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memcmp problem with bidimensional const array

 
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memcmp problem with bidimensional const array
PostPosted: Wed Jul 25, 2007 1:08 pm     Reply with quote
if I use

unsigned char R[10][8] = .....
if (memcmp(&R[j][0],&buffer[1],8) == 0) ....

all is OK, but if I try

const unsigned char R[10][8] = .....
if (memcmp(&R[j][0],&buffer[1],8) == 0) ....

to use const array I have a compiler error. Why?

Best regards
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Wed Jul 25, 2007 1:40 pm     Reply with quote
It probably doesn't work because traditionally, in CCS, the "mem"
functions require both parameters to be RAM arrays.

For me to test it further, you need to:

1. Post the declaration statement for the 'buffer' array.

2. Finish the code. Show the initializations that are shown as "...".

3. Post your compiler version.

4. Post your PIC.

5. Post the error message that you're getting.
firefox78



Joined: 25 Jan 2005
Posts: 5

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PostPosted: Thu Jul 26, 2007 3:02 pm     Reply with quote
My compiler version is "CCS PCH C Compiler, Version 4.013, 28193", pic is PIC18F4550 and the error is on the follow line
if (memcmp(&Richieste[j][0],&buffer[1],l1) == 0)
there is the error and is Expecting an identifire. All this errors are onli if I use CONST before array!!!! Why ? The full source code is the follow:

Code:

#include <18F4550>
#include <string.h>

#fuses INTRC_IO, NOWDT, NOBROWNOUT, PUT, NOLVP, NOMCLR, NOXINST
#use delay(clock=8000000)
#use RS232 (stream=uart, baud=9600, UART1, PARITY=N, BITS=8)

signed int16 l1 = -1;
signed int16 l2 = -1;
unsigned int16 t = 0;
unsigned char buffer[20];
int bancataricevuta = 0;

#define NRichieste 20
const unsigned char Richieste[NRichieste][8] =
                       {
                        {0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01},
                        {0x01, 0x02, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01},
                        {0x01, 0x03, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01},
                       };

const unsigned char Risposte[NRichieste][8] =
                       {
                        {0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01},
                        {0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02},
                        {0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03},
                        {0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04},
                       };


#int_TIMER2
void TIMER2_isr()
{
   t++;

   if ((t >= 100) && (l1>=0))
   {
     t = 0;
     bancataricevuta = 1;
   }
}

#INT_RDA
void irx()
{
     unsigned char x;
     while(kbhit(uart) == 1)
     {
        t = 0;
        l1++;
        x = getch(uart);
        buffer[l1] = x;
     }
}

void main()
{
   int16 i = 0;
   int16 j = 0;
   int8 trovato = 0;

   setup_wdt(WDT_OFF);
   setup_timer_0(RTCC_INTERNAL);
   setup_timer_1(T1_DISABLED);
   setup_timer_2(T2_DIV_BY_1,124,16);
   enable_interrupts(INT_TIMER2);
   enable_interrupts(INT_RDA);
   enable_interrupts(GLOBAL);

   while(1)
   {
      if (bancataricevuta == 1)
      {
              trovato = 0;
              j = 0;
              while ((trovato == 0) && (j < NRichieste))
              {
                   if (memcmp(&Richieste[j][0],&buffer[1],l1) == 0)
                   {
                      l2++;
                      write_eeprom(l2,j);

                      trovato = 1;

                      output_high(PIN_B4);
                      delay_ms(10);
                      output_low(PIN_B4);

                      for (i=0;i<8; i++) putc(Risposte[j][i]);
                   }
                   j++;
              }

              if (trovato == 0)
              {
                 output_high(PIN_B7);
                 for (i=0; i<=l1; i++)
                 {
                    l2++;
                    write_eeprom(l2,buffer[i]);
                 }
                 delay_ms(10);
                 output_low(PIN_B7);
              }
           }

           l1 = -1;
           bancataricevuta = 0;
   }

}


I have only const array and I need for memory reasons that all array must be placed as CONST.

Best regards.
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Fri Jul 27, 2007 5:40 pm     Reply with quote
You need to copy the 'const' array elements into a temporary RAM buffer
before you use the memcmp() function. To do this, make the changes
shown below.

Code:
const unsigned char Risposte[NRichieste][8] =
{
 {0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01},
 {0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02},
 {0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03},
 {0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04},
};

unsigned char tempbuf[8];    // ADD THIS LINE



Code:

while ((trovato == 0) && (j < NRichieste))
   {
    memcpy(tempbuf, Richieste[j], 8);         // ADD THIS LINE   
    if(memcmp(tempbuf, &buffer[1], l1) == 0)  // ADD THIS LINE

// COMMENT OUT THE FOLLOWING LINE:
//  if(memcmp(&Richieste[j][0], &buffer[1],l1) == 0)
       {
 
firefox78



Joined: 25 Jan 2005
Posts: 5

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PostPosted: Sun Jul 29, 2007 1:33 pm     Reply with quote
PCM programmer wrote:
You need to copy the 'const' array elements into a temporary RAM buffer
before you use the memcmp() function. To do this, make the changes
shown below.

Code:
const unsigned char Risposte[NRichieste][8] =
{
 {0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01},
 {0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02},
 {0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03},
 {0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04},
};

unsigned char tempbuf[8];    // ADD THIS LINE



Code:

while ((trovato == 0) && (j < NRichieste))
   {
    memcpy(tempbuf, Richieste[j], 8);         // ADD THIS LINE   
    if(memcmp(tempbuf, &buffer[1], l1) == 0)  // ADD THIS LINE

// COMMENT OUT THE FOLLOWING LINE:
//  if(memcmp(&Richieste[j][0], &buffer[1],l1) == 0)
       {
 


OK Perfect, tankyou very much
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