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<?xml version="1.0" encoding="ISO-8859-1"?>
<fpdoc-descriptions>
<package name="fcl">
<!--
====================================================================
nullstream
====================================================================
-->
<module name="nullstream">
<short>Unit to implement a null stream</short>
<descr>
The <var>nullstream</var> unit implements <link id="TNullStream"/>, a stream which acts more or less as the <var>/dev/null</var> device on unix:
all read and write operations will succeed, but the data is discarded on write, or null bytes are read.
</descr>
<!-- uses unit Visibility: default -->
<element name="Classes">
<short>Definition of <var>TStream</var></short>
</element>
<!-- class Visibility: default -->
<element name="ENullStreamError">
<short>Exception for erroneous seeks</short>
<descr>
<var>ENullStreamError</var> is the exception raised when <link id="TNullStream.Seek"/> results in an invalid position.
</descr>
<seealso>
<link id="TNullStream.Seek"/>
</seealso>
</element>
<!-- class Visibility: default -->
<element name="TNullStream">
<short>Empty data stream</short>
<descr>
<var>TNullStream</var> discards any data written to it (but keeps a virtual size) and returns 0 bytes when read from.
It emulates a <link id="#rtl.classes.TMemoryStream"/>: When writing to the stream, the size is increased as needed.
When reading, the maximum number of returned bytes is limited to the size of the stream.
</descr>
<seealso>
<link id="TNullStream.Read"/>
<link id="TNullStream.Write"/>
<link id="#rtl.classes.TStream.Size"/>
</seealso>
</element>
<!-- function Visibility: public -->
<element name="TNullStream.Read">
<short>Read null bytes from the stream </short>
<descr>
<var>Read</var> reads <var>Count</var> null bytes from the stream. <var>Count</var> can be at most <var>Size</var>.
The <var>Buffer</var> will be filled with null bytes, effectively zeroing out the memory.
The size can be increased using <var>Write</var> or by explicitly setting <var>Size</var>.
</descr>
<seealso>
<link id="TNullStream.Write"/>
<link id="#rtl.classes.TStream.Size"/>
</seealso>
</element>
<!-- function result Visibility: default -->
<element name="TNullStream.Read.Result">
<short>Actual number or zero bytes</short>
</element>
<!-- argument Visibility: default -->
<element name="TNullStream.Read.Buffer">
<short>Buffer to zero out.</short>
</element>
<!-- argument Visibility: default -->
<element name="TNullStream.Read.Count">
<short>Maximum number of bytes to zero out</short>
</element>
<!-- function Visibility: public -->
<element name="TNullStream.Write">
<short>Write to stream</short>
<descr>
<var>Write</var> simulates a write operation: no data is actually written from <var>Buffer</var>,
but the size of the stream is enlarged if the amount of bytes <var>Count</var> and current position
in the stream make this necessary.
</descr>
<seealso>
<link id="TNullStream.Read"/>
<link id="#rtl.classes.TStream.Size"/>
</seealso>
</element>
<!-- function result Visibility: default -->
<element name="TNullStream.Write.Result">
<short>Always equal to <var>Count</var></short>
</element>
<!-- argument Visibility: default -->
<element name="TNullStream.Write.Buffer">
<short>Buffer to write data from (ignored)</short>
</element>
<!-- argument Visibility: default -->
<element name="TNullStream.Write.Count">
<short>Max number of bytes to write.</short>
</element>
<!-- function Visibility: public -->
<element name="TNullStream.Seek">
<short>Set current position in the stream</short>
<descr>
<var>Seek</var> sets the current position in the stream. It simulates this operation by keeping a "virtual" position.
See <link id="#rtl.classes.TStream.Seek"/> for more info about the arguments.
</descr>
<errors>
If the requested operation would cause the position to fall outside of the allowed range (0 to <var>Size</var>) then a <link id="ENullStreamError"/> exception is raised.
</errors>
<seealso>
<link id="TNullStream.Read"/>
<link id="TNullStream.Write"/>
<link id="#rtl.classes.TStream.Seek"/>
</seealso>
</element>
<!-- function result Visibility: default -->
<element name="TNullStream.Seek.Result">
<short>The new position</short>
</element>
<!-- argument Visibility: default -->
<element name="TNullStream.Seek.Offset">
<short>Offset from origin, in bytes.</short>
</element>
<!-- argument Visibility: default -->
<element name="TNullStream.Seek.Origin">
<short>Origin of seek operation</short>
</element>
<!-- constructor Visibility: public -->
<element name="TNullStream.Create">
<short>Create a new instance</short>
<descr>
<var>Create</var> initializes the size and position of the stream to zero.
</descr>
<seealso>
<link id="#rtl.classes.TStream.Position"/>
<link id="#rtl.classes.TStream.Size"/>
</seealso>
</element>
</module> <!-- nullstream -->
</package>
</fpdoc-descriptions>
|
