how to change part of argument passed to a function in C? - c

Question

I have function
Oled_logo(const unsigned char *image)
so if i pass
unsigned char giphy_0 [] = { 0x80, 0x81, 0x03, 0x07,
0x0f, 0x1f, 0x1f, 0x3f, 0x7f, 0xff, 0 };
e.g. -
Oled_logo(giphy_0);
it works
but i got 14 such images naming giphy_0 ,giphy_1 ... giphy_14
so i want to run these one by one to get an animation
i just want to pass arguments to Oled_logo like Oled_logo(giphy_0) or Oled_log(giphy_1) or Oleg_logo(giphy_2) ,so instead of doing it for 14 times ,i want to call Oled_logo function in loop and change part of argument giphy_imagenumber in loop.
So instead of writing code to call Oled_logo function for 14 times ,i want a loop where i pass giphy_imagenumber to function Oled_logo and this imagenumber is replaced by loop variable ,so i have to write only few lines in a loop.
following i tried
unsigned char x[] = "giphy_0";
volatile unsigned char y ;
while(1)
{
for(int image_gif = 0 ; image_gif<=14;image_gif++)
{
x[6] = image_gif + 0x30;
Oled_logo(x);
ssd1306_UpdateScreen();
HAL_Delay(4000);
}
}
No error came ,but output is some garbage
I tried with strcat ,converted loop variable to string and concatanate with giphy_ and passed to Oled_logo function
Same problem
What i am doing wrong ?

Answer 1

{ 0x80, 0x81, 0x03, 0x07, 0x0f, 0x1f, 0x1f, 0x3f, 0x7f, 0xff, 0 }
is different from
"giphy_0"
What you are trying to achieve seems wrong or you are missing a piece.
My guess is you want an array like { giphy_0, giphy_1, ... } and then use the index in this array.

Answer 2

What you're attempting to do is pass in a string with the name of the variable in question an expecting the program to automatically replace this string with the contents of the variable of that name. That's not how C works.
The real problem here is how you've defined the arrays. Rather than having a set of arrays with names containing the array number:
unsigned char giphy_0 [] = { 0x80, 0x81, 0x03, 0x07, 0x0f, 0x1f, 0x1f, 0x3f, 0x7f, 0xff, 0 };
unsigned char giphy_1 [] = { 0x80, 0x81, 0x03, 0x07, 0x0f, 0x1f, 0x1f, 0x3f, 0x7f, 0xff, 0 };
unsigned char giphy_2 [] = { 0x80, 0x81, 0x03, 0x07, 0x0f, 0x1f, 0x1f, 0x3f, 0x7f, 0xff, 0 };
...
unsigned char giphy_14 [] = { 0x80, 0x81, 0x03, 0x07, 0x0f, 0x1f, 0x1f, 0x3f, 0x7f, 0xff, 0 };
Create an array of arrays:
unsigned char giphy[][11] = {
{ 0x80, 0x81, 0x03, 0x07, 0x0f, 0x1f, 0x1f, 0x3f, 0x7f, 0xff, 0 },
{ 0x80, 0x81, 0x03, 0x07, 0x0f, 0x1f, 0x1f, 0x3f, 0x7f, 0xff, 0 },
{ 0x80, 0x81, 0x03, 0x07, 0x0f, 0x1f, 0x1f, 0x3f, 0x7f, 0xff, 0 },
...
{ 0x80, 0x81, 0x03, 0x07, 0x0f, 0x1f, 0x1f, 0x3f, 0x7f, 0xff, 0 },
};
And pass loop through the outer dimension:
for(int image_gif = 0 ; image_gif<=14; image_gif++)
{
Oled_logo(giphy[image_gif]);
ssd1306_UpdateScreen();
HAL_Delay(4000);
}