《Programming in Lua 3》读书笔记(二十五)

#include <limits.h>
#define BITS_PER_WORD (CHAR_BIT*sizeof(unsigned int))
#define I_WORD(i)             ((unsigned int)(i) / BIT_PER_WORD)
#define I_BIT(i)                  (1 << ((unsigned int)(i) % BIT_PER_WORD))

e.g.
typedef struct NumArray
{
     int size;
     unsigned int values[1];
} NumArray;

e.g.
     sizeof(NumArray) + I_WORD( n -1 ) * sizeof(unsigned int)

 void* lua_newuserdata(lua_State *L,size_t size);

e.g.
static int newarray(lua_State *L)
{
     int i;
     size_t nbytes;
     NumArray *a;

     int n = luaL_checkint(L,1);
     luaL_argcheck(L,n >= 1,1,"invalid siez");
     nbytes = sizeof(NumArray) + I_WORD(n -1)*sizeof(unsigned int);
     a = (NumArray*)lua_newuserdata(L,nbytes);

     a->size = n;
     for(i = 0;i <= I_WORD(n -1); i++)
          a->values[i] = 0;

          return 1;

}

static int setarray(lua_State *L)
{
     NumArray *a = (NumArray*)lua_touserdata(L,1);
     int index = luaL_checkint(L,2) - 1;

     luaL_argcheck(L,a != NULL,1,"'array' expected");
     luaL_argcheck(L,0 <= index && index < a->size,2,"index out of range");
     luaL_checkany(L,3);

     if(lua_toboolean(L,3))
          a->values[I_WORD(index)] != I_BIT(index);
     else
          a->values[I_WORD(index)] &= ~I_BIT(index);

     return 0;
}

e.g.
array.set(0,11,0)
     --stdin:1: bad argument #1 to 'set' ('array' expected) 这里的意思是第一个参数必须是数组'array'类型的
array.set(a,1)
     --stdin:1: bad argument #3 to 'set' (value expected) 这里函数只传递两个参数，因此报错的是少了第三个参数，第三个参数必须有值。

static int getarray(lua_State *L)
{
     NumArray *a = (NumArray*)lua_touserdata(L,1);
     int index = luaL_checkint(L,2) - 1;

     luaL_argcheck(L, a != NULL,1,"'array' expected");
     luaL_argcheck(L,0 <= index && index < a->size,2,"index out range");

     lua_pushboolean(L,a->value[I_WORD(index)] & I_BIT(index));

     return 1;
}

static int getsize (lua_State *L)
{
     NumArray *a = (NumArray*)lua_touserdata(L,1);
     luaL_argcheck(L, a != NULL,1"'array' expected");
     lua_pushinteger(L,a->size);
     return 1;
}

static const struct luaL_Reg arraylib [] =
{
     {"new",newarray},
     {"set",setarray},
     {"get",getarray},
     {"size",getsize},
     {NULL,NULL}
};


int luaopen_array(lua_State *L)
{
     luaL_newlib(L,arraylib);
     return 1;
}

a = array.new(1000)
print(a)               --> user data
print(array.size(a))     --> 1000
for i = 1,1000 do
     array.set(a,i,i % 5 == 0)     --设定
end
print(array.get(a,10))          --true     --得到

int luaL_newtatable(lua_State *L,const char *tname);
void luaL_getmetatable(lua_State *L,const char *tname);
void *luaL_checkudata(lua_State *L,int index,const char *tname);

int luaopen_array(lua_State *L)

{
     luaL_newmetatable(L,"LuaBook.array");          /* 这里加入了创建metatable 的功能 */
     luaL_newlib(L,arraylib);
     return 1;
}

static int newarray(lua_State *L)
{
     //new
     luaL_getmetatable(L,"LuaBook.array");
     lua_setmetatable(L,-2);

     return 1;
}

a = array.new(1000)
print(a:size())          --使用了冒号操作符
a:set(10,true)
…

local metaarray = getmetatable(array.new(1))
metaarray.__index = metarray
metaarray.set = array.set
metaarray.get = array.get
metaarray.size = array.size

static const struct luaL_Reg arraylib_f [] =
{
     {"new",newarray},
     {NULL,NULL}
};

static const struct luaL_Reg arraylib_m [] =
{
     {"set",setarray},
     {"get",getarray},
     {"size",getsize},
     {NULL,NULL}
};

int luaopen_array(lua_State *L)
{
     luaL_newmetatable(L,"LuaBook.array");

     lua_pushvalue(L,-1);
     lua_setfield(L,-2,"__index");

     luaL_setfuncs(L,arraylib_m,0);
     luaL_newlib(L,arraylib_f);
     return 1;
}

e.g.
local metaarray = getmetatable(array.new(1))
metaarray.__index = array.get
metaarray.__newindex = array.set
metaarray.__len = array.size

a = array.new(1000)
a[10] = true          --     'setarray'
print(a[10])           --     'getarray'
print(#a)               --     'getsize'