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