1 | /* $Id: Helper.cpp 96407 2022-08-22 17:43:14Z vboxsync $ */
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2 | /** @file
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3 | *
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4 | * VBox frontends: VBoxSDL (simple frontend based on SDL):
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5 | * Miscellaneous helpers
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6 | */
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7 |
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8 | /*
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9 | * Copyright (C) 2006-2022 Oracle and/or its affiliates.
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10 | *
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11 | * This file is part of VirtualBox base platform packages, as
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12 | * available from https://www.virtualbox.org.
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13 | *
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14 | * This program is free software; you can redistribute it and/or
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15 | * modify it under the terms of the GNU General Public License
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16 | * as published by the Free Software Foundation, in version 3 of the
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17 | * License.
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18 | *
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19 | * This program is distributed in the hope that it will be useful, but
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20 | * WITHOUT ANY WARRANTY; without even the implied warranty of
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21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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22 | * General Public License for more details.
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23 | *
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24 | * You should have received a copy of the GNU General Public License
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25 | * along with this program; if not, see <https://www.gnu.org/licenses>.
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26 | *
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27 | * SPDX-License-Identifier: GPL-3.0-only
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28 | */
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29 |
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30 | #define LOG_GROUP LOG_GROUP_GUI
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31 | #include <iprt/errcore.h>
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32 | #include <VBox/log.h>
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33 | #include <iprt/asm.h>
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34 | #include <iprt/assert.h>
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35 | #include <iprt/thread.h>
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36 | #include <iprt/semaphore.h>
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37 | #include "VBoxSDL.h"
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38 | #include "Helper.h"
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39 |
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40 |
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41 | /**
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42 | * Globals
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43 | */
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44 |
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45 |
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46 | #ifdef USE_XPCOM_QUEUE_THREAD
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47 |
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48 | /** global flag indicating that the event queue thread should terminate */
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49 | static bool volatile g_fTerminateXPCOMQueueThread = false;
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50 |
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51 | /** How many XPCOM user events are on air. Only allow one pending event to
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52 | * prevent an overflow of the SDL event queue. */
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53 | static volatile int32_t g_s32XPCOMEventsPending;
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54 |
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55 | /** Semaphore the XPCOM event thread will sleep on while it waits for the main thread to process pending requests. */
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56 | RTSEMEVENT g_EventSemXPCOMQueueThread = NULL;
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57 |
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58 | /**
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59 | * Thread method to wait for XPCOM events and notify the SDL thread.
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60 | *
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61 | * @returns Error code
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62 | * @param thread Thread ID
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63 | * @param pvUser User specific parameter, the file descriptor
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64 | * of the event queue socket
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65 | */
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66 | DECLCALLBACK(int) xpcomEventThread(RTTHREAD hThreadSelf, void *pvUser)
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67 | {
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68 | RT_NOREF(hThreadSelf);
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69 | int eqFD = (intptr_t)pvUser;
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70 | unsigned cErrors = 0;
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71 | int rc;
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72 |
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73 | /* Wait with the processing till the main thread needs it. */
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74 | RTSemEventWait(g_EventSemXPCOMQueueThread, 2500);
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75 |
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76 | do
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77 | {
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78 | fd_set fdset;
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79 | FD_ZERO(&fdset);
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80 | FD_SET(eqFD, &fdset);
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81 | int n = select(eqFD + 1, &fdset, NULL, NULL, NULL);
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82 |
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83 | /* are there any events to process? */
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84 | if ((n > 0) && !g_fTerminateXPCOMQueueThread)
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85 | {
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86 | /*
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87 | * Wait until all XPCOM events are processed. 1s just for sanity.
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88 | */
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89 | int iWait = 1000;
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90 | /*
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91 | * Don't post an event if there is a pending XPCOM event to prevent an
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92 | * overflow of the SDL event queue.
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93 | */
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94 | if (g_s32XPCOMEventsPending < 1)
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95 | {
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96 | /*
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97 | * Post the event and wait for it to be processed. If we don't wait,
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98 | * we'll flood the queue on SMP systems and when the main thread is busy.
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99 | * In the event of a push error, we'll yield the timeslice and retry.
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100 | */
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101 | SDL_Event event = {0};
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102 | event.type = SDL_USEREVENT;
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103 | event.user.type = SDL_USER_EVENT_XPCOM_EVENTQUEUE;
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104 | rc = SDL_PushEvent(&event);
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105 | if (!rc)
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106 | {
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107 | /* success */
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108 | ASMAtomicIncS32(&g_s32XPCOMEventsPending);
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109 | cErrors = 0;
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110 | }
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111 | else
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112 | {
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113 | /* failure */
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114 | cErrors++;
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115 | if (!RTThreadYield())
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116 | RTThreadSleep(2);
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117 | iWait = (cErrors >= 10) ? RT_MIN(cErrors - 8, 50) : 0;
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118 | }
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119 | }
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120 | else
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121 | Log2(("not enqueueing SDL XPCOM event (%d)\n", g_s32XPCOMEventsPending));
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122 |
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123 | if (iWait)
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124 | RTSemEventWait(g_EventSemXPCOMQueueThread, iWait);
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125 | }
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126 | } while (!g_fTerminateXPCOMQueueThread);
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127 | return VINF_SUCCESS;
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128 | }
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129 |
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130 | /**
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131 | * Creates the XPCOM event thread
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132 | *
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133 | * @returns VBOX status code
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134 | * @param eqFD XPCOM event queue file descriptor
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135 | */
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136 | int startXPCOMEventQueueThread(int eqFD)
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137 | {
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138 | int rc = RTSemEventCreate(&g_EventSemXPCOMQueueThread);
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139 | if (RT_SUCCESS(rc))
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140 | {
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141 | RTTHREAD Thread;
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142 | rc = RTThreadCreate(&Thread, xpcomEventThread, (void *)(intptr_t)eqFD,
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143 | 0, RTTHREADTYPE_MSG_PUMP, 0, "XPCOMEvent");
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144 | }
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145 | AssertRC(rc);
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146 | return rc;
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147 | }
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148 |
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149 | /**
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150 | * Notify the XPCOM thread that we consumed an XPCOM event.
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151 | */
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152 | void consumedXPCOMUserEvent(void)
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153 | {
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154 | ASMAtomicDecS32(&g_s32XPCOMEventsPending);
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155 | }
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156 |
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157 | /**
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158 | * Signal to the XPCOM even queue thread that it should select for more events.
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159 | */
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160 | void signalXPCOMEventQueueThread(void)
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161 | {
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162 | int rc = RTSemEventSignal(g_EventSemXPCOMQueueThread);
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163 | AssertRC(rc);
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164 | }
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165 |
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166 | /**
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167 | * Indicates to the XPCOM thread that it should terminate now.
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168 | */
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169 | void terminateXPCOMQueueThread(void)
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170 | {
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171 | g_fTerminateXPCOMQueueThread = true;
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172 | if (g_EventSemXPCOMQueueThread)
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173 | {
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174 | RTSemEventSignal(g_EventSemXPCOMQueueThread);
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175 | RTThreadYield();
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176 | }
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177 | }
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178 |
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179 | #endif /* USE_XPCOM_QUEUE_THREAD */
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