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butting two arrays

erik malund

I have a project where data is received to array a, reformatted to array b, then reformatted to array c. The arrays are different sizes. The process is relevant as different parts of array b are reformatted to array c at different times.

There is a possibility that array a may overflow ever so slightly; however if it overflows into array c, it will not be a problem.

The question is:
can I 'trick' the linker to place array c immeddiately following array a in memory.

Thanx,

Erik

Parents
  • 0

    Further thoughts:

    1. Could you use a union, so that you're actually getting the compiler to some "overlaying?"

    2. Or something like this:

    U8 b[SIZE_A];
{
   U8 a[SIZE_B];
   // get data into a[]
   :

   // format data from a[] into b[]
   :
}
{
   U8 c[SIZE_C];
   // reformat data from b[] into c[]
   :
}
    By defining a[] and c[] in separate blocks, their "lifetimes" do not overlap, so the Linker can overlay them.

    I've assumed that your process is a[] --> b[] --> c[], so that the data in a[] is no longer required when you start processing b[] into c[] - but I could be wrong there?

Reply
  • 0

    Further thoughts:

    1. Could you use a union, so that you're actually getting the compiler to some "overlaying?"

    2. Or something like this:

    U8 b[SIZE_A];
{
   U8 a[SIZE_B];
   // get data into a[]
   :

   // format data from a[] into b[]
   :
}
{
   U8 c[SIZE_C];
   // reformat data from b[] into c[]
   :
}
    By defining a[] and c[] in separate blocks, their "lifetimes" do not overlap, so the Linker can overlay them.

    I've assumed that your process is a[] --> b[] --> c[], so that the data in a[] is no longer required when you start processing b[] into c[] - but I could be wrong there?

Children
  • 0 in reply to Andy Neil

    I've assumed that your process is a[] --> b[] --> c[], so that the data in a[] is no longer required when you start processing b[] into c[] - but I could be wrong there?
    A receives compressed data which is uncompressed to b for fast upload to C. B may contain several data blocks one of which is uploaded to c every 3 seconds. Since the operation following data -> a ->b always require a refresh of c overflow is not a problem if it occor into c; however some input data is added to b rather than replacing it, so b must be preserved at all times.

  • 0 in reply to erik malund

    "...b must be preserved at all times."

    My suggestion has b[] outside both blocks, so it would be preserved (only a[] and c[] would be overlayed)

    Does this work for you?

  • 0 in reply to Andrew Neil

    Gave up and made it in assembler, not too big a deal since these 3 buffers/arrays is the only XDATA used.

    Thanks for the suggestions

    Erik