// Copyright (C) 2006 Davis E. King (davis@dlib.net)
// License: Boost Software License See LICENSE.txt for the full license.
#undef DLIB_PIPE_KERNEl_ABSTRACT_
#ifdef DLIB_PIPE_KERNEl_ABSTRACT_
#include "../threads.h"
namespace dlib
{
template <
typename T
>
class pipe
{
/*!
REQUIREMENTS ON T
T must be swappable by a global swap()
T must have a default constructor
INITIAL VALUE
size() == 0
is_enabled() == true
is_enqueue_enabled() == true
is_dequeue_enabled() == true
WHAT THIS OBJECT REPRESENTS
This is a first in first out queue with a fixed maximum size containing
items of type T. It is suitable for passing objects between threads.
THREAD SAFETY
All methods of this class are thread safe. You may call them from any
thread and any number of threads my call them at once.
!*/
public:
typedef T type;
explicit pipe (
unsigned long maximum_size
);
/*!
ensures
- #*this is properly initialized
- #max_size() == maximum_size
throws
- std::bad_alloc
- dlib::thread_error
!*/
virtual ~pipe (
);
/*!
ensures
- any resources associated with *this have been released
- disables (i.e. sets is_enabled() == false) this object so that
all calls currently blocking on it will return immediately.
!*/
void enable (
);
/*!
ensures
- #is_enabled() == true
!*/
void disable (
);
/*!
ensures
- #is_enabled() == false
- causes all current and future calls to enqueue(), dequeue(),
enqueue_or_timeout() and dequeue_or_timeout() to not block but
to return false immediately until enable() is called.
- causes all current and future calls to wait_until_empty() and
wait_for_num_blocked_dequeues() to not block but return
immediately until enable() is called.
!*/
bool is_enabled (
) const;
/*!
ensures
- returns true if this pipe is currently enabled, false otherwise.
!*/
void empty (
);
/*!
ensures
- #size() == 0
!*/
void wait_until_empty (
) const;
/*!
ensures
- blocks until one of the following is the case:
- size() == 0
- is_enabled() == false
- is_dequeue_enabled() == false
!*/
void wait_for_num_blocked_dequeues (
unsigned long num
) const;
/*!
ensures
- blocks until one of the following is the case:
- size() == 0 and the number of threads blocked on calls
to dequeue() and dequeue_or_timeout() is greater than
or equal to num.
- is_enabled() == false
- is_dequeue_enabled() == false
!*/
bool is_enqueue_enabled (
) const;
/*!
ensures
- returns true if the enqueue() and enqueue_or_timeout() functions are
currently enabled, returns false otherwise. (note that the higher
level is_enabled() function can overrule this one. So if
is_enabled() == false then enqueue functions are still disabled even
if is_enqueue_enabled() returns true. But if is_enqueue_enabled() == false
then enqueue functions are always disabled no matter the state of
is_enabled())
!*/
void disable_enqueue (
);
/*!
ensures
- #is_enqueue_enabled() == false
- causes all current and future calls to enqueue() and
enqueue_or_timeout() to not block but to return false
immediately until enable_enqueue() is called.
!*/
void enable_enqueue (
);
/*!
ensures
- #is_enqueue_enabled() == true
!*/
bool is_dequeue_enabled (
) const;
/*!
ensures
- returns true if the dequeue() and dequeue_or_timeout() functions are
currently enabled, returns false otherwise. (note that the higher
level is_enabled() function can overrule this one. So if
is_enabled() == false then dequeue functions are still disabled even
if is_dequeue_enabled() returns true. But if is_dequeue_enabled() == false
then dequeue functions are always disabled no matter the state of
is_enabled())
!*/
void disable_dequeue (
);
/*!
ensures
- #is_dequeue_enabled() == false
- causes all current and future calls to dequeue() and
dequeue_or_timeout() to not block but to return false
immediately until enable_dequeue() is called.
!*/
void enable_dequeue (
);
/*!
ensures
- #is_dequeue_enabled() == true
!*/
unsigned long max_size (
) const;
/*!
ensures
- returns the maximum number of objects of type T that this
pipe can contain.
!*/
unsigned long size (
) const;
/*!
ensures
- returns the number of objects of type T that this
object currently contains.
!*/
bool enqueue (
T& item
);
/*!
ensures
- if (size() == max_size()) then
- this call to enqueue() blocks until one of the following is the case:
- there is room in the pipe for another item
- max_size() == 0 and another thread is trying to dequeue from this
pipe and we can pass our item object directly to that thread.
- someone calls disable()
- someone calls disable_enqueue()
- else
- this call does not block.
- if (this call to enqueue() returns true) then
- #is_enabled() == true
- #is_enqueue_enabled() == true
- if (max_size() == 0) then
- using global swap, item was passed directly to a
thread attempting to dequeue from this pipe
- else
- using global swap, item was added into this pipe.
- #item is in an undefined but valid state for its type
- else
- item was NOT added into the pipe
- #item == item (i.e. the value of item is unchanged)
!*/
bool enqueue (T&& item) { return enqueue(item); }
/*!
enable enqueueing from rvalues
!*/
bool enqueue_or_timeout (
T& item,
unsigned long timeout
);
/*!
ensures
- if (size() == max_size() && timeout > 0) then
- this call to enqueue_or_timeout() blocks until one of the following is the case:
- there is room in the pipe to add another item
- max_size() == 0 and another thread is trying to dequeue from this pipe
and we can pass our item object directly to that thread.
- someone calls disable()
- someone calls disable_enqueue()
- timeout milliseconds passes
- else
- this call does not block.
- if (this call to enqueue() returns true) then
- #is_enabled() == true
- #is_enqueue_enabled() == true
- if (max_size() == 0) then
- using global swap, item was passed directly to a
thread attempting to dequeue from this pipe
- else
- using global swap, item was added into this pipe.
- #item is in an undefined but valid state for its type
- else
- item was NOT added into the pipe
- #item == item (i.e. the value of item is unchanged)
!*/
bool enqueue_or_timeout (T&& item, unsigned long timeout) { return enqueue_or_timeout(item,timeout); }
/*!
enable enqueueing from rvalues
!*/
bool dequeue (
T& item
);
/*!
ensures
- if (size() == 0) then
- this call to dequeue() blocks until one of the following is the case:
- there is something in the pipe we can dequeue
- max_size() == 0 and another thread is trying to enqueue an item
onto this pipe and we can receive our item directly from that thread.
- someone calls disable()
- someone calls disable_dequeue()
- else
- this call does not block.
- if (this call to dequeue() returns true) then
- #is_enabled() == true
- #is_dequeue_enabled() == true
- the oldest item that was enqueued into this pipe has been
swapped into #item.
- else
- nothing was dequeued from this pipe.
- #item == item (i.e. the value of item is unchanged)
!*/
bool dequeue_or_timeout (
T& item,
unsigned long timeout
);
/*!
ensures
- if (size() == 0 && timeout > 0) then
- this call to dequeue_or_timeout() blocks until one of the following is the case:
- there is something in the pipe we can dequeue
- max_size() == 0 and another thread is trying to enqueue an item onto this
pipe and we can receive our item directly from that thread.
- someone calls disable()
- someone calls disable_dequeue()
- timeout milliseconds passes
- else
- this call does not block.
- if (this call to dequeue_or_timeout() returns true) then
- #is_enabled() == true
- #is_dequeue_enabled() == true
- the oldest item that was enqueued into this pipe has been
swapped into #item.
- else
- nothing was dequeued from this pipe.
- #item == item (i.e. the value of item is unchanged)
!*/
private:
// restricted functions
pipe(const pipe&); // copy constructor
pipe& operator=(const pipe&); // assignment operator
};
}
#endif // DLIB_PIPE_KERNEl_ABSTRACT_