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Implementing a basic jump table for dynamic command parsing filter_list
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Implementing a basic jump table for dynamic command parsing #1
So, was in a PM with another member who was complaining about having to have a massive command parser with a shitload of if-strncmp's in it. I gave him this C code to solve that problem and be more clean, maybe you guys will like it as well:

Code:
#define ALLOWED_COMMANDS 2

void helpfunc(void)
{
   printf("help message\n");
}
void clearfunc(void)
{
   // some clear function
}

struct jmp_tbl_s
{
   const char *command;
   void (*handler)(void);
} jump_table[ALLOWED_COMMANDS] =
{
   (struct jmp_tbl_s)
   {
       .command = "help",
       .handler = &helpfunc
   },
   (struct jmp_tbl_s)
   {
       .command = "clear",
       .handler = &clearfunc
   }
};

void processCommand(const char *command)
{
   int i;
   size_t cmdlen;
   const size_t len = strlen(command);
   for (i = 0; i < ALLOWED_COMMANDS; ++i)
   {
       cmdlen = strlen(jump_table[i].command);
       if (!strncpy(jump_table[i].command, command, len > cmdlen ? cmdlen : len))
       {
           *(jump_table[i].handler)();
           break;
       }
   }
}

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RE: Implementing a basic jump table for dynamic command parsing #2
Great code! Easily editable and works great. But what about if the functions needed arguments based on user input?

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RE: Implementing a basic jump table for dynamic command parsing #3
(04-19-2018, 04:17 PM)0xAeschylus Wrote: Great code! Easily editable and works great. But what about if the functions needed arguments based on user input?

There's 2 ways of attacking that:

Option 1 is to pass the c-string of the command to every function called, and then have a va_list on each of the prototypes, allowing each function to read the rest of the arglist (or parse it ahead of time).
Option 2 is to parse out the arglist based on the command inside that if statement and let every function have a different number of args. To do this, simply remove the void from the proto in the struct, and then C won't enforce the argument list checks and you can pass as many or as few as you need.

I'd advise option 2, then add a "group" field to make it easier

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