/** * 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. */ #define _XOPEN_SOURCE 700 #include "bus.h" #include #include #include #include #include #include #include #include #include /** * Semaphore used to signal `bus_write` that `bus_read` is ready */ #define S 0 /** * Semaphore for making `bus_write` wait while `bus_read` is reseting `S` */ #define W 1 /** * Binary semaphore for making `bus_write` exclusively locked */ #define X 2 /** * Semaphore used to cue `bus_read` that it may read the shared memory */ #define Q 3 /** * The number of semaphores in the semaphore array */ #define BUS_SEMAPHORES 4 /** * Decrease the value of a semaphore by 1 * * @param bus:const bus_t * The bus * @param semaphore:unsigned short The index of the semaphore, `S`, `W`, `X` or `Q` * @param flags:short `SEM_UNDO` if the action should be undone when the program exits * @return :int 0 on success, -1 on error */ #define acquire_semaphore(bus, semaphore, flags) \ semaphore_op(bus, semaphore, -1, flags) /** * Increase the value of a semaphore by 1 * * @param bus:const bus_t * The bus * @param semaphore:unsigned short The index of the semaphore, `S`, `W`, `X` or `Q` * @param flags:short `SEM_UNDO` if the action should be undone when the program exits * @return :int 0 on success, -1 on error */ #define release_semaphore(bus, semaphore, flags) \ semaphore_op(bus, semaphore, +1, flags) /** * Wait for the value of a semphore to become 0 * * @param bus:const bus_t * The bus * @param semaphore:unsigned short The index of the semaphore, `S`, `W`, `X` or `Q` * @return :int 0 on success, -1 on error */ #define zero_semaphore(bus, semaphore) \ semaphore_op(bus, semaphore, 0, 0) /** * Open the semaphore array * * @param bus:const bus_t * The bus * @return :int 0 on success, -1 on error */ #define open_semaphores(bus) \ (((bus)->sem_id = semget((bus)->key_sem, BUS_SEMAPHORES, 0600)) == -1 ? -1 : 0) /** * Write a message to the shared memory * * @param bus:const bus_t * The bus * @param msg:const char * The message * @return :int 0 on success, -1 on error */ #define write_shared_memory(bus, msg) \ (memcpy((bus)->message, msg, (strlen(msg) + 1) * sizeof(char))) /** * Statement wrapper that goes to `fail` on failure */ #define t(inst) \ if ((inst) == -1) goto fail #ifdef _SEM_SEMUN_UNDEFINED union semun { int val; struct semid_ds *buf; unsigned short *array; }; #endif /** * Create a semaphore array for the bus * * @param bus Bus information to fill with the key of the created semaphore array * @return 0 on success, -1 on error */ static int create_semaphores(bus_t *bus) { int id = -1, rint, saved_errno; double r; union semun values; values.array = NULL; /* Create semaphore array. */ for (;;) { rint = rand(); r = (double)rint; r /= (double)RAND_MAX + 1; r *= (1 << (8 * sizeof(key_t) - 2)) - 1; bus->key_sem = (key_t)r + 1; if (bus->key_sem == IPC_PRIVATE) continue; id = semget(bus->key_sem, BUS_SEMAPHORES, IPC_CREAT | IPC_EXCL | 0600); if (id != -1) break; if ((errno != EEXIST) && (errno != EINTR)) goto fail; } /* Initialise the array. */ values.array = calloc(BUS_SEMAPHORES, sizeof(unsigned short)); values.array[X] = 1; if (!values.array) goto fail; if (semctl(id, 0, SETALL, values.array) == -1) goto fail; free(values.array); values.array = NULL; return 0; fail: saved_errno = errno; if (id != -1) semctl(id, 0, IPC_RMID); free(values.array); errno = saved_errno; return -1; } /** * Create a shared memory for the bus * * @param bus Bus information to fill with the key of the created shared memory * @return 0 on success, -1 on error */ static int create_shared_memory(bus_t *bus) { int id = -1, rint, saved_errno; double r; struct shmid_ds _info; /* Create shared memory. */ for (;;) { rint = rand(); r = (double)rint; r /= (double)RAND_MAX + 1; r *= (1 << (8 * sizeof(key_t) - 2)) - 1; bus->key_shm = (key_t)r + 1; if (bus->key_shm == IPC_PRIVATE) continue; id = shmget(bus->key_shm, BUS_MEMORY_SIZE, IPC_CREAT | IPC_EXCL | 0600); if (id != -1) break; if ((errno != EEXIST) && (errno != EINTR)) goto fail; } return 0; fail: saved_errno = errno; if (id != -1) shmctl(id, IPC_RMID, &_info); errno = saved_errno; return -1; } /** * Remove the semaphore array for the bus * * @param bus Bus information * @return 0 on success, -1 on error */ static int remove_semaphores(const bus_t *bus) { int id = semget(bus->key_sem, BUS_SEMAPHORES, 0600); return ((id == -1) || (semctl(id, 0, IPC_RMID) == -1)) ? -1 : 0; } /** * Remove the shared memory for the bus * * @param bus Bus information * @return 0 on success, -1 on error */ static int remove_shared_memory(const bus_t *bus) { struct shmid_ds _info; int id = shmget(bus->key_shm, BUS_MEMORY_SIZE, 0600); return ((id == -1) || (shmctl(id, IPC_RMID, &_info) == -1)) ? -1 : 0; } /** * Increase or decrease the value of a semaphore, or wait the it to become 0 * * @param bus Bus information * @param semaphore The index of the semaphore, `S`, `W`, `X` or `Q` * @param delta The adjustment to make to the semaphore's value, 0 to wait for it to become 0 * @param flags `SEM_UNDO` if the action should be undone when the program exits * @return 0 on success, -1 on error */ static int semaphore_op(const bus_t *bus, unsigned short semaphore, short delta, short flags) { struct sembuf op; op.sem_op = delta; op.sem_num = semaphore; op.sem_flg = flags; return semop(bus->sem_id, &op, 1); } /** * Set the value of a semaphore * * @param bus Bus information * @param semaphore The index of the semaphore, `S`, `W`, `X` or `Q` * @param value The new value of the semaphore * @return 0 on success, -1 on error */ static int write_semaphore(const bus_t *bus, unsigned short semaphore, int value) { union semun semval; semval.val = value; return semctl(bus->sem_id, semaphore, SETVAL, semval); } /** * Open the shared memory for the bus * * @param bus Bus information * @param flags `BUS_RDONLY`, `BUS_WRONLY` or `BUS_RDWR` * @return 0 on success, -1 on error */ static int open_shared_memory(bus_t *bus, int flags) { int id; void *address; t(id = shmget(bus->key_shm, BUS_MEMORY_SIZE, 0600)); address = shmat(id, NULL, (flags & BUS_RDONLY) ? SHM_RDONLY : 0); if ((address == (void *)-1) || !address) goto fail; bus->message = (char *)address; return 0; fail: return -1; } /** * Close the shared memory for the bus * * @param bus Bus information * @return 0 on success, -1 on error */ static int close_shared_memory(bus_t *bus) { t(shmdt(bus->message)); bus->message = NULL; return 0; fail: return -1; } /** * 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 * @return The pathname of the bus, `NULL` on error */ const char * bus_create(const char *file, int flags) { int saved_errno; bus_t bus; bus.sem_id = -1; bus.key_sem = -1; bus.key_shm = -1; bus.message = NULL; srand((unsigned int)time(NULL) + (unsigned int)rand()); /* TODO */ (void) file; (void) flags; t(create_semaphores(&bus)); t(create_shared_memory(&bus)); return NULL; fail: saved_errno = errno; if (bus.key_sem) remove_semaphores(&bus); if (bus.key_shm) remove_shared_memory(&bus); errno = saved_errno; return NULL; } /** * Remove a bus * * @param file The pathname of the bus * @return 0 on success, -1 on error */ int bus_unlink(const char *file) { int r = 0, saved_errno = 0; bus_t bus; t(bus_open(&bus, file, -1)); r |= remove_semaphores(&bus); if (r && !saved_errno) saved_errno = errno; r |= remove_shared_memory(&bus); if (r && !saved_errno) saved_errno = errno; r |= unlink(file); if (r && !saved_errno) saved_errno = errno; errno = saved_errno; return r; fail: return -1; } /** * 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` * any negative value is used internally * for telling the function to not actually * opening the bus, but just to parse the file * @return 0 on success, -1 on error */ int bus_open(bus_t *bus, const char *file, int flags) { int saved_errno; char *line = NULL; size_t len = 0; FILE *f; bus->sem_id = -1; bus->key_sem = -1; bus->key_shm = -1; bus->message = NULL; f = fopen(file, "r"); t(getline(&line, &len, f)); t(bus->key_sem = (key_t)atoll(line)); free(line), line = NULL, len = 0; t(getline(&line, &len, f)); t(bus->key_shm = (key_t)atoll(line)); free(line), line = NULL; fclose(f); if (flags >= 0) { t(open_semaphores(bus)); t(open_shared_memory(bus, flags)); } return 0; fail: saved_errno = errno; free(line); errno = saved_errno; return -1; } /** * Close a bus * * @param bus Bus information * @return 0 on success, -1 on error */ int bus_close(bus_t *bus) { bus->sem_id = -1; if (bus->message) t(close_shared_memory(bus)); bus->message = NULL; return 0; fail: return -1; } /** * Broadcast a message a bus * * @param bus Bus information * @param message The message to write, may not be longer than * `BUS_MEMORY_SIZE` including the NUL-termination * @return 0 on success, -1 on error */ int bus_write(const bus_t *bus, const char *message) { t(acquire_semaphore(bus, X, SEM_UNDO)); t(zero_semaphore(bus, W)); write_shared_memory(bus, message); t(write_semaphore(bus, Q, 0)); t(zero_semaphore(bus, S)); t(release_semaphore(bus, X, SEM_UNDO)); return 0; fail: return -1; } /** * 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 * @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) { int r; t(release_semaphore(bus, S, SEM_UNDO)); for (;;) { t(release_semaphore(bus, Q, 0)); t(zero_semaphore(bus, Q)); t(r = callback(bus->message, user_data)); if (!r) { t(acquire_semaphore(bus, S, SEM_UNDO)); return 0; } t(release_semaphore(bus, W, SEM_UNDO)); t(acquire_semaphore(bus, S, SEM_UNDO)); t(zero_semaphore(bus, S)); t(release_semaphore(bus, S, SEM_UNDO)); t(acquire_semaphore(bus, W, SEM_UNDO)); } fail: return -1; }