How to access and array of strings

[JasonWB007]

Hi everyone,

Sorry if this is too simple, but I am trying to figure out how to access an array of strings, using an index for the string. I have:

typedef struct
{
PARMTYPE parmtype;
_iq* parmptr;
int num_indices;
const char *(indices[10]);
// const char *indices;
} PARMTAB;

and I want to be able to access an array of strings, such as:

// PD biquad coefficients
#define NUM_PD_COEFF_INDICES COEFFS_PER_BIQUAD*NBIQ*NUM_PID_LOOPS
const char PD_Coeff_Indices[NUM_PD_COEFF_INDICES][MAX_CONTROLPARMINDEXLIST_ITEM_SIZE] =
{
"Speed a2\0", "Speed a1\0", "Speed b2\0", "Speed b1\0", "Speed b0\0",
"Temp a2\0", "Temp a1\0", "Temp b2\0", "Temp b1\0", "Temp b0\0"
};

// Offset all the way into the individual string
// parm_index_ptr = parmtab[parm_index].indices + 10*index;
parm_index_ptr = parmtab[parm_index].indices[index];

The commented ways were the old ones that worked, but I would really like to be able to specify which character array I want by an index, not by a bunch of silly math. Any ideas?

Thanks,

Jason

 

[Salem]

Just watch the position of the parentheses in the member declaration in the struct.

#include <stdio.h>
#include <stdlib.h>

#define NUM_PD_COEFF_INDICES                10
#define MAX_CONTROLPARMINDEXLIST_ITEM_SIZE  10

const char PD_Coeff_Indices[NUM_PD_COEFF_INDICES][MAX_CONTROLPARMINDEXLIST_ITEM_SIZE] =
{
  "Speed a2",   "Speed a1",   "Speed b2",   "Speed b1",   "Speed b0",
  "Temp a2",    "Temp a1",    "Temp b2",    "Temp b1",    "Temp b0"
};

typedef struct
{
  const char        (*indices)[MAX_CONTROLPARMINDEXLIST_ITEM_SIZE];
} PARMTAB;

int main(void)
{
  PARMTAB foo;
  foo.indices = PD_Coeff_Indices;
  printf( "A string = %s\n", foo.indices[5] );    /* temp a2 */
  printf( "A char   = %c\n", foo.indices[5][2] ); /* 'm' of the above string */
  return 0;
}

Use the [tt][ignore]

[/ignore][/tt] tags when posting code.

--

 

[JasonWB007]

OK, I think I am getting closer to figuring this out - thanks! But if I am right, this declares an array of 10 pointers. What I want to do is declare a "pointer to an array of character arrays, each of which is 10 characters (max) long". The idea being I would like to store a single pointer to the array and then use and index to find the string I want, not a pointer to each entry. Is that possible?

Thanks,

Jason

 

[Salem]

> But if I am right, this declares an array of 10 pointers.
No it doesn't.
[tt]char *arr[10]; [/tt]is an array of 10 pointers
[tt]char (*arr)[10]; [/tt]is a pointer to an array of 10 characters
The () are extremely important here.

> The idea being I would like to store a single pointer to the array and then use and index to find the string I want,
> not a pointer to each entry. Is that possible?
Which is EXACTLY what I posted.

Just do sizeof() on the struct and you'll see that there is only one pointer there, not 10 of them.

--

 

[JasonWB007]

OK, thanks. Sorry for the confusion! I do appreciate your replies.

Jason