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