feat: add a new module channel similar to Golang's channel

See example `examples/channel.lua`.

Signed-off-by: Jianhui Zhao <zhaojh329@gmail.com>

Author: zhaojh329

CMakeLists.txt

@@ -192,7 +192,7 @@ install(
 
 install(
     FILES time.lua sys.lua file.lua dns.lua socket.lua packet.lua mqtt.lua
-        websocket.lua sync.lua nl.lua genl.lua ip.lua nl80211.lua
+        websocket.lua sync.lua channel.lua nl.lua genl.lua ip.lua nl80211.lua
     DESTINATION ${LUA_INSTALL_PREFIX}/eco
 )
 

README.md

@@ -37,6 +37,7 @@ Lua-eco also provides some modules for you to build applications quickly:
 * `dns`: Provides a DNS client implementation for Lua-eco applications, allowing you to perform DNS lookups and resolve domain names.
 * `ubus`: Provides a Lua interface to the [ubus] system in OpenWrt, allowing you to interact with system services and daemons.
 * `sync`: Provides operations for synchronization between coroutines.
+* `channel`: Provides a mechanism for communication between coroutines by sending and receiving values.
 * `netlink`: Provides operations for inter-process communication (IPC) between both the kernel and userspace processes.
 * `nl80211`: Show/manipulate wireless devices and their configuration.
 * `termios`: Bind unix API for terminal/serial I/O.

README_ZH.md

@@ -40,6 +40,7 @@ Lua-eco 还提供了一些有用的模块，方便您快速构建应用程序:
 * `dns`: 为 Lua-eco 应用程序提供了一个 DNS 客户端实现，允许您执行 DNS 查找和解析域名。
 * `ubus`: 提供了一个 Lua 接口，用于 OpenWrt 中的 [ubus] 系统，允许您与系统服务和守护程序交互。
 * `sync`: 提供了协程间同步的操作。
+* `channel`: 提供了一种协程间通信的机制，通过发送和接收数据。
 * `netlink`: 为内核和用户空间进程之间的进程间通信（IPC）提供操作。
 * `nl80211`: 显示/操作无线设备及其配置。
 * `termios`: 绑定 unix 接口用于操作终端和串口。

channel.lua

@@ -0,0 +1,110 @@
+-- SPDX-License-Identifier: MIT
+-- Author: Jianhui Zhao <zhaojh329@gmail.com>
+
+local sync = require 'eco.sync'
+
+local M = {}
+
+local methods = {}
+
+function methods:length()
+    return #self.buf
+end
+
+function methods:close()
+    if self.closed then
+        return
+    end
+
+    self.closed = true
+    self.cond_recv:signal()
+end
+
+-- On success, true is returned
+-- On error, false is returned with a string describing the error
+function methods:send(v, timeout)
+    assert(not self.closed, 'sending on closed channel')
+
+    local buf = self.buf
+
+    if #buf == self.capacity then
+        local ok, err = self.cond_send:wait(timeout)
+        if not ok then
+            return false, err
+        end
+    end
+
+    buf[#buf + 1] = v
+
+    self.cond_recv:signal()
+
+    return true
+end
+
+-- On success, the value received is returned
+-- On closed, nil is returned
+-- On error, nil is returned with a string describing the error
+function methods:recv(timeout)
+    local buf = self.buf
+
+    if #buf < 1 then
+        if self.closed then
+            return nil
+        end
+
+        local ok, err = self.cond_recv:wait(timeout)
+        if not ok then
+            return nil, err
+        end
+    end
+
+    if #buf < 1  then
+        return nil
+    end
+
+    local v = buf[1]
+
+    table.remove(buf,  1)
+
+    self.cond_send:signal()
+
+    return v
+end
+
+local metatable = {
+    __index = methods
+}
+
+--[[
+A channel provides a mechanism for communication between coroutines by sending and receiving values.
+
+When a coroutine sends data to a channel, if the channel is full, the sending operation is blocked
+until another coroutine has taken data from the channel.
+
+Similarly, when a coroutine receives data from a channel, if there is no data available in the channel,
+the receiving operation will be blocked until another coroutine has sent data to the channel.
+
+Closing a channel notifies other coroutines that the channel is no longer in use. After a channel is closed,
+other coroutines can still receive data from it, but they can no longer send data to it.
+
+A channel can have a buffer, default is 1.
+--]]
+function M.new(capacity)
+    assert(capacity == nil or math.type(capacity) == 'integer', 'capacity must be an integer')
+
+    if not capacity or capacity < 1 then
+        capacity = 1
+    end
+
+    local ch = {
+        cond_send = sync.cond(),
+        cond_recv = sync.cond(),
+        capacity = capacity,
+        closed = false,
+        buf = {}
+    }
+
+    return setmetatable(ch, metatable)
+end
+
+return M

examples/channel.lua

@@ -0,0 +1,41 @@
+#!/usr/bin/env eco
+
+local channel = require 'eco.channel'
+local time = require 'eco.time'
+
+-- Create a channel with 5 buffers.
+local ch = channel.new(5)
+
+eco.run(function()
+    local i = 1
+    while true do
+        ch:send(i)
+
+        print(os.time(), 'send', i)
+
+        if i == 5 then
+            ch:close()
+            break
+        end
+
+        i = i + 1
+        time.sleep(1)
+    end
+end)
+
+eco.run(function()
+    time.sleep(2)
+    while true do
+        local v = ch:recv()
+        if v then
+            print(os.time(), 'recv:', v)
+        else
+            print(os.time(), 'closed')
+            break
+        end
+    end
+end)
+
+while true do
+    time.sleep(1)
+end