From bceb7d53289bfb9fe51366967bb4b3bbfa5ddcf0 Mon Sep 17 00:00:00 2001
From: Vitaliy Filippov <vitalif@yourcmc.ru>
Date: Sat, 23 Oct 2021 23:55:38 +0300
Subject: [PATCH] Zero-copy read

---
 pingpong.c | 26 ++++++++++++++++++++++----
 1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/pingpong.c b/pingpong.c
index 7be1eff..cf842a6 100644
--- a/pingpong.c
+++ b/pingpong.c
@@ -72,9 +72,21 @@ int loop(void *arg)
             }
             else if (events[i].events & EPOLLIN)
             {
-                size_t readlen = vppcom_session_read(events[i].data.fd, buf, message_size);
+                vppcom_data_segment_t seg[8];
+                size_t readlen = vppcom_session_read_segments(
+                    events[i].data.fd, seg, sizeof(seg)/sizeof(seg[0]), message_size
+                );
                 if (readlen > 0)
-                    vppcom_session_write(events[i].data.fd, buf, readlen);
+                {
+                    size_t left = readlen;
+                    for (int i = 0; left > 0; i++)
+                    {
+                        vppcom_session_write(events[i].data.fd, seg[i].data, seg[i].len);
+                        left -= seg[i].len;
+                    }
+                    // FIXME: I'm not sure if I can do that. Maybe the buffer can't be freed until it's really sent
+                    vppcom_session_free_segments(events[i].data.fd, readlen);
+                }
                 else
                 {
                     vppcom_epoll_ctl(epfd, EPOLL_CTL_DEL, events[i].data.fd, NULL);
@@ -129,6 +141,7 @@ int loop_client(void *arg)
         if (events[i].events & (EPOLLHUP|EPOLLERR))
         {
             /* Simply close socket */
+            printf("Error event\n");
             vppcom_epoll_ctl(epfd, EPOLL_CTL_DEL, events[i].data.fd, NULL);
             vppcom_session_close(events[i].data.fd);
             sigint_handler(SIGINT);
@@ -139,9 +152,14 @@ int loop_client(void *arg)
             /* Read everything back */
             if (to_read > 0)
             {
-                len = vppcom_session_read(events[i].data.fd, buf, message_size);
+                vppcom_data_segment_t seg[8];
+                len = vppcom_session_read_segments(
+                    events[i].data.fd, seg, sizeof(seg)/sizeof(seg[0]), to_read
+                );
                 if (len > 0)
                     to_read = to_read > len ? to_read-len : 0;
+                // FIXME: I'm not sure if I can do that. Maybe the buffer can't be freed until it's really sent
+                vppcom_session_free_segments(events[i].data.fd, len);
                 if (to_read == 0)
                 {
                     /* Calculate latency */
@@ -297,7 +315,7 @@ int main(int argc, char *argv[])
 
     assert((epfd = vppcom_epoll_create()) > 0);
     ev.data.fd = sockfd;
-    ev.events = (server ? EPOLLOUT : 0) | EPOLLIN|EPOLLHUP;
+    ev.events = (server ? EPOLLOUT : 0) | EPOLLIN|EPOLLHUP|EPOLLET;
     rv = vppcom_epoll_ctl(epfd, EPOLL_CTL_ADD, sockfd, &ev);
     if (rv < 0)
     {