test-example-projects/c++_projects/280w-mysql-8.0.18/vio/vioshm.cc

/* Copyright (c) 2010, 2019, Oracle and/or its affiliates. All rights reserved.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License, version 2.0,
   as published by the Free Software Foundation.

   This program is also distributed with certain software (including
   but not limited to OpenSSL) that is licensed under separate terms,
   as designated in a particular file or component or in included license
   documentation.  The authors of MySQL hereby grant you an additional
   permission to link the program and your derivative works with the
   separately licensed software that they have included with MySQL.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License, version 2.0, for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */

#include "vio_priv.h"

#include "my_byteorder.h"
#include "my_shm_defaults.h"

size_t vio_read_shared_memory(Vio *vio, uchar *buf, size_t size) {
  size_t length;
  size_t remain_local;
  uchar *current_position;
  HANDLE events[2];
  DWORD timeout;
  DBUG_TRACE;

  remain_local = size;
  current_position = buf;
  timeout = vio->read_timeout >= 0 ? vio->read_timeout : INFINITE;

  events[0] = vio->event_server_wrote;
  events[1] = vio->event_conn_closed;

  do {
    if (vio->shared_memory_remain == 0) {
      DWORD wait_status;

      wait_status = WaitForMultipleObjects(array_elements(events), events,
                                           false, timeout);

      /*
         WaitForMultipleObjects can return next values:
         WAIT_OBJECT_0+0 - event from vio->event_server_wrote
         WAIT_OBJECT_0+1 - event from vio->event_conn_closed.
                           We can't read anything
         WAIT_ABANDONED_0 and WAIT_TIMEOUT - fail.  We can't read anything
      */
      if (wait_status != WAIT_OBJECT_0) {
        /*
          If wait_status is WAIT_TIMEOUT, set error code to indicate a
          timeout error. If vio->event_conn_closed was set, use an EOF
          condition (return value of zero) to indicate that the operation
          has been aborted.
        */
        if (wait_status == WAIT_TIMEOUT)
          SetLastError(SOCKET_ETIMEDOUT);
        else if (wait_status == (WAIT_OBJECT_0 + 1))
          return 0;

        return -1;
      }

      vio->shared_memory_pos = vio->handle_map;
      vio->shared_memory_remain = uint4korr(vio->shared_memory_pos);
      vio->shared_memory_pos += 4;
    }

    length = size;

    if (vio->shared_memory_remain < length) length = vio->shared_memory_remain;
    if (length > remain_local) length = remain_local;

    memcpy(current_position, vio->shared_memory_pos, length);

    vio->shared_memory_remain -= length;
    vio->shared_memory_pos += length;
    current_position += length;
    remain_local -= length;

    if (!vio->shared_memory_remain) {
      if (!SetEvent(vio->event_client_read)) return -1;
    }
  } while (remain_local);
  length = size;

  return length;
}

size_t vio_write_shared_memory(Vio *vio, const uchar *buf, size_t size) {
  size_t length, remain, sz;
  HANDLE pos;
  const uchar *current_position;
  HANDLE events[2];
  DWORD timeout;
  DBUG_TRACE;

  remain = size;
  current_position = buf;
  timeout = vio->write_timeout >= 0 ? vio->write_timeout : INFINITE;

  events[0] = vio->event_server_read;
  events[1] = vio->event_conn_closed;

  while (remain != 0) {
    DWORD wait_status;

    wait_status =
        WaitForMultipleObjects(array_elements(events), events, false, timeout);

    if (wait_status != WAIT_OBJECT_0) {
      /* Set error code to indicate a timeout error or disconnect. */
      if (wait_status == WAIT_TIMEOUT)
        SetLastError(SOCKET_ETIMEDOUT);
      else
        SetLastError(ERROR_GRACEFUL_DISCONNECT);

      return (size_t)-1;
    }

    sz = (remain > shared_memory_buffer_length ? shared_memory_buffer_length
                                               : remain);

    int4store(vio->handle_map, (uint32)sz);
    pos = vio->handle_map + 4;
    memcpy(pos, current_position, sz);
    remain -= sz;
    current_position += sz;
    if (!SetEvent(vio->event_client_wrote)) return (size_t)-1;
  }
  length = size;

  return length;
}

bool vio_is_connected_shared_memory(Vio *vio) {
  return (WaitForSingleObject(vio->event_conn_closed, 0) != WAIT_OBJECT_0);
}

void vio_delete_shared_memory(Vio *vio) {
  DBUG_TRACE;

  if (!vio) return;

  if (vio->inactive == false) vio->vioshutdown(vio);

  /*
    Close all handlers. UnmapViewOfFile and CloseHandle return non-zero
    result if they are success.
  */
  if (UnmapViewOfFile(vio->handle_map) == 0)
    DBUG_PRINT("vio_error", ("UnmapViewOfFile() failed"));

  if (CloseHandle(vio->event_server_wrote) == 0)
    DBUG_PRINT("vio_error", ("CloseHandle(vio->esw) failed"));

  if (CloseHandle(vio->event_server_read) == 0)
    DBUG_PRINT("vio_error", ("CloseHandle(vio->esr) failed"));

  if (CloseHandle(vio->event_client_wrote) == 0)
    DBUG_PRINT("vio_error", ("CloseHandle(vio->ecw) failed"));

  if (CloseHandle(vio->event_client_read) == 0)
    DBUG_PRINT("vio_error", ("CloseHandle(vio->ecr) failed"));

  if (CloseHandle(vio->handle_file_map) == 0)
    DBUG_PRINT("vio_error", ("CloseHandle(vio->hfm) failed"));

  if (CloseHandle(vio->event_conn_closed) == 0)
    DBUG_PRINT("vio_error", ("CloseHandle(vio->ecc) failed"));

  vio_delete(vio);
}

/*
  When "kill connection xx" is executed on an arbitrary thread it calls
  THD::shutdown_active_vio() on the THD referred to by xx. Since the
  thread serving the connection xx might be in the middle of a vio_read
  or vio_write, we cannot unmap the shared memory here.

  Therefore we here just signal the connection_closed event and give
  the thread servicing connection xx a chance to gracefully exit.
  All handles are closed and the VIO is cleaned up when vio_delete() is
  called and this completes the vio cleanup operation in its entirety.
*/
int vio_shutdown_shared_memory(Vio *vio) {
  DBUG_TRACE;
  if (vio->inactive == false) {
    /*
      Set event_conn_closed for notification of both client and server that
      connection is closed
    */
    SetEvent(vio->event_conn_closed);
  }

  vio->inactive = true;
  vio->mysql_socket = MYSQL_INVALID_SOCKET;

  return 0;
}