1 files changed, 104 insertions, 1 deletions

diff --git a/bas.c b/bas.c
index e90d96c..fc5517b 100644
--- a/bas.c
+++ b/bas.c
@@ -155,6 +155,10 @@ void adjust_vntable_size(int oldsize, int newsize) {
 	}
 }
 
+unsigned char get_vartype(unsigned char tok) {
+	return program[vvstart + (tok & 0x7f) * 8] >> 6;
+}
+
 /* return true if the variable name table is OK */
 int vntable_ok(void) {
 	int vp, bad;
@@ -249,10 +253,109 @@ void open_output(const char *name) {
 	output_file = open_file(name, "wb");
 }
 
-extern void set_self(const char *argv0) {
+void set_self(const char *argv0) {
 	char *p;
 
 	self = argv0;
 	p = strrchr(self, '/');
 	if(p) self = p + 1;
 }
+
+/* callbacks */
+CALLBACK_PTR(on_start_line);
+CALLBACK_PTR(on_bad_line_length);
+CALLBACK_PTR(on_end_line);
+CALLBACK_PTR(on_start_stmt);
+CALLBACK_PTR(on_end_stmt);
+CALLBACK_PTR(on_cmd_token);
+CALLBACK_PTR(on_text);
+CALLBACK_PTR(on_exp_token);
+CALLBACK_PTR(on_var_token);
+CALLBACK_PTR(on_string_const);
+CALLBACK_PTR(on_num_const);
+
+#define CALL(x) if(x) (*x)(lineno, pos, program[pos], end)
+
+void walk_code(unsigned int startlineno, unsigned int endlineno) {
+	int linepos, nextpos, offset, soffset, lineno, pos, end, tok;
+
+	linepos = codestart;
+	while(linepos < filelen) { /* loop over lines */
+		lineno = getword(linepos);
+		offset = program[linepos + 2];
+		nextpos = linepos + offset;
+
+		end = nextpos;
+		pos = linepos;
+
+		if(offset < 6) {
+			CALL(on_bad_line_length);
+			offset = program[linepos + 2]; /* on_bad_line_length fixed it (we hope) */
+			if(offset < 6)
+				die("Program is code-protected; unprotect it first.");
+		}
+
+		if(lineno < startlineno) {
+			linepos = nextpos;
+			continue;
+		}
+
+		CALL(on_start_line);
+
+		pos = linepos + 3;
+		while(pos < nextpos) { /* loop over statements within a line */
+			soffset = program[pos];
+			end = linepos + soffset;
+			CALL(on_start_stmt);
+
+			while(pos < end) {  /* loop over tokens within a statement */
+				pos++;
+				CALL(on_cmd_token);
+				switch(program[pos]) {
+					case CMD_REM:
+					case CMD_DATA:
+					case CMD_ERROR:
+						pos++;
+						CALL(on_text);
+						pos = end;
+						break;
+					default:
+						pos++;
+						break;
+				}
+
+				while(pos < end) {     /* loop over operators */
+					tok = program[pos];
+					switch(tok) {
+						case OP_NUMCONST:
+							CALL(on_exp_token);
+							pos++;
+							CALL(on_num_const);
+							pos += 6;
+							break;
+						case OP_STRCONST:
+							CALL(on_exp_token);
+							pos++;
+							CALL(on_string_const);
+							pos += program[pos] + 1;
+							break;
+						default:
+							if(tok & 0x80) {
+								CALL(on_var_token);
+							} else {
+								CALL(on_exp_token);
+							}
+							pos++;
+							break;
+					}
+				}
+				CALL(on_end_stmt);
+			}
+		}
+
+		CALL(on_end_line);
+
+		if(lineno >= endlineno) break;
+		linepos = nextpos;
+	}
+}