void clean() {
while (cache_map.size() > cache_size) {
auto mv_node = cache_list.end();
--mv_node;
cache_map.erase(mv_node->first);
cache_list.pop_back();
}
}
int get(int key) {
auto got = cache_map.find(key);
if (got == cache_map.end())
return -1;
cache_list.splice(cache_list.begin(), cache_list, got->second);
return got->second->second;
}
void set(int key, int value) {
auto got = cache_map.find(key);
if (got != cache_map.end()) {
cache_list.erase(got->second);
cache_map.erase(got);
}
cache_list.push_front(make_pair(key, value));
cache_map.insert(make_pair(key, cache_list.begin()));
clean();
}
void cache_display()
{
HTTP_header* http_hdr;
HTTP_pointer* ptr;
CACHE_LIST::iterator N;//use a standard iterator variable to move through the cache
string LR_key, last;
time_t last_accessed;
cout<<endl;
cout<<"_____________________Files Cache____________________________"<<endl;
N= cache.begin();
while(N != cache.end())
{
LR_key = N->first;//first element in cache
ptr = N->second;//pointer to the next
http_hdr = ptr->getHeader();
last_accessed = http_hdr->get_last_accessed();
last = UTC_convert(last_accessed);
cout<<"page: "<<LR_key<<", was last accessed at: "<<last<<endl;
N++;
}
}
//Incase you find the requested webpage in the cache of the proxy server
HTTP_pointer* found_in_cache(string url,int do_now)
{
int current, expire_int;
CACHE_LIST::iterator N;
HTTP_pointer* ptr;
N = cache.find(url);
ptr = N->second;
//get the expiration time
string expires = ptr->getHeader()->get_expires();
//if Expires field is not there, use the Last-modified or the Date field, in that order
if(expires.empty())
{
expires = ptr->getHeader()->get_last_modified();
if(expires.empty())
expires = ptr->getHeader()->get_date();
}
time_t expire_time = convert_time_format(expires); //convert to time_t format
if(expire_time <= 0) //handle spl cases
{
cout<<"Format for Expires is not suitable: "<<expires;
expire_int = -1;
}
else
expire_int = int(expire_time);
current = int(time_current());
if(current > expire_int)
{
//this means that the page has expired in the cache so we will check for a 304 statement
cout<<"Requested webpage has expired in proxy cache"<<endl;
int* length_page;
//we download the expired page with information on ifModified
string expired_page = download_WEB(url, length_page, expires,do_now);
//this being a conditional get, we need to make sure we need this to be downloaded again
if(!expired_page.empty())//if we get no page ---------> no download necessary
{
HTTP_pointer* new_ptr = parseResponse(expired_page, *length_page);
update_cache(url, new_ptr,1);
cout<<"The page----->"<<url<<" has been refreshed in cache"<<endl;
return new_ptr; //return the page from the server
}
else
{
cout<<"The page----->"<<url<<"is fresh no need to re-download------->Sending from Cache"<<endl;
ptr = set_Time(ptr); //send from cache itself and set its last access time
return ptr;
}
}
else
{
//if page hasnt expired in the cache
cout<<"The page "<<url<<" has been found in cache and there is no need to refresh the page"<<endl;
ptr = set_Time(ptr);
return ptr;
}
}
int main(int argc, char*argv[])
{
if(argc == 3)
{
int max_clients = 5;//you can select the number of MAX clients. But please also change MAX in header file
//initialization of various buffers variables etc that we will use in this program
int i, fd_client, fdmax;
struct sockaddr_in SERVER;
struct sockaddr_in CLIENT;
fd_set readfds;
FD_ZERO(&readfds);
fd_set master;
FD_ZERO(&master);
short port;
char copybuffer[1024];
char proxy_buffer[1024];
int fd_server = socket(AF_INET, SOCK_STREAM, 0);
if(fd_server < 0)
{
perror("Server socket creation error\n");
exit(1);
}
int yes = 1;
if(setsockopt(fd_server, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int)) == -1)
{
perror("setsockopt error");
exit(-1);
}
//assigning of the server's file descriptor
bzero((char*) &SERVER, sizeof(struct sockaddr_in));
SERVER.sin_family= AF_INET;
port = htons(atoi(argv[2]));
SERVER.sin_port = port;
inet_pton(AF_INET, argv[1], &SERVER.sin_addr);
//bind the server to a port
if(bind(fd_server, (struct sockaddr*) &SERVER, sizeof(SERVER))<0)
{
perror("Server bind error\n");
exit(-2);
}
//listen on max_clients number of ports
if(listen(fd_server, max_clients) < 0)
{
perror("Listen error");
exit(-33);
}
cout<<"Proxy Server is Waiting for New Connections"<<endl;
FD_SET(fd_server, &master);
fdmax = fd_server;
u_int leg;
while(1)
{
printf("\n");
readfds = master;
bzero(copybuffer,sizeof(copybuffer));
bzero(proxy_buffer,sizeof(proxy_buffer));
if(select(fdmax+1, &readfds, NULL, NULL, NULL) == -1)
{
perror("Select error\n");
exit(1);
}
//ignore the first two descriptors as they belong to server and web-server
for(i=3; i<=fdmax; i++)
{
if(FD_ISSET(i, &readfds))
{
if(i == fd_server)
{
leg = sizeof(CLIENT);
fd_client = accept(fd_server, (struct sockaddr*) &CLIENT, &leg);
if(fd_client >= 0)
{
FD_SET(fd_client, &master);
if(fd_client > fdmax)
fdmax = fd_client;
}
else
{
perror("Could not accept connection\n");
}
}
else
{
int b = recv(i, proxy_buffer, sizeof(proxy_buffer), 0);
if(b <= 0)
{
FD_CLR(i, &master);
continue;
}
string str(proxy_buffer, b);
//parse the request
strcpy(copybuffer, proxy_buffer);
char* token = (char*)malloc(sizeof(char*));
token = strtok(copybuffer, " ");
char* tokens[3];
int NN = 0;
while(token != NULL)
{
tokens[NN] = token;
token = strtok(NULL, " ");
NN++;
}
//now get the url
string url(tokens[1]);
string http_body_extract;
cout<<"Requested Page: "<<url<<endl;
//if we find the page we are looking for in cache we use found_in_cache
if(cache.count(url) != 0)
{ int now = 1;
HTTP_pointer* ptr_found = found_in_cache(url,now);
http_body_extract = ptr_found->get_http_body();//returns the http response body
send(i, http_body_extract.c_str(), http_body_extract.length(),0);
cache_display();
}
else
{
//else we use the function not_found_in_cache
int now = 0;
HTTP_pointer* ptr_not_found = not_found_in_cache(url,now);
http_body_extract = ptr_not_found->get_http_body(); //returns the http body
cout<<http_body_extract.length()<<endl<<endl<<endl<<endl<<endl;
send(i, http_body_extract.c_str(), http_body_extract.length(),0);
cache_display();
}
}
}
}
}
close(fd_server);
return 0;
}
else
{
perror("Usage:./server server-IP server-Port");
exit(1);
}
return -1;
}
void update_cache(string url, HTTP_pointer* entity,int status)
{
if(status == 0)
{
//first check if cache has empty places
double MTD=INT_MIN;//minimum access time
time_t currentTime = time_current();
if(cache.size() < MAX)
{
//just insert it and return
cout<<"Current size of cache: "<<cache.size()<<endl;
entity = set_Time(entity);
cache.insert(make_pair(url, entity));
return;
}
//now if cache is full, find the entry with the oldest access time
//
int i=0;
CACHE_LIST::iterator Least_recent_key;
CACHE_LIST::iterator N = cache.begin();
time_t last;
for(; N != cache.end(); N++)
{
HTTP_pointer* en = N->second;
last = en->getHeader()->get_last_accessed();
double timediff = difftime(currentTime, last);
if(timediff > MTD)
{
MTD = timediff;//find the minima
Least_recent_key = N;
}
i++;
}
//now we have the least recently used key in index leastRecent
cout<<"The least recently used(LRU) page is "<<Least_recent_key->first<<", hence this entry will be deleted in the cache"<<endl;
cache.erase(Least_recent_key);
cache.insert(make_pair(url, entity));
}
else
{
//method to replace existing entries in cache
string key;
CACHE_LIST::iterator N = cache.begin();
for(; N != cache.end(); N++)
{
key = N->first;
if(key == url)
{
cout<<"Entry found for page "<<key<<", this will be replaced with the new page now"<<endl;
cache.erase(key);
entity = set_Time(entity);
cache.insert(make_pair(url, entity));
break;
}
}
}
}
