hook.c

   1 /*
   2 Copyright (C) 2020 Cloudwalk
   3
   4 This program is free software; you can redistribute it and/or
   5 modify it under the terms of the GNU General Public License
   6 as published by the Free Software Foundation; either version 2
   7 of the License, or (at your option) any later version.
   8
   9 This program is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  12
  13 See the GNU General Public License for more details.
  14
  15 You should have received a copy of the GNU General Public License
  16 along with this program; if not, write to the Free Software
  17 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  18
  19 */
  20
  21 #include "quakedef.h"
  22 #include "hook.h"
  23
  24 mempool_t *hooks;
  25
  26 hook_t *_Hook_Register(hook_t *hook, const char *name, void *func, unsigned int argc)
  27 {
  28         if (hook) {
  29                 Con_Printf("Hook %s already registered\n",hook->name);
  30         } else {
  31                 hook = (hook_t *)Mem_Alloc(hooks, sizeof(hook_t));
  32                 hook->name = Mem_Alloc(hooks, strlen(name) + 1);
  33                 hook->arg = Mem_Alloc(hooks, sizeof(hook_val_t) * argc);
  34
  35                 memcpy(hook->name, name, strlen(name) + 1);
  36                 hook->func = func;
  37                 hook->argc = argc;
  38         }
  39         return hook;
  40 }
  41
  42 // Needs NULL pad to know when va_list ends.
  43 hook_val_t *_Hook_Call(hook_t *hook, ... )
  44 {
  45         uintptr_t arg_ptr; // Align to platform size
  46         va_list arg_list;
  47         unsigned int i = 0;
  48
  49         if(!hook)
  50                 return (hook_val_t *)NULL;
  51
  52         va_start(arg_list, hook);
  53
  54         arg_ptr = va_arg(arg_list,intptr_t);
  55
  56         if((void *)arg_ptr && !hook->argc)
  57                 goto overflow;
  58
  59         // Loop until we encounter that NULL pad, but stop if we overflow.
  60         while ((void *)arg_ptr != NULL && i != hook->argc)
  61         {
  62                 if (i > hook->argc)
  63                         goto overflow;
  64                 hook->arg[i].val = arg_ptr;
  65                 arg_ptr = va_arg(arg_list,intptr_t);
  66                 i++;
  67         }
  68
  69         va_end(arg_list);
  70
  71         // Should be fairly obvious why it's bad if args don't match
  72         if(i != hook->argc)
  73                 goto underflow;
  74         // Call it
  75         hook->ret.uval = (uintptr_t)hook->func(hook->arg);
  76
  77         if (hook->ret.val)
  78                 return &hook->ret;
  79         return (hook_val_t *)NULL;
  80
  81 underflow:
  82         Sys_Error("Hook_Call: Attempt to call hook '%s' with incorrect number of arguments. Got %i, expected %i\n", hook->name, i, hook->argc);
  83 overflow:
  84         Sys_Error("Hook_Call: Stack overflow calling hook '%s' (argc = %u)\n", hook->name, hook->argc);
  85
  86 }
  87
  88 void Hook_Init(void)
  89 {
  90         hooks = Mem_AllocPool("hooks",0,NULL);
  91         return;
  92 }