David McNab <[EMAIL PROTECTED]> wrote:
> // define a macro to create a 'function pointer table handle'
> #define pgm_get_functab(tab) (FuncPtrTable)(&tab[0])
&tab[0] is the same as tab.
> I tried the approach of:
> fptr = (FuncPtr)pgm_read_word(&funcs_table[0] + i * 2);
> but it has a huge footprint of 48 bytes ...
Does it?
foo.c:
#include <avr/pgmspace.h>
typedef void (*FuncPtr)(void);
void func1(void);
void func2(void);
void func3(void);
FuncPtr funcs_table[] PROGMEM = {
func1,
func2,
func3
};
void
dorun(int i)
{
FuncPtr fptr;
fptr = (FuncPtr)pgm_read_word(funcs_table + i);
fptr();
}
yields:
..global dorun
.type dorun, @function
dorun:
movw r30,r24
lsl r30
rol r31
subi r30,lo8(-(funcs_table))
sbci r31,hi8(-(funcs_table))
lpm r24, Z+
lpm r25, Z
movw r30,r24
icall
ret
Btw., you apparently have problems still understanding how pointers
are calculated in C. The complicated "&tab[0]" construct is a slight
indication of that, but you've also made the error of trying to
manually multiply by 2 in your access macro. I left that off, as it
would have given completely wrong code.
--
cheers, J"org .-.-. --... ...-- -.. . DL8DTL
http://www.sax.de/~joerg/ NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)
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