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<concept id="GUID-6468F3CB-7828-5746-A868-AD525EB7D6BD" xml:lang="en"><title>Introduction

to dynamic buffers</title><shortdesc>Description of flat and segmented buffers in Symbian platform.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>A buffer is an area of memory which may contain data. Managing data in

buffers can be more or less complex, depending on the requirements:</p>

<ul>

<li id="GUID-2892A824-D918-5998-9730-B780BBDE254C"><p>if the data is of fixed

length, a fixed-length area of memory may be allocated, either on the stack

or the heap; a buffer descriptor (<codeph>TBuf</codeph>) may be used for this.</p> </li>

<li id="GUID-22EC8B3D-2230-597D-935D-37A5DBCF1094"><p>if the data is of varying

length, but the variation is relatively small, it may still be appropriate

to allocate the data within a non-extensible buffer such as <codeph>TBuf</codeph>:

programming is simple, and only a little memory is wasted</p> </li>

<li id="GUID-75E026E3-8C69-575C-A893-1A41192E9073"><p>if the data is of significantly

varying length, the memory can be allocated on the heap, and the allocation

extended when necessary. The <codeph>CBufFlat</codeph> class is provided to

manage this</p> </li>

<li id="GUID-C4B11D3C-A514-56FE-AAB1-24D658CDF921"><p>if the data’s length

varies so much that a single heap cell cannot reasonably be expected to hold

it all, then the data must be held in several heap cells, but these must appear

as one for convenience. The <codeph>CBufSeg</codeph> class is provided to

manage this</p> </li>

</ul>

<p>Symbian platform provides <i>flat buffers</i>, objects of type <codeph>CBufFlat</codeph>,

which are used to allocate and manage storage in a single allocated cell</p>

<p>Symbian platform provides <i>segmented buffers</i>, objects of type <codeph>CBufSeg</codeph>,

which are used to allocate and manage storage in several alloc cells.</p>

<p>Both types of buffer have a common base class, <codeph>CBufBase</codeph>.

This class specifies the main aspects of the programming interface. Having

a common base class allows the decision as to whether to use flat or segmented

buffers to be changed during program development, with minimal impact on code.</p>