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iv_examples(3) [debian man page]

ivykis(3)						    ivykis programmer's manual							 ivykis(3)

NAME
iv_examples - ivykis examples EXAMPLE
ivykis is initialised by calling iv_init(3). This function is the first function to call when dealing with ivykis -- it has to be called before registering file descriptors or timers. The ivykis main event loop is started by calling iv_main(3). This function generally does not return, except when iv_quit(3) is called somewhere during execution of the program. An application asks ivykis to monitor a certain file descriptor by filling out a structure of type 'struct iv_fd' with a file descriptor number and a callback function, and calling the function iv_fd_register. The first example program waits for data from standard input, and writes a message to standard out whenever something is received: #include <stdio.h> #include <stdlib.h> #include <iv.h> struct iv_fd fd_stdin; static void callback(void *dummy) { char buf[1024]; int len; len = read(fd_stdin.fd, buf, sizeof(buf)); if (len <= 0) { if (len < 0) { if (errno == EAGAIN) return; perror("read"); } exit(1); } printf("read %d bytes of data from stdin ", len); } int main() { iv_init(); IV_FD_INIT(&fd_stdin); fd_stdin.fd = 0; fd_stdin.handler_in = callback; iv_fd_register(&fd_stdin); iv_main(); iv_deinit(); return 0; } The application is responsible for memory management of 'struct iv_fd's passed to ivykis. For example, it should not free memory that con- tains such structures that are still registered with ivykis (i.e. haven't had iv_fd_unregister called on them). iv_fd_register transparently sets the passed file descriptor to nonblocking mode, in anticipation of its future usage. File descriptor callbacks are called in a level-triggered fashion. Therefore, the way of dealing with fd_stdin in the example callback function is safe. In case there arrives data between read and detecting EAGAIN, ivykis will re-call the callback function after it returns. Also, if there are more than 1024 bytes waiting in the input buffer, ivykis will re-call the callback function until all data from stdin have been drained. EXAMPLE 2 The second example accepts connections on TCP port 6667, and waits on each of the connections for data. When data is received on any con- nection, a message is printed to standard out. #include <stdio.h> #include <stdlib.h> #include <iv.h> #include <netinet/in.h> struct connection { struct iv_fd fd; /* other per-connection data goes here */ }; struct listening_socket { struct iv_fd fd; /* other per-listening socket data goes here */ }; static void connection_handler(void *_conn) { struct connection *conn = (struct connection *)_conn; char buf[1024]; int len; len = read(conn->fd.fd, buf, sizeof(buf)); if (len <= 0) { if (len < 0 && errno == EAGAIN) return; iv_fd_unregister(&conn->fd); close(conn->fd.fd); free(conn); return; } printf("got %d bytes of data from %p ", len, conn); } static void listening_socket_handler(void *_sock) { struct listening_socket *sock = (struct listening_socket *)_sock; struct sockaddr_in addr; socklen_t addrlen; struct connection *conn; int fd; addrlen = sizeof(addr); fd = accept(sock->fd.fd, (struct sockaddr *)&addr, &addrlen); if (fd < 0) { if (errno == EAGAIN) return; perror("accept"); exit(1); } conn = malloc(sizeof(*conn)); if (conn == NULL) { fprintf(stderr, "listening_socket_handler: memory allocation error, dropping connection"); close(fd); return; } IV_FD_INIT(&conn->fd); conn->fd.fd = fd; conn->fd.cookie = (void *)conn; conn->fd.handler_in = connection_handler; iv_fd_register(&conn->fd); } int main() { struct listening_socket s; struct sockaddr_in addr; int fd; fd = socket(AF_INET, SOCK_STREAM, 0); if (fd < 0) { perror("socket"); exit(1); } addr.sin_family = AF_INET; addr.sin_addr.s_addr = htonl(INADDR_ANY); addr.sin_port = htons(6667); if (bind(fd, (struct sockaddr *)&addr, sizeof(addr)) < 0) { perror("bind"); exit(1); } if (listen(fd, 4) < 0) { perror("listen"); exit(1); } iv_init(); IV_FD_INIT(&s.fd); s.fd.fd = fd; s.fd.cookie = (void *)&s; s.fd.handler_in = listening_socket_handler; iv_fd_register(&s.fd); iv_main(); iv_deinit(); return 0; } As illustrated, it is possible to pass cookies into callback functions. This is useful for conveying information on which higher-level entity (such as 'connection' or 'listening socket') generated the event for which the callback was called. Note how it is possible to unregister and even free a 'struct iv_fd' in its own callback function. There is logic in ivykis to deal with this case. EXAMPLE 3 This example extends the previous example by a per-connection timer that disconnects the client after too long a period of inactivity. Lines not present in example 2 or different than in example 2 are indicated by '//XXXX' in the right-hand margin. #include <stdio.h> #include <stdlib.h> #include <iv.h> #include <netinet/in.h> #define CONNECTION_TIMEOUT(10) struct connection { struct iv_fd fd; struct iv_timer disconnect_timeout; //XXXX /* other per-connection data goes here */ }; struct listening_socket { struct iv_fd fd; /* other per-listening socket data goes here */ }; static void connection_handler(void *_conn) { struct connection *conn = (struct connection *)_conn; char buf[1024]; int len; len = read(conn->fd.fd, buf, sizeof(buf)); if (len <= 0) { if (len < 0 && errno == EAGAIN) return; iv_timer_unregister(&conn->disconnect_timeout); //XXXX iv_fd_unregister(&conn->fd); close(conn->fd.fd); free(conn); return; } printf("got %d bytes of data from %p ", len, conn); iv_timer_unregister(&conn->disconnect_timeout); //XXXX iv_validate_now(); //XXXX conn->disconnect_timeout.expires = iv_now; //XXXX conn->disconnect_timeout.expires.tv_sec += CONNECTION_TIMEOUT;//XXXX iv_timer_register(&conn->disconnect_timeout); //XXXX } static void disconnect_timeout_expired(void *_conn) //XXXX { //XXXX struct connection *conn = (struct connection *)_conn; //XXXX iv_fd_unregister(&conn->fd); //XXXX close(conn->fd.fd); //XXXX free(conn); //XXXX } //XXXX static void listening_socket_handler(void *_sock) { struct listening_socket *sock = (struct listening_socket *)_sock; struct sockaddr_in addr; socklen_t addrlen; struct connection *conn; int fd; addrlen = sizeof(addr); fd = accept(sock->fd.fd, (struct sockaddr *)&addr, &addrlen); if (fd < 0) { if (errno == EAGAIN) return; perror("accept"); exit(1); } conn = malloc(sizeof(*conn)); if (conn == NULL) { fprintf(stderr, "listening_socket_handler: memory allocation error, dropping connection"); close(fd); return; } IV_FD_INIT(&conn->fd); conn->fd.fd = fd; conn->fd.cookie = (void *)conn; conn->fd.handler_in = connection_handler; iv_fd_register(&conn->fd); IV_TIMER_INIT(&conn->disconnect_timeout); //XXXX iv_validate_now(); //XXXX conn->disconnect_timeout.cookie = (void *)conn; //XXXX conn->disconnect_timeout.handler = disconnect_timeout_expired;//XXXX conn->disconnect_timeout.expires = iv_now; //XXXX conn->disconnect_timeout.expires.tv_sec += CONNECTION_TIMEOUT;//XXXX iv_timer_register(&conn->disconnect_timeout); //XXXX } int main() { struct listening_socket s; struct sockaddr_in addr; int fd; fd = socket(AF_INET, SOCK_STREAM, 0); if (fd < 0) { perror("socket"); exit(1); } addr.sin_family = AF_INET; addr.sin_addr.s_addr = htonl(INADDR_ANY); addr.sin_port = htons(6667); if (bind(fd, (struct sockaddr *)&addr, sizeof(addr)) < 0) { perror("bind"); exit(1); } if (listen(fd, 4) < 0) { perror("listen"); exit(1); } iv_init(); IV_FD_INIT(&s.fd); s.fd.fd = fd; s.fd.cookie = (void *)&s; s.fd.handler_in = listening_socket_handler; iv_fd_register(&s.fd); iv_main(); iv_deinit(); return 0; } The global variable 'iv_now' contains the current time-of-day. However, it is updated lazily, and its contents might be stale at any given time. Before using it, iv_validate_now(3) must be called. EXAMPLE 4 The fourth example demonstrates how to use a custom fatal error handler that does not write the message to syslog. #include <stdio.h> #include <iv.h> static void fatal_error(const char *msg) { fprintf(stderr, "ivykis: FATAL ERROR: %s ", msg); } int main() { iv_init(); iv_set_fatal_msg_handler(fatal_error); iv_fatal("Programmatically triggered fatal error %d.", 42); printf("This code is never reached. "); iv_deinit(); return 0; } This program will abort immediately, with the error message printed to the standard error stream. SEE ALSO
ivykis(3), iv_fatal(3), iv_fd(3), iv_timer(3), iv_task(3), iv_init(3), iv_time(3) ivykis 2003-03-29 ivykis(3)

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