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<concept id="GUID-C8C2645A-F5A4-53F0-8F43-485FC0B472DC" xml:lang="en"><title>External

and internal representations</title><shortdesc>Describes the <codeph>Internalize()</codeph> and <codeph>Externalize()</codeph> functions

for representing objects.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>Since packages may be used to describe an object of any type, and may be

conveniently written to a file and sent over communications links, it is tempting

to use them to transmit all application data types.</p>

<p><note>This is strongly discouraged in Symbian platform programming.</note> </p>

<p>Packages directly package the <i>internal</i> representation of an object.

They should only be used when the internal representation is expected by all

recipients of the package. This would be the case, say, with inter thread

data transfer or certain rare types of file.</p>

<p>When an object is stored on file, or sent over a link, it is usually desirable

to define an <i>external</i> representation which may be safely read by <i>any</i> Symbian

platform implementation, even on a machine with different endianness, different

compiler options, and different machine word size.</p>

<p>In such a case, writing a struct directly is inappropriate. Instead, the <codeph>InternalizeL()</codeph> and <codeph>ExternalizeL()</codeph> functions

should be implemented for the object and should encapsulate all internalisation

and externalisation. The stream interface should be used, which may refer

to file, communications, clipboard and a number of other possibilities.</p>