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Arrays ALWAYS contiguous in memory?
Posted: Thu Jun 19, 2008 12:19 am
by Amiga5k
I know linked lists can theoretically be all over the place in memory (even though their internal pointers point to the correct next and previous link), but can
arrays always be expected to be contiguous in memory? For example, is it safe to do this?
Code: Select all
Structure TTest
a.l
b.l
EndStructure
Global Dim arr1.TTest(5)
; ...fill arr1
Global Dim arr2.TTest(5)
CopyMemory(@arr1(0),@arr2(0),SizeOf(TTest) * 6)
...or should all of the array elements be copied one at a time?
Thanks
Russell
Posted: Thu Jun 19, 2008 12:29 am
by Kaeru Gaman
afaik, yes.
never heard the converse...
even ReDim or again Dim is safe.
Posted: Thu Jun 19, 2008 12:43 am
by pdwyer
I'm screwed if they are not!
Posted: Thu Jun 19, 2008 1:12 am
by Amiga5k
lol
(Me, too, as I am asking this question after having used this trick many, many times already...). Saving an array of structures to disk is very convenient using this method:
Code: Select all
Structure TTest
x.l
y.l
author.s{40}
_data.l[1000]
EndStructure
Global Dim level.TTest(10)
; Fill level array with data...
OpenFile(0,"Test")
WriteData(0,@level(0),SizeOf(level) * 11)
CloseFile(0)
Sure beats field by field copying!
Russell
[Edit: Added _ to the data.l long field in TTest. Also, in reality I would of course check to make sure the file had been opened successfully first... But this is just an example
]
Posted: Thu Jun 19, 2008 1:38 am
by Kaeru Gaman
sure, it's much faster than element by element.
my example is 1. older 2. should show the concept of dynamic mapsizes.
you can use WriteData / ReadData with my example, too.
additionally, you can put a sole pointer into the structure and
allocate the Mem for the Array on-the-fly after reading the dimensions.