/*
** State and stack handling.
** Copyright (C) 2005-2010 Mike Pall. See Copyright Notice in luajit.h
**
** Portions taken verbatim or adapted from the Lua interpreter.
** Copyright (C) 1994-2008 Lua.org, PUC-Rio. See Copyright Notice in lua.h
*/

#define lj_state_c
#define LUA_CORE

#include "lj_obj.h"
#include "lj_gc.h"
#include "lj_err.h"
#include "lj_str.h"
#include "lj_tab.h"
#include "lj_func.h"
#include "lj_meta.h"
#include "lj_state.h"
#include "lj_frame.h"
#include "lj_trace.h"
#include "lj_dispatch.h"
#include "lj_vm.h"
#include "lj_lex.h"
#include "lj_alloc.h"

/* -- Stack handling ------------------------------------------------------ */

/* Stack sizes. */
#define LJ_STACK_MIN	LUA_MINSTACK	/* Min. stack size. */
#define LJ_STACK_MAX	LUAI_MAXSTACK	/* Max. stack size. */
#define LJ_STACK_START	(2*LJ_STACK_MIN)	/* Starting stack size. */
#define LJ_STACK_MAXEX	(LJ_STACK_MAX + 1 + LJ_STACK_EXTRA)

/* Explanation of LJ_STACK_EXTRA:
**
** Calls to metamethods store their arguments beyond the current top
** without checking for the stack limit. This avoids stack resizes which
** would invalidate passed TValue pointers. The stack check is performed
** later by the call gate. This can safely resize the stack or raise an
** error. Thus we need some extra slots beyond the current stack limit.
**
** Most metamethods need 4 slots above top (cont, mobj, arg1, arg2) plus
** one extra slot if mobj is not a function. Only lj_meta_tset needs 5
** slots above top, but then mobj is always a function. So we can get by
** with 5 extra slots.
*/

/* Resize stack slots and adjust pointers in state. */
static void resizestack(lua_State *L, MSize n)
{
  TValue *oldst = L->stack;
  ptrdiff_t delta;
  MSize realsize = n + 1 + LJ_STACK_EXTRA;
  GCobj *up;
  lua_assert((MSize)(L->maxstack-L->stack) == L->stacksize-LJ_STACK_EXTRA-1);
  lj_mem_reallocvec(L, L->stack, L->stacksize, realsize, TValue);
  delta = (char *)L->stack - (char *)oldst;
  L->maxstack = L->stack + n;
  L->stacksize = realsize;
  L->base = (TValue *)((char *)L->base + delta);
  L->top = (TValue *)((char *)L->top + delta);
  for (up = gcref(L->openupval); up != NULL; up = gcnext(up))
    setmref(gco2uv(up)->v, (TValue *)((char *)uvval(gco2uv(up)) + delta));
  if (obj2gco(L) == gcref(G(L)->jit_L))
    setmref(G(L)->jit_base, mref(G(L)->jit_base, char) + delta);
}

/* Relimit stack after error, in case the limit was overdrawn. */
void lj_state_relimitstack(lua_State *L)
{
  if (L->stacksize > LJ_STACK_MAXEX && L->top - L->stack < LJ_STACK_MAX-1)
    resizestack(L, LJ_STACK_MAX);
}

/* Try to shrink the stack (called from GC). */
void lj_state_shrinkstack(lua_State *L, MSize used)
{
  if (L->stacksize > LJ_STACK_MAXEX)
    return;  /* Avoid stack shrinking while handling stack overflow. */
  if (4*used < L->stacksize &&
      2*(LJ_STACK_START+LJ_STACK_EXTRA) < L->stacksize &&
      obj2gco(L) != gcref(G(L)->jit_L))  /* Don't shrink stack of live trace. */
    resizestack(L, L->stacksize >> 1);
}

/* Try to grow stack. */
void LJ_FASTCALL lj_state_growstack(lua_State *L, MSize need)
{
  if (L->stacksize > LJ_STACK_MAXEX)  /* overflow while handling overflow? */
    lj_err_throw(L, LUA_ERRERR);
  resizestack(L, L->stacksize + (need > L->stacksize ? need : L->stacksize));
  if (L->stacksize > LJ_STACK_MAXEX) {
    if (curr_funcisL(L)) {  /* Clear slots of incomplete Lua frame. */
      TValue *top = curr_topL(L);
      while (--top >= L->top) setnilV(top);
    }
    lj_err_msg(L, LJ_ERR_STKOV);  /* ... to allow L->top = curr_topL(L). */
  }
}

void LJ_FASTCALL lj_state_growstack1(lua_State *L)
{
  lj_state_growstack(L, 1);
}

/* Allocate basic stack for new state. */
static void stack_init(lua_State *L1, lua_State *L)
{
  L1->stack = lj_mem_newvec(L, LJ_STACK_START + LJ_STACK_EXTRA, TValue);
  L1->stacksize = LJ_STACK_START + LJ_STACK_EXTRA;
  L1->top = L1->stack;
  L1->maxstack = L1->stack+(L1->stacksize - LJ_STACK_EXTRA)-1;
  setthreadV(L1, L1->top, L1);  /* needed for curr_funcisL() on empty stack */
  setnilV(L1->top);  /* but clear its type */
  L1->base = ++L1->top;
}

/* -- State handling ------------------------------------------------------ */

/* Open parts that may cause memory-allocation errors. */
static TValue *cpluaopen(lua_State *L, lua_CFunction dummy, void *ud)
{
  global_State *g = G(L);
  UNUSED(dummy);
  UNUSED(ud);
  stack_init(L, L);
  /* NOBARRIER: State initialization, all objects are white. */
  setgcref(L->env, obj2gco(lj_tab_new(L, 0, LJ_MIN_GLOBAL)));
  settabV(L, registry(L), lj_tab_new(L, 0, LJ_MIN_REGISTRY));
  lj_str_resize(L, LJ_MIN_STRTAB-1);
  lj_meta_init(L);
  lj_lex_init(L);
  fixstring(lj_err_str(L, LJ_ERR_ERRMEM));  /* Preallocate memory error msg. */
  g->gc.threshold = 4*g->gc.total;
  return NULL;
}

static void close_state(lua_State *L)
{
  global_State *g = G(L);
#ifndef LUAJIT_USE_SYSMALLOC
  if (g->allocf == lj_alloc_f) {
    lj_alloc_destroy(g->allocd);
  } else
#endif
  {
    lj_func_closeuv(L, L->stack);
    lj_gc_freeall(g);
    lua_assert(gcref(g->gc.root) == obj2gco(L));
    lua_assert(g->strnum == 0);
    lj_trace_freestate(g);
    lj_mem_freevec(g, g->strhash, g->strmask+1, GCRef);
    lj_str_freebuf(g, &g->tmpbuf);
    lj_mem_freevec(g, L->stack, L->stacksize, TValue);
    lua_assert(g->gc.total == sizeof(GG_State));
    g->allocf(g->allocd, G2GG(g), sizeof(GG_State), 0);
  }
}

LUA_API lua_State *lua_newstate(lua_Alloc f, void *ud)
{
  GG_State *GG = cast(GG_State *, f(ud, NULL, 0, sizeof(GG_State)));
  lua_State *L = &GG->L;
  global_State *g = &GG->g;
  if (GG == NULL || !checkptr32(GG)) return NULL;
  memset(GG, 0, sizeof(GG_State));
  L->gct = ~LJ_TTHREAD;
  L->marked = LJ_GC_WHITE0 | LJ_GC_FIXED | LJ_GC_SFIXED;  /* Prevent free. */
  L->dummy_ffid = FF_C;
  setmref(L->glref, g);
  g->gc.currentwhite = LJ_GC_WHITE0 | LJ_GC_FIXED;
  g->allocf = f;
  g->allocd = ud;
  setgcref(g->mainthref, obj2gco(L));
  setgcref(g->uvhead.prev, obj2gco(&g->uvhead));
  setgcref(g->uvhead.next, obj2gco(&g->uvhead));
  g->strmask = ~(MSize)0;
  setnilV(registry(L));
  setnilV(&g->nilnode.val);
  setnilV(&g->nilnode.key);
  lj_str_initbuf(L, &g->tmpbuf);
  g->gc.state = GCSpause;
  setgcref(g->gc.root, obj2gco(L));
  g->gc.sweep = &g->gc.root;
  g->gc.total = sizeof(GG_State);
  g->gc.pause = LUAI_GCPAUSE;
  g->gc.stepmul = LUAI_GCMUL;
  lj_dispatch_init((GG_State *)L);
  L->status = LUA_ERRERR+1;  /* Avoid touching the stack upon memory error. */
  if (lj_vm_cpcall(L, NULL, NULL, cpluaopen) != 0) {
    /* Memory allocation error: free partial state. */
    close_state(L);
    return NULL;
  }
  L->status = 0;
  return L;
}

static TValue *cpfinalize(lua_State *L, lua_CFunction dummy, void *ud)
{
  UNUSED(dummy);
  UNUSED(ud);
  lj_gc_finalizeudata(L);
  /* Frame pop omitted. */
  return NULL;
}

LUA_API void lua_close(lua_State *L)
{
  global_State *g = G(L);
  L = mainthread(g);  /* Only the main thread can be closed. */
  lj_func_closeuv(L, L->stack);
  lj_gc_separateudata(g, 1);  /* Separate udata which have GC metamethods. */
#if LJ_HASJIT
  G2J(g)->flags &= ~JIT_F_ON;
  G2J(g)->state = LJ_TRACE_IDLE;
  lj_dispatch_update(g);
#endif
  do {
    hook_enter(g);
    L->status = 0;
    L->cframe = NULL;
    L->base = L->top = L->stack + 1;
  } while (lj_vm_cpcall(L, NULL, NULL, cpfinalize) != 0);
  close_state(L);
}

lua_State *lj_state_new(lua_State *L)
{
  lua_State *L1 = lj_mem_newobj(L, lua_State);
  L1->gct = ~LJ_TTHREAD;
  L1->dummy_ffid = FF_C;
  L1->status = 0;
  L1->stacksize = 0;
  L1->stack = NULL;
  L1->cframe = NULL;
  /* NOBARRIER: The lua_State is new (marked white). */
  setgcrefnull(L1->openupval);
  setmrefr(L1->glref, L->glref);
  setgcrefr(L1->env, L->env);
  stack_init(L1, L);  /* init stack */
  lua_assert(iswhite(obj2gco(L1)));
  return L1;
}

void LJ_FASTCALL lj_state_free(global_State *g, lua_State *L)
{
  lua_assert(L != mainthread(g));
  lj_func_closeuv(L, L->stack);
  lua_assert(gcref(L->openupval) == NULL);
  lj_mem_freevec(g, L->stack, L->stacksize, TValue);
  lj_mem_freet(g, L);
}