lua 1.1 源码阅读总结

GC

1. 怎么回收的lua 中所有已经分配的数据都会用一些指令的数据结构来记录，当需要回收时，先遍历当前栈内所有 object，把 ref 标志位打上 1，遍历符号表(这部分不能回收）,反符号表中的所有对象的 ref 标志位也打上 1， 如果有其它不用回收的也同样操作。回收也比较简单，这里遍历所有内部数据结构，如果是 0 就直接释放， 如果是 1 就置 0（可能下次就回收了), 这样就结束了
2. 何时回收
这个 1.1 有个内部阀值，当新加 object 的数量到达阀值时，就会触发回收机制。

数据结构

　　Hash

　　

typedef struct Hash
{
     char           mark;
     unsigned int   nhash;
     Node         **list;
} Hash;

typedef struct node
{
     Object ref;
     Object val;
     struct node *next;
} Node;

typedef union
{
     Cfunction 	 f;
     real    	 n;
     char      	*s;
     Byte      	*b;
     struct Hash    *a;
     void           *u;
} Value;

typedef struct Object
{
 Type  tag;
 Value value;
} Object;

typedef struct
{
     char   *name;
     Object  object;
} Symbol;

　　全局数据区

　　

extern Symbol *lua_table;       /* key - value 表*/
extern Word    lua_ntable;

static Symbol  		tablebuffer[MAXSYMBOL] = {
                                    {"type",{T_CFUNCTION,{lua_type}}},
                                    ...
                                    };
/* list 和数组的结合使用，目地是用 list 和 array 的特性, 参考 lua_findsymbol
在 list 中查找，找到放到头（这样效率高点，下次再被用的概率大点）， 没找到，就在头
节点上加一个
  */
Symbol	       	       *lua_table=tablebuffer;
Word   	 		lua_ntable=7;
static struct List o6={ tablebuffer+6, 0};
static struct List o5={ tablebuffer+5, &o6 };
static struct List o4={ tablebuffer+4, &o5 };
static struct List o3={ tablebuffer+3, &o4 };
static struct List o2={ tablebuffer+2, &o3 };
static struct List o1={ tablebuffer+1, &o2 };
static struct List o0={ tablebuffer+0, &o1 };
static struct List *searchlist=&o0;

extern char  **lua_constant;    /* 常量表 */
extern Word    lua_nconstant;
static char tm[] = " mark";
static char  	       *constantbuffer[MAXCONSTANT] = {tm+1, ti+1,
                        ...
                        };

extern char  **lua_string;    /* 就是普通的字符指针数组 *、
extern Word    lua_nstring;
static char 	       *stringbuffer[MAXSTRING];
char  		      **lua_string = stringbuffer;
Word    		lua_nstring=0;

extern Hash  **lua_array;
extern Word    lua_narray;

extern char   *lua_file[];    /* 记录指针的数组 */
extern int     lua_nfile;

　　ps: lua_next 和 lua_nextval 可以看下，这个有点像迭代器的实现

虚拟指令

这个还是建议读下，主要就是对 stack 和 pc 的操作。

/*
** Execute the given opcode. Return 0 in success or 1 on error.
*/
int lua_execute (Byte *pc)
{
 Object *oldbase = base;
 base = top;
 while (1)
 {
  OpCode opcode;
  switch (opcode = (OpCode)*pc++)
  {
   case PUSHNIL: tag(top++) = T_NIL; break;

   case PUSH0: tag(top) = T_NUMBER; nvalue(top++) = 0; break;
   case PUSH1: tag(top) = T_NUMBER; nvalue(top++) = 1; break;
   case PUSH2: tag(top) = T_NUMBER; nvalue(top++) = 2; break;

   case PUSHBYTE: tag(top) = T_NUMBER; nvalue(top++) = *pc++; break;

   case PUSHWORD:
   {
    CodeWord code;
    get_word(code,pc);
    tag(top) = T_NUMBER; nvalue(top++) = code.w;
   }
   break;

   case PUSHFLOAT:
   {
    CodeFloat code;
    get_float(code,pc);
    tag(top) = T_NUMBER; nvalue(top++) = code.f;
   }
   break;

   case PUSHSTRING:
   {
    CodeWord code;
    get_word(code,pc);
    tag(top) = T_STRING; svalue(top++) = lua_constant[code.w];
   }
   break;

   case PUSHLOCAL0: case PUSHLOCAL1: case PUSHLOCAL2:
   case PUSHLOCAL3: case PUSHLOCAL4: case PUSHLOCAL5:
   case PUSHLOCAL6: case PUSHLOCAL7: case PUSHLOCAL8:
   case PUSHLOCAL9: *top++ = *(base + (int)(opcode-PUSHLOCAL0)); break;

   case PUSHLOCAL: *top++ = *(base + (*pc++)); break;

   case PUSHGLOBAL:
   {
    CodeWord code;
    get_word(code,pc);
    *top++ = s_object(code.w);
   }
   break;

   case PUSHINDEXED:
    --top;
    if (tag(top-1) != T_ARRAY)
    {
     lua_reportbug ("indexed expression not a table");
     return 1;
    }
    {
     Object *h = lua_hashdefine (avalue(top-1), top);
     if (h == NULL) return 1;
     *(top-1) = *h;
    }
   break;

   case PUSHMARK: tag(top++) = T_MARK; break;

   case PUSHOBJECT: *top = *(top-3); top++; break;

   case STORELOCAL0: case STORELOCAL1: case STORELOCAL2:
   case STORELOCAL3: case STORELOCAL4: case STORELOCAL5:
   case STORELOCAL6: case STORELOCAL7: case STORELOCAL8:
   case STORELOCAL9: *(base + (int)(opcode-STORELOCAL0)) = *(--top); break;

   case STORELOCAL: *(base + (*pc++)) = *(--top); break;

   case STOREGLOBAL:
   {
    CodeWord code;
    get_word(code,pc);
    s_object(code.w) = *(--top);
   }
   break;

   case STOREINDEXED0:
    if (tag(top-3) != T_ARRAY)
    {
     lua_reportbug ("indexed expression not a table");
     return 1;
    }
    {
     Object *h = lua_hashdefine (avalue(top-3), top-2);
     if (h == NULL) return 1;
     *h = *(top-1);
    }
    top -= 3;
   break;

   case STOREINDEXED:
   {
    int n = *pc++;
    if (tag(top-3-n) != T_ARRAY)
    {
     lua_reportbug ("indexed expression not a table");
     return 1;
    }
    {
     Object *h = lua_hashdefine (avalue(top-3-n), top-2-n);
     if (h == NULL) return 1;
     *h = *(top-1);
    }
    top--;
   }
   break;

   case STORELIST0:
   case STORELIST:
   {
    int m, n;
    Object *arr;
    if (opcode == STORELIST0) m = 0;
    else m = *(pc++) * FIELDS_PER_FLUSH;
    n = *(pc++);
    arr = top-n-1;
    if (tag(arr) != T_ARRAY)
    {
     lua_reportbug ("internal error - table expected");
     return 1;
    }
    while (n)
    {
     tag(top) = T_NUMBER; nvalue(top) = n+m;
     *(lua_hashdefine (avalue(arr), top)) = *(top-1);
     top--;
     n--;
    }
   }
   break;

   case STORERECORD:
   {
    int n = *(pc++);
    Object *arr = top-n-1;
    if (tag(arr) != T_ARRAY)
    {
     lua_reportbug ("internal error - table expected");
     return 1;
    }
    while (n)
    {
     CodeWord code;
     get_word(code,pc);
     tag(top) = T_STRING; svalue(top) = lua_constant[code.w];
     *(lua_hashdefine (avalue(arr), top)) = *(top-1);
     top--;
     n--;
    }
   }
   break;

   case ADJUST:
   {
    Object *newtop = base + *(pc++);
    while (top < newtop) tag(top++) = T_NIL;
    top = newtop;  /* top could be bigger than newtop */
   }
   break;

   case CREATEARRAY:
    if (tag(top-1) == T_NIL)
     nvalue(top-1) = 101;
    else
    {
     if (tonumber(top-1)) return 1;
     if (nvalue(top-1) <= 0) nvalue(top-1) = 101;
    }
    avalue(top-1) = lua_createarray(nvalue(top-1));
    if (avalue(top-1) == NULL)
     return 1;
    tag(top-1) = T_ARRAY;
   break;

   case EQOP:
   {
    Object *l = top-2;
    Object *r = top-1;
    --top;
    if (tag(l) != tag(r))
     tag(top-1) = T_NIL;
    else
    {
     switch (tag(l))
     {
      case T_NIL:       tag(top-1) = T_NUMBER; break;
      case T_NUMBER:    tag(top-1) = (nvalue(l) == nvalue(r)) ? T_NUMBER : T_NIL; break;
      case T_ARRAY:     tag(top-1) = (avalue(l) == avalue(r)) ? T_NUMBER : T_NIL; break;
      case T_FUNCTION:  tag(top-1) = (bvalue(l) == bvalue(r)) ? T_NUMBER : T_NIL; break;
      case T_CFUNCTION: tag(top-1) = (fvalue(l) == fvalue(r)) ? T_NUMBER : T_NIL; break;
      case T_USERDATA:  tag(top-1) = (uvalue(l) == uvalue(r)) ? T_NUMBER : T_NIL; break;
      case T_STRING:    tag(top-1) = (strcmp (svalue(l), svalue(r)) == 0) ? T_NUMBER : T_NIL; break;
      case T_MARK:      return 1;
     }
    }
    nvalue(top-1) = 1;
   }
   break;

   case LTOP:
   {
    Object *l = top-2;
    Object *r = top-1;
    --top;
    if (tag(l) == T_NUMBER && tag(r) == T_NUMBER)
     tag(top-1) = (nvalue(l) < nvalue(r)) ? T_NUMBER : T_NIL;
    else
    {
     if (tostring(l) || tostring(r))
      return 1;
     tag(top-1) = (strcmp (svalue(l), svalue(r)) < 0) ? T_NUMBER : T_NIL;
    }
    nvalue(top-1) = 1;
   }
   break;

   case LEOP:
   {
    Object *l = top-2;
    Object *r = top-1;
    --top;
    if (tag(l) == T_NUMBER && tag(r) == T_NUMBER)
     tag(top-1) = (nvalue(l) <= nvalue(r)) ? T_NUMBER : T_NIL;
    else
    {
     if (tostring(l) || tostring(r))
      return 1;
     tag(top-1) = (strcmp (svalue(l), svalue(r)) <= 0) ? T_NUMBER : T_NIL;
    }
    nvalue(top-1) = 1;
   }
   break;

   case ADDOP:
   {
    Object *l = top-2;
    Object *r = top-1;
    if (tonumber(r) || tonumber(l))
     return 1;
    nvalue(l) += nvalue(r);
    --top;
   }
   break; 

   case SUBOP:
   {
    Object *l = top-2;
    Object *r = top-1;
    if (tonumber(r) || tonumber(l))
     return 1;
    nvalue(l) -= nvalue(r);
    --top;
   }
   break; 

   case MULTOP:
   {
    Object *l = top-2;
    Object *r = top-1;
    if (tonumber(r) || tonumber(l))
     return 1;
    nvalue(l) *= nvalue(r);
    --top;
   }
   break; 

   case DIVOP:
   {
    Object *l = top-2;
    Object *r = top-1;
    if (tonumber(r) || tonumber(l))
     return 1;
    nvalue(l) /= nvalue(r);
    --top;
   }
   break; 

   case CONCOP:
   {
    Object *l = top-2;
    Object *r = top-1;
    if (tostring(r) || tostring(l))
     return 1;
    svalue(l) = lua_createstring (lua_strconc(svalue(l),svalue(r)));
    if (svalue(l) == NULL)
     return 1;
    --top;
   }
   break; 

   case MINUSOP:
    if (tonumber(top-1))
     return 1;
    nvalue(top-1) = - nvalue(top-1);
   break; 

   case NOTOP:
    tag(top-1) = tag(top-1) == T_NIL ? T_NUMBER : T_NIL;
   break; 

   case ONTJMP:
   {
    CodeWord code;
    get_word(code,pc);
    if (tag(top-1) != T_NIL) pc += code.w;
   }
   break;

   case ONFJMP:
   {
    CodeWord code;
    get_word(code,pc);
    if (tag(top-1) == T_NIL) pc += code.w;
   }
   break;

   case JMP:
   {
    CodeWord code;
    get_word(code,pc);
    pc += code.w;
   }
   break;

   case UPJMP:
   {
    CodeWord code;
    get_word(code,pc);
    pc -= code.w;
   }
   break;

   case IFFJMP:
   {
    CodeWord code;
    get_word(code,pc);
    top--;
    if (tag(top) == T_NIL) pc += code.w;
   }
   break;

   case IFFUPJMP:
   {
    CodeWord code;
    get_word(code,pc);
    top--;
    if (tag(top) == T_NIL) pc -= code.w;
   }
   break;

   case POP: --top; break;

   case CALLFUNC:
   {
    Byte *newpc;
    Object *b = top-1;
    while (tag(b) != T_MARK) b--;
    if (tag(b-1) == T_FUNCTION)
    {
     lua_debugline = 0;			/* always reset debug flag */
     newpc = bvalue(b-1);
     bvalue(b-1) = pc;		        /* store return code */
     nvalue(b) = (base-stack);		/* store base value */
     base = b+1;
     pc = newpc;
     if (MAXSTACK-(base-stack) < STACKGAP)
     {
      lua_error ("stack overflow");
      return 1;
     }
    }
    else if (tag(b-1) == T_CFUNCTION)
    {
     int nparam;
     lua_debugline = 0;			/* always reset debug flag */
     nvalue(b) = (base-stack);		/* store base value */
     base = b+1;
     nparam = top-base;			/* number of parameters */
     (fvalue(b-1))();			/* call C function */

     /* shift returned values */
     {
      int i;
      int nretval = top - base - nparam;
      top = base - 2;
      base = stack + (int) nvalue(base-1);
      for (i=0; i<nretval; i++)
      {
       *top = *(top+nparam+2);
       ++top;
      }
     }
    }
    else
    {
     lua_reportbug ("call expression not a function");
     return 1;
    }
   }
   break;

   case RETCODE:
   {
    int i;
    int shift = *pc++;
    int nretval = top - base - shift;
    top = base - 2;
    pc = bvalue(base-2);
    base = stack + (int) nvalue(base-1);
    for (i=0; i<nretval; i++)
    {
     *top = *(top+shift+2);
     ++top;
    }
   }
   break;

   case HALT:
    base = oldbase;
   return 0;		/* success */

   case SETFUNCTION:
   {
    CodeWord file, func;
    get_word(file,pc);
    get_word(func,pc);
    if (lua_pushfunction (file.w, func.w))
     return 1;
   }
   break;

   case SETLINE:
   {
    CodeWord code;
    get_word(code,pc);
    lua_debugline = code.w;
   }
   break;

   case RESET:
    lua_popfunction ();
   break;

   default:
    lua_error ("internal error - opcode didn't match");
   return 1;
  }
 }
}