/** * MIT/X Consortium License * * Copyright © 2015 Mattias Andrée * * Permission is hereby granted, free of charge, to any person obtaining a * copy of this software and associated documentation files (the "Software"), * to deal in the Software without restriction, including without limitation * the rights to use, copy, modify, merge, publish, distribute, sublicense, * and/or sell copies of the Software, and to permit persons to whom the * Software is furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER * DEALINGS IN THE SOFTWARE. */ #ifndef BUS_H #define BUS_H #ifndef _DEFAULT_SOURCE # define _DEFAULT_SOURCE #endif #include #include /** * Open the bus for reading only */ #define BUS_RDONLY 1 /** * Open the bus for writing only */ #define BUS_WRONLY 0 /** * Open the bus for both reading and writing only */ #define BUS_RDWR 0 /** * Fail to create bus if its file already exists */ #define BUS_EXCL 2 /** * Fail if interrupted */ #define BUS_INTR 4 /** * Function shall fail with errno set to `EAGAIN` * if the it would block and this flag is used */ #define BUS_NOWAIT 1 /** * The number of bytes in storeable in the shared memory, * note that this includes the NUL-termination. * This means that message can be at most one byte smaller. */ #define BUS_MEMORY_SIZE 2048 /** * Bus information */ typedef struct bus { /** * The key for the semaphore array */ key_t key_sem; /** * The key for the shared memory */ key_t key_shm; /** * The ID of the semaphore array */ int sem_id; /** * The address of the shared memory */ char *message; /** * Non-zero if and only if `bus_poll` has not been * called since the last `bus_poll_start`, or * if `bus_poll` failed during reading */ int first_poll; } bus_t; /** * Create a new bus * * @param file The pathname of the bus, `NULL` to create a random one * @param flags `BUS_EXCL` (if `file` is not `NULL`) to fail if the file * already exists, otherwise if the file exists, nothing * will happen; * `BUS_INTR` to fail if interrupted * @param out_file Output parameter for the pathname of the bus * @return 0 on success, -1 on error */ int bus_create(const char *file, int flags, char **out_file); /** * Remove a bus * * @param file The pathname of the bus * @return 0 on success, -1 on error */ int bus_unlink(const char *file); /** * Open an existing bus * * @param bus Bus information to fill * @param file The filename of the bus * @param flags `BUS_RDONLY`, `BUS_WRONLY` or `BUS_RDWR`, * the value must not be negative * @return 0 on success, -1 on error */ int bus_open(bus_t *bus, const char *file, int flags); /** * Close a bus * * @param bus Bus information * @return 0 on success, -1 on error */ int bus_close(bus_t *bus); /** * Broadcast a message on a bus * * @param bus Bus information * @param message The message to write, may not be longer than * `BUS_MEMORY_SIZE` including the NUL-termination * @param flags `BUS_NOWAIT` if this function shall fail if * another process is currently running this * procedure * @return 0 on success, -1 on error */ int bus_write(const bus_t *bus, const char *message, int flags); /** * Broadcast a message on a bus * * @param bus Bus information * @param message The message to write, may not be longer than * `BUS_MEMORY_SIZE` including the NUL-termination * @param timeout The time the operation shall fail with errno set * to `EAGAIN` if not completed * @param clockid The ID of the clock the `timeout` is measured with, * it most be a predictable clock * @return 0 on success, -1 on error */ int bus_write_timed(const bus_t *bus, const char *message, const struct timespec *timeout, clockid_t clockid); /** * Listen (in a loop, forever) for new message on a bus * * @param bus Bus information * @param callback Function to call when a message is received, the * input parameters will be the read message and * `user_data` from `bus_read`'s parameter with the * same name. The message must have been parsed or * copied when `callback` returns as it may be over * overridden after that time. `callback` should * return either of the the values: * * 0: stop listening * * 1: continue listening * * -1: an error has occurred * However, the function [`bus_read`] will invoke * `callback` with `message` set to `NULL`one time * directly after it has started listening on the * bus. This is to the the program now it can safely * continue with any action that requires that the * programs is listening on the bus. * @param user_data Parameter passed to `callback` * @return 0 on success, -1 on error */ int bus_read(const bus_t *bus, int (*callback)(const char *message, void *user_data), void *user_data); /** * Listen (in a loop, forever) for new message on a bus * * @param bus Bus information * @param callback Function to call when a message is received, the * input parameters will be the read message and * `user_data` from `bus_read`'s parameter with the * same name. The message must have been parsed or * copied when `callback` returns as it may be over * overridden after that time. `callback` should * return either of the the values: * * 0: stop listening * * 1: continue listening * * -1: an error has occurred * However, the function [`bus_read`] will invoke * `callback` with `message` set to `NULL`one time * directly after it has started listening on the * bus. This is to the the program now it can safely * continue with any action that requires that the * programs is listening on the bus. * @param user_data Parameter passed to `callback` * @param timeout The time the operation shall fail with errno set * to `EAGAIN` if not completed, note that the callback * function may or may not have been called * @param clockid The ID of the clock the `timeout` is measured with, * it most be a predictable clock * @return 0 on success, -1 on error */ int bus_read_timed(const bus_t *bus, int (*callback)(const char *message, void *user_data), void *user_data, const struct timespec *timeout, clockid_t clockid); /** * Announce that the thread is listening on the bus. * This is required so the will does not miss any * messages due to race conditions. Additionally, * not calling this function will cause the bus the * misbehave, is `bus_poll` is written to expect * this function to have been called. * * @param bus Bus information * @return 0 on success, -1 on error */ int bus_poll_start(bus_t *bus); /** * Announce that the thread has stopped listening on the bus. * This is required so that the thread does not cause others * to wait indefinitely. * * @param bus Bus information * @return 0 on success, -1 on error */ int bus_poll_stop(const bus_t *bus); /** * Wait for a message to be broadcasted on the bus. * The caller should make a copy of the received message, * without freeing the original copy, and parse it in a * separate thread. When the new thread has started be * started, the caller of this function should then * either call `bus_poll` again or `bus_poll_stop`. * * @param bus Bus information * @param flags `BUS_NOWAIT` if the bus should fail and set `errno` to * `EAGAIN` if there isn't already a message available on the bus * @return The received message, `NULL` on error */ const char *bus_poll(bus_t *bus, int flags); /** * Wait for a message to be broadcasted on the bus. * The caller should make a copy of the received message, * without freeing the original copy, and parse it in a * separate thread. When the new thread has started be * started, the caller of this function should then * either call `bus_poll_timed` again or `bus_poll_stop`. * * @param bus Bus information * @param timeout The time the operation shall fail with errno set * to `EAGAIN` if not completed * @param clockid The ID of the clock the `timeout` is measured with, * it most be a predictable clock * @return The received message, `NULL` on error */ const char *bus_poll_timed(bus_t *bus, const struct timespec *timeout, clockid_t clockid); /** * Change the ownership of a bus * * `stat(2)` can be used of the bus's associated file to get the bus's ownership * * @param file The pathname of the bus * @param owner The user ID of the bus's new owner * @param group The group ID of the bus's new group * @return 0 on success, -1 on error */ int bus_chown(const char *file, uid_t owner, gid_t group); /** * Change the permissions for a bus * * `stat(2)` can be used of the bus's associated file to get the bus's permissions * * @param file The pathname of the bus * @param mode The permissions of the bus, any permission for a user implies * full permissions for that user, except only the owner may * edit the bus's associated file * @return 0 on success, -1 on error */ int bus_chmod(const char *file, mode_t mode); #endif