词典/ LUT在C中的实现

Question

I have 500 frames for which I have stored the length of each frame in an array as the frames are in ascending order.

const char header_length = {23,34, 45, 12, 23,56,......,2,4};

Here frame 1 is of length 23 bytes, frame 2 is of length 34 bytes. Now when I am requested frame with header 4 I would have to reply with frame with header 7, frame with header 8 would require a reply frame with header 60. The co-relation is a constant, header 4 frame will always reply header 7 frame. So I need a look up table sort of implementation here. I plan to implement this using a multidimensional array. Although is there a better way to implement this?

Answer 1

I am answering based on OP's comment above, otherwise OP's question just does not make any sense.

Assuming that the maximum frame size is limited by a considerably small N , then it may be better to just keep another array as the following,

const char header_length[] = {23,34, 45, 12, 23,56,......,2,4};
const int to_be_replied[N+1] = {...,0,...,2,...,0,...,4,...}; /* fill remaining */
/* here are their positions        @12   @23    @34  @45  */ 

and use the following during the reply.

int frame_num, reply_frame_num;
frame_num = get_frame_number(); /* some function */
reply_frame_num = to_be_replied[header_length[frame_num]];