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<concept id="GUID-82862A69-5E86-5924-BFF0-F7655FCBFAF0" xml:lang="en"><title>Contiguousness</title><shortdesc>Description of contiguous data in flat and segmented buffers.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>In flat buffers, all data is contiguous. The <codeph>Ptr()</codeph> function

always returns a pointer descriptor from the buffer position specified to

the end of the data, and the <codeph>BackPtr()</codeph> function always returns

a pointer descriptor from the beginning of the buffer to the buffer position

specified.</p>

<p>In segmented buffers, data is contained in segments and the maximum length

of contiguous data is the granularity of the buffer. The extent of contiguous

data contained in a segment may vary between a single byte, and the granularity,

if the insertion and deletion pattern is arbitrary.</p>

<p>However, the following guarantee is made: if the number of bytes inserted

or deleted in <i>all</i> insertion and deletion operations is a multiple of

some number <i>n</i>, and the granularity is also a multiple of this number <i>n</i>,

then all data extents will be a multiple of <i>n</i> in length. This implies

that the <codeph>Ptr()</codeph> function, given a buffer position which is

a multiple of <i>n</i>, will always return a pointer descriptor referring

to at least <i>n</i> bytes.</p>

<p>This property of segmented descriptors is exploited by the <codeph>CArrayFixBase</codeph>, <codeph>CArrayVarBase</codeph> and <codeph>CArrayPakBase</codeph> derived array classes. In these classes, all insertion or deletion operations

are always done in terms of the (fixed) length of data stored in the buffer.

Therefore, the data for an individual array element is always contiguous.</p>

</conbody><related-links>

<link>

<desc><xref href="GUID-2F64B579-73D3-548A-9104-16483AF77BCB.dita">Dynamic Arrays</xref></desc>

</link>