Parsing Animation Metadata

Animation metadata includes an SDL_Rect array used to identify frame coordinates in the sprite texture.

I decided to replace the manual definition of the array values with a file in the following format:

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x1,y1,w1,h1
x2,y2,w2,h2
...
xn,yn,wn,hn

Where:

• x, y, w, and h are the input values of an SDL_Rect, known as the source rectangle in SDL_RenderCopy.
• Each row represents a single animation frame.

Reading Files

I was able to read the contents of a file using the SDL_LoadFile function.

Parsing the Animation File Content

Parsing the animation data was more challenging than expected.

There isn’t a straightforward way to split a string in C. I found an approach using strtok on Stack Overflow, but I ended up implementing a simpler parsing algorithm that doesn’t require splitting a string.

The simpler algorithm iterates over the characters in the file content, populating a smaller array with a fixed number of characters (max length of 6, supporting the representation of positive integers up to 99999) with digits until a , or \n character is encountered. It then creates the new SDL_Rect value when a \n character is encountered.

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static bool load_animation_data(AnimationData *animation, const char *path) {
  size_t size;
  char *data = SDL_LoadFile(path, &size);
  if (data == NULL) {
    fprintf(stderr, "Failed to load data!\n");
    return false;
  }

  // Supports integers up to 99999
  char num[6], c;
  int rect[4], row = 0, num_i = 0, rect_i = 0;
  for (int i = 0; i < size; i++) {
    c = data[i];
    if (c == ',' || c == '\n') {
      num[num_i] = '\0';
      rect[rect_i++] = atoi(num);
      num_i = 0;
      if (c == '\n') {
        animation->sprite_clips[row++] = (SDL_Rect){
            .x = rect[0],
            .y = rect[1],
            .w = rect[2],
            .h = rect[3],
        };
        rect_i = 0;
      }
    } else {
      num[num_i++] = c;
    }
  }

  SDL_free(data);
  return true;
}