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    10 <!DOCTYPE concept

    11   PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">

    12 <concept id="GUID-DE17BEA2-C821-50B8-9128-9C4D35D95599" xml:lang="en"><title>Array

    13 Implementation</title><shortdesc>Describes the features of arrays and the ways in which they are

    14 implemented.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

    15 <p>All arrays have an array buffer allocated from the heap. The implementation

    16 of this buffer and the way it is used depends on the specific type of array.</p>

    17 <p>In arrays of elements which all have the same length, the elements are

    18 contained within the array buffer itself.</p>

    19 <p>In arrays of elements with varying length, each element is contained within

    20 its own heap cell and the array buffer contains <i>pointers</i> to the elements.</p>

    21 <p>In packed arrays, the elements are contained within the array buffer. A

    22 packed array is an array of elements of varying length where the length information

    23 for an element precedes that element within the array buffer.</p>

    24 <p>Logically, an array buffer is linear but, physically, it can be organised

    25 either as a flat buffer or a segmented buffer.</p>

    26 <p>In general, you can choose between array classes which use a flat buffer

    27 and array classes which use a segmented buffer. The choice depends on how

    28 the array is to be used.</p>

    29 <p>A segmented array buffer is implemented using a <codeph>CBufSeg</codeph> object.</p>

    30 <p>A flat array buffer is implemented either:</p>

    31 <ul>

    32 <li id="GUID-56BE93C2-0A0A-50DD-807C-4F25A2B6981D"><p>directly by the array

    33 as a piece of linear memory.</p> </li>

    34 </ul>

    35 <p>or</p>

    36 <ul>

    37 <li id="GUID-2165BEC5-BF75-5E0D-8ED0-074FF23A390A"><p>using a <codeph>CBufFlat</codeph> object.</p> </li>

    38 </ul>

    39 <p>The first type is a simple and efficient implementation but has some restrictions

    40 on the size of an array element and is limited to holding elements which have

    41 the same length. The second is a more general implementation and is only limited

    42 by the available memory.</p>

    43 <section id="GUID-1A671F26-FA1C-4943-B6FD-43F3FD831464"><title>See also</title> <p><xref href="GUID-112AAFA5-B4C9-5B62-A106-FB5097C13A0E.dita">Using

    44 Dynamic Buffers</xref>.</p> </section>

    45 </conbody></concept>