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<a name="1204893"> </a><font color="#003366" face="Verdana, Arial, Helvetica, sans-serif">5.14 Task data</font>
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<a name="1204894"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">OS20 provides one word of "task-data" per task. This can be used by the application to store data which is specific to the task, but which needs to be accessed uniformly from multiple tasks.</font>
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<a name="1204895"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">This is typically used to store data which is required by a library, when the library can be used from multiple tasks but the data is specific to the task. For example, a library which manages an I/O channel may be called by multiple tasks, each of which has its own I/O buffers. To avoid having to pass an I/O descriptor into every call it could be stored in task-data.</font>
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<a name="1204896"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">Although only one word of storage is provided, this is usually treated as a pointer, which points to a user defined data structure which can be as large as required.</font>
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<a name="1204897"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">Two functions provide access to the task-data pointer:</font>
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<a name="1204899"> </a><font size=2 face=Courier><strong>void* task_data_set (task_t* Task, void* NewData);<br></strong></font>
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<a name="1204900"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif"><font size=2 face=Courier><strong>task_data_set()</strong></font> sets the task-data pointer of the task specified by <font size=2 face=Courier><strong>Task</strong></font>.</font>
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<a name="1204902"> </a><font size=2 face=Courier><strong>void* task_data(task_t* Task);<br></strong></font>
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<a name="1204903"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif"><font size=2 face=Courier><strong>task_data()</strong></font> retrieves the task-data pointer of the task specified by <font size=2 face=Courier><strong>Task</strong></font>.</font>
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<a name="1204904"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">If <font size=2 face=Courier><strong>Task</strong></font> is <font size=2 face=Courier><strong>NULL</strong></font>, both functions use the currently active task.</font>
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<a name="1204906"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">When a task is first created (including the root task), its task-data pointer is set to <font size=2 face=Courier><strong>NULL</strong></font> (<font size=2 face=Courier><strong>0</strong></font>). For example:</font>
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<a name="1204907"> </a><font size=2 face=Courier><strong>typedef struct {<br>⌨️ 快捷键说明
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