memory allocation performance

[semedao]

Hi,
I have some loop that should copy X amount of bytes to some byte[] buffer.
the byte buffer array is fixed length during the loop
but outside the loop the length can change.
the loop can be called also inside other loop...
If I have this code for example when
What will be better performance , to check for buffer length before
re-allocate it , or to re-allocate it every time?
what coast more? the Length property + if , or the allocating ? (if we speak
about 10-100 bytes memory , and that the call change it every 10 times)

fooA()
{
do
{
fooB(***some value that can change every call***);
}
}

fooB(int CurrentLength){
if(_buffer.Length != CurrentLength)
{
_buffer = new byte[CurrentLength];

}

do

{

_buffer = ....data....

}

}

 

[Walter Wang [MSFT]]

Hi,

Comparing two int32 values will be much faster than re-allocating a byte
array. If possible, you should avoid re-allocating the buffer in a loop.

Taking StringBuilder for example, it's internally allocating a bigger
enough buffer to hold possible strings that will be appended to it. When
the buffer is not big enough, it will re-allocate a bigger buffer again
(probably double the buffer size), the purpose it to minimize possible
memory re-allocating times. That's why we always recommend to use
StringBuilder if you're repeatedly add strings up.


Sincerely,
Walter Wang ([email protected], remove 'online.')
Microsoft Online Community Support

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[semedao]

thanks