Class LoanableCollection

Inheritance Relationships

Derived Types

Class Documentation

class LoanableCollection

A collection of generic opaque pointers that can receive the buffer from outside (loan).

This is an abstract class. See LoanableSequence for details.

Subclassed by eprosima::fastdds::dds::LoanableTypedCollection< T, std::true_type >, eprosima::fastdds::dds::LoanableTypedCollection< T, _NonConstEnabler >, eprosima::fastdds::dds::UserAllocatedSequence

Public Types

using size_type = int32_t
using element_type = void*

Public Functions

inline const element_type *buffer() const

Get the pointer to the elements buffer.

The returned value may be nullptr if maximum() is 0. Otherwise it is guaranteed that up to maximum() elements can be accessed.

Returns:

the pointer to the elements buffer.

inline bool has_ownership() const

Get the ownership flag.

Returns:

whether the collection has ownership of the buffer.

inline size_type maximum() const

Get the maximum number of elements currently allocated.

Returns:

the maximum number of elements currently allocated.

inline size_type length() const

Get the number of elements currently accessible.

Returns:

the number of elements currently accessible.

inline bool length(size_type new_length)

Set the number of elements currently accessible.

This method tells the collection that a certain number of elements should be accessible. If the new length is greater than the current maximum() the collection should allocate space for the new elements. If this is the case and the collection does not own the buffer (i.e. has_ownership() is false) then no allocation will be performed, the length will remain unchanged, and false will be returned.

Parameters:

new_length – [in] New number of elements to be accessible.

Pre:

new_length >= 0

Returns:

true if the new length was correctly set.

Post:

length() == new_length

Post:

maximum() >= new_length

inline bool loan(element_type *buffer, size_type new_maximum, size_type new_length)

Loan a buffer to the collection.

Parameters:

  • buffer – [in] pointer to the buffer to be loaned.

  • new_maximum – [in] number of allocated elements in buffer.

  • new_length – [in] number of accessible elements in buffer.

Pre:

(has_ownership() == false) || (maximum() == 0)

Pre:

new_maximum > 0

Pre:

new_maximum >= new_length

Pre:

buffer != nullptr

Returns:

false if preconditions are not met.

Returns:

true if operation succeeds.

Post:

buffer() == buffer

Post:

has_ownership() == false

Post:

maximum() == new_maximum

Post:

length() == new_length

inline element_type *unloan(size_type &maximum, size_type &length)

Remove the loan from the collection.

Parameters:

  • maximum – [out] number of allocated elements on the returned buffer.

  • length – [out] number of accessible elements on the returned buffer.

Pre:

has_ownership() == false

Returns:

nullptr if preconditions are not met.

Returns:

pointer to the previously loaned buffer of elements.

Post:

buffer() == nullptr

Post:

has_ownership() == true

Post:

length() == 0

Post:

maximum() == 0

inline element_type *unloan()

Remove the loan from the collection.

Pre:

has_ownership() == false

Returns:

nullptr if preconditions are not met.

Returns:

pointer to the previously loaned buffer of elements.

Post:

buffer() == nullptr

Post:

has_ownership() == true

Post:

length() == 0

Post:

maximum() == 0

Protected Functions

LoanableCollection() = default

Default constructor.

Creates the loanable collection with no data.

Post:

buffer() == nullptr

Post:

has_ownership() == true

Post:

length() == 0

Post:

maximum() == 0

virtual void resize(size_type new_length) = 0

Protected Attributes

size_type maximum_ = 0
size_type length_ = 0
element_type *elements_ = nullptr
bool has_ownership_ = true