>var > CromaMX = packed array of TSample; > CromaMXFast = array of TSample; >begin >LoadFromDisk(CromaMX); > CromaMXFast:= CromaMX; <-- won't work >end;>> >Second problem: >I suppose that if CromaMX is a packed array of TSample, then TSample >should be also packed. Right?
The point is to PACK the record, not the array, and NOT to create two different types. Adding packed to the array makes no difference (in this case, at least with D2007) to the SizeOf for an element or for the whole array, whether or not TSample is packed. You need to add packed to the record to make a difference. For a single record, the Packed/unpacked issue would really not make any measurable performance difference (given that one of your 3 bytes has to be on the "wrong" alignment anyway). The problem in your case is that the second array element (e.g.) will start misaligned and hence so most of the structure will be misaligned for every access. Personally, I would declare it packed, use the types that are defined not to change (as mentioned in another post), and then add 1 byte "reserved" to make sure the structure remained a nice round 16 bytes long to preserve alignment, and accept that this means that it will use 1/15 more disk space than necessary. Alternatively I'd look at whether I really need to store the Boolean separately, or could I pack it as 1 bit into one of the other fields. I did exactly that for data I was preparing for an embedded airborne system where I needed a single bit flag - the max value I was storing in one of the WORD fields could never use 16 bits, so I "stole" the top bit to be the Boolean and accepted that I had to mask it in and out. The small penalty on accessing this flag was acceptable in relation to the effect on storage requirements. Ken _______________________________________________ Delphi mailing list -> [email protected] http://www.elists.org/mailman/listinfo/delphi
