/**
* MIT/X Consortium License
*
* Copyright © 2015 Mattias Andrée <maandree@member.fsf.org>
*
* 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 <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <sys/shm.h>
/**
* 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) == -1))
perror(argv0);
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) == -1))
perror(argv0);
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(sem_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(const 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;
this->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(const bus_t *bus)
{
t(shmdt(this->message));
this->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());
t(create_semaphores(&bus));
t(create_shared_memory(&bus));
return NULL; /* TODO */
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)
{
bus->sem_id = -1;
bus->key_sem = -1;
bus->key_shm = -1;
bus->message = NULL;
/* TODO */
if (flags >= 0) {
t(open_semaphores(bus));
t(open_shared_memory(bus, flags));
}
return 0;
fail:
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->address)
t(close_shared_memory(bus));
bus->address = 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));
t(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;
}
