--- t2sami/trunk/PS.cpp	2007/09/09 23:26:20	254
+++ t2sami/trunk/PS.cpp	2011/04/25 03:37:29	255
@@ -204,13 +204,14 @@
 
 	for(;;) {
 
-		if( buf[pos] != 0 )
-			if( buf_len-pos > 4 ) {
+		if( buf_len-pos > 4 )
+			if( buf[pos] != 0 ) {
 
 				byte *p = (byte *)memchr( &buf[pos], 0, buf_len-pos );
 				if( p != NULL ) {
 
 					ptrdiff_t nch = p - &buf[pos];
+					assert(nch >= 0);
 					pos += nch;
 					dif += nch;
 
@@ -262,6 +263,7 @@
 
 void CPs::skip_info(int n_bytes)
 {
+	assert(n_bytes >= 0);
 	check_buffer(n_bytes);
 	pos=pos+n_bytes;
 }
@@ -269,6 +271,7 @@
 int CPs::ret_value(int n_bytes)
 {
 	int val;
+	assert(n_bytes >= 0);
 	check_buffer(n_bytes);
 	val = b.ret_value(buf,(int)pos,(int)pos+n_bytes-1);
 	pos=pos+n_bytes;
@@ -324,6 +327,7 @@
 
 void CPs::go_back(int step)
 {
+	assert(-step <= pos);
 	pos=pos-step;
 }