micropython-samples/uasyncio_iostream/tests/iotest2.py

# iotest2.py Test PR #3836. User class write() performs buffered writing.
# Reading is unbuffered.

import io, pyb
import uasyncio as asyncio
import micropython
micropython.alloc_emergency_exception_buf(100)

MP_STREAM_POLL_RD = const(1)
MP_STREAM_POLL_WR = const(4)
MP_STREAM_POLL = const(3)
MP_STREAM_ERROR = const(-1)

def printbuf(this_io):
    print(bytes(this_io.wbuf[:this_io.wprint_len]).decode(), end='')
    this_io.wbuf = b''

class MyIO(io.IOBase):
    def __init__(self):
        self.ready_rd = False
        self.ready_wr = False
        self.wbuf = b''
        self.wprint_len = 0
        self.ridx = 0
        self.rbuf = b'ready\n'  # Read buffer
        pyb.Timer(4, freq = 1, callback = self.do_input)
        pyb.Timer(5, freq = 10, callback = self.do_output)

    # Read callback: emulate asynchronous input from hardware.
    # Typically would put bytes into a ring buffer and set .ready_rd.
    def do_input(self, t):
        self.ready_rd = True  # Data is ready to read

    # Write timer callback. Emulate hardware: if there's data in the buffer
    # write some or all of it
    def do_output(self, t):
        if self.wbuf:
            self.wprint_len = self.wbuf.find(b'\n') + 1
            micropython.schedule(printbuf, self)


    def ioctl(self, req, arg):  # see ports/stm32/uart.c
#        print('ioctl', req, arg)
        ret = MP_STREAM_ERROR
        if req == MP_STREAM_POLL:
            ret = 0
            if arg & MP_STREAM_POLL_RD:
                if self.ready_rd:
                    ret |= MP_STREAM_POLL_RD
            if arg & MP_STREAM_POLL_WR:
                if not self.wch:
                    ret |= MP_STREAM_POLL_WR  # Ready if no char pending
        return ret

    # Test of device that produces one character at a time
    def readline(self):
        self.ready_rd = False
        ch = self.rbuf[self.ridx]
        if ch == ord('\n'):
            self.ridx = 0
        else:
            self.ridx += 1
        return chr(ch)

    def write(self, buf, off, sz):
        self.wbuf = buf[:]
        return sz  # No. of bytes written. uasyncio waits on ioctl write ready

myio = MyIO()

async def receiver():
    sreader = asyncio.StreamReader(myio)
    while True:
        res = await sreader.readline()
        print('Received', res)

async def sender():
    swriter = asyncio.StreamWriter(myio, {})
    await asyncio.sleep(5)
    count = 0
    while True:
        count += 1
        tosend = 'Wrote Hello MyIO {}\n'.format(count)
        await swriter.awrite(tosend.encode('UTF8'))
        await asyncio.sleep(2)

loop = asyncio.get_event_loop()
loop.create_task(receiver())
loop.create_task(sender())
loop.run_forever()