/*
** $Id: lstate.c,v 2.35 2005/10/06 20:46:25 roberto Exp roberto $
** Global State
** See Copyright Notice in lua.h
*/


#include <stddef.h>

#define lstate_c
#define LUA_CORE

#include "lua.h"

#include "ldebug.h"
#include "ldo.h"
#include "lfunc.h"
#include "lgc.h"
#include "llex.h"
#include "lmem.h"
#include "lstate.h"
#include "lstring.h"
#include "ltable.h"
#include "ltm.h"


#define state_size(x)	(sizeof(x) + LUAI_EXTRASPACE)
#define fromstate(l)	(cast(lu_byte *, (l)) - LUAI_EXTRASPACE)
#define tostate(l)   (cast(lua_State *, cast(lu_byte *, l) + LUAI_EXTRASPACE))


/*
** Main thread combines a thread state and the global state
*/
typedef struct LG {
  lua_State l;
  global_State g;
} LG;
  

// 以L作为操作的发起方，初始化L1的 CallInfo array、虚拟栈
static void stack_init (lua_State *L1, lua_State *L) {
  /* initialize CallInfo array */
  L1->base_ci = luaM_newvector(L, BASIC_CI_SIZE, CallInfo);
  L1->ci = L1->base_ci;
  L1->size_ci = BASIC_CI_SIZE;
  L1->end_ci = L1->base_ci + L1->size_ci - 1;
  /* initialize stack array */
  L1->stack = luaM_newvector(L, BASIC_STACK_SIZE + EXTRA_STACK, TValue);
  L1->stacksize = BASIC_STACK_SIZE + EXTRA_STACK;
  L1->top = L1->stack;
  L1->stack_last = L1->stack+(L1->stacksize - EXTRA_STACK)-1;

  /* initialize first ci */

  // CallInfo array[0].func = 虚拟栈首个槽位的地址
  L1->ci->func = L1->top;

  // CallInfo array[0].func = 虚拟栈首个槽位的地址 = lua nil, top指针上移
  setnilvalue(L1->top++);  /* `function' entry for this `ci' */

  // 此时栈底为nil，top指向自栈底向上的第2个槽位，两段连续赋值，让 CallInfo array[0].base 和 lua_State.base都指向虚拟栈的第2个槽位
  L1->base = L1->ci->base = L1->top;

  // CallInfo array[0].top = 虚拟栈自底向上的第22个槽位
  L1->ci->top = L1->top + LUA_MINSTACK;

  // CallInfo array[0].func = lua nil，且虚拟栈的第一个槽位不会被使用到，它就是永远空着在那，原因和“用一个虚节点作为链表头”类似
  // 当执行某个函数层级时报错，要将异常上抛，我们就不用判断当前是否已经处于最上的函数层级中，有虚节点存在，那么代码实现上就无需多一步判断，直接上抛即可
}

// 回收thread的虚拟栈，和CallInfo数组
static void freestack (lua_State *L, lua_State *L1) {
  luaM_freearray(L, L1->base_ci, L1->size_ci, CallInfo);
  luaM_freearray(L, L1->stack, L1->stacksize, TValue);
}


/*
** open parts that may cause memory-allocation errors
** 执行可能引起内存分配错误的语句（这里通常就是内存不够才会报错啦）
*/
static void f_luaopen (lua_State *L, void *ud) {
  global_State *g = G(L);
  UNUSED(ud);

  stack_init(L, L);  /* init stack */

  // 创建2个lua table，一个作为global全局表(_G)，一个作为global_State的注册表
  sethvalue(L, gt(L), luaH_new(L, 0, 2));  /* table of globals */
  sethvalue(L, registry(L), luaH_new(L, 0, 2));  /* registry */

  // 初始化lua vm内部化字符串所用的hash数组
  luaS_resize(L, MINSTRTABSIZE);  /* initial size of string table */

  // 初始化global_State的tmname, 一组短字符串，TString，元表key值，不会被gc流程collect
  luaT_init(L);
  // 构建一组TString，lua语法中的关键字，不会被gc流程collect
  luaX_init(L);
  // 内部化字符串 MEMERRMSG
  luaS_fix(luaS_newliteral(L, MEMERRMSG));
  // 初始的gc门槛？
  g->GCthreshold = 4*g->totalbytes;
}


static void preinit_state (lua_State *L, global_State *g) {
  G(L) = g;
  L->stack = NULL;
  L->stacksize = 0;
  L->errorJmp = NULL;
  L->hook = NULL;
  L->hookmask = 0;
  L->basehookcount = 0;
  L->allowhook = 1;
  resethookcount(L);
  L->openupval = NULL;
  L->size_ci = 0;
  L->nCcalls = 0;
  L->status = 0;
  L->base_ci = L->ci = NULL;
  L->savedpc = NULL;
  L->errfunc = 0;
  setnilvalue(gt(L));
}


static void close_state (lua_State *L) {
  global_State *g = G(L);
  luaF_close(L, L->stack);  /* close all upvalues for this thread */
  luaC_freeall(L);  /* collect all objects */
  lua_assert(g->rootgc == obj2gco(L));
  lua_assert(g->strt.nuse == 0);
  // 回收掉字符串内部化数组的内存占用
  luaM_freearray(L, G(L)->strt.hash, G(L)->strt.size, TString *);
  // 回收字符串拼接缓冲区
  luaZ_freebuffer(L, &g->buff);

  // 回收mainthread的虚拟栈，和CallInfo数组
  freestack(L, L);
  lua_assert(g->totalbytes == sizeof(LG));
  // 最后回收掉struct mainthread和global_State
  (*g->frealloc)(g->ud, fromstate(L), state_size(LG), 0);
}


lua_State *luaE_newthread (lua_State *L) {
  lua_State *L1 = tostate(luaM_malloc(L, state_size(lua_State)));
  luaC_link(L, obj2gco(L1), LUA_TTHREAD);
  preinit_state(L1, G(L));
  stack_init(L1, L);  /* init stack */
  setobj2n(L, gt(L1), gt(L));  /* share table of globals */
  L1->hookmask = L->hookmask;
  L1->basehookcount = L->basehookcount;
  L1->hook = L->hook;
  resethookcount(L1);
  lua_assert(iswhite(obj2gco(L1)));
  return L1;
}

// 回收1个lua_State（协程）
void luaE_freethread (lua_State *L, lua_State *L1) {
  luaF_close(L1, L1->stack);  /* close all upvalues for this thread */
  lua_assert(L1->openupval == NULL);
  luai_userstatefree(L1);
  // 回收虚拟栈和CallInfo数组
  freestack(L, L1);
  // 回收掉lua_State结构
  luaM_freemem(L, fromstate(L1), state_size(lua_State));
}


LUA_API lua_State *lua_newstate (lua_Alloc f, void *ud) {
  int i;
  lua_State *L; // mainthread
  global_State *g;

  // 申请堆内存来放struct LG实例
  void *l = (*f)(ud, NULL, 0, state_size(LG));
  if (l == NULL) return NULL;
  L = tostate(l); // 内存地址偏移，令L指向LG实例l域的起始地址
  g = &((LG *)L)->g; // LG实例l域的起始地址 = LG实例的起始地址，所以 (LG *)L 的取址写法是ok的

  L->next = NULL;
  L->tt = LUA_TTHREAD;
  g->currentwhite = bit2mask(WHITE0BIT, FIXEDBIT); // 初始currentwhite为WHITE0BIT，0010 0001
  L->marked = luaC_white(g);
  set2bits(L->marked, FIXEDBIT, SFIXEDBIT);
  preinit_state(L, g); // 初始化 mainthread
  g->frealloc = f;
  g->ud = ud;
  g->mainthread = L;
  g->uvhead.u.l.prev = &g->uvhead;
  g->uvhead.u.l.next = &g->uvhead;
  g->GCthreshold = 0;  /* mark it as unfinished state */
  g->strt.size = 0;
  g->strt.nuse = 0;
  g->strt.hash = NULL;
  setnilvalue(registry(L));
  luaZ_initbuffer(L, &g->buff);
  g->panic = NULL;
  g->gcstate = GCSpause; // gc流程的初始状态
  g->rootgc = obj2gco(L); // mainthread被作为gc链表的链表头
  g->sweepstrgc = 0;
  g->sweepgc = &g->rootgc;
  g->gray = NULL;
  g->grayagain = NULL;
  g->weak = NULL;
  g->tmudata = NULL;
  g->totalbytes = sizeof(LG);
  g->gcpause = LUAI_GCPAUSE;
  g->gcstepmul = LUAI_GCMUL;
  g->gcdept = 0;

  for (i=0; i<NUM_TAGS; i++) g->mt[i] = NULL; // 把整个数组置NULL而已

  // 初始，maintread的errorJmp = NULL，在保护模式下执行f_luaopen；luaD_rawrunprotected()返回0表示成功
  if (luaD_rawrunprotected(L, f_luaopen, NULL) != 0) {
    /* memory allocation error: free partial state */
    close_state(L);
    L = NULL;
  }
  else
    luai_userstateopen(L); // 允许用户进行自定义的接口，具体看注释吧，作者说得很清楚了hh

  return L;
}


static void callallgcTM (lua_State *L, void *ud) {
  UNUSED(ud);
  luaC_callGCTM(L);  /* call GC metamethods for all udata */
}


LUA_API void lua_close (lua_State *L) {
  L = G(L)->mainthread;  /* only the main thread can be closed */
  lua_lock(L);
  // 又是upvalues，立个flag在这先
  luaF_close(L, L->stack);  /* close all upvalues for this thread */
  // 所有的full userdata都需要回收了
  luaC_separateudata(L, 1);  /* separate udata that have GC metamethods */
  L->errfunc = 0;  /* no error function during GC metamethods */
  // 以保护模式执行所有__gc元方法，因为__gc元方法执行过程中可能因为报错抛出异常而中断掉callallgcTM的执行，所以在有报错的时候while重试，继续执行
  do {  /* repeat until no more errors */
    L->ci = L->base_ci;
    L->base = L->top = L->ci->base;
    L->nCcalls = 0;
  } while (luaD_rawrunprotected(L, callallgcTM, NULL) != 0);

  lua_assert(G(L)->tmudata == NULL);
  luai_userstateclose(L); // 用户自定行为接口
  close_state(L);
}