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1 /**************************************************************************** |
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2 ** |
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3 ** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies). |
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4 ** All rights reserved. |
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5 ** Contact: Nokia Corporation (qt-info@nokia.com) |
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6 ** |
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7 ** This file is part of the QtCore module of the Qt Toolkit. |
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8 ** |
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9 ** $QT_BEGIN_LICENSE:LGPL$ |
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10 ** No Commercial Usage |
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11 ** This file contains pre-release code and may not be distributed. |
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12 ** You may use this file in accordance with the terms and conditions |
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13 ** contained in the Technology Preview License Agreement accompanying |
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14 ** this package. |
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15 ** |
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16 ** GNU Lesser General Public License Usage |
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17 ** Alternatively, this file may be used under the terms of the GNU Lesser |
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18 ** General Public License version 2.1 as published by the Free Software |
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19 ** Foundation and appearing in the file LICENSE.LGPL included in the |
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20 ** packaging of this file. Please review the following information to |
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21 ** ensure the GNU Lesser General Public License version 2.1 requirements |
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22 ** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html. |
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23 ** |
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24 ** In addition, as a special exception, Nokia gives you certain additional |
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25 ** rights. These rights are described in the Nokia Qt LGPL Exception |
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26 ** version 1.1, included in the file LGPL_EXCEPTION.txt in this package. |
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27 ** |
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28 ** If you have questions regarding the use of this file, please contact |
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29 ** Nokia at qt-info@nokia.com. |
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30 ** |
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31 ** |
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32 ** |
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33 ** |
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34 ** |
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35 ** |
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36 ** |
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37 ** |
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38 ** $QT_END_LICENSE$ |
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39 ** |
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40 ****************************************************************************/ |
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41 |
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42 /*! |
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43 \headerfile <QtConcurrentRun> |
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44 \title Asynchronous Run |
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45 |
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46 \brief The <QtConcurrentRun> header provides a way to run a function in a |
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47 separate thread. |
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48 |
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49 \ingroup thread |
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50 |
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51 This function is a part of the \l {Concurrent Programming}{Qt Concurrent} framework. |
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52 |
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53 The QtConcurrent::run() function runs a function in a separate thread. |
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54 The return value of the function is made available through the QFuture API. |
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55 |
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56 \section1 Running a Function in a Separate Thread |
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57 |
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58 To run a function in another thread, use QtConcurrent::run(): |
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59 |
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60 \snippet doc/src/snippets/code/src_corelib_concurrent_qtconcurrentrun.cpp 0 |
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61 |
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62 This will run \e aFunction in a separate thread obtained from the default |
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63 QThreadPool. You can use the QFuture and QFutureWatcher classes to monitor |
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64 the status of the function. |
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65 |
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66 \section1 Passing Arguments to the Function |
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67 |
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68 Passing arguments to the function is done by adding them to the |
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69 QtConcurrent::run() call immediately after the function name. For example: |
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70 |
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71 \snippet doc/src/snippets/code/src_corelib_concurrent_qtconcurrentrun.cpp 1 |
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72 |
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73 A copy of each argument is made at the point where QtConcurrent::run() is |
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74 called, and these values are passed to the thread when it begins executing |
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75 the function. Changes made to the arguments after calling |
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76 QtConcurrent::run() are \e not visible to the thread. |
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77 |
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78 \section1 Returning Values from the Function |
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79 |
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80 Any return value from the function is available via QFuture: |
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81 |
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82 \snippet doc/src/snippets/code/src_corelib_concurrent_qtconcurrentrun.cpp 2 |
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83 |
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84 As documented above, passing arguments is done like this: |
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85 |
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86 \snippet doc/src/snippets/code/src_corelib_concurrent_qtconcurrentrun.cpp 3 |
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87 |
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88 Note that the QFuture::result() function blocks and waits for the result |
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89 to become available. Use QFutureWatcher to get notification when the |
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90 function has finished execution and the result is available. |
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91 |
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92 \section1 Additional API Features |
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93 |
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94 \section2 Using Member Functions |
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95 |
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96 QtConcurrent::run() also accepts pointers to member functions. The first |
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97 argument must be either a const reference or a pointer to an instance of |
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98 the class. Passing by const reference is useful when calling const member |
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99 functions; passing by pointer is useful for calling non-const member |
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100 functions that modify the instance. |
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101 |
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102 For example, calling QString::split() (a const member function) in a |
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103 separate thread is done like this: |
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104 |
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105 \snippet doc/src/snippets/code/src_corelib_concurrent_qtconcurrentrun.cpp 4 |
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106 |
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107 Calling a non-const member function is done like this: |
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108 |
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109 \snippet doc/src/snippets/code/src_corelib_concurrent_qtconcurrentrun.cpp 5 |
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110 |
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111 \section2 Using Bound Function Arguments |
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112 |
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113 Note that Qt does not provide support for bound functions. This is |
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114 provided by 3rd party libraries like |
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115 \l{http://www.boost.org/libs/bind/bind.html}{Boost} or |
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116 \l{http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1836.pdf} |
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117 {C++ TR1 Library Extensions}. |
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118 |
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119 You can use boost::bind() or std::tr1::bind() to \e bind a number of |
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120 arguments to a function when called. There are number of reasons for doing |
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121 this: |
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122 |
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123 \list |
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124 \o To call a function that takes more than 5 arguments. |
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125 \o To simplify calling a function with constant arguments. |
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126 \o Changing the order of arguments. |
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127 \endlist |
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128 |
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129 See the documentation for the relevant functions for details on how to use |
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130 the bind API. |
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131 |
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132 Calling a bound function is done like this: |
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133 |
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134 \snippet doc/src/snippets/code/src_corelib_concurrent_qtconcurrentrun.cpp 6 |
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135 */ |
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136 |
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137 /*! |
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138 \fn QFuture<T> QtConcurrent::run(Function function, ...); |
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139 \relates <QtConcurrentRun> |
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140 |
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141 Runs \a function in a separate thread. The thread is taken from the global |
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142 QThreadPool. Note that the function may not run immediately; the function |
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143 will only be run when a thread is available. |
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144 |
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145 T is the same type as the return value of \a function. Non-void return |
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146 values can be accessed via the QFuture::result() function. |
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147 |
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148 Note that the QFuture returned by QtConcurrent::run() does not support |
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149 canceling, pausing, or progress reporting. The QFuture returned can only |
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150 be used to query for the running/finished status and the return value of |
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151 the function. |
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152 */ |