reduce the chance of blocking in FTP connection

diff --git a/knetfile.c b/knetfile.c
index 9029ee4c6f93fecd353866ad6a3cbc6cb723c0e5..12dc2d17af733d2c5bb93870a3285833fdb063cd 100644 (file)
--- a/knetfile.c
+++ b/knetfile.c
@@ -1,3 +1,4 @@
+#include <time.h>
 #include <stdio.h>
 #include <netdb.h>
 #include <ctype.h>
@@ -9,11 +10,27 @@
 #include <sys/socket.h>
 #include "knetfile.h"
 
+static int socket_wait(int fd, int is_read)
+{
+       fd_set fds, *fdr = 0, *fdw = 0;
+       struct timeval tv;
+       int ret;
+       tv.tv_sec = 5; tv.tv_usec = 0; // 5 seconds time out
+       FD_ZERO(&fds);
+       FD_SET(fd, &fds);
+       if (is_read) fdr = &fds;
+       else fdw = &fds;
+       ret = select(fd+1, fdr, fdw, 0, &tv);
+       if (ret == -1) perror("select");
+       return ret;
+}
+
 static int kftp_get_response(knetFile *ftp)
 {
        unsigned char c;
        int n = 0;
        char *p;
+       if (socket_wait(ftp->ctrl_fd, 1) <= 0) return 0;
        while (read(ftp->ctrl_fd, &c, 1)) { // FIXME: this is *VERY BAD* for unbuffered I/O
                //fputc(c, stderr);
                if (n >= ftp->max_response) {
@@ -35,6 +52,7 @@ static int kftp_get_response(knetFile *ftp)
 
 static int kftp_send_cmd(knetFile *ftp, const char *cmd, int is_get)
 {
+       if (socket_wait(ftp->ctrl_fd, 0) <= 0) return -1; // socket is not ready for writing
        write(ftp->ctrl_fd, cmd, strlen(cmd));
        return is_get? kftp_get_response(ftp) : 0;
 }
@@ -218,6 +236,7 @@ off_t knet_read(knetFile *fp, void *buf, off_t len)
                        fp->is_ready = 1;
                }
                while (rest) {
+                       if (socket_wait(fp->fd, 1) <= 0) break; // socket is not ready for reading
                        curr = read(fp->fd, buf + l, rest);
                        if (curr == 0) break; // FIXME: end of file or bad network? I do not know...
                        l += curr; rest -= curr;