lstate.c

/*
** $Id: lstate.c,v 2.133.1.1 2017/04/19 17:39:34 roberto Exp $
** Global State
** 全局状态机 管理全局信息
** See Copyright Notice in lua.h
*/

#define lstate_c
#define LUA_CORE

#include "lprefix.h"


#include <stddef.h>
#include <string.h>

#include "lua.h"

#include "lapi.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"


#if !defined(LUAI_GCPAUSE)
#define LUAI_GCPAUSE	200  /* 200% */
#endif

#if !defined(LUAI_GCMUL)
#define LUAI_GCMUL	200 /* GC runs 'twice the speed' of memory allocation */
#endif


/*
** a macro to help the creation of a unique random seed when a state is
** created; the seed is used to randomize hashes.
*/
#if !defined(luai_makeseed)
#include <time.h>
#define luai_makeseed()		cast(unsigned int, time(NULL))
#endif



/*
** thread state + extra space
*/
typedef struct LX {
  lu_byte extra_[LUA_EXTRASPACE];
  lua_State l;
} LX;


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



#define fromstate(L)	(cast(LX *, cast(lu_byte *, (L)) - offsetof(LX, l)))


/*
** Compute an initial seed as random as possible. Rely on Address Space
** Layout Randomization (if present) to increase randomness..
*/
#define addbuff(b,p,e) \
  { size_t t = cast(size_t, e); \
    memcpy(b + p, &t, sizeof(t)); p += sizeof(t); }

static unsigned int makeseed (lua_State *L) {
  char buff[4 * sizeof(size_t)];
  unsigned int h = luai_makeseed();
  int p = 0;
  addbuff(buff, p, L);  /* heap variable */
  addbuff(buff, p, &h);  /* local variable */
  addbuff(buff, p, luaO_nilobject);  /* global variable */
  addbuff(buff, p, &lua_newstate);  /* public function */
  lua_assert(p == sizeof(buff));
  return luaS_hash(buff, p, h);
}


/*
** set GCdebt to a new value keeping the value (totalbytes + GCdebt)
** invariant (and avoiding underflows in 'totalbytes')
*/
void luaE_setdebt (global_State *g, l_mem debt) {
  l_mem tb = gettotalbytes(g);
  lua_assert(tb > 0);
  if (debt < tb - MAX_LMEM)
    debt = tb - MAX_LMEM;  /* will make 'totalbytes == MAX_LMEM' */
  g->totalbytes = tb - debt;
  g->GCdebt = debt;
}


CallInfo *luaE_extendCI (lua_State *L) {
  CallInfo *ci = luaM_new(L, CallInfo);
  lua_assert(L->ci->next == NULL);
  L->ci->next = ci;
  ci->previous = L->ci;
  ci->next = NULL;
  L->nci++;
  return ci;
}


/*
** free all CallInfo structures not in use by a thread
*/
void luaE_freeCI (lua_State *L) {
  CallInfo *ci = L->ci;
  CallInfo *next = ci->next;
  ci->next = NULL;
  while ((ci = next) != NULL) {
    next = ci->next;
    luaM_free(L, ci);
    L->nci--;
  }
}


/*
** free half of the CallInfo structures not in use by a thread
*/
void luaE_shrinkCI (lua_State *L) {
  CallInfo *ci = L->ci;
  CallInfo *next2;  /* next's next */
  /* while there are two nexts */
  while (ci->next != NULL && (next2 = ci->next->next) != NULL) {
    luaM_free(L, ci->next);  /* free next */
    L->nci--;
    ci->next = next2;  /* remove 'next' from the list */
    next2->previous = ci;
    ci = next2;  /* keep next's next */
  }
}


/*
** 初始化栈(分为数据栈和调用栈)
*/
static void stack_init (lua_State *L1, lua_State *L) {
  int i; CallInfo *ci;
  /* initialize stack array - 默认分配一个大小为40的栈 */
  L1->stack = luaM_newvector(L, BASIC_STACK_SIZE, TValue);
  L1->stacksize = BASIC_STACK_SIZE;
  for (i = 0; i < BASIC_STACK_SIZE; i++)
    setnilvalue(L1->stack + i);  /* erase new stack */
  L1->top = L1->stack;
  /* 留空EXTRA_STACK=5个作为空闲buf,用于元表调用或错误处理的栈操作,
     也就是说这些空闲buf可以让某些操作不用考虑栈空间是否足够 */
  L1->stack_last = L1->stack + L1->stacksize - EXTRA_STACK;
  /* initialize first ci */
  ci = &L1->base_ci;
  ci->next = ci->previous = NULL;
  ci->callstatus = 0;
  ci->func = L1->top;  /* 指向当前栈顶 */
  setnilvalue(L1->top++);  /* 'function' entry for this 'ci' */
  ci->top = L1->top + LUA_MINSTACK; /* 指向当前栈顶 + LUA_MINSTACK=20的位置 */
  L1->ci = ci;
}


/*
** 释放栈结构内存
*/
static void freestack (lua_State *L) {
  if (L->stack == NULL)
    return;  /* stack not completely built yet */
  L->ci = &L->base_ci;  /* free the entire 'ci' list */
  luaE_freeCI(L);
  lua_assert(L->nci == 0);
  luaM_freearray(L, L->stack, L->stacksize);  /* free stack array */
}


/*
** 注册表G->l_registry,是在主线程栈创建的时候进行初始化的
** 初始化第一步,创建一个Table类型的表,并将表赋值到G->l_registry
** 然后默认初始化LUA_RIDX_MAINTHREAD(主线程索引)和LUA_RIDX_GLOBALS(全局环境变量)
*/


/*
** Create registry table and its predefined values
** 创建一个注册表,并且定义默认值
*/
static void init_registry (lua_State *L, global_State *g) {
  TValue temp;
  /* create registry */
  Table *registry = luaH_new(L);  /* 创建一个Table */
  sethvalue(L, &g->l_registry, registry);
  luaH_resize(L, registry, LUA_RIDX_LAST, 0);
  /* registry[LUA_RIDX_MAINTHREAD] = L */
  setthvalue(L, &temp, L);  /* temp = L */
  luaH_setint(L, registry, LUA_RIDX_MAINTHREAD, &temp);
  /* registry[LUA_RIDX_GLOBALS] = table of globals */
  sethvalue(L, &temp, luaH_new(L));  /* temp = new table (global table) */
  luaH_setint(L, registry, LUA_RIDX_GLOBALS, &temp);
}


/*
** open parts of the state that may cause memory-allocation errors.
** ('g->version' != NULL flags that the state was completely build)
** 启动Lua程序
** 初始化栈、初始化注册表、初始化字符串结构、初始化元方法、初始化保留字实现
*/
static void f_luaopen (lua_State *L, void *ud) {
  global_State *g = G(L);
  UNUSED(ud);
  stack_init(L, L);  /* init stack - 初始化栈 */
  init_registry(L, g);  /* 初始化注册表 */
  luaS_init(L);  /* 初始化字符串结构 */
  luaT_init(L);  /* 初始化元方法 */
  luaX_init(L);  /* 初始化保留字实现 */
  g->gcrunning = 1;  /* allow gc */
  g->version = lua_version(NULL);
  luai_userstateopen(L);
}


/*
** preinitialize a thread with consistent values without allocating
** any memory (to avoid errors)
*/
static void preinit_thread (lua_State *L, global_State *g) {
  G(L) = g;
  L->stack = NULL;
  L->ci = NULL;
  L->nci = 0;
  L->stacksize = 0;
  L->twups = L;  /* thread has no upvalues */
  L->errorJmp = NULL;
  L->nCcalls = 0;
  L->hook = NULL;
  L->hookmask = 0;
  L->basehookcount = 0;
  L->allowhook = 1;
  resethookcount(L);
  L->openupval = NULL;
  L->nny = 1;
  L->status = LUA_OK;
  L->errfunc = 0;
}


/*
** 释放Lua栈结构
*/
static void close_state (lua_State *L) {
  global_State *g = G(L);
  luaF_close(L, L->stack);  /* close all upvalues for this thread */
  luaC_freeallobjects(L);  /* collect all objects - 释放全部对象 */
  if (g->version)  /* closing a fully built state? */
    luai_userstateclose(L);
  luaM_freearray(L, G(L)->strt.hash, G(L)->strt.size);
  freestack(L);
  lua_assert(gettotalbytes(g) == sizeof(LG));
  (*g->frealloc)(g->ud, fromstate(L), sizeof(LG), 0);  /* free main block */
}


/*
** 创建一个新的线程栈
** Lua在main函数中,调用luaL_newstate方法,创建了主线程(即lua_State* L)
** 主要用于实现Lua的协程实现(Lua没有多线程实现)
*/
LUA_API lua_State *lua_newthread (lua_State *L) {
  global_State *g = G(L);
  lua_State *L1;
  lua_lock(L);
  luaC_checkGC(L);
  /* create new thread */
  L1 = &cast(LX *, luaM_newobject(L, LUA_TTHREAD, sizeof(LX)))->l;
  L1->marked = luaC_white(g);
  L1->tt = LUA_TTHREAD;
  /* link it on list 'allgc' */
  L1->next = g->allgc;
  g->allgc = obj2gco(L1);
  /* anchor it on L stack */
  setthvalue(L, L->top, L1);  /* 在栈顶上设置一个新的L1对象 */
  api_incr_top(L);
  preinit_thread(L1, g);
  L1->hookmask = L->hookmask;
  L1->basehookcount = L->basehookcount;
  L1->hook = L->hook;
  resethookcount(L1);
  /* initialize L1 extra space */
  memcpy(lua_getextraspace(L1), lua_getextraspace(g->mainthread),
         LUA_EXTRASPACE);
  luai_userstatethread(L, L1);
  stack_init(L1, L);  /* init stack */
  lua_unlock(L);
  return L1;
}


void luaE_freethread (lua_State *L, lua_State *L1) {
  LX *l = fromstate(L1);
  luaF_close(L1, L1->stack);  /* close all upvalues for this thread */
  lua_assert(L1->openupval == NULL);
  luai_userstatefree(L, L1);
  freestack(L1);
  luaM_free(L, l);
}


/*
** 分配lua_State和global_State
** global_State全局表会挂载在lua_State结构上,此方法分配的是主线程栈,如果实现协程,则通过lua_newthread分配新的lua_State栈
** 通过LG结构方式,每个线程会独立维护自己的线程栈和函数栈
** 对外通过lua_State结构暴露给用户,而global_State挂载在lua_State结构上
** 主要管理全局数据,全局字符串表,内存管理函数,GC把所有对象串联起来的信息,内存等
** global_State - 全局状态机
** lua_State - 主线程结构
*/
LUA_API lua_State *lua_newstate (lua_Alloc f, void *ud) {
  int i;
  lua_State *L;
  global_State *g;
  /* 分配一块lua_State结构的内容块 */
  LG *l = cast(LG *, (*f)(ud, NULL, LUA_TTHREAD, sizeof(LG)));
  if (l == NULL) return NULL;
  L = &l->l.l;
  g = &l->g;
  L->next = NULL;
  L->tt = LUA_TTHREAD;
  g->currentwhite = bitmask(WHITE0BIT);
  L->marked = luaC_white(g);
  /* 初始化一个线程的栈结构数据 */
  preinit_thread(L, g);
  g->frealloc = f;  /* 赋值 */
  g->ud = ud;
  g->mainthread = L;
  g->seed = makeseed(L);
  g->gcrunning = 0;  /* no GC while building state */
  g->GCestimate = 0;
  g->strt.size = g->strt.nuse = 0;
  g->strt.hash = NULL;
  setnilvalue(&g->l_registry);
  g->panic = NULL;
  g->version = NULL;
  g->gcstate = GCSpause;
  g->gckind = KGC_NORMAL;
  g->allgc = g->finobj = g->tobefnz = g->fixedgc = NULL;
  g->sweepgc = NULL;
  g->gray = g->grayagain = NULL;
  g->weak = g->ephemeron = g->allweak = NULL;
  g->twups = NULL;
  g->totalbytes = sizeof(LG);
  g->GCdebt = 0;
  g->gcfinnum = 0;
  g->gcpause = LUAI_GCPAUSE;
  g->gcstepmul = LUAI_GCMUL;
  for (i=0; i < LUA_NUMTAGS; i++) g->mt[i] = NULL;
  /* f_luaopen函数中调用了stack_init函数 */
  if (luaD_rawrunprotected(L, f_luaopen, NULL) != LUA_OK) {
    /* memory allocation error: free partial state */
    close_state(L);
    L = NULL;
  }
  return L;
}


/*
** 关闭Lua
** 销毁主线程栈结构
*/
LUA_API void lua_close (lua_State *L) {
  L = G(L)->mainthread;  /* only the main thread can be closed */
  lua_lock(L);
  close_state(L);
}