csystem-verilogsystem-verilog-dpi

How to Pass array from C to SV using SV-DPI?


My objective is to pass an array from C to SV and print the array contents in SV, I have tried the following C program of converting some text file(data_file.txt) (given full source in the link below) to an array and trying to read back the array by using DPI calls in SystemVeilog(SV), in "C" I have passed the array values to my function(mydisplay) which is inside the main func.(please correct me if I am wrong here) also it seems the array values are not read back to the SV environment as I would expect what could be the reason, is there an efficient way to get back the array in SV?

c code:

 void mydisplay(svOpenArrayHandle h) {
  int *a; 
  a =(int*)svGetArrayPtr(h);
  for( i=0;i<idx;i++) {
    io_printf("C: values[%2zu]=0x%02x\n",i,values[i]);
    a[i] = values[i];
    }   
  }   

sv code:

program automatic top; 
   int a[32000];
   import "DPI-C" function void mydisplay(inout int h[]);
   initial begin
      mydisplay(a);
      foreach(a[i]) $display("SV after DPI: a[%0d]=%0d",i,a[i]);
   end 
endprogram

source at EDAplayground


Solution

  • After some trials I've finally found the solution and able to pass the processed text data from C to SV by a small tweak, I just imported a function and called the exported function using already available context method in the SV-DPI as per LRM, also only used the user defined function and removed the main from native "C" lang., this way I was able to read back the values in the array values from C to SV, provided below the code samples, updated code at EDAPlayground

    C code:

    #include <stdio.h>
    #include <stdlib.h> /* for strtol               */
    #include <string.h> /* for strchr               */
    #include <limits.h> /* for INT_MIN/INT_MAX      */
    #include <errno.h>  /* for errno                */
    extern int dV(int r);
    
    #define MAXL 50000
    
    unsigned long xstrtoul (char *p, char **ep, int base);
    
    int mydisplay() 
    {
        int v[15];
        int sd;
        int d;
        FILE *fp = fopen ("data_file.txt", "r");
        char line[MAXL] = {0};
        unsigned values[MAXL] = {0};
        int base = 16;
        size_t i, idx = 0;
    
        if (!fp) { /* validate file open */
            fprintf (stderr, "error: file open failen '%s'.\n", fp);
            return 1;
        }
    
        /* read each line in file (up to MAXL chars per-line) */
        while (fgets (line, MAXL, fp)) {
    
            char *p = line;
            char *ep = p;
            char digits[3] = {0};
            errno = 0;
    
            /* convert each string of digits into number */
            while (errno == 0) {
    
                /* skip any non-digit characters */
                if (!(p = strchr (p, 'x'))) break;
                strncpy (digits, ++p, 2);
                digits[2] = 0;  /* nul-terminate */
    
                /* convert string to number */
                values[idx++] = (unsigned)xstrtoul (digits, &ep, base);
    
                if (errno || idx == MAXL) {   /* check for error */
                    fprintf (stderr, "warning: MAXL values reached.\n");
                    break;
                }
                p += 2;
            }
        }
        if (fp != stdin) fclose (fp);
    
        /* print results */
        for (i = 0; i < idx; i++)
        {
            printf ("C values[%2zu] : 0x%02x\t", i, values[i]);
            v[d]=values[i];
            sd = dV(v[d]);
         }
    return(sd);
    }
    
    /** string to unsigned long with error checking */
    unsigned long xstrtoul (char *p, char **ep, int base)
    {
        errno = 0;
    
        unsigned long tmp = strtoul (p, ep, base);
    
        /* Check for various possible errors */
        if ((errno == ERANGE && (tmp == ULONG_MAX)) ||
            (errno != 0 && tmp == 0)) {
            perror ("strtoul");
            exit (EXIT_FAILURE);
        }
    
        if (*ep == p) {
            fprintf (stderr, "No digits were found\n");
            exit (EXIT_FAILURE);
        }
    
        return tmp;
    }
    

    SV code:

    program automatic top();
    int res;
    
    import "DPI" context mydisplay= function int mD();
    export "DPI" dV =function mydisplay;
    
    function int mydisplay(input int xyz);
      $display ("SV after DPI: %0d\n",xyz);
      return -1;
    endfunction
    
    initial begin
      #5 res=mD();
      $display("Finished reading values...\n");
    end
    
    endprogram