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Add possibility to wait several times on a semaphore

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This commit is contained in:
Johan Wikman
2017-04-24 15:38:08 +03:00
parent 19cf8c489e
commit 1eb409a666
3 changed files with 155 additions and 12 deletions
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143
include/maxscale/semaphore.hh
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@ -95,7 +95,7 @@ public:
/**
* @brief Waits on the semaphore.
*
* If the semaphore count is greater that zero, decrements the count and
* If the semaphore count is greater than zero, decrements the count and
* returns immediately. Otherwise blocks the caller until someone posts
* the semaphore.
*
@ -120,6 +120,39 @@ public:
return rc == 0;
}
/**
* @brief Waits multiple times on the semaphore.
*
* If the semaphore count is greater than or equal to the specified amount,
* decrements the count and returns immediately. Otherwise blocks the caller
* until the semaphore has been posted the required number of times.
*
* @param n_wait How many times should be waited.
* @param signal_approach Whether signals should be ignored or honoured.
*
* @return How many times the semaphore has been waited on.
*
* @attention The function can return a different number than `n_wait` only
* if `signal_approach` is `HONOUR_SIGNALS`.
*/
size_t wait_n(size_t n_wait,
signal_approach_t signal_approach = IGNORE_SIGNALS) const
{
bool waited = true;
size_t n_waited = 0;
while (waited && n_wait--)
{
waited = wait(signal_approach);
if (waited)
{
++n_waited;
}
}
return n_waited;
}
/**
* @brief Waits on the semaphore.
*
@ -190,6 +223,46 @@ public:
return rc == 0;
}
/**
* @brief Waits on the semaphore.
*
* Waits on the sempahore the specified number of times, at most until the
* specified time.
*
* @param n_wait How many times should be waited.
* @param ts The *absolute* time until which the waiting at
* most is performed.
* @param signal_approach Whether signals should be ignored or honoured.
*
* @return How many times the semaphore has been waited on. If the
* function times out or is interrupted, then the returned
* value will be less than `n_wait`.
*
* @attention If the function returns a value less than `n_count` and
* `signal_approch` is `HONOUR_SIGNALS` then the caller must check
* the value of `errno` to find out whether the call was timed out or
* interrupted. In the former case the value will be `ETIMEDOUT`
* and in the latter `EINTR.
*/
size_t timedwait_n(size_t n_wait,
struct timespec& ts,
signal_approach_t signal_approach = IGNORE_SIGNALS) const
{
bool waited = true;
size_t n_waited = 0;
while (waited && n_wait--)
{
waited = timedwait(ts, signal_approach);
if (waited)
{
++n_waited;
}
}
return n_waited;
}
/**
* @brief Waits on the semaphore.
*
@ -212,7 +285,43 @@ public:
*/
bool timedwait(time_t seconds,
long nseconds,
signal_approach_t signal_approach = IGNORE_SIGNALS) const;
signal_approach_t signal_approach = IGNORE_SIGNALS) const
{
timespec ts;
get_current_timespec(seconds, nseconds, &ts);
return timedwait(ts, signal_approach);
}
/**
* @brief Waits on the semaphore.
*
* Waits on the sempahore the specified number of times at most until the
* specified time.
*
* @param n_wait How many times should be waited.
* @param seconds How many seconds to wait at most.
* @param nseconds How many nanonseconds to wait at most.
* @param signal_approach Whether signals should be ignored or honoured.
*
* @return How many times the semaphore has been waited on. If the
* function times out or is interrupted, then the returned
* value will be less than `n_wait`.
*
* @attention If the function returns a value less than `n_count` and
* `signal_approch` is `HONOUR_SIGNALS` then the caller must check
* the value of `errno` to find out whether the call was timed out or
* interrupted. In the former case the value will be `ETIMEDOUT`
* and in the latter `EINTR.
*/
size_t timedwait_n(size_t n_wait,
time_t seconds,
long nseconds,
signal_approach_t signal_approach = IGNORE_SIGNALS) const
{
timespec ts;
get_current_timespec(seconds, nseconds, &ts);
return timedwait_n(n_wait, ts, signal_approach);
}
/**
* @brief Waits on the semaphore.
@ -237,6 +346,36 @@ public:
return timedwait(seconds, 0, signal_approach);
}
/**
* @brief Waits on the semaphore.
*
* Waits on the sempahore the specified number of times at most until the
* specified time.
*
* @param n_wait How many times should be waited.
* @param seconds How many seconds to wait at most.
* @param signal_approach Whether signals should be ignored or honoured.
*
* @return How many times the semaphore has been waited on. If the
* function times out or is interrupted, then the returned
* value will be less than `n_wait`.
*
* @attention If the function returns a value less than `n_count` and
* `signal_approch` is `HONOUR_SIGNALS` then the caller must check
* the value of `errno` to find out whether the call was timed out or
* interrupted. In the former case the value will be `ETIMEDOUT`
* and in the latter `EINTR.
*/
bool timedwait_n(size_t n_wait,
time_t seconds,
signal_approach_t signal_approach = IGNORE_SIGNALS) const
{
return timedwait_n(n_wait, seconds, 0, signal_approach);
}
private:
static void get_current_timespec(time_t seconds, long nseconds, timespec* pTs);
private:
mutable sem_t m_sem;
};