add lex.h and lex.c except next_token

include/lex.h

@@ -0,0 +1,39 @@
+#pragma once
+
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "globals.h"
+
+#define LEX_BUF_SIZE 4096
+
+typedef struct Lexer {
+    uint32_t linepos;
+    uint32_t lineno;
+
+    FILE *source;
+
+    int flag_EOF;
+
+    char *buffer;
+    char *curr;
+
+    size_t bytes_in_buffer;
+} Lexer;
+
+Lexer *new_lexer();
+
+void lexer_set_source(Lexer *lexer, FILE *source);
+
+void lexer_fill_buffer(Lexer *lexer);
+
+void lexer_consume(Lexer *lexer);
+
+char lexer_curr(Lexer *lexer);
+
+char lexer_peek(Lexer *lexer);
+
+Token lexer_next_token(Lexer *lexer);
+
+void free_lexer(Lexer *lexer);