CODEWITHSUNDEEP
c++deque
user1132655
user1132655

Reputation: 243

will stl deque reallocate my elements (c++)?

Hi I need an stl container which can be indexed like a vector but does not move old elements in the memory like a vector would do with resize or reserve (Unless I call reserve once at the beginning with a capacity enough for all elements, which is not good for me). (Note I do address binding to the elements so I expect the address of these elements to never change). So I've found this deque. Do you think it is good for this purpose? Important: I need only pushback but I need to grow the container on demand in small chunks.

Upvotes: 10

Views: 3294

Answers (2)

tadman
tadman

Reputation: 211590

A careful reading of the documentation seems to indicate that so long as you insert at the beginning or the end it will not invalidate pointers, and invalidating pointers is a sign that the data is being copied or moved.

The way it's constructed is not quite like a linked list, where each element is allocated individually, but as a set of linked arrays presumably for performance reasons. Altering the order of elements in the middle will necessitate moving data around.

Upvotes: 5

Fred Foo
Fred Foo

Reputation: 363577

std::deque "never invalidates pointers or references to the rest of the elements" when adding or removing elements at its back or front, so yes, when you only push_back the elements stay in place.

Upvotes: 13

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