memberAttributes = _ } = let
+            descriptor = constants!!((fromIntegral descriptorIndex) - 1)
+        in case descriptor of
+            Utf8Info descriptorText -> descriptorText
+            _ -> ("Invalid Item at Constant pool index " ++ show descriptorIndex)
+
+
+memberInfoName :: [ConstantInfo] -> MemberInfo -> String
+memberInfoName constants MemberInfo {
+    memberAccessFlags = _,
+    memberNameIndex = nameIndex,
+    memberDescriptorIndex = _,
+    memberAttributes = _ } = let
+            name = constants!!((fromIntegral nameIndex) - 1)
+        in case name of
+            Utf8Info nameText -> nameText
+            _ -> ("Invalid Item at Constant pool index " ++ show nameIndex)
+
+
+returnOperation :: DataType -> Operation
+returnOperation dtype
+    | elem dtype ["int", "char", "boolean"] = Opireturn
+    | otherwise                             = Opareturn
+
+binaryOperation :: BinaryOperator -> Operation
+binaryOperation Addition       = Opiadd
+binaryOperation Subtraction    = Opisub
+binaryOperation Multiplication = Opimul
+binaryOperation Division       = Opidiv
+binaryOperation BitwiseAnd     = Opiand
+binaryOperation BitwiseOr      = Opior
+binaryOperation BitwiseXor     = Opixor
+
+comparisonOperation :: BinaryOperator -> Word16 -> Operation
+comparisonOperation CompareEqual          branchLocation = Opif_icmpeq branchLocation
+comparisonOperation CompareNotEqual       branchLocation = Opif_icmpne branchLocation
+comparisonOperation CompareLessThan       branchLocation = Opif_icmplt branchLocation
+comparisonOperation CompareLessOrEqual    branchLocation = Opif_icmple branchLocation
+comparisonOperation CompareGreaterThan    branchLocation = Opif_icmpgt branchLocation
+comparisonOperation CompareGreaterOrEqual branchLocation = Opif_icmpge branchLocation

src/Main.hs

@@ -4,7 +4,8 @@ import Example
 import Typecheck
 import Parser.Lexer (alexScanTokens)
 import Parser.JavaParser
-import ByteCode.ClassFile.Generator
+import ByteCode.Generation.Generator
+import ByteCode.Generation.Builder.Class
 import ByteCode.ClassFile
 import Data.ByteString (pack, writeFile)
 

src/Typecheck.hs

@@ -25,7 +25,7 @@ typeCheckMethodDeclaration (MethodDeclaration retType name params body) classFie
         checkedBody = typeCheckStatement body initialSymtab classes
         bodyType = getTypeFromStmt checkedBody
         -- Check if the type of the body matches the declared return type
-    in if bodyType == retType || (bodyType == "void" && retType == "void")
+    in if bodyType == retType || (bodyType == "void" && retType == "void") || (bodyType == "null" && isObjectType retType)
        then MethodDeclaration retType name params checkedBody
        else error $ "Return type mismatch in method " ++ name ++ ": expected " ++ retType ++ ", found " ++ bodyType