讲讲table.insert

先看table.insert调用的C函数:

static int tinsert (lua_State *L) {
  int e = aux_getn(L, 1) + 1;  /* first empty element */
  int pos;  /* where to insert new element */
  switch (lua_gettop(L)) {
    case 2: {  /* called with only 2 arguments */
      pos = e;  /* insert new element at the end */
      break;
    }
    case 3: {
      int i;
      pos = luaL_checkint(L, 2);  /* 2nd argument is the position */
      luaL_argcheck(L, 1 <= pos && pos <= e, 2, "position out of bounds");
      for (i = e; i > pos; i--) {  /* move up elements */
        lua_rawgeti(L, 1, i-1);
        lua_rawseti(L, 1, i);  /* t[i] = t[i-1] */
      }
      break;
    }
    default: {
      return luaL_error(L, "wrong number of arguments to " LUA_QL("insert"));
    }
  }
  lua_rawseti(L, 1, pos);  /* t[pos] = v */
  return 0;
}

aux_getn最终调用的是luaH_getn函数获取此table的长度，加1得到将入插入的位置，重点看看lua_rawseti:

LUA_API void lua_rawseti (lua_State *L, int idx, int n) {
  StkId t;
  lua_lock(L);
  api_checknelems(L, 1);
  t = index2addr(L, idx);
  api_check(L, ttistable(t), "table expected");
  luaH_setint(L, hvalue(t), n, L->top - 1);
  luaC_barrierback(L, gcvalue(t), L->top-1);
  L->top--;
  lua_unlock(L);
}

最终调用luaH_setint函数:

void luaH_setint (lua_State *L, Table *t, int key, TValue *value) {
  const TValue *p = luaH_getint(t, key);
  TValue *cell;
  if (p != luaO_nilobject)
    cell = cast(TValue *, p);
  else {
    TValue k;
    setnvalue(&k, cast_num(key));
    cell = luaH_newkey(L, t, &k);
  }
  setobj2t(L, cell, value);
}

此孙数key为table.insert要插入的pos,就是int e = aux_getn(L, 1) + 1的e,value就是要插入的值,看luaH_getint:

/*
** search function for integers
*/
const TValue *luaH_getint (Table *t, int key) {
  /* (1 <= key && key <= t->sizearray) */
  if (cast(unsigned int, key-1) < cast(unsigned int, t->sizearray))
    return &t->array[key-1];
  else {
    lua_Number nk = cast_num(key);
    Node *n = hashnum(t, nk);
    do {  /* check whether `key' is somewhere in the chain */
      if (ttisnumber(gkey(n)) && luai_numeq(nvalue(gkey(n)), nk))
        return gval(n);  /* that's it */
      else n = gnext(n);
    } while (n);
    return luaO_nilobject;
  }
}

从此函数的注释可以知道，就是查找一个整形key是否存在(包括数组和hash).假如此key存在，刚赋值，不存在，刚新newkey，看luaH_newkey函数:

TValue *luaH_newkey (lua_State *L, Table *t, const TValue *key) {
  Node *mp;
  if (ttisnil(key)) luaG_runerror(L, "table index is nil");
  else if (ttisnumber(key) && luai_numisnan(L, nvalue(key)))
    luaG_runerror(L, "table index is NaN");
  mp = mainposition(t, key);
  if (!ttisnil(gval(mp)) || isdummy(mp)) {  /* main position is taken? */
    Node *othern;
    Node *n = getfreepos(t);  /* get a free place */
    if (n == NULL) {  /* cannot find a free place? */
      rehash(L, t, key);  /* grow table */
      /* whatever called 'newkey' take care of TM cache and GC barrier */
      return luaH_set(L, t, key);  /* insert key into grown table */
    }
    lua_assert(!isdummy(n));
    othern = mainposition(t, gkey(mp));
    if (othern != mp) {  /* is colliding node out of its main position? */
      /* yes; move colliding node into free position */
      while (gnext(othern) != mp) othern = gnext(othern);  /* find previous */
      gnext(othern) = n;  /* redo the chain with `n' in place of `mp' */
      *n = *mp;  /* copy colliding node into free pos. (mp->next also goes) */
      gnext(mp) = NULL;  /* now `mp' is free */
      setnilvalue(gval(mp));
    }
    else {  /* colliding node is in its own main position */
      /* new node will go into free position */
      gnext(n) = gnext(mp);  /* chain new position */
      gnext(mp) = n;
      mp = n;
    }
  }
  setobj2t(L, gkey(mp), key);
  luaC_barrierback(L, obj2gco(t), key);
  lua_assert(ttisnil(gval(mp)));
  return gval(mp);
}

此函数就是把刚才要插入的key放到hash部分，如果hash已满刚rehash(rehash函数有点复杂，有空再写)，到这里，就知道table.insert的值有可能进入到hash，这就是为什么
获得table长度的时候为什么要进入到unbound_search表的hash部分了。

再讲一点，table的构告是由指令OP_NEWTABLE执行,初始化数组操作是由OP_SETLIST执行(赋值时元素个数是由语法解析生成的)，key value赋值是由OP_SETTABLE执行再加上table.insert和table.remove这两 个函数就组成了table所有的外部操作了。