#include <assert.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>
#include <fcntl.h>
#include <poll.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <netinet/ip.h>
#include <string>
#include <vector>
#include <map>
static void msg(const char *msg) {
fprintf(stderr, "%s\n", msg);
}
static void die(const char *msg) {
int err = errno;
fprintf(stderr, "[%d] %s\n", err, msg);
abort();
}
static void fd_set_nb(int fd) {
errno = 0;
int flags = fcntl(fd, F_GETFL, 0);
if (errno) {
die("fcntl error");
return;
}
flags |= O_NONBLOCK;
errno = 0;
(void)fcntl(fd, F_SETFL, flags);
if (errno) {
die("fcntl error");
}
}
const size_t k_max_msg = 4096;
enum {
STATE_REQ = 0,
STATE_RES = 1,
STATE_END = 2, // mark the connection for deletion
};
struct Conn {
int fd = -1;
uint32_t state = 0; // either STATE_REQ or STATE_RES
// buffer for reading
size_t rbuf_size = 0;
uint8_t rbuf[4 + k_max_msg];
// buffer for writing
size_t wbuf_size = 0;
size_t wbuf_sent = 0;
uint8_t wbuf[4 + k_max_msg];
};
static void conn_put(std::vector<Conn *> &fd2conn, struct Conn *conn) {
if (fd2conn.size() <= (size_t)conn->fd) {
fd2conn.resize(conn->fd + 1);
}
fd2conn[conn->fd] = conn;
}
static int32_t accept_new_conn(std::vector<Conn *> &fd2conn, int fd) {
// accept
struct sockaddr_in client_addr = {};
socklen_t socklen = sizeof(client_addr);
int connfd = accept(fd, (struct sockaddr *)&client_addr, &socklen);
if (connfd < 0) {
msg("accept() error");
return -1; // error
}
// set the new connection fd to nonblocking mode
fd_set_nb(connfd);
// creating the struct Conn
struct Conn *conn = (struct Conn *)malloc(sizeof(struct Conn));
if (!conn) {
close(connfd);
return -1;
}
conn->fd = connfd;
conn->state = STATE_REQ;
conn->rbuf_size = 0;
conn->wbuf_size = 0;
conn->wbuf_sent = 0;
conn_put(fd2conn, conn);
return 0;
}
static void state_req(Conn *conn);
static void state_res(Conn *conn);
const size_t k_max_args = 1024;
static int32_t parse_req(
const uint8_t *data, size_t len, std::vector<std::string> &out)
{
if (len < 4) {
return -1;
}
uint32_t n = 0;
memcpy(&n, &data[0], 4);
if (n > k_max_args) {
return -1;
}
size_t pos = 4;
while (n--) {
if (pos + 4 > len) {
return -1;
}
uint32_t sz = 0;
memcpy(&sz, &data[pos], 4);
if (pos + 4 + sz > len) {
return -1;
}
out.push_back(std::string((char *)&data[pos + 4], sz));
pos += 4 + sz;
}
if (pos != len) {
return -1; // trailing garbage
}
return 0;
}
enum {
RES_OK = 0,
RES_ERR = 1,
RES_NX = 2,
};
// The data structure for the key space. This is just a placeholder
// until we implement a hashtable in the next chapter.
static std::map<std::string, std::string> g_map;
static uint32_t do_get(
const std::vector<std::string> &cmd, uint8_t *res, uint32_t *reslen)
{
if (!g_map.count(cmd[1])) {
return RES_NX;
}
std::string &val = g_map[cmd[1]];
assert(val.size() <= k_max_msg);
memcpy(res, val.data(), val.size());
*reslen = (uint32_t)val.size();
return RES_OK;
}
static uint32_t do_set(
const std::vector<std::string> &cmd, uint8_t *res, uint32_t *reslen)
{
(void)res;
(void)reslen;
g_map[cmd[1]] = cmd[2];
return RES_OK;
}
static uint32_t do_del(
const std::vector<std::string> &cmd, uint8_t *res, uint32_t *reslen)
{
(void)res;
(void)reslen;
g_map.erase(cmd[1]);
return RES_OK;
}
static bool cmd_is(const std::string &word, const char *cmd) {
return 0 == strcasecmp(word.c_str(), cmd);
}
static int32_t do_request(
const uint8_t *req, uint32_t reqlen,
uint32_t *rescode, uint8_t *res, uint32_t *reslen)
{
std::vector<std::string> cmd;
if (0 != parse_req(req, reqlen, cmd)) {
msg("bad req");
return -1;
}
if (cmd.size() == 2 && cmd_is(cmd[0], "get")) {
*rescode = do_get(cmd, res, reslen);
} else if (cmd.size() == 3 && cmd_is(cmd[0], "set")) {
*rescode = do_set(cmd, res, reslen);
} else if (cmd.size() == 2 && cmd_is(cmd[0], "del")) {
*rescode = do_del(cmd, res, reslen);
} else {
// cmd is not recognized
*rescode = RES_ERR;
const char *msg = "Unknown cmd";
strcpy((char *)res, msg);
*reslen = strlen(msg);
return 0;
}
return 0;
}
static bool try_one_request(Conn *conn) {
// try to parse a request from the buffer
if (conn->rbuf_size < 4) {
// not enough data in the buffer. Will retry in the next iteration
return false;
}
uint32_t len = 0;
memcpy(&len, &conn->rbuf[0], 4);
if (len > k_max_msg) {
msg("too long");
conn->state = STATE_END;
return false;
}
if (4 + len > conn->rbuf_size) {
// not enough data in the buffer. Will retry in the next iteration
return false;
}
// got one request, generate the response.
uint32_t rescode = 0;
uint32_t wlen = 0;
int32_t err = do_request(
&conn->rbuf[4], len,
&rescode, &conn->wbuf[4 + 4], &wlen
);
if (err) {
conn->state = STATE_END;
return false;
}
wlen += 4;
memcpy(&conn->wbuf[0], &wlen, 4);
memcpy(&conn->wbuf[4], &rescode, 4);
conn->wbuf_size = 4 + wlen;
// remove the request from the buffer.
// note: frequent memmove is inefficient.
// note: need better handling for production code.
size_t remain = conn->rbuf_size - 4 - len;
if (remain) {
memmove(conn->rbuf, &conn->rbuf[4 + len], remain);
}
conn->rbuf_size = remain;
// change state
conn->state = STATE_RES;
state_res(conn);
// continue the outer loop if the request was fully processed
return (conn->state == STATE_REQ);
}
static bool try_fill_buffer(Conn *conn) {
// try to fill the buffer
assert(conn->rbuf_size < sizeof(conn->rbuf));
ssize_t rv = 0;
do {
size_t cap = sizeof(conn->rbuf) - conn->rbuf_size;
rv = read(conn->fd, &conn->rbuf[conn->rbuf_size], cap);
} while (rv < 0 && errno == EINTR);
if (rv < 0 && errno == EAGAIN) {
// got EAGAIN, stop.
return false;
}
if (rv < 0) {
msg("read() error");
conn->state = STATE_END;
return false;
}
if (rv == 0) {
if (conn->rbuf_size > 0) {
msg("unexpected EOF");
} else {
msg("EOF");
}
conn->state = STATE_END;
return false;
}
conn->rbuf_size += (size_t)rv;
assert(conn->rbuf_size <= sizeof(conn->rbuf));
// Try to process requests one by one.
// Why is there a loop? Please read the explanation of "pipelining".
while (try_one_request(conn)) {}
return (conn->state == STATE_REQ);
}
static void state_req(Conn *conn) {
while (try_fill_buffer(conn)) {}
}
static bool try_flush_buffer(Conn *conn) {
ssize_t rv = 0;
do {
size_t remain = conn->wbuf_size - conn->wbuf_sent;
rv = write(conn->fd, &conn->wbuf[conn->wbuf_sent], remain);
} while (rv < 0 && errno == EINTR);
if (rv < 0 && errno == EAGAIN) {
// got EAGAIN, stop.
return false;
}
if (rv < 0) {
msg("write() error");
conn->state = STATE_END;
return false;
}
conn->wbuf_sent += (size_t)rv;
assert(conn->wbuf_sent <= conn->wbuf_size);
if (conn->wbuf_sent == conn->wbuf_size) {
// response was fully sent, change state back
conn->state = STATE_REQ;
conn->wbuf_sent = 0;
conn->wbuf_size = 0;
return false;
}
// still got some data in wbuf, could try to write again
return true;
}
static void state_res(Conn *conn) {
while (try_flush_buffer(conn)) {}
}
static void connection_io(Conn *conn) {
if (conn->state == STATE_REQ) {
state_req(conn);
} else if (conn->state == STATE_RES) {
state_res(conn);
} else {
assert(0); // not expected
}
}
int main() {
int fd = socket(AF_INET, SOCK_STREAM, 0);
if (fd < 0) {
die("socket()");
}
int val = 1;
setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));
// bind
struct sockaddr_in addr = {};
addr.sin_family = AF_INET;
addr.sin_port = ntohs(1234);
addr.sin_addr.s_addr = ntohl(0); // wildcard address 0.0.0.0
int rv = bind(fd, (const sockaddr *)&addr, sizeof(addr));
if (rv) {
die("bind()");
}
// listen
rv = listen(fd, SOMAXCONN);
if (rv) {
die("listen()");
}
// a map of all client connections, keyed by fd
std::vector<Conn *> fd2conn;
// set the listen fd to nonblocking mode
fd_set_nb(fd);
// the event loop
std::vector<struct pollfd> poll_args;
while (true) {
// prepare the arguments of the poll()
poll_args.clear();
// for convenience, the listening fd is put in the first position
struct pollfd pfd = {fd, POLLIN, 0};
poll_args.push_back(pfd);
// connection fds
for (Conn *conn : fd2conn) {
if (!conn) {
continue;
}
struct pollfd pfd = {};
pfd.fd = conn->fd;
pfd.events = (conn->state == STATE_REQ) ? POLLIN : POLLOUT;
pfd.events = pfd.events | POLLERR;
poll_args.push_back(pfd);
}
// poll for active fds
// the timeout argument doesn't matter here
int rv = poll(poll_args.data(), (nfds_t)poll_args.size(), 1000);
if (rv < 0) {
die("poll");
}
// process active connections
for (size_t i = 1; i < poll_args.size(); ++i) {
if (poll_args[i].revents) {
Conn *conn = fd2conn[poll_args[i].fd];
connection_io(conn);
if (conn->state == STATE_END) {
// client closed normally, or something bad happened.
// destroy this connection
fd2conn[conn->fd] = NULL;
(void)close(conn->fd);
free(conn);
}
}
}
// try to accept a new connection if the listening fd is active
if (poll_args[0].revents) {
(void)accept_new_conn(fd2conn, fd);
}
}
return 0;
}redis/07/07_server.cpp
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