Lua queue implemented with C API.

main.lua

local queue = require "lqueue"

local q = queue:new()

-- local min, max = 1, 1
local min, max = 1, 10

for i = min, max do 
	q:push(string.char(math.random(97, 97 + 26)))
end

print("长度为: ", q:len())
print("pop :", q:pop())

for item, typename in q:next() do
	print("Iteration:", item, typename, #item)
end

queue.c

#define LUA_LIB

#include <core.h>

struct lua_queue_item {
  int32_t ref;    /* 在注册表的引用位置 */
  struct lua_queue_item *next;
};

struct lua_queue {
  int64_t cap;
  struct lua_queue_item *head;  /* 链表首部 */
  struct lua_queue_item *tail;  /* 链表尾部 */
};

/* 创建元素 */
static inline struct lua_queue_item* new_queue_item(void) {
  struct lua_queue_item* q = xmalloc(sizeof(struct lua_queue_item));
  if (!q)
    return NULL;
  /* 初始化数据结构属性 */
  q->ref = LUA_NOREF; q->next = NULL;
  return q;
}

/* 销毁元素 */
static inline void free_queue_item(struct lua_queue_item* q) {
  xfree(q);
}

/* 插入一个元素到队列中 */
static int linsert(lua_State *L) {
  struct lua_queue* q = luaL_testudata(L, 1, "__LUA_QUEUE__");
  if (!q)
    return luaL_error(L, "Need a lua_queue object but get other value (%s).", lua_typename(L, lua_type(L, 1)));

  struct lua_queue_item* qitem = new_queue_item();
  if (!qitem)
    return luaL_error(L, "lua_queue Queue addition failed: out of memory.");

  /* 插入并调整队列 */
  if (!q->head) {
    q->tail = q->head = qitem;
  } else {
    q->tail->next = qitem;
    q->tail = qitem;
  }

  qitem->ref = luaL_ref(L, LUA_REGISTRYINDEX);
  // 增加容量计数.
  q->cap++;
  return 0;
}

/* 从队列内取出一个元素 */
static int lremove(lua_State *L) {
  struct lua_queue* q = luaL_testudata(L, 1, "__LUA_QUEUE__");
  if (!q)
    return luaL_error(L, "Need a lua_queue object but get other value (%s).", lua_typename(L, lua_type(L, 1)));

  struct lua_queue_item* qitem = q->head;
  if (!qitem)
    return 0;

  lua_rawgeti(L, LUA_REGISTRYINDEX, qitem->ref);
  lua_pushstring(L, lua_typename(L, lua_type(L, -1)));
  luaL_unref(L, LUA_REGISTRYINDEX, qitem->ref);

  /* 删除并调整队列 */
  if (qitem->next) {
    q->head = qitem->next;
  } else {
    q->head = NULL;
    q->tail = NULL;
  }

  q->cap--;

  free_queue_item(qitem);
  return 2;
}

/* 获取队列长度 */
static int llen(lua_State *L) {
  struct lua_queue* q = luaL_testudata(L, 1, "__LUA_QUEUE__");
  if (!q)
    return luaL_error(L, "Need a lua_queue object but get othe value (%s).", lua_typename(L, lua_type(L, 1)));

  lua_pushinteger(L, q->cap);
  return 1;
}

/* 迭代器函数 */
static int lnext(lua_State *L) {
  struct lua_queue* q = luaL_testudata(L, 1, "__LUA_QUEUE__");
  if (!q)
    return luaL_error(L, "Need a lua_queue object but get othe value (%s).", lua_typename(L, lua_type(L, 1)));

  lua_pushcfunction(L, lremove);
  lua_pushvalue(L, -2);
  lua_pushinteger(L, 0);
  return 3;
}

/* 触发gc后的动作 */
static int lgc(lua_State *L) {
  struct lua_queue* q = luaL_testudata(L, 1, "__LUA_QUEUE__");
  while (q->head != NULL) {
    struct lua_queue_item* qitem = q->head;
    struct lua_queue_item* qnext = q->head->next;
    luaL_unref(L, LUA_REGISTRYINDEX, qitem->ref);
    free_queue_item(qitem);
    if (qnext)
      q->head = qnext;
  }
  return 0;
}

/* 创建队列对象 */
static int lnew(lua_State *L) {
  struct lua_queue* q = lua_newuserdata(L, sizeof(struct lua_queue));
  if (!q) 
    return luaL_error(L, "lua_queue Failed to create object: out of memory.");

  /* 初始化数据结构属性 */
  q->cap = 0; q->head = NULL; q->tail = NULL;

  /* 设置元表 */
  luaL_setmetatable(L, "__LUA_QUEUE__");

  return 1;
}

int luaopen_lqueue(lua_State *L) {
  luaL_checkversion(L);
  luaL_newmetatable(L, "__LUA_QUEUE__");
  lua_pushstring (L, "__index");
  lua_pushvalue(L, -2);
  lua_rawset(L, -3);
  lua_pushliteral(L, "__mode");
  lua_pushliteral(L, "kv");
  lua_rawset(L, -3);
  lua_pushliteral(L, "version");
  lua_pushnumber(L, 0.1);
  lua_rawset(L, -3);
  luaL_Reg queue_lib1[] = {
    {"push", linsert},
    {"pop", lremove},
    {"next", lnext},
    {"len", llen},
    {"__gc", lgc},
    {NULL, NULL},
  };
  luaL_setfuncs(L, queue_lib1, 0);
  luaL_Reg queue_lib2[] = {
    {"new", lnew},
    {NULL, NULL},
  };
  luaL_newlib(L, queue_lib2);
  lua_pushliteral(L, "version");
  lua_pushnumber(L, 0.1);
  lua_rawset(L, -3);
  return 1;
}