Best choice for very simple lookup table - c

Question

I am reading a file with commands that are [a-zA-Z][a-zA-Z0-9], i.e., two chars. There is a total of 43 different commands, and I would like to transform the two chars to a number (1..43).
How would you proceed? I was thinking on creating an array of 43 unsigned shorts (two bytes) each corresponding to the two chars of each command, and then doing something like:
//char1: first char of cmd, char2: second char of cmd, lut: array of 43 shorts.
unsigned short tag;
tag = (char1 << 8) | char2;
for(int i=1;i<=43;i++) {
if(tag==lut[i-1]) return i;
}
return 0;
The thing is I'm not sure if this is the best way for doing what I want. I guess that with just 43 elements it won't matter, but that list might increase in the future.

Answer 1

Here is a method I used on an old project. One big drawback to this method is the lookup table and enum are dependent on each other and need to be kept synchronized. I got this method from an online article quite a few years ago, but don't remember where. This is a complete example:
#include <stdio.h>
#include <string.h>
#define CMDSIZE 2
const char* cmd_table[] = { "qu",
"qr",
"fi",
"he"};
enum { CMD_QUIT,
CMD_QUIT_RESTART,
CMD_FILE,
CMD_HELP,
CMD_NONE };
int lookup(char command[])
{
int i = 0;
int cmdlength = strlen(command);
for (i = 0; i < cmdlength; i++)
{
command[i] = tolower(command[i]);
}
const int valid_cmd = sizeof cmd_table / sizeof *cmd_table;
for (i = 0; i < valid_cmd; i++)
{
if (strcmp(command, cmd_table[i]) == 0)
return i;
}
return CMD_NONE;
}
int main()
{
char key_in[BUFSIZ];
char command[CMDSIZE+1];
// Wait for command
do
{
printf("Enter command: ");
fgets(key_in, BUFSIZ, stdin);
key_in[strlen(key_in)-1] = '\0';
strncpy(command, key_in, CMDSIZE);
command[CMDSIZE] = '\0';
switch (lookup(command))
{
case CMD_QUIT:
printf ("quit\n");
break;
case CMD_QUIT_RESTART:
printf ("quit & restart\n");
break;
case CMD_FILE:
printf ("file\n");
break;
case CMD_HELP:
printf("help\n");
break;
case CMD_NONE:
if(strcmp(key_in, ""))
printf("\"%s\" is not a valid command\n", key_in);
break;
}
} while (strcmp(command, "qu"));
return 0;
}
EDIT:
I found the article I mentioned:
https://www.daniweb.com/software-development/cpp/threads/65343/lookup-tables-how-to-perform-a-switch-using-a-string