C: Pointers to array of struct in function

Question

I want to create a function that will enable or disable the some parts of the functions with conditions. I have created a struct that contains 4 members (enum types, uint8 catNumber, char Name, bool flag).

typedef struct MYSTRUCT
{
 enum modes;
 uint8 catNumber;
 char name;
 bool flag;
 }mystruct;

Enum contains:

typedef emum MODES {mode1, mode2, mode3}modes;

So after creating a struct template, I have declare a array variable of struct type. i.e. Struct mystruct variable[3]. And I have initialized the each member of mystruct.

mystruct  Variable[3] = 
{
[0] ={.modes=mode1,
.catNumber=1,.name = “catA”,
.flag=false},

[1] = {.modes =mode2,
.catNumber=2,.name = “catB”,
.flag=false},

[2] = {.modes =mode3,
.catNumber=3,.name = “catC”,
.flag=false},
};

So the user has to enter the category number and the true/false Flag to enable or disable the part of the function i.e different categories from struct and with each corresponding mode print a mode name to check it is enable. So the task is the user can enable one or more than one category. For eg . User enters: 1 2 true. Which enables the both categories 1 and 2.

Could anyone guide me how do I do this task? And is it possible not to pass the whole struct data type as an func argument. I just want to declare pointers as an argument to point struct array elements in main().

user5329483 · Accepted Answer · 2019-10-23 18:13:40Z

1

There are basically two ways to send a variable length array from one function to another. One variant is to provide the array (basically a pointer to its first element) and the number of elements. The other option is to define a special terminating element. Just like strings in C - they are terminated with a special character with the code 0. Here my code, based on your code and some corrections.

#include <stdio.h>
#include <stdint.h>

typedef enum MODES {mode1, mode2, mode3, modeTerminus} modes;

typedef struct MYSTRUCT
{
    enum MODES modes;
    int8_t catNumber;
    const char * name; //As we intend to store a string here, a simple 'char name' is insufficient
    bool flag;
} mystruct;

mystruct Variable[] =
{
    [0] ={
        .modes=mode1,
        .catNumber=1,.name = "catA",
        .flag=false
    },

    [1] = {
        .modes =mode2,
        .catNumber=2,.name = "catB",
        .flag=false
    },

    [2] = {
        .modes =mode3,
        .catNumber=3,.name = "catC",
        .flag=false
    },
    [3] = {
        .modes =modeTerminus
    },
};
void theDataProcessor1(mystruct* theList)
{
   for (const mystruct* theItem=theList; theItem->modes!=modeTerminus; theItem++)
      printf("theDataProcessor1: modes=%d catNumber=%d name=%s flag=%d\n",
              theItem->modes,
              theItem->catNumber,
              theItem->name,
              theItem->flag
            );
}
void theDataProcessor2(mystruct* theList, int Count)
{
    for (int i=0; i<Count; i++)
      printf("theDataProcessor2: modes=%d catNumber=%d name=%s flag=%d\n",
              theList[i].modes,
              theList[i].catNumber,
              theList[i].name,
              theList[i].flag
            );
}
int main()
{
    theDataProcessor1(Variable);
    theDataProcessor2(Variable, 3);
    return 0;
}

answered Oct 23, 2019 at 18:13

user5329483

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2 Comments

Yasir Ali Over a year ago

Is it possible to indirectly access each elements of struct array with pointers without declaring it as struct type?

user5329483 Over a year ago

I don't understand why you want to avoid a struct. In your OP you write that the user provides a category and a boolean flag for that category. Why not glue them together and pack them in a struct?

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