<?xml version="1.0" encoding="UTF-8"?>
<!--

Documentation for LCL (Lazarus Component Library) and LazUtils (Lazarus 
Utilities) are published under the Creative Commons Attribution-ShareAlike 4.0 
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Copyright (c) 1997-2023, by the Lazarus Development Team.

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<fpdoc-descriptions>
<package name="lcl">
<!--
====================================================================
AsyncProcess
====================================================================
-->
<module name="AsyncProcess">
<short>
Implements a process with asynchronous event notifications.
</short>
<descr>
<p>
<file>asyncprocess.pp</file> implements a process with asynchronous event 
notifications for data availability and process termination. The following 
components are added to the Lazarus IDE component palette:
</p>
<p>
<b>System</b> Tab
</p>
<ul>
<li>TAsyncProcess</li>
</ul>
<p>
<file>asynprocess.pp</file> is part of the Lazarus Component Library (LCL).
</p>
</descr>

<!-- unresolved references -->
<element name="Classes"/>
<element name="Process"/>
<element name="FileUtil"/>
<element name="UTF8Process"/>
<element name="InterfaceBase"/>
<element name="LCLIntf"/>

<element name="TAsyncProcess">
<short>
Implements a process with asynchronous notifications for data and termination.
</short>
<descr>
<p>
<var>TAsyncProcess</var> is a <var>TProcessUTF8</var> descendant which 
implements support for asynchronous notifications when data is available for 
the process. Internally, TAsyncProcess uses pipe and process handlers to 
detect when data is written to the <var>Output</var> handle, and when the 
process is terminated. TAsyncProcess provides <var>OnReadData</var> and 
<var>OnTerminate</var> event handlers signalled for the corresponding 
asynchronous notifications.
</p>
</descr>
<seealso>
<link id="TAsyncProcess.OnReadData"/>
<link id="TAsyncProcess.OnTerminate"/>
<link id="#lazutils.utf8process.TProcessUTF8">TProcessUTF8</link>
<link id="#fcl.process.TProcess.Output">TProcess.Output</link>
</seealso>
</element>

<element name="TAsyncProcess.FPipeHandler"/>
<element name="TAsyncProcess.FProcessHandler"/>
<element name="TAsyncProcess.FOnReadData"/>
<element name="TAsyncProcess.FOnTerminate"/>

<element name="TAsyncProcess.GetNumBytesAvailable">
<short>
Gets the value for the NumBytesAvailable property.
</short>
<descr>
<p>
<var>GetNumBytesAvailable</var> is a <var>dword</var> function used to get 
the value for the <var>NumBytesAvailable</var> property. The return value 
contains the value from <var>Output.NumBytesAvailable</var>, or 0 (zero) when 
<var>Options</var> does not include the value <var>poUsePipes</var>.
</p>
<p>
Use <var>NumBytesAvailable</var> to access the value for the property.
</p>
<p>
Use <var>Options</var> to specify the process options enabled for the class 
instance.
</p>
</descr>
<seealso>
<link id="TAsyncProcess.NumBytesAvailable"/>
<link id="TAsyncProcess.GetNumBytesAvailable"/>
<link id="#fcl.process.TProcess.Options">TProcess.Options</link>
</seealso>
</element>
<element name="TAsyncProcess.GetNumBytesAvailable.Result">
<short>Value for the property.</short>
</element>

<element name="TAsyncProcess.HandlePipeInput">
<short>
Implements asynchronous notifications during execution of the process.
</short>
<descr>
<p>
<var>HandlePipeInput</var> is a procedure which implements support for 
asynchronous notifications which occur during execution of the process. 
HandlePipeInput is assigned using <var>AddPipeEventHandler</var> when 
<var>Execute</var> is called.
</p>
<p>
HandlePipeInput examines values in <var>AReasons</var> to determine the 
action for the notification. When AReasons includes the value 
<var>prBroken</var>, the pipe has been closed and <var>UnhookPipeHandle</var> 
is called. When <var>prDataAvailable</var> is included in AReasons, the 
<var>OnReadData</var> event handler is signalled (when assigned).
</p>
<p>
Use <var>OnReadData</var> to respond to arrival of data on the handle for the 
process. Use <var>NumBytesAvailable</var> is determine the number of bytes 
available.
</p>
</descr>
<seealso>
<link id="TAsyncProcess.OnReadData"/>
<link id="TAsyncProcess.NumBytesAvailable"/>
</seealso>
</element>
<element name="TAsyncProcess.HandlePipeInput.AData">
<short>Data available on the input handle.</short>
</element>
<element name="TAsyncProcess.HandlePipeInput.AReasons">
<short>Reason the data was written for the handler.</short>
</element>

<element name="TAsyncProcess.HandleProcessTermination">
<short>
Performs actions needed when the process is terminated.
</short>
<descr>
<p>
<var>HandleProcessTermination</var> is a procedure which performs actions 
needed when the process is terminated. HandleProcessTermination is assigned 
using <var>AddProcessEventHandler</var> when <var>Execute</var> is called.
</p>
<p>
HandleProcessTermination calls <var>UnhookProcessHandle</var> and 
<var>UnhookPipeHandle</var> to release the handlers in the class instance. 
HandleProcessTermination signals the <var>OnTerminate</var> event handler 
when it has been assigned.
</p>
</descr>
<seealso>
<link id="TAsyncProcess.Execute"/>
<link id="TAsyncProcess.UnhookProcessHandle"/>
<link id="TAsyncProcess.UnhookPipeHandle"/>
<link id="TAsyncProcess.OnTerminate"/>
</seealso>
</element>
<element name="TAsyncProcess.HandleProcessTermination.AData">
<short>Data for the process notification.</short>
</element>
<element name="TAsyncProcess.HandleProcessTermination.AReason">
<short>Reason(s) for the process notification.</short>
</element>
<element name="TAsyncProcess.HandleProcessTermination.AInfo">
<short>Process exit code.</short>
</element>

<element name="TAsyncProcess.UnhookPipeHandle">
<short>
Removes the pipe handler assigned for the process.
</short>
<descr>
<p>
<var>UnhookPipeHandle</var> is a procedure used to remove the pipe handler 
assigned for the process in the <var>Execute</var> method. UnhookPipeHandle 
calls <var>RemovePipeEventHandler</var> when a pipe handler has been assigned.
</p>
<p>
<var>UnhookPipeHandle</var> is called from the <var>Destroy</var> method, and 
from <var>HandlePipeInput</var> when the <var>prBroken</var> flag is found in 
the parameters passed to the method.
</p>
</descr>
<seealso>
<link id="TAsyncProcess.Execute"/>
<link id="#lcl.interfacebase.TPipeReason">TPipeReason</link>
</seealso>
</element>

<element name="TAsyncProcess.UnhookProcessHandle">
<short>
Removes the process handler assigned for the process.
</short>
<descr>
<p>
<var>UnhookProcessHandle</var> is a procedure used to remove the process 
handler assigned for the process in the <var>Execute</var> method. 
UnhookProcessHandle calls <var>RemoveProcessEventHandler</var> when a process 
handler has been assigned.
</p>
<p>
<var>UnhookProcessHandle</var> is called from the 
<var>HandleProcessTermination</var> and <var>Destroy</var> methods.
</p>
</descr>
<seealso>
<link id="TAsyncProcess.Execute"/>
<link id="TAsyncProcess.HandleProcessTermination"/>
<link id="TAsyncProcess.Destroy"/>
</seealso>
</element>

<element name="TAsyncProcess.Execute">
<short>
Executes the process.
</short>
<descr>
<p>
<var>Execute</var> is an overridden procedure used to execute the process. 
Execute calls the inherited Execute method on entry.
</p>
<p>
Execute uses values in <var>Options</var> to determine if a process or a pipe 
handler is needed for the class instance. When Options includes the value 
<var>poUsePipes</var>, <var>AddPipeEventHandler</var> is called using 
<var>HandlePipeInput</var> as the pipe handler routine. Set the values in 
Options prior to calling the Execute method.
</p>
<p>
Execute calls <var>AddProcessEventHandler</var> using 
<var>HandleProcessTermination</var> as the process handler routine.
</p>
</descr>
<seealso>
<link id="TAsyncProcess.HandlePipeInput"/>
<link id="TAsyncProcess.HandleProcessTermination"/>
<link id="#fcl.process.TProcess.Options">TProcess.Options</link>
</seealso>
</element>

<element name="TAsyncProcess.Destroy">
<short>
Destructor for the class instance.
</short>
<descr>
<p>
<var>Destroy</var> is the overridden destructor for the class instance. 
Destroy calls <var>UnhookProcessHandle</var> and <var>UnhookPipeHandle</var> 
to remove the handler(s) for the class instance. Destroy calls the inherited 
method to free resources allocated in the class instance and perform free 
notifications.
</p>
</descr>
<seealso>
<link id="TAsyncProcess.UnhookProcessHandle"/>
<link id="TAsyncProcess.UnhookPipeHandle"/>
<link id="#fcl.process.TProcess.Destroy">TProcess.Destroy</link>
</seealso>
</element>

<element name="TAsyncProcess.NumBytesAvailable">
<short>
Number of output bytes available from the process.
</short>
<descr>
<p>
<var>NumBytesAvailable</var> is a read-only <var>dword</var> property that 
indicates the number of bytes available on the <var>Output</var> handle for 
the process. <var>GetNumBytesAvailable</var> is the read access specifier for 
the property value. NumBytesAvailable contains the value in 
Output.NumBytesAvailable, or 0 (zero) when <var>Options</var> does not 
contain the value <var>poUsePipes</var>.
</p>
<p>
Set the values for the <var>Options</var> property prior to calling 
<var>Execute</var>.
</p>
<p>
Use <var>OnReadData</var> to respond to the process notification signalled 
when data is available.
</p>
</descr>
<seealso>
<link id="TAsyncProcess.Execute"/>
<link id="TAsyncProcess.OnReadData"/>
<link id="#fcl.process.TProcess.Options">TProcess.Options</link>
<link id="#fcl.process.TProcess.Output">TProcess.Output</link>
</seealso>
</element>

<element name="TAsyncProcess.OnReadData">
<short>
Event handler signalled when output data is available for the process.
</short>
<descr>
<p>
<var>OnReadData</var> is a <var>TNotifyEvent</var> property that implements 
the event handler signalled when data is available for the process. 
Applications should assign a procedure to the event handler that responds to 
the pipe notification. The procedure must handle all data available on the 
<var>Output</var> handle up to the number of bytes in 
<var>NumBytesAvailable</var>. All available data must be handled, or the 
procedure will be called repeatedly until no more data is available.
</p>
<p>
OnReadData is signalled (when assigned) from the <var>HandlePipeInput</var> 
method when the <var>prDataAvailable</var> flag is found in the parameters 
passed to the method.
</p>
</descr>
<seealso>
<link id="TAsyncProcess.NumBytesAvailable"/>
<link id="#lcl.interfacebase.TPipeReason">TPipeReason</link>
<link id="#fcl.process.TProcess.Output">TProcess.Output</link>
<link id="#rtl.classes.TNotifyEvent">TNotifyEvent</link>
</seealso>
</element>

<element name="TAsyncProcess.OnTerminate">
<short>
Event handler signalled when the process is terminated.
</short>
<descr>
<p>
<var>OnTerminate</var> is a <var>TNotifyEvent</var> property that implements 
the event handler signalled when the process is terminated. Applications can 
assign a procedure to the event handler to perform actions needed when the 
process is terminated.
</p>
<p>
OnTerminate is signalled (when assigned) from the 
<var>HandleProcessTermination</var> method, and occurs after the process and 
pipe handlers have been unhooked in the class instance.
</p>
</descr>
<seealso>
<link id="TAsyncProcess.HandleProcessTermination"/>
<link id="#rtl.classes.TNotifyEvent">TNotifyEvent</link>
</seealso>
</element>

<element name="Register">
<short>Registers components for use in the Lazarus IDE.</short>
<descr>
<p>
<var>Register</var> is the procedure used to register components for use in 
the Lazarus IDE. The following components are added to the Lazarus IDE 
component palette:
</p>
<p>
<b>System</b> Tab
</p>
<ul>
<li>TAsyncProcess</li>
</ul>
</descr>
<seealso/>
</element>

</module>
<!-- AsyncProcess -->
</package>
</fpdoc-descriptions>
