Refactored the scanner and updated the Token struct to store the length of its lexeme to avoid malloc()ing new strings for every token.

scanner.c

@@ -10,9 +10,9 @@ int current; //points to the character currently being considered.
 int length;
 int line = 1;
 
-char Advance(void);
+const char* Advance(void);
 int IsAtend(void);
-void ScanToken(void);
+void ScanToken(TokenList*);
 TokenList* CreateList(void);
 
 TokenList* ScanTokens(const char* source) {
@@ -23,12 +23,15 @@ TokenList* ScanTokens(const char* source) {
 
     if (length == 0) return NULL;
 
+    TokenList* tokens = CreateList();
+
     while(!IsAtend()) {
         start = current;
-        ScanToken();
+        ScanToken(tokens);
     }
 
     //Add EOF token and return list once that's set up.
+    return tokens;
 }
 
 TokenList* CreateList() {
@@ -57,7 +60,7 @@ void DestroyTokenList(TokenList* list) {
     if (!list) return;
 
     for(int i = 0; i < list->size; i++) {
-        free(list->tokens[i]->lexeme);
+        //free(list->tokens[i]->lexeme); This shouldn't be needed since the lexeme is a pointer into the source code.
         free(list->tokens[i]);
     }
 
@@ -65,7 +68,7 @@ void DestroyTokenList(TokenList* list) {
     free(list);
 }
 
-int AddTokenToList(TokenType type, char* lexeme, TokenList* tokens) {
+int AddTokenToList(TokenType type, const char* lexeme, int length, TokenList* tokens) {
     if (!tokens) return 0;
     Token* token = calloc(1, sizeof(Token));
 
@@ -76,6 +79,7 @@ int AddTokenToList(TokenType type, char* lexeme, TokenList* tokens) {
 
     token->lexeme = lexeme;
     token->type = type;
+    token->length = length; //Set the length of the lexeme (which is just a pointer into the complete soure listing).
 
     if ((tokens->size + 1) > tokens->capacity) {
         void* new_ptr = realloc(tokens->tokens, sizeof(Token*) * tokens->capacity * 2);//calloc(tokens->capacity * 2, sizeof(Token*));
@@ -95,28 +99,47 @@ int AddTokenToList(TokenType type, char* lexeme, TokenList* tokens) {
     return 1;
 }
 
-void ScanToken() {
-    char c = Advance();
+void ScanToken(TokenList* tokens) {
+    const char* c = Advance();
 
-    switch (c) {
+    switch (*c) {
     case '(':
+        AddTokenToList(LParen, c, 1, tokens);
+        break;
     case ')':
+        AddTokenToList(RParen, c, 1, tokens);
+        break;
     case '{':
+        AddTokenToList(LBrace, c, 1, tokens);
+        break;
     case '}':
+        AddTokenToList(RBrace, c, 1, tokens);
+        break;
     case ',':
+        AddTokenToList(Comma, c, 1, tokens);
+        break;
     case '.':
+        AddTokenToList(Dot, c, 1, tokens);
+        break;
     case '-':
+        AddTokenToList(Minus, c, 1, tokens);
+        break;
     case '+':
+        AddTokenToList(Plus, c, 1, tokens);
+        break;
     case ';':
+        AddTokenToList(Semicolon, c, 1, tokens);
+        break;
     case '*':
-    break;
+        AddTokenToList(Star, c, 1, tokens);
+        break;
     }
 }
 
-int IsAtEnd() {
+int IsAtend() {
     return current >= length;
 }
 
-char Advance() {
-    return source_code[current++];
+const char* Advance() {
+    return &source_code[current++];
 }