scc

commit 7e64989ca1442f6e678a2621a31548df17e99c03
parent 022614703265153d42104e0a13e4236c5ff2b5a2
Author: Roberto E. Vargas Caballero <k0ga@shike2.com>
Date:   Tue, 19 Sep 2017 14:48:35 +0100

[as] Add basic lexer

This is only a basic skeleton of the work that must be done in the lexer.
This work also suggest that it may be interesting to allow to have different
syntaxs based in the target processor.

Diffstat:
M
as/Makefile
 | 
2
+-
M
as/as.h
 | 
2
+-
M
as/expr.c
 | 
124
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-----

3 files changed, 119 insertions(+), 9 deletions(-)
diff --git a/as/Makefile b/as/Makefile
@@ -6,7 +6,7 @@ include $(LIBDIR)/libdep.mk
 
 OBJ = main.o emit.o ins.o parser.o expr.o
 HDR = ../inc/scc.h as.h
-MOREFLAGS = $(AS_CFLAGS)
+MOREFLAGS = -I../inc/$(STD) $(AS_CFLAGS)
 
 all:
 
diff --git a/as/as.h b/as/as.h
@@ -116,7 +116,7 @@ extern int nextline(FILE *fp, struct line *linep);
 #endif
 
 /* expr.c */
-extern Node *expr(void);
+extern Node *expr(char *s);
 
 /*
  * Definition of global variables
diff --git a/as/expr.c b/as/expr.c
@@ -1,7 +1,9 @@
 static char sccsid[] = "@(#) ./as/node.c";
 
+#include <ctype.h>
 #include <string.h>
 
+#include <cstd.h>
 #include "../inc/scc.h"
 #include "as.h"
 
@@ -9,17 +11,20 @@ static char sccsid[] = "@(#) ./as/node.c";
 
 enum tokens {
 	IDEN = 1,
+	NUMBER,
+	REG,
 	CHAR,
 	STRING,
 	SHL,
 	SHR,
 	GE,
-	LT,
+	LE,
 };
 
 static Alloc *arena;
 static int yytoken;
-static char *yytext;
+static char yytext[INTIDENTSIZ+1], *textp, *endp;
+static size_t yylen;
 
 #define accept(t) (yytoken == (t) ? next() : 0)
 
@@ -50,9 +55,97 @@ unary(int op, Node *np)
 }
 
 static int
+follow(int expect1, int expect2, int ifyes1, int ifyes2, int ifno)
+{
+	int c;
+
+	if ((c = *++textp) == expect1)
+		return ifyes1;
+	if (c == expect2)
+		return ifyes2;
+	--textp;
+	return ifno;
+}
+
+static void
+tok2str(void)
+{
+	if ((yylen = endp - textp) > INTIDENTSIZ) {
+		error("token too big");
+		yylen = INTIDENTSIZ;
+	}
+	memcpy(yytext, textp, yylen);
+	yytext[yylen] = '\0';
+	textp = endp;
+}
+
+static int
+iden(void)
+{
+	int c;
+	char *p;
+
+	for (endp = textp; isalnum(c = *endp) || c == '_' || c == '.'; ++endp)
+		/* nothing */;
+	return IDEN;
+}
+
+static int
+number(void)
+{
+	int c;
+	char *p;
+
+	for (endp = textp; isxdigit(*endp); ++endp)
+		/* nothing */;
+	return NUMBER;
+}
+
+static int
+character(void)
+{
+	int c;
+	char *p;
+
+	for (endp = textp+1; *endp != '\''; ++endp)
+		/* nothing */;
+	return CHAR;
+}
+
+static int
+string(void)
+{
+	int c;
+	char *p;
+
+	for (endp = textp+1; *endp != '"'; ++endp)
+		/* nothing */;
+	return STRING;
+}
+
+static int
 next(void)
 {
-	return 0;
+	int c;
+
+	while (isspace(*textp))
+		++textp;
+	c = *textp;
+	if (isalpha(c) || c == '_' || c == '.')
+		c = iden();
+	else if (isdigit(c))
+		c = number();
+	else if (c == '>')
+		c = follow('=', '>', LE, SHL, '>');
+	else if (c == '<')
+		c = follow('=', '<', GE, SHR, '>');
+	else if (c == '\'')
+		c = character();
+	else if (c == '\"')
+		c = string();
+	tok2str();
+
+	return c;
 }
 
 static void
@@ -73,12 +166,15 @@ expect(int token)
 /* grammar functions                                                     */
 /*************************************************************************/
 
+static Node *or(void);
+
 static Node *
 primary(void)
 {
 	Node *np;
 
 	switch (yytoken) {
+	case NUMBER:
 	case IDEN:
 	case CHAR:
 	case STRING:
@@ -87,7 +183,7 @@ primary(void)
 		break;
 	case '(':
 		next();
-		np = expr();
+		np = or();
 		expect(')');
 		break;
 	default:
@@ -152,7 +248,7 @@ relational(void)
 		case '>':
 		case '=':
 		case GE:
-		case LT:
+		case LE:
 			next();
 			np = binary(op, np, add());
 			break;
@@ -184,8 +280,8 @@ and(void)
 	return np;
 }
 
-Node *
-expr(void)
+static Node *
+or(void)
 {
 	int op;
 	Node *np;
@@ -202,3 +298,17 @@ expr(void)
 		}
 	}
 }
+
+Node *
+expr(char *s)
+{
+	Node *np;
+
+	textp = s;
+	next();
+	np = or();
+
+	if (*textp != '\0')
+		error("trailing characters in expression '%s'", textp);
+	return np;
+}