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<concept id="GUID-DE17BEA2-C821-50B8-9128-9C4D35D95599" xml:lang="en"><title>Array
Implementation</title><shortdesc>Describes the features of arrays and the ways in which they are
implemented.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
<p>All arrays have an array buffer allocated from the heap. The implementation
of this buffer and the way it is used depends on the specific type of array.</p>
<p>In arrays of elements which all have the same length, the elements are
contained within the array buffer itself.</p>
<p>In arrays of elements with varying length, each element is contained within
its own heap cell and the array buffer contains <i>pointers</i> to the elements.</p>
<p>In packed arrays, the elements are contained within the array buffer. A
packed array is an array of elements of varying length where the length information
for an element precedes that element within the array buffer.</p>
<p>Logically, an array buffer is linear but, physically, it can be organised
either as a flat buffer or a segmented buffer.</p>
<p>In general, you can choose between array classes which use a flat buffer
and array classes which use a segmented buffer. The choice depends on how
the array is to be used.</p>
<p>A segmented array buffer is implemented using a <codeph>CBufSeg</codeph> object.</p>
<p>A flat array buffer is implemented either:</p>
<ul>
<li id="GUID-56BE93C2-0A0A-50DD-807C-4F25A2B6981D"><p>directly by the array
as a piece of linear memory.</p> </li>
</ul>
<p>or</p>
<ul>
<li id="GUID-2165BEC5-BF75-5E0D-8ED0-074FF23A390A"><p>using a <codeph>CBufFlat</codeph> object.</p> </li>
</ul>
<p>The first type is a simple and efficient implementation but has some restrictions
on the size of an array element and is limited to holding elements which have
the same length. The second is a more general implementation and is only limited
by the available memory.</p>
<section id="GUID-1A671F26-FA1C-4943-B6FD-43F3FD831464"><title>See also</title> <p><xref href="GUID-112AAFA5-B4C9-5B62-A106-FB5097C13A0E.dita">Using
Dynamic Buffers</xref>.</p> </section>
</conbody></concept>