结构c中的多维数组

Question

I've been trying this for a long time. Everything seems to work but i get a lot of warnings and just want to program it properly. The problem is the following: I'm making a game engine. I provide images in 3d arrays, where the first two indices are the position and the third is the colour. So a simple 4x4 image would be:

static const uint8_t font_image[2][2][3] = 
{
    {{255,255,255},{255,255,255}},
    {{255,255,255},{255,255,255}}
};

Now every entity struct has a sprite struct. All i want is to have a reference to the 3 dimensional array in the struct.

struct Sprite {
    uint32_t sizeX;
    uint32_t sizeY;
    uint8_t * data;
};

Every image can his its own width and height, so i can't make it

uint8_t [2][2][3] data;

I keep getting this warning:

Message 3 expected 'const uint8_t *' but argument is of type 'const uint8_t (*)[10][4][3]' C:\\Users\\Elmar\\Documents\\GitHub\\EVA-OS\\EVA-OS\\Libs\\Game\\sprite.h 28 10 EVA-OS

where this is the function to make a new sprite:

Sprite * sprite_new(uint32_t width, uint32_t height, const uint8_t * image)
{
    Sprite * sprite = malloc(sizeof(Sprite));
    sprite->data = image;
    sprite->sizeX = width;
    sprite->sizeY = height;
    return sprite;
}

Thanks in advance! :)

Answer 1

From your error message, it sounds like you're doing this somewhere else in your code:

uint8_t image[10][4][3] = { ... whatever ... };

Sprite *sprite = sprite_new(10, 4, image);

The problem with that is that the compiler considers the data type of image to be const uint8_t (*)[10][4][3] , not uint8_t * . You can make it work with a cast:

Sprite *sprite = sprite_new(10, 4, (uint8_t *)image);

As for how you declare your Sprite struct, user2357112 is correct. There's really no easy way to declare variable length arrays and pass them into functions in C with their size information preserved. C is kind of dumb in that regard. You always need to pass the size information as one or more separate parameters.

Answer 2

Before

sprite->data = image;

are you allocating space for the data?

I would assume you would have to allocate space for struct Sprite but that will only contain space for a pointer. Then you will need to allocate space for a regoin and have data point to it. Finallly, you can memcopy stuff in that space ...

Sprite * sprite = malloc(sizeof(Sprite));
sprite -> data  = malloc( width*length*sizeof(uint8_t)   );
memcopy( ...