From b095678769416713b4adb79446bb77639cf3c6c7 Mon Sep 17 00:00:00 2001
From: Christian Brier <i22003@hb.dhbw-stuttgart.de>
Date: Wed, 15 May 2024 10:01:01 +0200
Subject: [PATCH] add: local variable assembler

---
 src/ByteCode/ClassFile.hs           |  6 +++---
 src/ByteCode/ClassFile/Generator.hs | 23 +++++++++++++++++++++++
 2 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/src/ByteCode/ClassFile.hs b/src/ByteCode/ClassFile.hs
index 7798cf8..38cf88e 100644
--- a/src/ByteCode/ClassFile.hs
+++ b/src/ByteCode/ClassFile.hs
@@ -51,7 +51,7 @@ data Operation = Opiadd
                | Opastore Word16
                | Opistore Word16
                | Opputfield Word16
-               | OpgetField Word16
+               | Opgetfield Word16
     deriving (Show, Eq)
 
 
@@ -118,7 +118,7 @@ opcodeEncodingLength (Opiload _)            = 3
 opcodeEncodingLength (Opastore _)           = 3
 opcodeEncodingLength (Opistore _)           = 3
 opcodeEncodingLength (Opputfield _)         = 3
-opcodeEncodingLength (OpgetField _)         = 3
+opcodeEncodingLength (Opgetfield _)         = 3
 
 class Serializable a where
     serialize :: a -> [Word8]
@@ -168,7 +168,7 @@ instance Serializable Operation where
     serialize (Opastore index)          = [0xC4, 0x3A] ++ unpackWord16 index
     serialize (Opistore index)          = [0xC4, 0x36] ++ unpackWord16 index
     serialize (Opputfield index)        = 0xB5 : unpackWord16 index
-    serialize (OpgetField index)        = 0xB4 : unpackWord16 index
+    serialize (Opgetfield index)        = 0xB4 : unpackWord16 index
 
 instance Serializable Attribute where
     serialize (CodeAttribute { attributeMaxStack = maxStack,
diff --git a/src/ByteCode/ClassFile/Generator.hs b/src/ByteCode/ClassFile/Generator.hs
index 37919e0..2b6f0f1 100644
--- a/src/ByteCode/ClassFile/Generator.hs
+++ b/src/ByteCode/ClassFile/Generator.hs
@@ -37,6 +37,24 @@ 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
@@ -271,3 +289,8 @@ assembleExpression (constants, ops) (TypedExpression _ (UnaryOperation Minus exp
         (exprConstants, exprOps) = assembleExpression (constants, ops) expr
     in
         (exprConstants, exprOps ++ [Opineg])
+assembleExpression (constants, ops) (TypedExpression _ (FieldVariable name)) = let
+        fieldIndex = findFieldIndex constants name
+    in case fieldIndex of
+        Just index -> (constants, ops ++ [Opaload 0, Opgetfield (fromIntegral index)])
+        Nothing -> error ("No such field found in constant pool: " ++ name)