enhanced read to restart when interrupted, and to read until really done

fdiobuf.cpp

@@ -24,7 +24,24 @@ std::streambuf::int_type sc::io::fdiobuf::underflow() {
 }
 
 std::streamsize sc::io::fdiobuf::xsgetn(char* s, std::streamsize n) {
-	return ::read(_fd, s, n);
+	std::streamsize tot_read = 0;
+	std::streamsize next_amount = n;
+	while (next_amount) {
+		ssize_t num_read = ::read(_fd, s, next_amount);
+		if (num_read == -1) {
+			if (errno == EINTR) { // interrupted => restart
+				continue;
+			} else {
+				return -1; // real error
+			}
+		} else if (num_read == 0) { // EOF
+			break;
+		} else {
+			tot_read += num_read;
+			next_amount -= num_read;
+		}
+	}
+	return tot_read;
 }
 
 std::streambuf::int_type sc::io::fdiobuf::overflow(std::streambuf::int_type c) {