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FooSeq Struct Reference

<<interface>> <<generic>> A type-safe, ordered collection of elements. The type of these elements is referred to in this documentation as Foo. More...

Public Member Functions

FooSeqoperator= (const struct FooSeq &src_seq)
 Copy elements from another sequence, resizing the sequence if necessary.
 
bool copy_no_alloc (const struct FooSeq &src_seq)
 Copy elements from another sequence, only if the destination sequence has enough capacity.
 
bool from_array (const Foo array[], DDS_Long length)
 Copy elements from an array of elements, resizing the sequence if necessary. The original contents of the sequence (if any) are replaced.
 
bool to_array (Foo array[], DDS_Long length)
 Copy elements to an array of elements. The original contents of the array (if any) are replaced.
 
Foooperator[] (DDS_Long i)
 Set the i-th element of the sequence.
 
const Foooperator[] (DDS_Long i) const
 Get the i-th element for a const sequence.
 
DDS_Long length () const
 Get the logical length of this sequence.
 
bool length (DDS_Long new_length)
 Set the sequence to the desired length, and resize the sequence if necessary.
 
bool ensure_length (DDS_Long length, DDS_Long max)
 Set the sequence to the desired length, and resize the sequence if necessary.
 
DDS_Long maximum () const
 Get the current maximum number of elements that can be stored in this sequence.
 
bool maximum (DDS_Long new_max)
 Resize this sequence to a new desired maximum.
 
bool loan_contiguous (Foo *buffer, DDS_Long new_length, DDS_Long new_max)
 Loan a contiguous buffer to this sequence.
 
bool loan_discontiguous (Foo **buffer, DDS_Long new_length, DDS_Long new_max)
 Loan a discontiguous buffer to this sequence.
 
bool unloan ()
 Return the loaned buffer in the sequence and set the maximum to 0.
 
Fooget_contiguous_buffer () const
 Return the contiguous buffer of the sequence.
 
Foo ** get_discontiguous_buffer () const
 Return the discontiguous buffer of the sequence.
 
bool has_ownership ()
 Return the value of the owned flag.
 
 ~FooSeq ()
 Deallocate this sequence's buffer.
 
 FooSeq (DDS_Long new_max=0)
 Create a sequence with the given maximum.
 
 FooSeq (const struct FooSeq &foo_seq)
 Create a sequence by copying from an existing sequence.
 

Detailed Description

<<interface>> <<generic>> A type-safe, ordered collection of elements. The type of these elements is referred to in this documentation as Foo.

For users who define data types in OMG IDL, this type corresponds to the IDL express sequence<Foo>.

For any user-data type Foo that an application defines for the purpose of data-distribution with RTI Connext, a FooSeq is generated. The sequence offers a subset of the methods defined by the standard OMG IDL to C++ mapping for sequences. We refer to an IDL sequence<Foo> as FooSeq.

The state of a sequence is described by the properties 'maximum', 'length' and 'owned'.

  • The 'maximum' represents the size of the underlying buffer; this is the maximum number of elements it can possibly hold. It is returned by the FooSeq::maximum() operation.
  • The 'length' represents the actual number of elements it currently holds. It is returned by the FooSeq::length() operation.
  • The 'owned' flag represents whether the sequence owns the underlying buffer. It is returned by the FooSeq::has_ownership operation. If the sequence does not own the underlying buffer, the underlying buffer is loaned from somewhere else. This flag influences the lifecycle of the sequence and what operations are allowed on it. The general guidelines are provided below and more details are described in detail as pre-conditions and post-conditions of each of the sequence's operations:
    • If owned == DDS_BOOLEAN_TRUE, the sequence has ownership on the buffer. It is then responsible for destroying the buffer when the sequence is destroyed.

    • If the owned == DDS_BOOLEAN_FALSE, the sequence does not have ownership on the buffer. This implies that the sequence is loaning the buffer. The sequence cannot be destroyed until the loan is returned.

    • A sequence with a zero maximum always has owned == DDS_BOOLEAN_TRUE
See Also
FooDataWriter, FooDataReader, FooTypeSupport, rtiddsgen

Constructor & Destructor Documentation

FooSeq::~FooSeq ( )

Deallocate this sequence's buffer.

Precondition
(owned == DDS_BOOLEAN_TRUE). If this precondition is not met, no memory will be freed and an error will be logged.
Postcondition
maximum == 0 and the underlying buffer is freed.
See Also
FooSeq::maximum(), FooSeq::unloan
FooSeq::FooSeq ( DDS_Long  new_max = 0)

Create a sequence with the given maximum.

This is a constructor for the sequence. The constructor will automatically allocate memory to hold new_max elements of type Foo.

This constructor will be used when the application creates a sequence using one of the following:

FooSeq mySeq(5);
// or
FooSeq mySeq;
// or
FooSeq* mySeqPtr = new FooSeq(5);
Postcondition
maximum == new_max
length == 0
owned == DDS_BOOLEAN_TRUE,
Parameters
new_maxMust be >= 0. Otherwise the sequence will be initialized to a new_max=0.
FooSeq::FooSeq ( const struct FooSeq foo_seq)

Create a sequence by copying from an existing sequence.

This is a constructor for the sequence. The constructor will automatically allocate memory to hold foo_seq::maximum() elements of type Foo and will copy the current contents of foo_seq into the new sequence.

This constructor will be used when the application creates a sequence using one of the following:

FooSeq mySeq(foo_seq);
// or
FooSeq mySeq = foo_seq;
// or
FooSeq *mySeqPtr = new FooSeq(foo_seq);
Postcondition
this::maximum == foo_seq::maximum
this::length == foo_seq::length
this[i] == foo_seq[i] for 0 <= i < foo_seq::length
this::owned == DDS_BOOLEAN_TRUE
Note
If the pre-conditions are not met, the constructor will initialize the new sequence to a maximum of zero.

Member Function Documentation

FooSeq& FooSeq::operator= ( const struct FooSeq src_seq)

Copy elements from another sequence, resizing the sequence if necessary.

This method invokes FooSeq::copy_no_alloc after ensuring that the sequence has enough capacity to hold the elements to be copied.

This operator is invoked when the following expression appears in the code:

target_seq = src_seq

Important: This method will allocate memory if this::maximum < src_seq::length.

Therefore, to programatically detect the successful completion of the operator it is recommended that the application first sets the length of this sequence to zero, makes the assignment, and then checks that the length of this sequence matches that of src_seq.

Parameters
src_seq<<in>> the sequence from which to copy
See Also
FooSeq::copy_no_alloc
bool FooSeq::copy_no_alloc ( const struct FooSeq src_seq)

Copy elements from another sequence, only if the destination sequence has enough capacity.

Fill the elements in this sequence by copying the corresponding elements in src_seq. The original contents in this sequence are replaced via the element assignment operation (Foo_copy() function). By default, elements are discarded; 'delete' is not invoked on the discarded elements.

Precondition
this::maximum >= src_seq::length
this::owned == DDS_BOOLEAN_TRUE
Postcondition
this::length == src_seq::length
this[i] == src_seq[i] for 0 <= i < target_seq::length
this::owned == DDS_BOOLEAN_TRUE
Parameters
src_seq<<in>> the sequence from which to copy
Returns
DDS_BOOLEAN_TRUE if the sequence was successfully copied; DDS_BOOLEAN_FALSE otherwise.
Note
If the pre-conditions are not met, the operator will print a message to stdout and leave this sequence unchanged.
See Also
FooSeq::operator=
bool FooSeq::from_array ( const Foo  array[],
DDS_Long  length 
)

Copy elements from an array of elements, resizing the sequence if necessary. The original contents of the sequence (if any) are replaced.

Fill the elements in this sequence by copying the corresponding elements in array. The original contents in this sequence are replaced via the element assignment operation (Foo_copy() function). By default, elements are discarded; 'delete' is not invoked on the discarded elements.

Precondition
this::owned == DDS_BOOLEAN_TRUE
Postcondition
this::length == length
this[i] == array[i] for 0 <= i < length
this::owned == DDS_BOOLEAN_TRUE
Parameters
array<<in>> The array of elements to be copy elements from
length<<in>> The length of the array.
Returns
DDS_BOOLEAN_TRUE if the array was successfully copied; DDS_BOOLEAN_FALSE otherwise.
Note
If the pre-conditions are not met, the method will print a message to stdout and leave this sequence unchanged.
bool FooSeq::to_array ( Foo  array[],
DDS_Long  length 
)

Copy elements to an array of elements. The original contents of the array (if any) are replaced.

Copy the elements of this sequence to the corresponding elements in the array. The original contents of the array are replaced via the element assignment operation (Foo_copy() function). By default, elements are discarded; 'delete' is not invoked on the discarded elements.

Parameters
array<<in>> The array of elements to be filled with elements from this sequence
length<<in>> The number of elements to be copied.
Returns
DDS_BOOLEAN_TRUE if the elements of the sequence were successfully copied; DDS_BOOLEAN_FALSE otherwise.
Foo& FooSeq::operator[] ( DDS_Long  i)

Set the i-th element of the sequence.

This is the operator that is invoked when the application indexes into a non- const sequence:

myElement = mySequence[i];
mySequence[i] = myElement;

Note that a reference to the i-th element is returned (and not a copy).

Parameters
iindex of element to access, must be >= 0 and less than FooSeq::length()
Returns
the i-th element
const Foo& FooSeq::operator[] ( DDS_Long  i) const

Get the i-th element for a const sequence.

This is the operator that is invoked when the application indexes into a const sequence:

myElement = mySequence[i];

Note that a reference to the i-th element is returned (and not a copy).

Parameters
iindex of element to access, must be >= 0 and less than FooSeq::length()
Returns
the i-th element
DDS_Long FooSeq::length ( ) const

Get the logical length of this sequence.

Get the length that was last set, or zero if the length has never been set.

Returns
the length of the sequence
bool FooSeq::length ( DDS_Long  new_length)

Set the sequence to the desired length, and resize the sequence if necessary.

If the current maximum is greater than the desired length, then sequence is not resized.

Otherwise if this sequence owns its buffer, the sequence is resized to the new lengh by freeing and re-allocating the buffer. However, if the sequence does not own its buffer, this operation will fail.

For sequences that are part of a type declared in IDL, the length must not exceed the maximum established for the sequence in the IDL.

Parameters
new_lengththe new desired length. This value must be non-negative. Must be >= 0.
Returns
DDS_BOOLEAN_TRUE on sucess or DDS_BOOLEAN_FALSE on failure
bool FooSeq::ensure_length ( DDS_Long  length,
DDS_Long  max 
)

Set the sequence to the desired length, and resize the sequence if necessary.

If the current maximum is greater than the desired length, then sequence is not resized.

Otherwise if this sequence owns its buffer, the sequence is resized to the new maximum by freeing and re-allocating the buffer. However, if the sequence does not own its buffer, this operation will fail.

This function allows user to avoid unnecessary buffer re-allocation.

Precondition
length <= max
max <= maximum size for IDL bounded sequences
owned == DDS_BOOLEAN_TRUE if sequence needs to be resized
Postcondition
length == length
maximum == max if resized
Parameters
length<<in>> The new length that should be set. Must be >= 0.
max<<in>> If sequence need to be resized, this is the maximum that should be set. max >= length
Returns
DDS_BOOLEAN_TRUE on success, DDS_BOOLEAN_FALSE if the preconditions are not met. In that case the sequence is not modified.
DDS_Long FooSeq::maximum ( ) const

Get the current maximum number of elements that can be stored in this sequence.

The maximum of the sequence represents the maximum number of elements that the underlying buffer can hold. It does not represent the current number of elements.

The maximum is a non-negative number. It is initialized when the sequence is first created.

maximum can only be changed with the FooSeq::maximum(DDS_Long) operation.

Returns
the current maximum of the sequence.
See Also
FooSeq::length()
bool FooSeq::maximum ( DDS_Long  new_max)

Resize this sequence to a new desired maximum.

This operation does nothing if the new desired maximum matches the current maximum.

If this sequence owns its buffer and the new maximum is not equal to the old maximum, then the existing buffer will be freed and re-allocated.

Precondition
owned == DDS_BOOLEAN_TRUE
new_max <= maximum size for IDL bounded sequences.
Postcondition
owned == DDS_BOOLEAN_TRUE
length == MINIMUM(original length, new_max)
Parameters
new_maxMust be >= 0.
Returns
DDS_BOOLEAN_TRUE on success, DDS_BOOLEAN_FALSE if the preconditions are not met. In that case the sequence is not modified.
bool FooSeq::loan_contiguous ( Foo buffer,
DDS_Long  new_length,
DDS_Long  new_max 
)

Loan a contiguous buffer to this sequence.

This operation changes the owned flag of the sequence to DDS_BOOLEAN_FALSE and also sets the underlying buffer used by the sequence. See the User's Manual for more information about sequences and memory ownership.

Use this method if you want to manage the memory used by the sequence yourself. You must provide an array of elements and integers indicating how many elements are allocated in that array (i.e. the maximum) and how many elements are valid (i.e. the length). The sequence will subsequently use the memory you provide and will not permit it to be freed by a call to FooSeq::maximum(DDS_Long).

Once you have loaned a buffer to a sequence, make sure that you don't free it before calling FooSeq::unloan: the next time you access the sequence, you will be accessing freed memory!

You can use this method to wrap stack memory with a sequence interface, thereby avoiding dynamic memory allocation. Create a FooSeq and an array of type Foo and then loan the array to the sequence:

::Foo fooArray[10];
::FooSeq fooSeq;
fooSeq.loan_contiguous(fooArray, 0, 10);

By default, a sequence you create owns its memory unless you explicitly loan memory of your own to it. In a very few cases, RTI Connext will return a sequence to you that has a loan; those cases are documented as such. For example, if you call FooDataReader::read or FooDataReader::take and pass in sequences with no loan and no memory allocated, RTI Connext will loan memory to your sequences which must be unloaned with FooDataReader::return_loan. See the documentation of those methods for more information.

Precondition
FooSeq::maximum() == 0; i.e. the sequence has no memory allocated to it.
FooSeq::has_ownership == DDS_BOOLEAN_TRUE; i.e. the sequence does not already have an outstanding loan
Postcondition
The sequence will store its elements in the buffer provided.
FooSeq::has_ownership == DDS_BOOLEAN_FALSE
FooSeq::length() == new_length
FooSeq::maximum() == new_max
Parameters
bufferThe new buffer that the sequence will use. Must point to enough memory to hold new_max elements of type Foo. It may be NULL if new_max == 0.
new_lengthThe desired new length for the sequence. It must be the case that that 0 <= new_length <= new_max.
new_maxThe allocated number of elements that could fit in the loaned buffer.
Returns
DDS_BOOLEAN_TRUE if buffer is successfully loaned to this sequence or DDS_BOOLEAN_FALSE otherwise. Failure only occurs due to failing to meet the pre-conditions. Upon failure the sequence remains unmodified.
See Also
FooSeq::unloan , FooSeq::loan_discontiguous
bool FooSeq::loan_discontiguous ( Foo **  buffer,
DDS_Long  new_length,
DDS_Long  new_max 
)

Loan a discontiguous buffer to this sequence.

This method is exactly like FooSeq::loan_contiguous except that the buffer loaned is an array of Foo pointers, not an array of Foo.

Parameters
bufferThe new buffer that the sequence will use. Must point to enough memory to hold new_max elements of type Foo*. It may be NULL if new_max == 0.
new_lengthThe desired new length for the sequence. It must be the case that that 0 <= new_length <= new_max.
new_maxThe allocated number of elements that could fit in the loaned buffer.
See Also
FooSeq::unloan, FooSeq::loan_contiguous
bool FooSeq::unloan ( )

Return the loaned buffer in the sequence and set the maximum to 0.

This method affects only the state of this sequence; it does not change the contents of the buffer in any way.

Only the user who originally loaned a buffer should return that loan, as the user may have dependencies on that memory known only to them. Unloaning someone else's buffer may cause unspecified problems. For example, suppose a sequence is loaning memory from a custom memory pool. A user of the sequence likely has no way to release the memory back into the pool, so unloaning the sequence buffer would result in a resource leak. If the user were to then re-loan a different buffer, the original creator of the sequence would have no way to discover, when freeing the sequence, that the loan no longer referred to its own memory and would thus not free the user's memory properly, exacerbating the situation and leading to undefined behavior.

Precondition
owned == DDS_BOOLEAN_FALSE
Postcondition
owned == DDS_BOOLEAN_TRUE
maximum == 0
Returns
DDS_BOOLEAN_TRUE if the preconditions were met. Otherwise DDS_BOOLEAN_FALSE. The function only fails if the pre-conditions are not met, in which case it leaves the sequence unmodified.
See Also
FooSeq::loan_contiguous, FooSeq::loan_discontiguous, FooSeq::maximum(DDS_Long)
Foo* FooSeq::get_contiguous_buffer ( ) const

Return the contiguous buffer of the sequence.

Get the underlying buffer where contiguous elements of the sequence are stored. The size of the buffer matches the maximum of the sequence, but only the elements up to the FooSeq::length() of the sequence are valid.

This method provides almost no encapsulation of the sequence's underlying implementation. Certain operations, such as FooSeq::maximum(DDS_Long), may render the buffer invalid. In light of these caveats, this operation should be used with care.

Returns
buffer that stores contiguous elements in sequence.
Foo** FooSeq::get_discontiguous_buffer ( ) const

Return the discontiguous buffer of the sequence.

This operation returns the underlying buffer where discontiguous elements of the sequence are stored. The size of the buffer matches the maximum of this sequence, but only the elements up to the FooSeq::length() of the sequence are valid.

The same caveats apply to this method as to FooSeq::get_contiguous_buffer.

The sequence will dereference pointers in the discontiguous buffer to provide access to its elements by value in C and by reference in C++. If you access the discontiguous buffer directly by means of this method, do not store any NULL values into it, as acessing those values will result in a segmentation fault.

Returns
buffer that stores discontiguous elements in sequence.
bool FooSeq::has_ownership ( )

Return the value of the owned flag.

Returns
DDS_BOOLEAN_TRUE if sequence owns the underlying buffer, or DDS_BOOLEAN_FALSE if it has an outstanding loan.

RTI Connext Traditional C++ API Version 6.0.0 Copyright © Sun Mar 3 2019 Real-Time Innovations, Inc