From 6ce26709de917607197f2cb155ec73c1f6930b2e Mon Sep 17 00:00:00 2001
From: Curle <curle@gemwire.uk>
Date: Wed, 25 Nov 2020 17:03:33 +0000
Subject: [PATCH] Start refactoring Symbols for scoping rework

---
 include/Defs.h |  2 +-
 src/Symbols.c  | 95 ++++++++++++++++++++++++++++++++++++--------------
 2 files changed, 70 insertions(+), 27 deletions(-)

diff --git a/include/Defs.h b/include/Defs.h
index e2c2ee4..09e96cd 100644
--- a/include/Defs.h
+++ b/include/Defs.h
@@ -325,7 +325,7 @@ struct ASTNode* PrintStatement(void);
 
 int FindSymbol(char* Symbol);
 
-int AddSymbol(char* Name, int Type, int Structure, int Size);
+int AddSymbol(char* Name, int Type, int Structure, int Storage, int EndLabel, int Length);
 
 int AddFunctionSymbol(char* Name, int Type, int Structure, int EndLabel, int Size);
 
diff --git a/src/Symbols.c b/src/Symbols.c
index 267e02d..20366b1 100644
--- a/src/Symbols.c
+++ b/src/Symbols.c
@@ -9,15 +9,15 @@
 
 static int GlobalSymbols = 0;
 
-/*
- * Find the position of a symbol in the symbol table.
- *  @Return the index into the symbol table if found,
- *      -1 if not found.
- */
-int FindSymbol(char* Symbol) {
+
+int FindSymbolImpl(char* Symbol, int Storage) {
     int Ind;
 
-    for(Ind = 0; Ind < GlobalSymbols; Ind++) {
+    for(Ind = 0; Ind < (Storage == SC_GLOBAL /* Are we global scope? */
+             ?  CurrentGlobal /* If so, start searching at the start */
+             : SYMBOLS /* Otherwise, start at the end and work backward */ 
+              ); Ind++) {
+
         if(*Symbol == *Symbols[Ind].Name && !strcmp(Symbol, Symbols[Ind].Name))
             return Ind;
     }
@@ -25,50 +25,93 @@ int FindSymbol(char* Symbol) {
     return -1;
 }
 
+/*
+ * Find the position of a symbol in the symbol table.
+ *  @Return the index into the symbol table if found,
+ *      -1 if not found.
+ *          Does not care about differentiating local or global.
+ *           It will only be consistent.
+ */
+int FindSymbol(char* Symbol) {
+    int Res;
+    // Prioritise local vars
+    if((Res = FindSymbolImpl(Symbol, SC_LOCAL)) == -1)
+        // Fallback to global vars.
+        return FindSymbolImpl(Symbol, SC_GLOBAL);
+    return Res;
+}
+
 /*
  * Append a new entry to the table of global symbols.
  *  @Return the index to the new entry
  * 
  * Will kill the program if we run out.
+ *  The death condition here is running into the local symbol table.
  *  //TODO: Dump symbols on death?
  */
-static int NewSymbol(void) {
+static int NewGlobalSymbol() {
     int Pos;
 
-    if((Pos = GlobalSymbols++) >= SYMBOLS)
-        Die("Too many symbols");
+    if((Pos = (CurrentGlobal++)) >= CurrentLocal)
+        Die("Too many Global symbols");
     
     return Pos;
 }
 
-// TODO: this is going weird!
+/*
+ * Append a new entry to the table of local (function-local) symbols.
+ *  @Return the index to the new entry
+ * 
+ * Will kill the program if we run out.
+ *  The death condition here is running into the global symbol table.
+ *  //TODO: Dump symbols on death?
+ */
+static int NewLocalSymbol() {
+    int Pos;
+    if((Pos = (CurrentLocal--)) <= CurrentGlobal)
+        Die("Too many Local symbols");
 
-int AddArraySymbol(char* Name, int Type, int Structure, int EndLabel, int Size) {
-    int Slot;
-    Slot = AddFunctionSymbol(Name, Type, Structure, EndLabel, Size);
-    return Slot;
+    return Pos;
 }
 
-int AddFunctionSymbol(char* Name, int Type, int Structure, int EndLabel, int Size) {
-    int Slot;
-    Slot = AddSymbol(Name, Type, Structure, Size);
-    Symbols[Slot].EndLabel = EndLabel;
-    return Slot;
-}
-
-int AddSymbol(char* Name, int Type, int Structure, int Size) {
+/*
+ * Add a symbol to the tables, and set all the metadata.
+ *  @param Name:      The string representing the name of the symbol.
+ *  @param Type:      The return type in terms of DataTypes enum values.
+ *  @param Structure: The type of symbol this is, in terms of StructureType enum.
+ *  @param Storage:   The storage scope of this symbol. For functions this is always SC_GLOBAL (for now). Vars and Arrays can be GLOBAL or SC_LOCAL.
+ *  @param EndLabel:  The label # to jump to to exit the function or array, where appropriate.  
+ *  @param Length:    The size of the struct/array in units of 1xbase
+ * 
+ *  @return The ID in the symbol table that now represents this symbol.
+ */
+int AddSymbol(char* Name, int Type, int Structure, int Storage, int EndLabel, int Length) {
 
     int TableSlot;
+    int SinkOffset = 0;
 
-    if((TableSlot = FindSymbol(Name) != -1))
+    if((TableSlot = FindSymbol(Name, Storage) != -1))
         return TableSlot;
     
-    TableSlot = NewSymbol();
+    // Instaed of spliting this up into AddLocalSymbol and AddGlobalSymbol,
+    //  we can use this switch to avoid duplicated code.
+    switch(Storage) {
+        case SC_GLOBAL:
+            TableSlot = NewGlobalSymbol();
+            AsGlobalSymbol(TableSlot);
+            break;
+        case SC_LOCAL:
+            TableSlot = NewLocalSymbol();
+            SinkOffset = AsCalcOffset(Type, 0);
+            break;
+    }
 
     Symbols[TableSlot].Name = strdup(Name);
     Symbols[TableSlot].Type = Type;
     Symbols[TableSlot].Structure = Structure;
-    Symbols[TableSlot].Length = Size;
+    Symbols[TableSlot].Storage = Storage;
+    Symbols[TableSlot].Length = Length;
+    Symbols[TableSlot].SinkOffset = SinkOffset;
 
     //printf("Adding new variable %s of type %s to the table at %d\n", CurrentIdentifier, Types[Type], TableSlot);
     return TableSlot;