Lua.LearningLua.5-document-for-luaL_findtable-function

Learning Lua: 5 - Document for luaL_findtable() function

文档中没有找到luaL_findtable()函数的说明，这里尝试补充。 

LUALIB_API const char *luaL_findtable (lua_State *L, int idx,
                                       const char *fname, int szhint);

@brief

luaL_findtable()在由参数idx标识的target-table中查找名字为fname的table。 fname支持"tableA.tableB.tableC"这种

级联的方式来命名要查找的table，其中在target-table中以"tableA"为key的field的值需要是table类型，否则会返回"tableA"。

@parameters

L: lua_State

idx: target-table在lua_State对象L中的位置

fname: 在target-table中所要查找的table的名字。支持"GrandfatherTableName.ParentTableName.TableName"这种形式。

szhint: 如果查找的table不存在，则会新创建fname对应的table，szhint是创建新table时non-array elements的提示值。参见"lua_createtable()"。

@return

成功：返回NULL; L中的top位置(即: -1的位置)会保留找到的table。

异常：返回fname中有问题的部分; L 会被复原为调用luaL_findtable()前的状态。 

luaL_findtable()代码如下:

LUALIB_API const char *luaL_findtable (lua_State *L, int idx,
                                       const char *fname, int szhint) {
  const char *e;
  lua_pushvalue(L, idx); // lua_pushvalue(): Pushes a copy of the element at the given valid index onto the stack. // A
  do {
    e = strchr(fname, '.');
    if (e == NULL) e = fname + strlen(fname);
    lua_pushlstring(L, fname, e - fname); // lua_pushlstring(): Pushes the string pointed to by s with size len onto the stack. // B
    lua_rawget(L, -2);　　　　// lua_rawget(): Similar to lua_gettable, but does a raw access  // C
    if (lua_isnil(L, -1)) {  /* no such field? */
      lua_pop(L, 1);  /* remove this nil */
      lua_createtable(L, 0, (*e == '.' ? 1 : szhint)); /* new table for field */　　　// D
      lua_pushlstring(L, fname, e - fname);
      lua_pushvalue(L, -2);
      lua_settable(L, -4);  /* set new table into field */　　　　　　　// E
    }
    else if (!lua_istable(L, -1)) {  /* field has a non-table value? */
      lua_pop(L, 2);  /* remove table and value */
      return fname;  /* return problematic part of the name */
    }
    lua_remove(L, -2);  /* remove previous table */　　　　// F
    fname = e + 1;
  } while (*e == '.');
  return NULL;
}

lua_gettable()

void lua_gettable (lua_State *L, int index);

"Pushes onto the stack the value t[k], where t is the value at the given valid index and k is the value at the top of the stack.

This function pops the key from the stack (putting the resulting value in its place). As in Lua, this function may trigger a metamethod for the "index" event " Ref[1]

lua_createtable()

void lua_createtable (lua_State *L, int narr, int nrec);

"Creates a new empty table and pushes it onto the stack. The new table has space pre-allocated for narr array elements and nrec non-array elements." Ref[1]

lua_settable()

void lua_settable (lua_State *L, int index);

"Does the equivalent to t[k] = v, where t is the value at the given valid index, v is the value at the top of the stack, and k is the value just below the top.

This function pops both the key and the value from the stack. As in Lua, this function may trigger a metamethod for the "newindex" event" Ref[1] 

lua_remove()

void lua_remove (lua_State *L, int index);

"Removes the element at the given valid index, shifting down the elements above this index to fill the gap. Cannot be called with a pseudo-index, because a pseudo-index is not an actual stack position." Ref[1] 

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Reference 

1. http://www.lua.org/manual/5.1/manual.html