[Basic] Copy data block to another one

Hello all

I have defined two data blocks as
DIM source% 1024
DIM target% 1024

After having filled the source% block, I would like to make a copy into the target% block.

Currently, i have defined a PROC

DEFPROCcopy_block(source%,target%,size%)
  FOR i%=0 TO size%
    ?(target%+i%)=?(source%+i%)
  NEXT
ENDPROC

Is there a better/faster/more efficient way to achieve this?

Thank you for your help.

François

Is there a better/faster/more efficient way to achieve this?

For a start, word by word would be quicker than byte by byte. We know that the blocksize is a multiple of 4.

DEFPROCcopy_block(source%,target%,size%)
  LOCAL last%
  last% = target% + size%
  WHILE target% < last%
   !target% = !source%:target%+=4:source%+=4
  ENDWHILE
ENDPROC

Thanks GavinWraith

Of course, asm would be best… but I am too old for this :)

Not as bad as you think. Fastest is to use LDM and STM. You load 8 words at a time into 8 registers, say R2-R10 (having set R0 to source% and R1 to target%)
and read them back:

LDMIA R0!,{R2-R10)
STMIA R1!,{R2-R10)

@Gavin
Haven’t I read that only early ARM processors had a speed advantage using LDM/STM and that they mostly unfold them into a series of LDR/STR? I am sure I will be put right on this. ;-) However, the assembler code is much neater.

There are couple of other ways to copy a block of memory without resorting to assembler.

You could use SYS"Wimp_TransferBlock" if you are running your program as a wimp task. It works inside a task as well as between tasks, but I would expect it to be inefficient for small blocks.

Of course, I also have to mention that Basalt can do it for you:

BLOCK source% ON|TO destination%

With ON the block is copied even if it overwrites the source, but with TO there would be an error.