tornado源码分析-iostream

tornado源码分析-iostream
1.iostream.py作用
用来异步读写文件，socket通信

2.使用示例

import tornado.ioloop
import tornado.iostream
import socket

def send_request():
    stream.write(b'GET / HTTP/1.1\r\nHost: www.sina.com.cn\r\nConnection: close\r\n\r\n')
    stream.read_until(b"\r\n\r\n", on_headers)

def on_headers(data):
    headers = {}
    for line in data.split(b"\r\n"):
        parts = line.split(b":")
        if len(parts) == 2:
            headers[parts[0]] = parts[1]
    stream.read_bytes(int(headers[b"Content-Length"]), on_body)

def on_body(data):
    print(data)
    with open('sina.html', 'wb') as f:
        f.write(data)
    stream.close()
    tornado.ioloop.IOLoop.current().stop()


if __name__ == '__main__':
    client_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    stream = tornado.iostream.IOStream(client_socket)
    stream.connect(("www.sina.com.cn", 80), send_request)
    tornado.ioloop.IOLoop.current().start()

与传统socket通信的区别是，iostream对socket进行了包装，可以进行异步的读写。

3.iostream主要功能

class IOStream(BaseIOStream):
	def read_until(self, delimiter, callback):
		future = self._set_read_callback(callback)
        self._read_delimiter = delimiter
        self._read_max_bytes = max_bytes
        try:
            self._try_inline_read()
		except:
			...
	def read_bytes(self, num_bytes, callback, streaming_callback=None)
		...
	def read_until_regex(self, regex, callback):
		...
	def read_until_close(self, callback, streaming_callback=None):
		...
	def write(self, data, callback=None):
		...
	
	def _handle_events(self, fd, events):
		...
    def _add_io_state(self, state):
		...
        if self._state is None:
            self._state = ioloop.IOLoop.ERROR | state
            with stack_context.NullContext():
                self.io_loop.add_handler(
                    self.fileno(), self._handle_events, self._state)
        elif not self._state & state:
            self._state = self._state | state
            self.io_loop.update_handler(self.fileno(), self._state)
	def connect(self, address, callback=None, server_hostname=None):
		...

    def _try_inline_read(self):
		# See if we've already got the data from a previous read
        self._run_streaming_callback()
	    pos = self._find_read_pos()
	    if pos is not None:
	        self._read_from_buffer(pos)
	        return
	    self._check_closed()
	    try:
	        pos = self._read_to_buffer_loop()
	    except Exception:
	       ...
	    if pos is not None:
	        self._read_from_buffer(pos)
	        return
	    if self.closed():
	        self._maybe_run_close_callback()
	    else:
	        self._add_io_state(ioloop.IOLoop.READ)
   	
	def _read_from_buffer(self, pos):
        self._read_bytes = self._read_delimiter = self._read_regex = None
        self._read_partial = False
        self._run_read_callback(pos, False)

    def _run_read_callback(self, size, streaming):
        if streaming:
            callback = self._streaming_callback
        else:
            callback = self._read_callback
            self._read_callback = self._streaming_callback = None
            if self._read_future is not None:
                assert callback is None
                future = self._read_future
                self._read_future = None
                future.set_result(self._consume(size))
        if callback is not None:
            assert (self._read_future is None) or streaming
            self._run_callback(callback, self._consume(size))
        else:
            self._maybe_add_error_listener()

	def _consume(self, loc):
		...

read_until:读到delimiter结束
read_bytes:读取num_bytes个字符后结束
read_until_regex:读取到正则匹配到后结束
read_until_close:读取到scoket关闭后结束
读流程：
self._run_streaming_callback()
字节流回调，待研究

future = self._set_read_callback(callback)
注册读完成回调事件

pos = self._find_read_pos()
读取位置

self._read_from_buffer(pos)
从缓存读取

pos = self._read_to_buffer_loop()
socket等待接收数据，放入缓存
self._read_from_buffer(pos)
从缓存读取

self._consume(size)
读缓冲器size个字节，从缓冲区删除并返回这些数据

_maybe_add_error_listener
没有可读数据，开启监听read事件，当read事件发生时再调用handle_read处理

_pending_callbacks
控制信号量，待研究

write:首先将data按数据块大小WRITE_BUFFER_CHUNK_SIZE分块写入write_buffer,
然后调用handle_write向socket发送数据

connect:建立非阻塞socket连接，注册ioloop可写事件

_add_io_state：为ioloop注册或更新READ,WRITE,ERROR事件，ioloop异步执行读socket，写socket操作等
handle_read：从socket读到缓冲区
handle_write:由缓冲区向socket写