1 <?xml version="1.0" encoding="utf-8"?>

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    10 <!DOCTYPE concept

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

    12 <concept id="GUID-C642BA79-0E9B-5C62-9DC7-C64759830CD4" xml:lang="en"><title>Dynamic

    13 buffers versus descriptors, arrays and heap cells</title><shortdesc>Explains the difference between various types of buffers.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

    14 <p>The essential difference between dynamic buffers and more straightforward

    15 means of storing binary data is that C arrays and descriptors provide essentially

    16 non-extensible buffers. Any attempt to write beyond the end of a C array results

    17 in undefined (and usually disastrous) consequences. Any attempt to write beyond

    18 the end of a descriptor results in a panic.</p>

    19 <p>Heap cells may be extended, but not without limit; it may be impossible

    20 to extend a heap cell further, because the heap is exhausted, or too fragmented

    21 to permit the extension. In addition, if heap cell re-allocation results in

    22 movement of the cell, re-allocation can be unduly expensive. If re-allocation

    23 is undesirable, then a buffer could be extended by allocating a new segment

    24 in a new allocation cell. Segmented buffers have this behaviour: flat buffers

    25 use re-allocation alone.</p>

    26 </conbody></concept>