moth/packages/cowbull/src/cowd.c

193 lines
4.2 KiB
C

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <time.h>
#include <string.h>
#include <sysexits.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#define TIMEOUT 30
#define NTOKENS 20
#define TOKENLEN 50
char tokens[NTOKENS][TOKENLEN];
int ntokens;
struct state {
time_t death;
uint16_t answer;
uint16_t guesses;
};
#define NSTATES 500
struct state states[NSTATES] = { 0 };
int
bind_port(struct in6_addr *addr, int fd, uint16_t port)
{
struct sockaddr_in6 saddr = { 0 };
saddr.sin6_family = AF_INET6;
saddr.sin6_port = htons(port);
memcpy(&saddr.sin6_addr, addr, sizeof *addr);
return bind(fd, (struct sockaddr *) &saddr, sizeof saddr);
}
struct newgame {
uint16_t offset;
uint16_t token;
};
void
new_game(int sock, time_t now, struct sockaddr_in6 *from,
socklen_t fromlen)
{
int i;
struct newgame g;
for (g.offset = 0; g.offset < NSTATES; g.offset += 1) {
struct state *s = &states[g.offset];
if (s->death < now) {
s->death = now + TIMEOUT;
s->guesses = 0;
s->answer = 0;
for (i = 0; i < 4; i += 1) {
s->answer = (s->answer << 4) | ((random() % 6) + 1);
}
break;
}
}
if (g.offset < NSTATES) {
sendto(sock, &g, sizeof(g), 0, (struct sockaddr *) from, fromlen);
}
}
struct guess {
uint16_t offset;
uint16_t token;
uint16_t guess;
};
void
loop(int sock)
{
struct guess g;
struct state *cur;
struct sockaddr_in6 from;
socklen_t fromlen = sizeof from;
time_t now = time(NULL);
/*
* Read guess
*/
{
ssize_t inlen;
inlen = recvfrom(sock, &g, sizeof g, 0,
(struct sockaddr *) &from, &fromlen);
if (inlen != sizeof g) {
return;
}
}
/*
* Bounds check
*/
if (g.offset >= NSTATES) {
g.offset = 0;
}
cur = &states[g.offset];
if ((g.token != cur->answer) || /* Wrong token? */
(cur->death < now) || /* Old game? */
(cur->guesses++ > 100)) { /* Too dumb? */
/*
* Start a new game
*/
new_game(sock, now, &from, fromlen);
return;
} else {
uint8_t reply;
int i;
for (i = 0; i < 4; i += 1) {
int s = (g.guess >> (i * 4)) & 0xf;
int a = (cur->answer >> (i * 4)) & 0xf;
if ((s < 1) || (s > 7)) {
reply = 0;
break;
} else if (s == a) {
reply += 0x10;
} else if (s & a) {
reply += 0x01;
}
}
if (reply == 0x40) {
if (cur->guesses > ntokens) {
sendto(sock, tokens[cur->guesses],
strlen(tokens[cur->guesses]), 0,
(struct sockaddr *) &from, fromlen);
}
} else {
sendto(sock, &reply, sizeof reply, 0, (struct sockaddr *) &from,
fromlen);
}
}
}
int
main(int argc, char *argv[])
{
long answer = 0;
int sock;
int i;
struct in6_addr addr;
srand(time(NULL));
if (argc > 1) {
if (0 >= inet_pton(AF_INET6, argv[1], &addr)) {
fprintf(stderr, "invalid address: %s\n", argv[1]);
return EX_IOERR;
}
} else {
memcpy(&addr, &in6addr_any, sizeof addr);
}
/*
* Read in tokens
*/
for (ntokens = 0; ntokens < NTOKENS; ntokens += 1) {
if (NULL == fgets(tokens[ntokens], TOKENLEN, stdin)) {
break;
}
}
printf("Read %d tokens.\n", ntokens);
/*
* Set up socket
*/
sock = socket(AF_INET6, SOCK_DGRAM, 0);
i = bind_port(&addr, sock, 3782);
if (-1 == i) {
perror("Bind port 3782");
return EX_IOERR;
}
for (i = 0; i < 4; i += 1) {
answer = (answer << 4) | ((random() % 6) + 1);
}
while (1) {
loop(sock);
}
return 0;
}