Shrink allocated memory with 'new'.
I have 2 sets created with 'new': (symbolic write)
set1 = {10, 15, 20, 21, 50}
set2 = {1, 5, 20, 21, 150}
I want to create the sum of sets so I allocate with
but the addition is:
set3 = {1, 5, 10, 15, 20, 21, 50, 150}
and it has 8 positions.
Can I shrink, after the addition operation, the heap block, without copying everything to a new buffer? Like realloc.
I use something like this in really big SparseVector and SparseMatrix so I don't want to use std::vector because it has 3 members instead of 2 than I use. (std::vector uses an extra member for capacity())
set1 = {10, 15, 20, 21, 50}
set2 = {1, 5, 20, 21, 150}
I want to create the sum of sets so I allocate with
new int[sizeof(set1) + sizeof(set2)] which is 5+5=10 positions.but the addition is:
set3 = {1, 5, 10, 15, 20, 21, 50, 150}
and it has 8 positions.
Can I shrink, after the addition operation, the heap block, without copying everything to a new buffer? Like realloc.
I use something like this in really big SparseVector and SparseMatrix so I don't want to use std::vector because it has 3 members instead of 2 than I use. (std::vector uses an extra member for capacity())
closed account (zb0S216C)
| chameleon wrote: |
|---|
| "Can I shrink, after the addition operation, the heap block, without copying everything to a new buffer? Like realloc." |
No; you'll have to do it manually.
| chameleon wrote: |
|---|
| "I don't want to use std::vector because it has 3 members instead of 2 than I use." |
Two members are for marking the end of the allocated region, while the other is for marking the next available slot. All three are required to create a safe storage container.
Wazzak
Last edited on
Thanks.
About std::vector members, they are:
start_pos
end_pos
capacity_pos
of course implementations can be differ.
About std::vector members, they are:
start_pos
end_pos
capacity_pos
of course implementations can be differ.
closed account (zb0S216C)
Indeed. Though, they behave the same - irrespective of the implementation. I implement my dynamic containers in this way.
Wazzak
Wazzak
Last edited on
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