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      1 /*	$NetBSD: lapi.h,v 1.11 2023/06/08 21:12:08 nikita Exp $	*/
      2 
      3 /*
      4 ** Id: lapi.h
      5 ** Auxiliary functions from Lua API
      6 ** See Copyright Notice in lua.h
      7 */
      8 
      9 #ifndef lapi_h
     10 #define lapi_h
     11 
     12 
     13 #include "llimits.h"
     14 #include "lstate.h"
     15 
     16 
     17 /* Increments 'L->top.p', checking for stack overflows */
     18 #define api_incr_top(L)	{L->top.p++; \
     19 			 api_check(L, L->top.p <= L->ci->top.p, \
     20 					"stack overflow");}
     21 
     22 
     23 /*
     24 ** If a call returns too many multiple returns, the callee may not have
     25 ** stack space to accommodate all results. In this case, this macro
     26 ** increases its stack space ('L->ci->top.p').
     27 */
     28 #define adjustresults(L,nres) \
     29     { if ((nres) <= LUA_MULTRET && L->ci->top.p < L->top.p) \
     30 	L->ci->top.p = L->top.p; }
     31 
     32 
     33 /* Ensure the stack has at least 'n' elements */
     34 #define api_checknelems(L,n) \
     35 	api_check(L, (n) < (L->top.p - L->ci->func.p), \
     36 			  "not enough elements in the stack")
     37 
     38 
     39 /*
     40 ** To reduce the overhead of returning from C functions, the presence of
     41 ** to-be-closed variables in these functions is coded in the CallInfo's
     42 ** field 'nresults', in a way that functions with no to-be-closed variables
     43 ** with zero, one, or "all" wanted results have no overhead. Functions
     44 ** with other number of wanted results, as well as functions with
     45 ** variables to be closed, have an extra check.
     46 */
     47 
     48 #define hastocloseCfunc(n)	((n) < LUA_MULTRET)
     49 
     50 /* Map [-1, inf) (range of 'nresults') into (-inf, -2] */
     51 #define codeNresults(n)		(-(n) - 3)
     52 #define decodeNresults(n)	(-(n) - 3)
     53 
     54 #endif
     55