/*
** $Id: lgc.h,v 2.15.1.1 2007/12/27 13:02:25 roberto Exp $
** Garbage Collector
** See Copyright Notice in lua.h
*/

#ifndef lgc_h
#define lgc_h


#include "lobject.h"


/*
** Possible states of the Garbage Collector
*/
#define GCSpause    0
#define GCSpropagate    1
#define GCSsweepstring  2
#define GCSsweep    3
#define GCSfinalize 4


/*
** some userful bit tricks
*/
#define resetbits(x,m)  ((x) &= cast(lu_byte, ~(m)))
#define setbits(x,m)    ((x) |= (m))
#define testbits(x,m)   ((x) & (m))
#define bitmask(b)  (1<<(b))
#define bit2mask(b1,b2) (bitmask(b1) | bitmask(b2))
#define l_setbit(x,b)   setbits(x, bitmask(b))
#define resetbit(x,b)   resetbits(x, bitmask(b))
#define testbit(x,b)    testbits(x, bitmask(b))
#define set2bits(x,b1,b2)   setbits(x, (bit2mask(b1, b2)))
#define reset2bits(x,b1,b2) resetbits(x, (bit2mask(b1, b2)))
#define test2bits(x,b1,b2)  testbits(x, (bit2mask(b1, b2)))



/*
** Layout for bit use in `marked' field:
** bit 0 - object is white (type 0)
** bit 1 - object is white (type 1)
** bit 2 - object is black
** bit 3 - for userdata: has been finalized
** bit 3 - for tables: has weak keys
** bit 4 - for tables: has weak values
** bit 5 - object is fixed (should not be collected)
** bit 6 - object is "super" fixed (only the main thread)
*/


#define WHITE0BIT   0
#define WHITE1BIT   1
#define BLACKBIT    2
#define FINALIZEDBIT    3
#define KEYWEAKBIT  3
#define VALUEWEAKBIT    4
#define FIXEDBIT    5
#define SFIXEDBIT   6
#define WHITEBITS   bit2mask(WHITE0BIT, WHITE1BIT)


#define iswhite(x)      test2bits((x)->gch.marked, WHITE0BIT, WHITE1BIT)
#define isblack(x)      testbit((x)->gch.marked, BLACKBIT)
#define isgray(x)   (!isblack(x) && !iswhite(x))

#define otherwhite(g)   (g->currentwhite ^ WHITEBITS)
#define isdead(g,v) ((v)->gch.marked & otherwhite(g) & WHITEBITS)

#define changewhite(x)  ((x)->gch.marked ^= WHITEBITS)
#define gray2black(x)   l_setbit((x)->gch.marked, BLACKBIT)

#define valiswhite(x)   (iscollectable(x) && iswhite(gcvalue(x)))

#define luaC_white(g)   cast(lu_byte, (g)->currentwhite & WHITEBITS)


#define luaC_checkGC(L) { \
        condhardstacktests(luaD_reallocstack(L, L->stacksize - EXTRA_STACK - 1)); \
        if (G(L)->totalbytes >= G(L)->GCthreshold) \
            luaC_step(L); }


#define luaC_barrier(L,p,v) { if (valiswhite(v) && isblack(obj2gco(p)))  \
            luaC_barrierf(L,obj2gco(p),gcvalue(v)); }

#define luaC_barriert(L,t,v) { if (valiswhite(v) && isblack(obj2gco(t)))  \
            luaC_barrierback(L,t); }

#define luaC_objbarrier(L,p,o)  \
    { if (iswhite(obj2gco(o)) && isblack(obj2gco(p))) \
            luaC_barrierf(L,obj2gco(p),obj2gco(o)); }

#define luaC_objbarriert(L,t,o)  \
    { if (iswhite(obj2gco(o)) && isblack(obj2gco(t))) luaC_barrierback(L,t); }

LUAI_FUNC size_t luaC_separateudata (lua_State* L, int all);
LUAI_FUNC void luaC_callGCTM (lua_State* L);
LUAI_FUNC void luaC_freeall (lua_State* L);
LUAI_FUNC void luaC_step (lua_State* L);
LUAI_FUNC void luaC_fullgc (lua_State* L);
LUAI_FUNC void luaC_link (lua_State* L, GCObject* o, lu_byte tt);
LUAI_FUNC void luaC_linkupval (lua_State* L, UpVal* uv);
LUAI_FUNC void luaC_barrierf (lua_State* L, GCObject* o, GCObject* v);
LUAI_FUNC void luaC_barrierback (lua_State* L, Table* t);


#endif
