mirror of
https://git.k-space.ee/arti/vt1200.git
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386 lines
16 KiB
Python
386 lines
16 KiB
Python
"""Tests for the host sender: pacing, chunking, and the status back-channel.
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The plan's acceptance run says "MAME with a tap interface: run vidsend.py for
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200 frames at 30 fps". That run cannot happen in this repository: the MAME
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driver creates no ``device_network_interface``, so the emulated LANCE is not
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attached to the host at all (ruling R11). What can be tested here is every
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layer below the socket, and that is what this file does:
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* the *schedule* -- frame ``n`` leaves at ``t0 + n/fps``, measured on an
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injected clock rather than by sleeping for real;
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* the *wire form* -- a frame is chunked at 1450 bytes, only the last datagram is
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padded to the 60-byte Ethernet minimum, and the pieces reassemble to exactly
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the bytes ``vidsrc.StripSource`` produced;
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* the *status* path -- a status frame is recognised in an Ethernet frame,
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decoded field by field, and ``drops``/``crc_err`` decide the exit status;
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* the *loop* -- a fake counterparty that reassembles datagrams, counts frames
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and answers with status frames, so a 200-frame run's verdict is exercised
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without a NIC or a terminal.
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No test here touches a socket, and none of them claims anything about whether a
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frame would arrive on a real wire.
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"""
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import io
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import struct
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import pytest
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from harness.udpstream import vidsend
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from harness.udpstream.frame import (BROADCAST, ETHERTYPE, HEADER_SIZE,
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KIND_STATUS, TERMINAL_MAC, ethernet_frame,
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pack_header, pack_status, unpack_header)
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from harness.udpstream.vidsrc import CHUNK, ROW_BYTES, StripSource
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#: The host's own address. Locally administered, so it cannot be mistaken for
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#: the terminal's (08:00:2b:16:4b:5a, TERMINAL_MAC) in a datagram assertion.
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HOST_MAC = b"\x02\x00\x00\x00\x00\x01"
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class FakeClock:
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"""A monotonic clock that only moves when something sleeps on it."""
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def __init__(self):
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self.t = 0.0
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self.sleeps = []
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def now(self):
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return self.t
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def sleep(self, seconds):
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self.sleeps.append(seconds)
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self.t += seconds
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class RecordingTransport:
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"""Stands in for the NIC: records each datagram and when it was sent."""
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def __init__(self, clock):
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self.clock = clock
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self.datagrams = []
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self.times = []
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def __call__(self, data):
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self.datagrams.append(data)
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self.times.append(self.clock.now())
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def make_sender(clock, transport, **kw):
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kw.setdefault("rows", 8)
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kw.setdefault("stretch", 128)
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kw.setdefault("fps", 10.0)
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kw.setdefault("status_wait", 0.0)
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kw.setdefault("out", io.StringIO())
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kw.setdefault("err", io.StringIO())
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kw.setdefault("src", HOST_MAC)
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return vidsend.Sender(transport=transport, clock=clock.now,
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sleep=clock.sleep, **kw)
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def status_frame(frames_rx=0, crc_err=0, drops=0, csr0=0x20F2, heap_free_kb=2048,
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frame_no=0, body=None):
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body = pack_status(frames_rx, crc_err, drops, csr0, heap_free_kb) \
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if body is None else body
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hdr = pack_header(KIND_STATUS, frame_no, len(body), 0, 0, payload=body)
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return ethernet_frame(hdr + body, src=TERMINAL_MAC)
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# --- pacing ---------------------------------------------------------------
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def test_frame_n_leaves_at_t0_plus_n_over_fps():
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"""The schedule, not "about 10 a second": exactly t0 + n/fps."""
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clock = FakeClock()
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transport = RecordingTransport(clock)
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sender = make_sender(clock, transport, fps=10.0, frames=5)
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sender.run() # the exit status is the status verdict, tested below
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assert transport.times == pytest.approx([0.0, 0.1, 0.2, 0.3, 0.4])
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# And the sleeps are the differences: the first frame does not sleep.
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assert clock.sleeps == pytest.approx([0.1, 0.1, 0.1, 0.1])
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def test_pacing_does_not_accumulate_drift():
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"""A slow frame is followed by a shorter sleep, not by a later schedule.
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``t0 + n/fps`` is absolute, so the sender catches up instead of falling
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behind by however long the previous frame took.
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"""
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clock = FakeClock()
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sent_at = []
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def transport(data):
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sent_at.append(clock.now())
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clock.t += 0.03 # this frame took 30 ms to send
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sender = make_sender(clock, transport, fps=10.0, frames=4)
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sender.run() # the exit status is the status verdict, tested below
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assert sent_at == pytest.approx([0.0, 0.1, 0.2, 0.3])
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def test_fps_zero_sends_unpaced():
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clock = FakeClock()
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transport = RecordingTransport(clock)
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sender = make_sender(clock, transport, fps=0.0, frames=3)
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sender.run() # the exit status is the status verdict, tested below
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assert transport.times == [0.0, 0.0, 0.0]
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assert clock.sleeps == []
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def test_a_csv_line_every_thirty_frames():
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clock = FakeClock()
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transport = RecordingTransport(clock)
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out = io.StringIO()
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sender = make_sender(clock, transport, fps=0.0, frames=65, out=out)
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sender.run() # the exit status is the status verdict, tested below
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lines = out.getvalue().strip().splitlines()
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assert lines[0] == vidsend.CSV_HEADER == "frame,elapsed_s,fps,bytes"
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# 30 and 60, not a line per frame and not 0 (nothing sent yet). stdout
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# carries the table only; the prose (status, verdict) goes to stderr.
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assert [ln.split(",")[0] for ln in lines[1:]] == ["30", "60"]
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frame_col, elapsed_col, _fps, bytes_col = lines[1].split(",")
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assert int(frame_col) == 30 and float(elapsed_col) == 0.0
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assert int(bytes_col) > 0
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# --- the wire form --------------------------------------------------------
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def test_only_the_last_datagram_is_short_and_none_is_padded_mid_frame():
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"""128 rows = 20,480 B: 15 datagrams at 1450, the last one alone short.
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Each datagram carries the 14-byte Ethernet header in front of its chunk,
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so a middle datagram is exactly CHUNK + 14 bytes; only the last one may be
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padded to the minimum and here it is already well over it.
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"""
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clock = FakeClock()
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transport = RecordingTransport(clock)
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sender = make_sender(clock, transport, rows=128, stretch=8, frames=1)
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sender.run() # the exit status is the status verdict, tested below
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dgrams = transport.datagrams
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assert len(dgrams) == 15
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assert [len(d) for d in dgrams[:-1]] == [CHUNK + 14] * 14
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assert len(dgrams[-1]) == 14 + (HEADER_SIZE + 128 * ROW_BYTES - 14 * CHUNK)
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def test_datagrams_reassemble_to_the_frame_the_encoder_built():
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"""What the receiver gets back is byte for byte vidsrc's frame."""
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clock = FakeClock()
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transport = RecordingTransport(clock)
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sender = make_sender(clock, transport, rows=8, stretch=128, frames=1)
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sender.run() # the exit status is the status verdict, tested below
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body = b"".join(d[14:] for d in transport.datagrams)
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want = StripSource(8, 128).encode(0, vidsend.bars(8, 0))
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assert body == b"".join(want)
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h = unpack_header(body)
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assert h["crc_ok"] is True and h["kind"] == 1 and h["rows"] == 8
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def test_a_datagram_carries_the_ethernet_header_and_padding():
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"""The smallest valid strip (8 rows x 128) is 1296 bytes: one datagram."""
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clock = FakeClock()
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transport = RecordingTransport(clock)
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sender = make_sender(clock, transport, rows=8, stretch=128, frames=1)
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sender.run() # the exit status is the status verdict, tested below
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(d,) = transport.datagrams
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assert len(d) == 14 + HEADER_SIZE + 8 * ROW_BYTES
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assert d[:6] == BROADCAST and d[6:12] == HOST_MAC
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assert d[12:14] == struct.pack(">H", ETHERTYPE)
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def test_a_short_last_datagram_is_padded_and_a_mid_one_is_not():
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"""The padding rule, stated where it can bite: Ethernet needs 60 bytes.
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The smallest valid strip is 1296 bytes; chunked at 1255 the second (and
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last) datagram carries 41 bytes of frame, so it must be padded to 60 while
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the 1255-byte chunk before it must not be. Padding a middle chunk would
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insert bytes into the frame body.
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"""
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clock = FakeClock()
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transport = RecordingTransport(clock)
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sender = make_sender(clock, transport, rows=8, stretch=128, frames=1,
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chunk=1255)
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sender.run() # the exit status is the status verdict, tested below
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sizes = [len(d) for d in transport.datagrams]
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assert sizes == [1255 + 14, 60] # 1296 - 1255 = 41 bytes of frame
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frame = b"".join(d[14:] for d in transport.datagrams)
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assert frame[:1296] == b"".join(
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StripSource(8, 128).encode(0, vidsend.bars(8, 0)))
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assert frame[1296:] == bytes(5) # the pad, and only at the end
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def test_frame_numbers_wrap_at_16_bits_and_bodies_differ_per_frame():
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"""frame_no is a u16 field; the pattern must move or a stream is not one."""
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assert vidsend.bars(8, 0) != vidsend.bars(8, 1)
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clock = FakeClock()
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transport = RecordingTransport(clock)
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sender = make_sender(clock, transport, fps=0.0, frames=2)
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sender.frame_offset = 0xFFFE # next two frames straddle the wrap
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sender.run() # the exit status is the status verdict, tested below
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nos = [unpack_header(d[14:])["frame_no"] for d in transport.datagrams]
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assert nos == [0xFFFE, 0xFFFF]
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# --- the status path ------------------------------------------------------
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def test_a_status_frame_is_decoded_from_an_ethernet_frame():
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d = vidsend.decode_status_frame(status_frame(frames_rx=200, csr0=0x20F2,
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heap_free_kb=2048))
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assert d is not None
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assert d["kind"] == KIND_STATUS and d["crc_ok"] is True
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assert d["frames_rx"] == 200 and d["drops"] == 0 and d["crc_err"] == 0
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assert d["csr0"] == 0x20F2 and d["heap_free_kb"] == 2048
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def test_a_strip_frame_is_not_mistaken_for_a_status():
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clock = FakeClock()
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transport = RecordingTransport(clock)
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sender = make_sender(clock, transport, fps=0.0, frames=1)
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sender.run() # the exit status is the status verdict, tested below
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assert vidsend.decode_status_frame(transport.datagrams[0]) is None
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def test_a_status_frame_with_a_corrupt_header_is_flagged_not_decoded():
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bad = bytearray(status_frame(frames_rx=1))
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bad[14 + 8] ^= 0x01 # rows byte, inside the CRC prefix
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d = vidsend.decode_status_frame(bytes(bad))
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assert d is not None and d["crc_ok"] is False
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def test_a_status_in_a_foreign_ethertype_is_ignored():
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body = pack_status(1, 0, 0, 0, 0)
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hdr = pack_header(KIND_STATUS, 0, len(body), 0, 0)
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data = (BROADCAST + TERMINAL_MAC + struct.pack(">H", 0x88B6) + hdr + body)
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assert vidsend.decode_status_frame(data) is None
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# --- the verdict ----------------------------------------------------------
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def run_with_statuses(*status_bytes, frames=3):
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clock = FakeClock()
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transport = RecordingTransport(clock)
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pending = list(status_bytes)
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def recv():
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out, pending[:] = list(pending), []
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return out
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out, err = io.StringIO(), io.StringIO()
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sender = vidsend.Sender(transport=transport, receive=recv, src=HOST_MAC,
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clock=clock.now, sleep=clock.sleep, frames=frames,
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fps=0.0, status_wait=0.0, rows=8, stretch=128,
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out=out, err=err)
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code = sender.run()
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return sender, code, out.getvalue() + err.getvalue()
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def test_exit_zero_only_when_drops_and_crc_err_are_clean():
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_, code, text = run_with_statuses(status_frame(frames_rx=3))
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assert code == 0
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assert "drops=0" in text and "crc_err=0" in text
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_, code, _ = run_with_statuses(status_frame(frames_rx=3, drops=1))
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assert code == 1
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_, code, _ = run_with_statuses(status_frame(frames_rx=3, crc_err=2))
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assert code == 1
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def test_exit_is_non_zero_when_no_status_arrives():
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"""No status means the two conditions were never observed, so no PASS."""
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_, code, text = run_with_statuses()
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assert code == 1
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assert "no status" in text.lower()
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def test_a_status_with_a_bad_header_crc_does_not_count():
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bad = bytearray(status_frame(frames_rx=3))
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bad[14 + 3] ^= 0x01 # kind byte, inside the CRC prefix
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_, code, text = run_with_statuses(bytes(bad))
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assert code == 1
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assert "crc" in text.lower()
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# --- the whole loop, with a fake counterparty -----------------------------
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class FakeTerminal:
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"""Reassembles the sender's datagrams and answers with status frames.
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This is the sender's counterparty, not a VT1200 model: it counts what
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arrived and every 64 accepted frames hands back the status frame the
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payload would send. It exists to exercise vidsend.py's loop, not to stand
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in for the terminal -- the terminal's own status emission is checked in
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MAME (VT1200_MODE=stream) and decoded by vidstream_status_check.py.
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"""
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def __init__(self, every=64, drops=0, crc_err=0):
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self.every = every
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self.drops = drops
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self.crc_err = crc_err
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self.buf = b""
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self.frames_rx = 0
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self.reported = []
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self.pending = []
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def send(self, data):
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if data[12:14] != struct.pack(">H", ETHERTYPE):
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return
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self.buf += data[14:]
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if len(self.buf) < HEADER_SIZE:
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return
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plen = struct.unpack_from("<H", self.buf, 6)[0]
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if len(self.buf) < HEADER_SIZE + plen:
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return
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frame, self.buf = self.buf[:HEADER_SIZE + plen], b""
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h = unpack_header(frame)
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assert h["crc_ok"], "the sender built a frame the parser rejects"
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self.frames_rx += 1
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if self.frames_rx % self.every == 0:
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self.reported.append(self.frames_rx)
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self.pending.append(status_frame(
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frames_rx=self.frames_rx, drops=self.drops,
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crc_err=self.crc_err, frame_no=len(self.reported)))
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def recv(self):
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out, self.pending = self.pending, []
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return out
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def test_two_hundred_frames_get_three_periodic_statuses_and_a_clean_verdict():
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"""The brief's run on the layer below the socket.
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200 frames at 30 fps, a status every 64 accepted: 64, 128, 192, each with
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drops=0 and crc_err=0, so the verdict is PASS. The brief's final reading,
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``frames_rx == 200``, needs one more thing the sender cannot assume: the
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terminal only reports on its 64th frame, so the last report is 192 unless
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the terminal is told the stream ended -- in MAME that is the RX_EOF cell,
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see vidstream.lua and the task-6 report.
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"""
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clock = FakeClock()
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term = FakeTerminal()
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out, err = io.StringIO(), io.StringIO()
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sender = vidsend.Sender(transport=term.send, receive=term.recv,
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src=HOST_MAC, clock=clock.now,
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sleep=clock.sleep, rows=8, stretch=128,
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frames=200, fps=30.0, status_wait=0.0, out=out,
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err=err)
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code = sender.run()
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assert code == 0
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assert term.frames_rx == 200
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assert term.reported == [64, 128, 192]
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assert [s["frames_rx"] for s in sender.statuses] == [64, 128, 192]
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# The schedule: 200 frames at 30 fps take 199/30 s of virtual time.
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assert clock.now() == pytest.approx(199 / 30.0)
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assert "PASS" in err.getvalue()
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def test_a_terminal_reporting_drops_makes_the_verdict_fail():
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"""drops is the terminal's number, not something the sender invents."""
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clock = FakeClock()
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term = FakeTerminal(drops=1)
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out, err = io.StringIO(), io.StringIO()
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sender = vidsend.Sender(transport=term.send, receive=term.recv,
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src=HOST_MAC, clock=clock.now,
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sleep=clock.sleep, rows=8, stretch=128,
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frames=64, fps=0.0, status_wait=0.0, out=out,
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err=err)
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assert sender.run() == 1
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assert "drops=1" in err.getvalue()
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assert "FAIL" in err.getvalue()
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