/*
** $Id: lstate.h,v 2.133.1.1 2017/04/19 17:39:34 roberto Exp $
** Global State
** See Copyright Notice in lua.h
*/

#ifndef lstate_h
#define lstate_h

#include "lua.h"

#include "lobject.h"
#include "ltm.h"
#include "lzio.h"


/*

** Some notes about garbage-collected objects: All objects in Lua must
** be kept somehow accessible until being freed, so all objects always
** belong to one (and only one) of these lists, using field 'next' of
** the 'CommonHeader' for the link:
**
** 'allgc': all objects not marked for finalization;
** 'finobj': all objects marked for finalization;
** 'tobefnz': all objects ready to be finalized;
** 'fixedgc': all objects that are not to be collected (currently
** only small strings, such as reserved words).
**
** Moreover, there is another set of lists that control gray objects.
** These lists are linked by fields 'gclist'. (All objects that
** can become gray have such a field. The field is not the same
** in all objects, but it always has this name.)  Any gray object
** must belong to one of these lists, and all objects in these lists
** must be gray:
**
** 'gray': regular gray objects, still waiting to be visited.
** 'grayagain': objects that must be revisited at the atomic phase.
**   That includes
**   - black objects got in a write barrier;
**   - all kinds of weak tables during propagation phase;
**   - all threads.
** 'weak': tables with weak values to be cleared;
** 'ephemeron': ephemeron tables with white->white entries;
** 'allweak': tables with weak keys and/or weak values to be cleared.
** The last three lists are used only during the atomic phase.

*/


struct lua_longjmp;  /* defined in ldo.c */


/*
** Atomic type (relative to signals) to better ensure that 'lua_sethook'
** is thread safe
*/
#if !defined(l_signalT)
#include <signal.h>
#define l_signalT	sig_atomic_t
#endif


/* extra stack space to handle TM calls and some other extras */
#define EXTRA_STACK   5


#define BASIC_STACK_SIZE        (2*LUA_MINSTACK)


/* kinds of Garbage Collection */
#define KGC_NORMAL	0
#define KGC_EMERGENCY	1	/* gc was forced by an allocation failure */


typedef struct stringtable {
  TString **hash;
  int nuse;  /* number of elements */
  int size;  // 散列表数组的长度
} stringtable;


/*
** Information about a call.
** When a thread yields, 'func' is adjusted to pretend that the
** top function has only the yielded values in its stack; in that
** case, the actual 'func' value is saved in field 'extra'.
** When a function calls another with a continuation, 'extra' keeps
** the function index so that, in case of errors, the continuation
** function can be called with the correct top.
*/
typedef struct CallInfo {
  // 该栈位置保存调用关联的函数所在栈位置引用
  StkId func;  /* function index in the stack */
  // 该函数的栈顶引用，[func, top]就是这个函数栈范围
  StkId	top;  /* top for this function */
  // 调用的双向链表
  struct CallInfo *previous, *next;  /* dynamic call link */
  union {
    // Lua函数
    struct {  /* only for Lua functions */
      // 栈基址，base往下这部分为函数的可变参数，base往上为函数的固定参数，和本地变量
      StkId base;  /* base for this function */
      // 正在执行指令
      const Instruction *savedpc;
    } l;
    // C函数, 延续函数的信息
    struct {  /* only for C functions */
      // 延续函数
      lua_KFunction k;  /* continuation in case of yields */
      ptrdiff_t old_errfunc;
      // 延续函数环境
      lua_KContext ctx;  /* context info. in case of yields */
    } c;
  } u;
  ptrdiff_t extra;
  short nresults;  /* expected number of results from this function */
  // 调用状态
  unsigned short callstatus;
} CallInfo;


/*
** Bits in CallInfo status
*/
#define CIST_OAH	(1<<0)	/* original value of 'allowhook' */
#define CIST_LUA	(1<<1)	/* call is running a Lua function */
#define CIST_HOOKED	(1<<2)	/* call is running a debug hook */
#define CIST_FRESH	(1<<3)	/* call is running on a fresh invocation
                                   of luaV_execute */
#define CIST_YPCALL	(1<<4)	/* call is a yieldable protected call */
#define CIST_TAIL	(1<<5)	/* call was tail called */
#define CIST_HOOKYIELD	(1<<6)	/* last hook called yielded */
#define CIST_LEQ	(1<<7)  /* using __lt for __le */
#define CIST_FIN	(1<<8)  /* call is running a finalizer  调用一个 __gc 元方法 */

#define isLua(ci)	((ci)->callstatus & CIST_LUA)

/* assume that CIST_OAH has offset 0 and that 'v' is strictly 0/1 */
#define setoah(st,v)	((st) = ((st) & ~CIST_OAH) | (v))
#define getoah(st)	((st) & CIST_OAH)


/*
** 'global state', shared by all threads of this state
*/
typedef struct global_State {
  // 内存分配函数，以及关联的用户数据
  lua_Alloc frealloc;  /* function to reallocate memory */
  void *ud;         /* auxiliary data to 'frealloc' */
  // Lua当前已分配的内存总量 - GCdebt，这个词有歧义，并不准确反映当前内存使用量
  // 新分配内存增加的是 GCdebt， 这个值更像为了配合 GCdebt 来计算 gettotalbytes
  l_mem totalbytes;  /* number of bytes currently allocated - GCdebt */
  // 债务内存量，即GC要做的工作量。其值为正时，表示当前 GC“欠债”，需要进行回收以恢复内存平衡；其为负数时，则表示没有垃圾回收工作需要进行。
  l_mem GCdebt;  /* bytes allocated not yet compensated by the collector */
  lu_mem GCmemtrav;  /* memory traversed by the GC  gc扫描过的内存量（工作量），统计用的中间量 */
  lu_mem GCestimate;  /* an estimate of the non-garbage memory in use 上轮 GC 回收完成时的内存占用估算值，通常等于总内存大小 totalbytes 加上一定的缓冲区值。*/
  // 短字符串哈希表
  stringtable strt;  /* hash table for strings */
   // 全局注册表
  TValue l_registry;
  // 随机函数种子
  unsigned int seed;  /* randomized seed for hashes */
  lu_byte currentwhite;
  // 当前的gc阶段
  lu_byte gcstate;  /* state of garbage collector */
  lu_byte gckind;  /* kind of GC running */
  lu_byte gcrunning;  /* true if GC is running 开启 GC ?  */
  GCObject *allgc;  /* list of all collectable objects */
  GCObject **sweepgc;  /* current position of sweep in list */
  GCObject *finobj;  /* list of collectable objects with finalizers */
  GCObject *gray;  /* list of gray objects */
  GCObject *grayagain;  /* list of objects to be traversed atomically */
  GCObject *weak;  /* list of tables with weak values */
  GCObject *ephemeron;  /* list of ephemeron tables (weak keys) */
  GCObject *allweak;  /* list of all-weak tables */
  GCObject *tobefnz;  /* list of userdata to be GC */
  GCObject *fixedgc;  /* list of objects not to be collected */
  struct lua_State *twups;  /* list of threads with open upvalues  有 upvalue 的 lua_State */
  unsigned int gcfinnum;  /* number of finalizers to call in each GC step */
  int gcpause;  /* size of pause between successive GCs  默认值200 */
  int gcstepmul;  /* GC 'granularity' 垃圾回收的“步长倍率”，表示单步回收工作的规模。倍率值越高，singlestep 执行得越多。默认 200 */
  // 终止函数
  lua_CFunction panic;  /* to be called in unprotected errors */
  // 主线程
  struct lua_State *mainthread;
  // 版本号
  const lua_Number *version;  /* pointer to version number */
  // 错误消息
  TString *memerrmsg;  /* memory-error message */
  // 元方法名，初始化在luaT_init
  TString *tmname[TM_N];  /* array with tag-method names */
  // 基本类型的元方法，表和userdata之外的元表放这儿
  struct Table *mt[LUA_NUMTAGS];  /* metatables for basic types */
  // 字符串的二级缓存容器
  TString *strcache[STRCACHE_N][STRCACHE_M];  /* cache for strings in API */
} global_State;


/*
** 'per thread' state
*/
struct lua_State {
  // lua_State 也是一个GC obj
  CommonHeader;
  // CallInfo数量，一个CallInfo代表一层函数调用
  unsigned short nci;  /* number of items in 'ci' list */
  // 线程状态
  lu_byte status;
  // 栈顶地址，StkId是TValue指针
  StkId top;  /* first free slot in the stack */
  // 全局状态
  global_State *l_G;
  // 当前函数的调用信息
  CallInfo *ci;  /* call info for current function */
  const Instruction *oldpc;  /* last pc traced */
  // 栈的最后地址
  StkId stack_last;  /* last free slot in the stack */
  // 栈的起始地址，可以看作是栈数组
  StkId stack;  /* stack base */
  UpVal *openupval;  /* list of open upvalues in this stack */
  GCObject *gclist;
  struct lua_State *twups;  /* list of threads with open upvalues */
  // 错误处理链表：当前的恢复点，看 luaD_rawrunprotected
  struct lua_longjmp *errorJmp;  /* current error recover point */
  // 初始调用信息
  CallInfo base_ci;  /* CallInfo for first level (C calling Lua) */
  volatile lua_Hook hook;
  ptrdiff_t errfunc;  /* current error handling function (stack index) */
  // 栈大小
  int stacksize;
  int basehookcount;
  int hookcount;
  unsigned short nny;  /* number of non-yieldable calls in stack */
  unsigned short nCcalls;  /* number of nested C calls */
  l_signalT hookmask;
  lu_byte allowhook;
};


#define G(L)	(L->l_G)


/*
** Union of all collectable objects (only for conversions)
*/
union GCUnion {
  GCObject gc;  /* common header */
  struct TString ts;
  struct Udata u;
  union Closure cl;
  struct Table h;
  struct Proto p;
  struct lua_State th;  /* thread */
};


#define cast_u(o)	cast(union GCUnion *, (o))

/* macros to convert a GCObject into a specific value */
// 这些宏是将对象由 GCObject 强转为实际的类型 
#define gco2ts(o)  \
	check_exp(novariant((o)->tt) == LUA_TSTRING, &((cast_u(o))->ts))
#define gco2u(o)  check_exp((o)->tt == LUA_TUSERDATA, &((cast_u(o))->u))
#define gco2lcl(o)  check_exp((o)->tt == LUA_TLCL, &((cast_u(o))->cl.l))
#define gco2ccl(o)  check_exp((o)->tt == LUA_TCCL, &((cast_u(o))->cl.c))
#define gco2cl(o)  \
	check_exp(novariant((o)->tt) == LUA_TFUNCTION, &((cast_u(o))->cl))
#define gco2t(o)  check_exp((o)->tt == LUA_TTABLE, &((cast_u(o))->h))
#define gco2p(o)  check_exp((o)->tt == LUA_TPROTO, &((cast_u(o))->p))
#define gco2th(o)  check_exp((o)->tt == LUA_TTHREAD, &((cast_u(o))->th))


/* macro to convert a Lua object into a GCObject */
// 和上面相反，对象强转为 GCObject 类型
#define obj2gco(v) \
	check_exp(novariant((v)->tt) < LUA_TDEADKEY, (&(cast_u(v)->gc)))


/* actual number of total bytes allocated */
#define gettotalbytes(g)	cast(lu_mem, (g)->totalbytes + (g)->GCdebt)

LUAI_FUNC void luaE_setdebt (global_State *g, l_mem debt);
LUAI_FUNC void luaE_freethread (lua_State *L, lua_State *L1);
LUAI_FUNC CallInfo *luaE_extendCI (lua_State *L);
LUAI_FUNC void luaE_freeCI (lua_State *L);
LUAI_FUNC void luaE_shrinkCI (lua_State *L);


#endif