Subject:
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Emulating arrays in NQC
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Newsgroups:
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lugnet.robotics.rcx.nqc
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Date:
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Thu, 6 Jan 2000 15:50:00 GMT
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Viewed:
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1811 times
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Hi all!
as I promised earlier, I am posting the code I've written to emulate arrays. I
tried to make it general, but it's difficult to do without compiler support.
Right now it implements a 32 items array of 4 bit variables. It can be quite
easily adapted for variables of power-of-2 size.
Good luck! And feel free to come with constructive criticism!
(A note: After writing all the comments in the file, I noticed compiling time
being much larger!)
/Vlad
------------------------
/*
ARRAY.NQC - simulating arrays of variables
with sizes smaller than 16 bit
(c) 2000 Vlad Dumitrescu vladdu@hotmail.com
This code is released under the Gnu public license. Please notify
the author if you are using this code for something meaningsful.
History:
version 1.0 - 2000.01.05 - Vlad Dumitrescu
While some things have been abstracted and generalized,
a lot has to be done manually in order to modify the present
size of the array (32) and of the variables (4 bit). Maybe
some support from the compiler would make that part of
the job less tedious.
Use only from one task! Global variables make it unsafe otherwise.
I believe the size of the compiled code (184 + 238 bytes) cannot be
shrunk in an impressive way. A switch statement would probably
bring the most improvement.
Using the array as a pool of 4 bit independent variables (ie only
with constant indexes) could benefit in a big way from compiler
support!
Good luck!
*/
#define BITSPERVAR 4
#define ARRSIZE 32
#define NUMVARS (((ARRSIZE-1)*BITSPERVAR)/16+1)
#define ITEMSPERVAR (16/BITSPERVAR)
int
arr0, arr1, arr2, arr3,
arr4, arr5, arr6, arr7,
arr_n, arr_val, arr_p, arr_m;
/*
some macros that might
*/
#define get_item(n, val) { arr_n=n; sub_get_item(); val = arr_val; }
#define set_item(n, val) { arr_n=n; arr_val=val; sub_set_item(); }
/* implementation */
#define MODMASK 0x03
#define VALMASK 0x0F
#define MULTMASK0 0x0001
#define MULTMASK1 0x0010
#define MULTMASK2 0x0100
#define MULTMASK3 0x1000
sub sub_get_item()
/*
input:
arr_n: index of element to get -- is preserved;
output:
arr_val: value
*/
{
arr_p = arr_n / ITEMSPERVAR;
arr_val = arr0;
if (arr_p==1) { arr_val = arr1; }
else if (arr_p==2) { arr_val = arr2; }
else if (arr_p==3) { arr_val = arr3; }
else if (arr_p==4) { arr_val = arr4; }
else if (arr_p==5) { arr_val = arr5; }
else if (arr_p==6) { arr_val = arr6; }
else if (arr_p==7) { arr_val = arr7; }
arr_p = arr_n & MODMASK;
if (arr_p==1) { arr_val /= 0x0010; }
else if (arr_p==2) { arr_val /= 0x0100; }
else if (arr_p==3) { arr_val /= 0x1000; }
arr_val &= VALMASK;
}
void _set(int& arr)
{
arr &= arr_m;
arr |= arr_val;
}
#define MASK0 0xFFF0
#define MASK1 0xFF0F
#define MASK2 0xF0FF
#define MASK3 0x0FFF
sub sub_set_item()
/*
input:
arr_n: index of element to get -- is NOT preserved;
arr_val: value to be set
output:
none
*/
{
arr_val &= VALMASK;
arr_p = arr_n & MODMASK;
arr_m = MASK0;
if (arr_p==1) { arr_val *= 0x0010; arr_m=MASK1; }
else if (arr_p==2) { arr_val *= 0x0100; arr_m=MASK2; }
else if (arr_p==3) { arr_val *= 0x1000; arr_m=MASK3; }
arr_n = arr_n / ITEMSPERVAR;
/* arr_p can be used as temp variable here, but this will
increase code size with 5 bytes
*/
_set(arr0);
if (arr_n==1) { _set(arr1); }
else if (arr_n==2) { _set(arr2); }
else if (arr_n==3) { _set(arr3); }
else if (arr_n==4) { _set(arr4); }
else if (arr_n==5) { _set(arr5); }
else if (arr_n==6) { _set(arr6); }
else if (arr_n==7) { _set(arr7); }
}
/* a dummy main task */
task main()
{
arr0=0;
arr1=0;
arr2=0;
arr3=0;
arr4=0;
arr5=0;
arr6=0;
arr7=0;
int v;
set_item(0, 5);
get_item(0, v);
}
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