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1 <?xml version="1.0" encoding="utf-8"?> |
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2 <!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. --> |
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3 <!-- This component and the accompanying materials are made available under the terms of the License |
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4 "Eclipse Public License v1.0" which accompanies this distribution, |
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5 and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". --> |
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6 <!-- Initial Contributors: |
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7 Nokia Corporation - initial contribution. |
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8 Contributors: |
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9 --> |
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10 <!DOCTYPE concept |
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11 PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> |
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12 <concept id="GUID-4ADD8234-4AFD-4E80-94A4-AC018FE83276" xml:lang="en"><title>Differences |
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13 between OSS and Symbian GLib</title><shortdesc/><prolog><metadata><keywords/></metadata></prolog><conbody> |
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14 <p>The three areas of difference between the way GLib is implemented in Symbian |
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15 platform and in OSS are as follows: </p> |
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16 <ul> |
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17 <li><p>Memory allocation</p></li> |
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18 <li><p>Spawn APIs</p></li> |
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19 <li><p>Libgmodule APIs </p></li> |
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20 </ul> |
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21 <section id="GUID-DFAD39D6-BA92-4293-B5EC-97077CE1FC1A-GENID-1-8-1-11-1-1-7-1-6-1-4-1-3-3"> <title>Memory |
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22 allocation</title> <p>The Symbian GLib implementation does not follow |
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23 the default OSS behavior. The default OSS behavior is such that in the event |
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24 of a memory allocation failure the application, using <codeph>g_malloc()</codeph> and |
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25 not <codeph>g_try_malloc()</codeph>, will call <codeph>abort()</codeph> and |
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26 thus terminate the application. </p><p>The Symbian implementation, on the |
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27 other hand will return NULL and not terminate the application in the event |
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28 of a memory allocation failure. Thus, it is the application’s responsibility |
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29 to check if the memory allocation failed due to the needed tasks.</p><p>Generally, |
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30 all the application code written using GLib does not perform memory allocation |
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31 failure checks. Hence, for Symbian GLib it is the application programmer's |
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32 responsibility to check for memory allocation failures. </p> </section> |
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33 <section id="GUID-DFAD39D6-BA92-4293-B5EC-97077CE1FC1A-GENID-1-8-1-11-1-1-7-1-6-1-4-1-3-4"> <title>Spawn |
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34 APIs</title> <p>GLib has a set of APIs for process spawning. Since Symbian |
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35 platform does not support the <codeph>fork()</codeph> and <codeph>exec()</codeph> APIs, |
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36 the <codeph>g_spawn*</codeph> APIs have limitations in their functionality. |
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37 The limitations are explained per API in detail below.</p><p><b><codeph>g_spawn_async_with_pipes</codeph></b></p><p>The |
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38 signature of this API is:</p><codeblock xml:space="preserve">gboolean g_spawn_async_with_pipes ( |
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39 const gchar *working_directoy, |
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40 gchar **argv, |
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41 gchar **envp, |
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42 GSpawnFlags flags, |
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43 GSpawnChildSetupFunc child_setup, |
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44 gpointer user_data, |
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45 GPid *child_pid, |
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46 gint *standard_input, |
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47 gint *standard_output, |
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48 gint *standard_error, |
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49 GError **error); </codeblock><p>This API executes the program asynchronously: |
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50 that is, the caller does not block for the spawned process to complete. The |
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51 setting of the following parameters does not have any effect in Symbian GLib:</p><ul> |
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52 <li><p><codeph>working_directory</codeph></p></li> |
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53 <li><p><codeph>envp</codeph></p></li> |
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54 </ul><p>If a value other than NULL is passed for <codeph>standard_input</codeph>, <codeph>standard_ouput</codeph>, |
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55 or <codeph>standard_error</codeph>, the value at the location is set to -1.</p><p><b><codeph>g_spawn_async</codeph></b></p><p>The |
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56 signature of the API is:</p><codeblock xml:space="preserve">gboolean g_spawn_async ( |
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57 const gchar *working_directory, |
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58 gchar **argv, |
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59 gchar **envp, |
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60 GSpawnFlags flags, |
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61 GSpawnChildSetupFunc child_setup, |
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62 gpointer user_data, |
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63 GPid *child_pid, |
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64 GError **error); </codeblock><p>This API calls <codeph>g_spawn_async_with_pipes</codeph> without |
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65 any pipes. The setting of the following parameters does not have any effect |
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66 in Symbian GLib:</p><ul> |
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67 <li><p><codeph>working_directory</codeph></p></li> |
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68 <li><p><codeph>envp</codeph></p></li> |
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69 </ul><p><b><codeph>g_spawn_sync</codeph></b></p><p>The signature of the API |
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70 is:</p><codeblock xml:space="preserve">gboolean g_spawn_sync( |
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71 const gchar *working_directory, |
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72 gchar **argv, |
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73 gchar **envp, |
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74 GSpawnFlags flags, |
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75 GSpawnChildSetupFunc child_setup, |
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76 gpointer user_data, |
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77 gchar **standard_output, |
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78 gchar **standard_error, |
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79 gint *exit_status, |
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80 GError **error); </codeblock><p>This API executes the program synchronously: |
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81 that is, the calling process waits for the spawned process to complete before |
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82 returning. The setting of the following parameters does not have any effect |
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83 on Symbian GLib: </p><ul> |
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84 <li><p><codeph>working_directory</codeph></p></li> |
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85 <li><p><codeph>envp</codeph></p></li> |
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86 </ul><p>If a value other than NULL is passed for<codeph> standard_output</codeph> or <codeph>standard_error</codeph>, |
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87 the value at the location is set to -1. </p><p><b><codeph>g_spawn_command_line_sync</codeph></b></p><p>The |
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88 signature of the API is:</p><codeblock xml:space="preserve">gboolean g_spawn_command_line_sync( |
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89 const gchar *command_line, |
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90 gchar **standard_output, |
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91 gchar **standard_error, |
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92 gint *exit_status, |
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93 GError **error); </codeblock><p>This API is a simple version of <codeph>g_spawn_sync</codeph> in |
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94 which there are fewer number of parameters involved, and it takes a command |
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95 line instead.</p><p>If a value other than NULL is passed for <codeph>standard_output</codeph> or <codeph>standard_error</codeph>, |
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96 the value at the location is set to -1.</p><p>In many spawn APIs a variable |
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97 of type <codeph>GSpawnFlags</codeph> is passed. The following flags have no |
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98 effect:</p><ul> |
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99 <li><p><codeph>G_SPAWN_LEAVE_DESCRIPTORS_OPEN</codeph></p></li> |
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100 <li><p><codeph>G_SPAWN_STDOUT_TO_DEV_NULL</codeph></p></li> |
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101 <li><p><codeph>G_SPAWN_STDERR_TO_DEV_NULL</codeph></p></li> |
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102 <li><p><codeph>G_SPAWN_CHILD_INHERITS_STDIN</codeph></p></li> |
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103 </ul> </section> |
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104 <section id="GUID-4B68F695-1BDB-4AA0-B77A-7F808A157E7A"><title>Libgmodule |
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105 APIs</title><p>Libgmodule has APIs that provide a portable method for dynamically |
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106 loading 'plug-ins' or, in other words, DLLs. There are some deviations in |
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107 the <codeph>libgmodule</codeph> APIs on Symbian platform as compared to the |
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108 OSS behavior. The APIs with their limitations are explained in detail below.</p><ul> |
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109 <li><p><b><codeph>g_module_open</codeph></b>: The signature of the API is:</p><codeblock xml:space="preserve">GModule *g_module_open (const gchar *file_name, GModuleFlags flags);</codeblock><p>This API is used to open a module. The default OSS behavior when file_name |
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110 is passed as NULL such that it obtains a <codeph>GModule</codeph> representing |
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111 the main program. In Symbian GLib, NULL is returned instead. Of all the <codeph>GModuleFlags</codeph> only <codeph>G_MODULE_BIND_LOCAL</codeph> is |
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112 honored. If the user passes any other flags, the module is still opened using |
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113 the flag <codeph>G_MODULE_BIND_LOCAL</codeph>. </p></li> |
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114 <li><p><b><codeph>g_module_symbol</codeph></b>: The signature of the API is:</p><codeblock xml:space="preserve">gboolean g_module_symbol (GModule *module, const gchar *symbol_name, gpointer *symbol);</codeblock><p>This API gets the symbol from the <codeph>GModule</codeph> opened using <codeph>g_module_open</codeph>. |
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115 In OSS, <codeph>symbol_name</codeph> is the name of the symbol that needs |
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116 to be queried from the <codeph>GModule</codeph>. In Symbian platform, the |
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117 ordinal number (passed as a string) of the symbol name must be passed and |
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118 not the symbol name.</p></li> |
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119 </ul><p>See also <xref href="GUID-01E7AE98-024C-4119-87D0-5BB9D53DA119.dita">Introduction |
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120 to libgmodule</xref> for more details about <codeph>libgmodule</codeph>. </p></section> |
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121 </conbody></concept> |