From 923349635d78a3e91ac95a4d820ddc82d187f813 Mon Sep 17 00:00:00 2001
From: ubuntu201711081 <201711081@jbnu.ac.kr>
Date: Fri, 4 Dec 2020 04:39:58 +0000
Subject: [PATCH] change implement of timeout_recv

---
 Makefile         | 10 ++++++----
 client.c         |  1 -
 server.c         |  1 -
 socket_wrapper.c | 49 +++++++++++++++++++-----------------------------
 socket_wrapper.h |  5 +----
 5 files changed, 26 insertions(+), 40 deletions(-)

diff --git a/Makefile b/Makefile
index 5405da0..76853c6 100644
--- a/Makefile
+++ b/Makefile
@@ -1,17 +1,19 @@
 CC = gcc
 CFLAGS = -lm -Wall -O2
 
+Bin = server client
+
 all:
-	make client
-	make server
+	make $(Bin)
 
 socket_wrapper.o: socket_wrapper.c socket_wrapper.h
-	$(CC) -c  socket_wrapper.c -o socket_wrapper.o $(CFLAGS)
+	$(CC) -c socket_wrapper.c -o socket_wrapper.o $(CFLAGS)
 
 client: socket_wrapper.o client.c
 	$(CC) -o client client.c socket_wrapper.o $(CFLAGS)
 server:
 	$(CC) -o server server.c socket_wrapper.o $(CFLAGS)
 
+.PHONY: clean
 clean:
-	rm *.o server client
+	rm *.o $(Bin)
diff --git a/client.c b/client.c
index 964804c..5eee530 100644
--- a/client.c
+++ b/client.c
@@ -123,7 +123,6 @@ int main(int argc, const char *argv[]){
     const char * server_name;
     in_port_t server_port = SERVER_PORT;
     int sock;
-    register_alarm();
     if (argc != 4){
         fprintf(stderr,"invaild arguments number.");
         return 1;
diff --git a/server.c b/server.c
index 1581068..f0dddb9 100644
--- a/server.c
+++ b/server.c
@@ -147,7 +147,6 @@ int main(int argc, const char *argv[]){
     socklen_t client_addr_len = sizeof(client_addr);
     int csock;
     int bufsize;
-    register_alarm();
     sock = socket(AF_INET,SOCK_STREAM,0);
     atexit(safe_exit);
     if(sock < 0){
diff --git a/socket_wrapper.c b/socket_wrapper.c
index f6dc431..fc7d19c 100644
--- a/socket_wrapper.c
+++ b/socket_wrapper.c
@@ -4,6 +4,8 @@
 #include <errno.h>
 #include <stdlib.h>
 #include <unistd.h>
+#include <poll.h>
+
 #include "socket_wrapper.h"
 
 int getBufferSizeFrom(int sock){
@@ -18,39 +20,26 @@ int getBufferSizeFrom(int sock){
     return buffer_sz;
 }
 
-static uint64_t timer_ticks = 0;
-static void alarm_handler(int signum){
-    timer_ticks++;
-}
-
-void register_alarm(){
-    struct sigaction sigact;
-    sigact.sa_flags = SA_INTERRUPT;
-    sigemptyset(&sigact.sa_mask);
-    sigaddset(&sigact.sa_mask,SIGALRM);
-    sigact.sa_handler = alarm_handler;
-    sigaction(SIGALRM, &sigact ,NULL);
-}
-
 ssize_t timeout_recv(int fd,void * buf,size_t n,int timeout)
 {
     ssize_t ret;
-    uint64_t cur = timer_ticks;
-    int die_count = 0;
-    for(;;){
-        alarm(timeout);
-        ret = recv(fd,buf,n,0);
-        if (ret < 0 && errno == EINTR && cur != timer_ticks)
-            return -2;
-        alarm(0);
-        if (ret == 0){
-            usleep(100000);
-            die_count++;
-            if(die_count > timeout*10){
-                return -2;
-            }
-        }
-        else break;
+    int poll_ret;
+    struct pollfd fd_single;
+    fd_single.fd = fd;
+    fd_single.events = POLL_IN;
+    poll_ret = (poll(&fd_single,1,timeout * 1000));
+    if (poll_ret < 0) return -1;
+    else if(poll_ret == 0) return -2;
+    switch (fd_single.revents){
+    case POLLHUP: //We'll treat hangups state like timeouts state.
+        return -2;
+    case POLLERR:
+    case POLLNVAL:
+        return -1;
+    case POLL_IN:
+        return recv(fd,buf,n,0);
+    default:
+        assert(0 && "unreachable");
     }
     return ret;
 }
diff --git a/socket_wrapper.h b/socket_wrapper.h
index 6bb7fd7..9a2fdac 100644
--- a/socket_wrapper.h
+++ b/socket_wrapper.h
@@ -43,13 +43,10 @@ struct TransferResult{
 
 int getBufferSizeFrom(int sock);
 
-/*register alarm for timeout_recv()*/
-void register_alarm();
 /*
 return -2 if timeout occur.
 otherwise, implement equal to 'recv'.
-you must call register_alarm() before you use this.
-Since alarm() is called by internal implementation, don't use it if other alarms already exist.
+`timeout` unit is second.
 */
 ssize_t timeout_recv(int fd,void * buf,size_t n,int timeout);
 /*