POSIX APIs
POSIX APIs 介绍
目前Armino平台posix接口仅支持FreeRTOS V10.4操作系统，默认关闭;
若打开使用，需要打开CONFIG_FREERTOS_POSIX配置开关
备注
在使用FreeRTOS的posix功能的时候，在引用posix相关头文件之前，需要先引用FreeRTOS_POSIX.h头文件；
可以在components/bk_rtos/freertos/posix/freertos_impl/include/portable/bk/FreeRTOS_POSIX_portable.h中自定义相关配置。
unistd APIs
#include <posix/unistd.h>
Defines the APIs related to system sleep
Header File
Functions
-
unsigned sleep(unsigned seconds)
Suspend execution for an interval of time.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/sleep.html
备注
Return value of a positive number is not yet supported.
- 参数
seconds – [in] The number of seconds to suspend execution.
- Return values
0 – - Upon successful completion.
-
int usleep(useconds_t usec)
Suspend execution for microsecond intervals.
This is a useful, non-POSIX function.
- 参数
usec – [in] The number of microseconds to suspend execution.
- Return values
0 – - Upon successful completion.
utils APIs
#include <posix/utils.h>
Define public interfaces
Header File
Functions
-
size_t UTILS_strnlen(const char *const pcString, size_t xMaxLength)
Calculates the length of pcString, up to xMaxLength.
- 参数
pcString – [in] The string to find the length of.
xMaxLength – [in] The limit when searching for the end of pcString.
- 返回
0 if pcString is NULL; otherwise, the length of pcString or xMaxLength, whichever is smaller.
-
int UTILS_AbsoluteTimespecToDeltaTicks(const struct timespec *const pxAbsoluteTime, const struct timespec *const pxCurrentTime, TickType_t *const pxResult)
Calculates the number of ticks between now and a given timespec.
- 参数
pxAbsoluteTime – [in] A time in the future, specified as seconds and nanoseconds since CLOCK_REALTIME’s 0.
pxCurrentTime – [in] current time, specified as seconds and nanoseconds.
pxResult – [out] Where the result of the conversion is stored. The result is rounded up for fractional ticks.
- 返回
0 on success. Otherwise, ETIMEDOUT if pxAbsoluteTime is in the past, or EINVAL for invalid parameters.
-
int UTILS_TimespecToTicks(const struct timespec *const pxTimespec, TickType_t *const pxResult)
Converts a struct timespec to FreeRTOS ticks.
- 参数
pxTimespec – [in] The timespec to convert.
Where – [out] the result of the conversion is stored. The result is rounded up for fractional ticks.
- 返回
0 on success. Otherwise, EINVAL for invalid parameters.
-
void UTILS_NanosecondsToTimespec(int64_t llSource, struct timespec *const pxDestination)
Converts an integer value to a timespec.
- 参数
llSource – [in] The value to convert.
pxDestination – [out] Where to store the converted value.
- 返回
No return value.
-
int UTILS_TimespecAdd(const struct timespec *const x, const struct timespec *const y, struct timespec *const pxResult)
Calculates pxResult = x + y.
- 参数
x – [in] The first argument for addition.
y – [in] The second argument for addition.
pxResult – [out] Where the result of the calculation is stored.
- 返回
-1 if any argument was NULL; 1 if result is negative (overflow); otherwise, 0.
-
int UTILS_TimespecAddNanoseconds(const struct timespec *const x, int64_t llNanoseconds, struct timespec *const pxResult)
Calculates pxResult = x + ( struct timespec ) nanosec.
- 参数
x – [in] The first argument for addition.
llNanoseconds – [in] The second argument for addition.
pxResult – [out] Where the result of the calculation is stored.
- 返回
-1 if pxResult or x was NULL; 1 if result is negative; otherwise, 0.
-
int UTILS_TimespecSubtract(const struct timespec *const x, const struct timespec *const y, struct timespec *const pxResult)
Calculates pxResult = x - y. If the result is negative contents of pResult are undefined.
- 参数
x – [in] The first argument for subtraction.
y – [in] The second argument for subtraction.
pxResult – [out] Where the result of the calculation is stored.
- 返回
-1 if any argument was NULL; 1 if result is negative; otherwise, 0.
errno APIs
Header files need to be include (#include <posix/errno.h>)
Define the meaning of the returned error value
Header File
Macros
-
EPERM
Operation not permitted.
-
ENOENT
No such file or directory.
-
EBADF
Bad file descriptor.
-
EAGAIN
Resource unavailable, try again.
-
ENOMEM
Not enough space.
-
EEXIST
File exists.
-
EBUSY
Device or resource busy.
-
EINVAL
Invalid argument.
-
ENOSPC
No space left on device.
-
ERANGE
Result too large.
-
ENAMETOOLONG
File name too long.
-
EDEADLK
Resource deadlock would occur.
-
EOVERFLOW
Value too large to be stored in data type.
-
ENOSYS
Function not supported.
-
EMSGSIZE
Message too long.
-
ENOTSUP
Operation not supported.
-
ETIMEDOUT
Connection timed out.
fcntl APIs
#include <posix/fcntl.h>;
Defines the macro definition related to fcntl
Header File
Macros
-
O_CLOEXEC
Close the file descriptor upon exec().
-
O_CREAT
Create file if it does not exist.
-
O_DIRECTORY
Fail if file is a non-directory file.
-
O_EXCL
Exclusive use flag.
-
O_NOCTTY
Do not assign controlling terminal.
-
O_NOFOLLOW
Do not follow symbolic links.
-
O_TRUNC
Truncate flag.
-
O_TTY_INIT
termios structure provides conforming behavior.
-
O_APPEND
Set append mode.
-
O_DSYNC
Write according to synchronized I/O data integrity completion.
-
O_NONBLOCK
Non-blocking mode.
-
O_RSYNC
Synchronized read I/O operations.
-
O_SYNC
Write according to synchronized I/O file integrity completion.
-
O_ACCMODE
-
O_EXEC
Open for execute only (non-directory files).
-
O_RDONLY
Open for reading only.
-
O_RDWR
Open for reading and writing.
-
O_SEARCH
Open directory for search only.
-
O_WRONLY
Open for writing only.
signal APIs
#include <posix/signal.h>;
Defines the signal related APIs
Header File
Unions
-
union sigval
- #include <signal.h>
Signal value.
Structures
-
struct sigevent
Signal event structure.
Macros
-
SIGEV_NONE
No asynchronous notification is delivered when the event of interest occurs.
-
SIGEV_SIGNAL
A queued signal, with an application-defined value, is generated when the event of interest occurs. Not supported.
-
SIGEV_THREAD
A notification function is called to perform notification.
mqueue APIs
#include <posix/mqueue.h>
Define interfaces related to system message queues
Header File
Functions
-
int mq_close(mqd_t mqdes)
Close a message queue.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/mq_close.html
@sideeffect Possible errno values
EBADF - The mqdes argument is not a valid message queue descriptor.
- Return values
0 – - Upon successful completion
-1 – - A error occurred. errno is also set.
-
int mq_getattr(mqd_t mqdes, struct mq_attr *mqstat)
Get message queue attributes.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/mq_getattr.html
@sideeffect Possible errno values
DBADF - The mqdes argument is not a valid message queue descriptor.
- Return values
0 – - Upon successful completion
-1 – - A error occurred. errno is also set.
-
mqd_t mq_open(const char *name, int oflag, mode_t mode, struct mq_attr *attr)
Open a message queue.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/mq_open.html
@sideeffect Possible errno values
EINVAL - name argument is invalid (not following name pattern), OR if O_CREAT is specified in oflag with attr argument not NULL and either mq_maxmsg or mq_msgsize is equal to or less than zero, OR either O_CREAT or O_EXCL is not set and a queue with the same name is unlinked but pending to be removed.
EEXIST - O_CREAT and O_EXCL are set and the named message queue already exists.
ENOSPC - There is insufficient space for the creation of the new message queue.
ENOENT - O_CREAT is not set and the named message queue does not exist.备注
Supported name pattern: leading <slash> character in name is always required; the maximum length (excluding null-terminator) of the name argument can be NAME_MAX. The default value of NAME_MAX in FreeRTOS_POSIX_portable_default.h is 64, which can be overwritten by user.
备注
mode argument is not supported.
备注
Supported oflags: O_RDWR, O_CREAT, O_EXCL, and O_NONBLOCK.
- Return values
Message – queue descriptor — Upon successful completion
(mqd_t) – - 1 — An error occurred. errno is also set.
-
ssize_t mq_receive(mqd_t mqdes, char *msg_ptr, size_t msg_len, unsigned int *msg_prio)
Receive a message from a message queue.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/mq_receive.html
@sideeffect Possible errno values
EBADF - The mqdes argument is not a valid message queue descriptor open for reading.
EMSGSIZE - The specified message buffer size, msg_len, is less than the message size attribute of the message queue.
ETIMEDOUT - The O_NONBLOCK flag was not set when the message queue was opened, but no message arrived on the queue before the specified timeout expired.
EAGAIN - O_NONBLOCK was set in the message description associated with mqdes, and the specified message queue is empty.备注
msg_prio argument is not supported. Messages are not checked for corruption.
- Return values
The – length of the selected message in bytes - Upon successful completion. The message is removed from the queue
-1 – - An error occurred. errno is also set.
-
int mq_send(mqd_t mqdes, const char *msg_ptr, size_t msg_len, unsigned msg_prio)
Send a message to a message queue.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/mq_send.html
@sideeffect Possible errno values
EBADF - The mqdes argument is not a valid message queue descriptor open for writing.
EMSGSIZE - The specified message length, msg_len, exceeds the message size attribute of the message queue, OR insufficient memory for the message to be sent.
ETIMEDOUT - The O_NONBLOCK flag was not set when the message queue was opened, but the timeout expired before the message could be added to the queue.
EAGAIN - The O_NONBLOCK flag is set in the message queue description associated with mqdes, and the specified message queue is full.备注
msg_prio argument is not supported.
- Return values
0 – - Upon successful completion.
-1 – - An error occurred. errno is also set.
-
ssize_t mq_timedreceive(mqd_t mqdes, char *msg_ptr, size_t msg_len, unsigned *msg_prio, const struct timespec *abstime)
Receive a message from a message queue with timeout.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/mq_timedreceive.html
@sideeffect Possible errno values
EBADF - The mqdes argument is not a valid message queue descriptor open for reading.
EMSGSIZE - The specified message buffer size, msg_len, is less than the message size attribute of the message queue.
EINVAL - The process or thread would have blocked, and the abstime parameter specified a nanoseconds field value less than zero or greater than or equal to 1000 million.
ETIMEDOUT - The O_NONBLOCK flag was not set when the message queue was opened, but no message arrived on the queue before the specified timeout expired.
EAGAIN - O_NONBLOCK was set in the message description associated with mqdes, and the specified message queue is empty.
备注
msg_prio argument is not supported. Messages are not checked for corruption.
- Return values
The – length of the selected message in bytes - Upon successful completion. The message is removed from the queue
-1 – - An error occurred. errno is also set.
-
int mq_timedsend(mqd_t mqdes, const char *msg_ptr, size_t msg_len, unsigned msg_prio, const struct timespec *abstime)
Send a message to a message queue with timeout.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/mq_timedsend.html
@sideeffect Possible errno values
EBADF - The mqdes argument is not a valid message queue descriptor open for writing.
EMSGSIZE - The specified message length, msg_len, exceeds the message size attribute of the message queue, OR insufficient memory for the message to be sent.
EINVAL - The process or thread would have blocked, and the abstime parameter specified a nanoseconds field value less than zero or greater than or equal to 1000 million.
ETIMEDOUT - The O_NONBLOCK flag was not set when the message queue was opened, but the timeout expired before the message could be added to the queue.
EAGAIN - The O_NONBLOCK flag is set in the message queue description associated with mqdes, and the specified message queue is full.
备注
msg_prio argument is not supported.
- Return values
0 – - Upon successful completion.
-1 – - An error occurred. errno is also set.
-
int mq_unlink(const char *name)
Remove a message queue.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/mq_unlink.html
@sideeffect Possible errno values
EINVAL - name argument is invalid. Refer to requirements on name argument in
mq_open().
ENOENT - The named message queue does not exist.
- Return values
0 – - Upon successful completion.
-1 – - An error occurred. errno is also set.
Structures
-
struct mq_attr
Message queue attributes.
Type Definitions
-
typedef void *mqd_t
Message queue descriptor.
pthread APIs
#include <posix/pthread.h>;
APIs related to system tasks, including creation, destruction, etc
Header File
Functions
-
int pthread_attr_destroy(pthread_attr_t *attr)
Destroy the thread attributes object.
- Return values
0 – - Upon successful completion.
-
int pthread_attr_getdetachstate(const pthread_attr_t *attr, int *detachstate)
Get detachstate attribute.
- Return values
0 – - Upon successful completion.
-
int pthread_attr_getschedparam(const pthread_attr_t *attr, struct sched_param *param)
Get schedparam attribute.
- Return values
0 – - Upon successful completion.
-
int pthread_attr_getstacksize(const pthread_attr_t *attr, size_t *stacksize)
Get stacksize attribute.
- Return values
0 – - Upon successful completion.
-
int pthread_attr_init(pthread_attr_t *attr)
Initialize the thread attributes object.
备注
Currently, only stack size, sched_param, and detach state attributes are supported. Also see pthread_attr_get*() and pthread_attr_set*().
- Return values
0 – - Upon successful completion.
-
int pthread_attr_setdetachstate(pthread_attr_t *attr, int detachstate)
Set detachstate attribute.
- Return values
0 – - Upon successful completion
EINVAL – - The value of detachstate is not valid. Currently, supported detach states are — PTHREAD_CREATE_DETACHED and PTHREAD_CREATE_JOINABLE.
-
int pthread_attr_setschedparam(pthread_attr_t *attr, const struct sched_param *param)
Set schedparam attribute.
- Return values
0 – - Upon successful completion.
EINVAL – - The value of param is not valid.
ENOTSUP – - An attempt was made to set the attribute to an unsupported value.
-
int pthread_attr_setschedpolicy(pthread_attr_t *attr, int policy)
Set the schedpolicy attribute.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_attr_setschedpolicy.html
警告
This function is a stub and always returns 0.
- Return values
0 – - Upon successful completion.
-
int pthread_attr_setstacksize(pthread_attr_t *attr, size_t stacksize)
Set stacksize attribute.
- Return values
0 – - Upon successful completion.
EINVAL – - The value of stacksize is less than {PTHREAD_STACK_MIN}.
-
int pthread_barrier_destroy(pthread_barrier_t *barrier)
Destroy a barrier object.
备注
This function does not validate whether there is any thread blocking on the barrier before destroying.
- Return values
0 – - Upon successful completion.
-
int pthread_barrier_init(pthread_barrier_t *barrier, const pthread_barrierattr_t *attr, unsigned count)
Initialize a barrier object.
备注
attr is ignored.
备注
pthread_barrier_init() is implemented with FreeRTOS event group. To ensure count fits in event group, count may be at most 8 when configUSE_16_BIT_TICKS is 1; it may be at most 24 otherwise. configUSE_16_BIT_TICKS is configured in application FreeRTOSConfig.h file, which defines how many bits tick count type has. See further details and limitation about event group and configUSE_16_BIT_TICKS in FreeRTOS site.
- Return values
0 – - Upon successful completion.
EINVAL – - The value specified by count is equal to zero.
ENOMEM – - count cannot fit into FreeRTOS event group type OR insufficient memory exists to initialize the barrier.
-
int pthread_barrier_wait(pthread_barrier_t *barrier)
Synchronize at a barrier.
- Return values
PTHREAD_BARRIER_SERIAL_THREAD – - Upon successful completion, the first thread.
0 – - Upon successful completion, other thread(s).
-
int pthread_create(pthread_t *thread, const pthread_attr_t *attr, void *(*startroutine)(void*), void *arg)
Thread creation.
- Return values
0 – - Upon successful completion.
EAGAIN – - Insufficient memory for either thread structure or task creation.
-
int pthread_cond_broadcast(pthread_cond_t *cond)
Broadcast a condition.
- Return values
0 – - Upon successful completion.
-
int pthread_cond_destroy(pthread_cond_t *cond)
Destroy condition variables.
- Return values
0 – - Upon successful completion.
-
int pthread_cond_init(pthread_cond_t *cond, const pthread_condattr_t *attr)
Initialize condition variables.
备注
attr is ignored and treated as NULL. Default setting is always used.
- Return values
0 – - Upon successful completion.
ENOMEM – - Insufficient memory exists to initialize the condition variable.
-
int pthread_cond_signal(pthread_cond_t *cond)
Signal a condition.
- Return values
0 – - Upon successful completion.
-
int pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex, const struct timespec *abstime)
Wait on a condition with a timeout.
- Return values
0 – - Upon successful completion.
EINVAL – - The abstime argument passed in does not refer to an initialized structure OR the abstime parameter specified a nanoseconds field value less than zero or greater than or equal to 1000 million.
ETIMEDOUT – - The time specified by abstime to pthread_cond_timedwait() has passed.
-
int pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
Wait on a condition.
- Return values
0 – - Upon successful completion.
-
int pthread_equal(pthread_t t1, pthread_t t2)
Compare thread IDs.
- Return values
0 – - t1 and t2 are both not NULL && equal.
non-zero – - otherwise.
-
void pthread_exit(void *value_ptr)
Thread termination.
- Return values
void – - this function cannot return to its caller.
-
int pthread_getschedparam(pthread_t thread, int *policy, struct sched_param *param)
Dynamic thread scheduling parameters access.
备注
policy is always set to SCHED_OTHER by this function.
- Return values
0 – - Upon successful completion.
-
int pthread_join(pthread_t thread, void **retval)
Wait for thread termination.
- Return values
0 – - Upon successful completion.
EDEADLK – - The value specified by the thread argument to pthread_join() does not refer to a joinable thread OR multiple simultaneous calls to pthread_join() specifying the same target thread OR the value specified by the thread argument to pthread_join() refers to the calling thread.
-
int pthread_mutex_destroy(pthread_mutex_t *mutex)
Destroy a mutex.
备注
If there exists a thread holding this mutex, this function returns 0 with mutex not being destroyed.
- Return values
0 – - Upon successful completion.
-
int pthread_mutex_init(pthread_mutex_t *mutex, const pthread_mutexattr_t *attr)
Initialize a mutex.
- Return values
0 – - Upon successful completion.
ENOMEM – - Insufficient memory exists to initialize the mutex structure.
EAGAIN – - Unable to initialize the mutex structure member(s).
-
int pthread_mutex_lock(pthread_mutex_t *mutex)
Lock a mutex.
- Return values
0 – - Upon successful completion.
EINVAL – - the abstime parameter specified a nanoseconds field value less than zero or greater than or equal to 1000 million.
EDEADLK – - The mutex type is PTHREAD_MUTEX_ERRORCHECK and the current thread already owns the mutex.
-
int pthread_mutex_timedlock(pthread_mutex_t *mutex, const struct timespec *abstime)
Lock a mutex with timeout.
- Return values
0 – - Upon successful completion.
EINVAL – - The abstime argument passed in does not refer to an initialized structure OR the abstime parameter specified a nanoseconds field value less than zero or greater than or equal to 1000 million.
EDEADLK – - The mutex type is PTHREAD_MUTEX_ERRORCHECK and the current thread already owns the mutex.
ETIMEDOUT – - The mutex could not be locked before the specified timeout expired.
-
int pthread_mutex_trylock(pthread_mutex_t *mutex)
Attempt to lock a mutex. Fail immediately if mutex is already locked.
- Return values
0 – - Upon successful completion.
EINVAL – - the abstime parameter specified a nanoseconds field value less than zero or greater than or equal to 1000 million.
EDEADLK – - The mutex type is PTHREAD_MUTEX_ERRORCHECK and the current thread already owns the mutex.
EBUSY – - The mutex could not be acquired because it was already locked.
-
int pthread_mutex_unlock(pthread_mutex_t *mutex)
Unlock a mutex.
- Return values
0 – - Upon successful completion.
EPERM – - The mutex type is PTHREAD_MUTEX_ERRORCHECK or PTHREAD_MUTEX_RECURSIVE, and the current thread does not own the mutex.
-
int pthread_mutexattr_destroy(pthread_mutexattr_t *attr)
Destroy the mutex attributes object.
- Return values
0 – - Upon successful completion.
-
int pthread_mutexattr_gettype(const pthread_mutexattr_t *attr, int *type)
Get the mutex type attribute.
- Return values
0 – - Upon successful completion.
-
int pthread_mutexattr_init(pthread_mutexattr_t *attr)
Initialize the mutex attributes object.
备注
Currently, only the type attribute is supported. Also see pthread_mutexattr_settype() and pthread_mutexattr_gettype().
- Return values
0 – - Upon successful completion.
-
int pthread_mutexattr_settype(pthread_mutexattr_t *attr, int type)
Set the mutex type attribute.
- Return values
0 – - Upon successful completion.
EINVAL – - The value type is invalid.
-
pthread_t pthread_self(void)
Get the calling thread ID.
- Return values
the – thread ID of the calling thread.
-
int pthread_setschedparam(pthread_t thread, int policy, const struct sched_param *param)
Dynamic thread scheduling parameters access.
备注
policy is ignored; only priority (param.sched_priority) may be changed.
- Return values
0 – - Upon successful completion.
Macros
-
PTHREAD_CREATE_DETACHED
Detached.
-
PTHREAD_CREATE_JOINABLE
Joinable (default).
-
PTHREAD_BARRIER_SERIAL_THREAD
-
PTHREAD_MUTEX_NORMAL
Non-robust, deadlock on relock, does not remember owner.
-
PTHREAD_MUTEX_ERRORCHECK
Non-robust, error on relock, remembers owner.
-
PTHREAD_MUTEX_RECURSIVE
Non-robust, recursive relock, remembers owner.
-
PTHREAD_MUTEX_DEFAULT
PTHREAD_MUTEX_NORMAL (default).
sched APIs
#include <posix/sched.h>;
APIs related to system scheduling
Header File
Functions
-
int sched_get_priority_max(int policy)
Get priority limit (max).
http://pubs.opengroup.org/onlinepubs/9699919799/functions/sched_get_priority_max.html
备注
policy is ignored.
- 返回
the maximum priority value (0-based) system configuration allows.
e.g. if configMAX_PRIORITIES == 7, this function returns (configMAX_PRIORITIES - 1). configMAX_PRIORITIES is configured in application FreeRTOSConfig.h file.
-
int sched_get_priority_min(int policy)
Get priority limit (min).
http://pubs.opengroup.org/onlinepubs/9699919799/functions/sched_get_priority_min.html
备注
policy is ignored.
-
int sched_yield(void)
Yield the processor.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/sched_yield.html
- Return values
0 – - Upon successful completion
Structures
Macros
-
SCHED_OTHER
Another scheduling policy.
semaphore APIs
#include <posix/semaphore.h>;
Defines the APIs related to semaphores
Header File
Functions
-
int sem_destroy(sem_t *sem)
Destroy an unnamed semaphore.
备注
Semaphore is destroyed regardless of whether there is any thread currently blocked on this semaphore.
- Return values
0 – - upon successful completion
-
int sem_getvalue(sem_t *sem, int *sval)
Get the value of a semaphore.
备注
If sem is locked, then the object to which sval points is set to zero.
- Return values
0 – - Upon successful completion
-
int sem_init(sem_t *sem, int pshared, unsigned value)
Initialize an unnamed semaphore.
@sideeffect Possible errno values
EINVAL - The value argument exceeds {SEM_VALUE_MAX}.
ENOSPC - A resource required to initialize the semaphore has been exhausted.备注
pshared is ignored. Semaphores will always be considered “shared”.
- Return values
0 – - upon successful completion
-1 – - otherwise. System error variable errno is also set in this case.
-
int sem_timedwait(sem_t *sem, const struct timespec *abstime)
Lock a semaphore with timeout.
@sideeffect Possible errno values
EINVAL - parameter specified a nanoseconds field value less than zero or greater than or equal to 1000 million
ETIMEDOUT - The semaphore could not be locked before the specified timeout expired.备注
Deadlock detection is not implemented.
- Return values
0 – - upon successful completion
-1 – - otherwise. System error variable errno is also set in this case.
-
int sem_trywait(sem_t *sem)
Lock a semaphore if available.
@sideeffect Possible errno values
EAGAIN - The semaphore was already locked, so it cannot be immediately locked by the
sem_trywait() operation.- Return values
0 – - upon successful completion
-1 – - otherwise. System error variable errno is also set in this case.
Type Definitions
-
typedef PosixSemType_t sem_t
Semaphore type.
time APIs
#include <posix/time.h>;
Defines APIs related to timers
Header File
Functions
-
clock_t clock(void)
Report CPU time used.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/clock.html
备注
This function does NOT report the number of ticks spent by the calling thread.
- 返回
The number of FreeRTOS ticks since the scheduler was started minus the ticks spent in the idle task.
-
int clock_getcpuclockid(pid_t pid, clockid_t *clock_id)
Access a process CPU-time clock.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/clock_getcpuclockid.html
备注
This function is currently unsupported.
- Return values
EPERM –
-
int clock_getres(clockid_t clock_id, struct timespec *res)
Returns the resolution of a clock.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/clock_getres.html
备注
clock_id is ignored
备注
This function stores the resolution of the FreeRTOS tick count in the object res points to.
- Return values
0 – - Upon successful execution
-
int clock_gettime(clockid_t clock_id, struct timespec *tp)
Returns the current value for the specified clock, clock_id.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/clock_gettime.html
备注
clock_id is ignored
备注
this function does not check for overflows of time_t.
- Return values
0 – - Upon successful completion.
-
int clock_nanosleep(clockid_t clock_id, int flags, const struct timespec *rqtp, struct timespec *rmtp)
High resolution sleep with specifiable clock.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/clock_nanosleep.html
备注
clock_id is ignored, as this function uses the FreeRTOS tick count as its clock.
备注
flags is ignored, if INCLUDE_vTaskDelayUntil is 0. i.e. the FreeRTOS function vTaskDelayUntil isn’t available.
备注
rmtp is also ignored, as signals are not implemented.
- Return values
0 – - Upon successful completion.
EINVAL – - The rqtp argument specified a nanosecond value less than zero or greater than or equal to 1000 million.
-
int clock_settime(clockid_t clock_id, const struct timespec *tp)
Sets the time for the specified clock.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/clock_settime.html
备注
This function is currently unsupported, as FreeRTOS does not provide a function to modify the tick count.
- Return values
-1 – with errno set to EPERM.
-
int nanosleep(const struct timespec *rqtp, struct timespec *rmtp)
High resolution sleep.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/nanosleep.html
备注
rmtp is ignored, as signals are not implemented.
- Return values
0 – - Upon successful completion.
-1 – - The rqtp argument is invalid OR the rqtp argument specified a nanosecond value less than zero or greater than or equal to 1000 million.
-
int timer_create(clockid_t clockid, struct sigevent *evp, timer_t *timerid)
Create a per-process timer.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_create.html
@sideeffect Possible errno values
ENOTSUP - If evp is NULL OR evp->sigen_notify == SIGEV_SIGNAL.
EAGAIN - The system lacks sufficient signal queuing resources to honor the request.备注
clock_id is ignored, as this function used the FreeRTOS tick count as its clock.
备注
evp.sigev_notify must be set to SIGEV_THREAD, since signals are currently not supported.
- Return values
0 – - Upon successful completion, with location referenced by timerid updated.
-1 – - If an error occurs. errno is also set.
-
int timer_delete(timer_t timerid)
Delete a per-process timer.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_delete.html
- Return values
0 – - Upon successful completion.
-
int timer_getoverrun(timer_t timerid)
Get the timer overrun count.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_getoverrun.html
- Return values
0 – - Always return 0, since signals are not supported.
-
int timer_gettime(timer_t timerid, struct itimerspec *value)
Get the amount of time until the timer expires.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_gettime.html
- Return values
0 – - Upon successful completion.
-
int timer_settime(timer_t timerid, int flags, const struct itimerspec *value, struct itimerspec *ovalue)
Set the time until the next expiration of the timer.
http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_settime.html
@sideeffect Possible errno values
EINVAL - A value structure specified a nanosecond value less than zero or greater than or equal to 1000 million, AND the it_value member of that structure did not specify zero seconds and nanoseconds.
- Return values
0 – - Upon successful completion.
-1 – - An error occurred, errno is also set.
Structures
-
struct timespec
represents an elapsed time
-
struct itimerspec
timer
Macros
-
MICROSECONDS_PER_SECOND
Microseconds per second.
-
NANOSECONDS_PER_SECOND
Nanoseconds per second.
-
NANOSECONDS_PER_TICK
Nanoseconds per FreeRTOS tick.
-
CLOCK_REALTIME
The identifier of the system-wide clock measuring real time.
-
CLOCK_MONOTONIC
The identifier for the system-wide monotonic clock.
-
CLOCKS_PER_SEC
-
TIMER_ABSTIME