Function test_read_partial_midframe

lib/cpp/test/TransportTest.cpp:643–698

template <class CoupledTransports>
void test_read_partial_midframe() {
  CoupledTransports transports;
  BOOST_REQUIRE(transports.in != nullptr);
  BOOST_REQUIRE(transports.out != nullptr);

  uint8_t write_buf[16];
  uint8_t read_buf[16];
  memset(write_buf, 'a', sizeof(write_buf));

  // Attempt to read 10 bytes, when only 9 are available, but after we have
  // already read part of the data that is available.  This exercises a
  // different code path for several of the transports.
  //
  // For transports that add their own framing (e.g., TFramedTransport and
  // TFileTransport), the two flush calls break up the data in to a 10 byte
  // frame and a 3 byte frame.  The first read then puts us partway through the
  // first frame, and then we attempt to read past the end of that frame, and
  // through the next frame, too.
  //
  // For buffered transports that perform read-ahead (e.g.,
  // TBufferedTransport), the read-ahead will most likely see all 13 bytes
  // written on the first read.  The next read will then attempt to read past
  // the end of the read-ahead buffer.
  //
  // Flush 10 bytes, then 3 bytes.  This creates 2 separate frames for
  // transports that track framing internally.
  transports.out->write(write_buf, 10);
  transports.out->flush();
  transports.out->write(write_buf, 3);
  transports.out->flush();

  // Now read 4 bytes, so that we are partway through the written data.
  uint32_t bytes_read = transports.in->read(read_buf, 4);
  BOOST_CHECK_EQUAL(bytes_read, (uint32_t)4);

  // Now attempt to read 10 bytes.  Only 9 more are available.
  //
  // We should be able to get all 9 bytes, but it might take multiple read
  // calls, since it is valid for read() to return fewer bytes than requested.
  // (Most transports do immediately return 9 bytes, but the framing transports
  // tend to only return to the end of the current frame, which is 6 bytes in
  // this case.)
  uint32_t total_read = 0;
  while (total_read < 9) {
    set_trigger(3, transports.out, 1);
    bytes_read = transports.in->read(read_buf, 10);
    BOOST_REQUIRE_EQUAL(g_numTriggersFired, (unsigned int)0);
    BOOST_REQUIRE_GT(bytes_read, (uint32_t)0);
    total_read += bytes_read;
    BOOST_REQUIRE_LE(total_read, (uint32_t)9);
  }

  BOOST_CHECK_EQUAL(total_read, (uint32_t)9);

  clear_triggers();
}

template <class CoupledTransports>