From edb42c0da8f087003af8f7b60d72107edb4feb71 Mon Sep 17 00:00:00 2001
From: Matthias Kruk <m@m10k.eu>
Date: Mon, 1 Jun 2020 08:39:06 +0900
Subject: [PATCH] lex: Add functions to the lexer so the tokens can be accessed
 more flexibly

---
 src/lex.c | 115 +++++++++++++++++++++++++++++++++++++++++++++++-------
 src/lex.h |   7 +++-
 2 files changed, 107 insertions(+), 15 deletions(-)

diff --git a/src/lex.c b/src/lex.c
index 6555098..dc0366e 100644
--- a/src/lex.c
+++ b/src/lex.c
@@ -34,8 +34,6 @@
 #define STATE_ZERO        23
 #define STATE_NUM         24
 
-#define STATE_DONE    8
-
 #define identifier_firstchr(_c) ((_c) == '_' ||			\
 				 (_c) >= 'a' && (_c) <= 'z' ||	\
 				 (_c) >= 'A' && (_c) <= 'Z')
@@ -43,12 +41,19 @@
 				 (_c) >= '0' && (_c) <= '9')
 
 static char _next = 0;
-static int _state = STATE_NONE;
 static int _line = 1;
 static int _col = 0;
 static int _pline = 1;
 static int _pcol = 1;
-static struct token *_next_token = NULL;
+
+struct token **_tokens;
+int _num_tokens;
+int _cur_token;
+
+struct tokenlist {
+	struct token *token;
+	struct tokenlist *next;
+};
 
 static int _getnextchar(void)
 {
@@ -107,16 +112,12 @@ static int _putnextchar(const char c)
 	return(ret_val);
 }
 
-struct token *lex_gettoken(void)
+struct token *_nexttoken(void)
 {
 	struct token *tok;
 	int state;
 	char c;
 
-	if(_next_token) {
-		return(_next_token);
-	}
-
 	state = STATE_NONE;
 	tok = NULL;
 
@@ -531,16 +532,102 @@ struct token *lex_gettoken(void)
 	return(tok);
 }
 
-int lex_puttoken(struct token *tok)
+void _initialize(void)
+{
+	struct tokenlist *list;
+	struct tokenlist *last;
+	struct token *tok;
+	int i;
+
+	list = NULL;
+	last = NULL;
+	_num_tokens = 0;
+
+	while((tok = _nexttoken())) {
+		struct tokenlist *item;
+
+		item = malloc(sizeof(*item));
+		assert(item);
+
+		item->token = tok;
+		item->next = NULL;
+
+		if(last) {
+			last->next = item;
+			last = item;
+		} else {
+			list = item;
+			last = item;
+		}
+
+		_num_tokens++;
+	}
+
+	_tokens = malloc(sizeof(struct token*) * (_num_tokens  + 1));
+	assert(_tokens);
+
+	for(i = 0; list; ) {
+		struct tokenlist *cur;
+
+		cur = list;
+		_tokens[i++] = cur->token;
+		list = cur->next;
+
+		free(cur);
+	}
+
+	_tokens[i] = NULL;
+	_cur_token = 0;
+
+	return;
+}
+
+int lex_getpos(void)
+{
+	return(_cur_token);
+}
+
+int lex_setpos(int pos)
 {
 	int ret_val;
 
-	if(_next_token) {
-		ret_val = -EALREADY;
-	} else {
-		_next_token = tok;
+	ret_val = -ERANGE;
+
+	if(pos >= 0 && pos <= _num_tokens) {
+		_cur_token = pos;
 		ret_val = 0;
 	}
 
 	return(ret_val);
 }
+
+int lex_next(void)
+{
+        return(lex_setpos(_cur_token + 1));
+}
+
+int lex_prev(void)
+{
+	return(lex_setpos(_cur_token - 1));
+}
+
+struct token *lex_gettoken(void)
+{
+	static int initialized = 0;
+
+	if(!initialized) {
+		_initialize();
+		initialized = 1;
+	}
+
+	if(_cur_token > _num_tokens) {
+		return(NULL);
+	}
+
+	return(_tokens[_cur_token++]);
+}
+
+struct token *lex_peek(void)
+{
+	return(_cur_token < _num_tokens ? _tokens[_cur_token] : NULL);
+}
diff --git a/src/lex.h b/src/lex.h
index a4fc46e..d614d5f 100644
--- a/src/lex.h
+++ b/src/lex.h
@@ -3,7 +3,12 @@
 
 #include "token.h"
 
+int lex_getpos(void);
+int lex_setpos(int);
+int lex_prev(void);
+int lex_next(void);
+
 struct token *lex_gettoken(void);
-int lex_puttoken(struct token*);
+struct token *lex_peek(void);
 
 #endif /* LEX_H */
-- 
2.47.3