lexer: Add TT_COLONDUB and putback buffer

Signed-off-by: Ian Moffett <ian@mirocom.org>

frontend/lexer.c

@@ -36,6 +36,40 @@ lexer_is_ws(char c)
     return false;
 }
 
+/*
+ * Place a character in the lexer putback buffer
+ *
+ * @state:   Quip state
+ * @c:       Character to insert
+ */
+static inline void
+lexer_putback(struct quip_state *state, char c)
+{
+    if (state == NULL) {
+        return;
+    }
+
+    state->lex_putback = c;
+}
+
+/*
+ * Pop the last character from the lexer putback
+ * buffer
+ */
+static inline char
+lexer_putback_pop(struct quip_state *state)
+{
+    char c;
+
+    if (state == NULL) {
+        return '\0';
+    }
+
+    c = state->lex_putback;
+    state->lex_putback = '\0';
+    return c;
+}
+
 /*
  * Consume a single character in a buffered manner from the
  * build source file.
@@ -88,6 +122,15 @@ lexer_consume(struct quip_state *state, bool skip_ws)
 {
     char c;
 
+    /*
+     * If there is anything in the putback buffer, take
+     * it.
+     */
+    if ((c = lexer_putback_pop(state)) != '\0') {
+        if (!skip_ws || !lexer_is_ws(c))
+            return c;
+    }
+
     while ((c = lexer_buffer_consume(state)) != '\0') {
         if (skip_ws && lexer_is_ws(c)) {
             continue;
@@ -118,8 +161,14 @@ lexer_scan(struct quip_state *state, struct token *tokres)
         tokres->c = c;
         return 0;
     case ':':
-        tokres->type = TT_COLON;
         tokres->c = c;
+        if ((c = lexer_consume(state, false)) == ':') {
+            tokres->type = TT_COLONDUB;
+            return 0;
+        }
+
+        lexer_putback(state, c);
+        tokres->type = TT_COLON;
         return 0;
     }
 

include/common/state.h

@@ -23,6 +23,7 @@
  * @lex_buf:        Used to reduce system call frequency
  * @lex_buf_cap:    Lexer buffer capacity
  * @lex_buf_i:      Lexer buffer index
+ * @lex_putback:    Lexer putback buffer
  */
 struct quip_state {
     int in_fd;
@@ -30,6 +31,7 @@ struct quip_state {
     char lex_buf[LEX_FILEBUF_LEN];
     size_t lex_buf_cap;
     size_t lex_buf_i;
+    char lex_putback;
 };
 
 /*

include/frontend/token.h

@@ -19,6 +19,7 @@ typedef enum {
     TT_NAME,        /* [name] */
     TT_NEWLINE,     /* [newline] */
     TT_COLON,       /* ':' */
+    TT_COLONDUB,    /* '::' */
 } tt_t;
 
 /*