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--!A cross-platform build utility based on Lua
--
-- Licensed under the Apache License, Version 2.0 (the "License");
-- you may not use this file except in compliance with the License.
-- You may obtain a copy of the License at
--
-- http://www.apache.org/licenses/LICENSE-2.0
--
-- Unless required by applicable law or agreed to in writing, software
-- distributed under the License is distributed on an "AS IS" BASIS,
-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-- See the License for the specific language governing permissions and
-- limitations under the License.
--
-- Copyright (C) 2015-present, Xmake Open Source Community.
--
-- @author ruki
-- @file queue.lua
--
-- load modules
local object = require("base/object")
-- define module
local queue = queue or object {_init = {"_first", "_last"}} {1, 0}
-- clear queue
function queue:clear()
self._first = 1
self._last = 0
end
-- push item to queue
function queue:push(item)
local last = self._last + 1
self._last = last
self[last] = item
end
-- pop item from queue
function queue:pop()
local first = self._first
if first > self._last then
return nil
end
local value = self[first]
self[first] = nil
self._first = first + 1
return value
end
-- get queue size
function queue:size()
return self._last - self._first + 1
end
-- is queue empty?
function queue:empty()
return self._first > self._last
end
-- peek the first item of queue
function queue:first()
if self._first > self._last then
return nil
end
return self[self._first]
end
-- peek the last item of queue
function queue:last()
if self._first > self._last then
return nil
end
return self[self._last]
end
-- iterator for all items (forward)
--
-- e.g.
--
-- for item in queue:items() do
-- print(item)
-- end
--
function queue:items()
local index = self._first - 1
local last = self._last
return function()
index = index + 1
if index <= last then
return self[index]
end
end
end
-- iterator for all items (reverse)
function queue:ritems()
local index = self._last + 1
local first = self._first
return function()
index = index - 1
if index >= first then
return self[index]
end
end
end
-- clone queue
function queue:clone()
local q = queue.new()
for i = self._first, self._last do
q:push(self[i])
end
return q
end
-- create a new FIFO queue
--
-- @return the queue instance
--
function queue.new()
return queue()
end
-- return module: queue
return queue
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