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<TITLE>Magick::Blob</TITLE>
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<META NAME="AUTHOR" CONTENT="Bob Friesenhahn">
<META NAME="CREATED" CONTENT="20020805;13502672">
<META NAME="CHANGEDBY" CONTENT="Bob Friesenhahn">
<META NAME="CHANGED" CONTENT="20020805;13521508">
<META NAME="DESCRIPTION" CONTENT="Documentation for Blob class.">
<META NAME="KEYWORDS" CONTENT="Magick++, GraphicsMagick, Blob">
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<H1 ALIGN=CENTER>Magick::Blob</H1>
<P>Blob provides the means to contain any opaque data. It is named
after the term "Binary Large OBject" commonly used to
describe unstructured data (such as encoded images) which is stored
in a database. While the function of Blob is very simple (store a
pointer and and size associated with allocated data), the Blob class
provides some very useful capabilities. In particular, it is fully
reference counted just like the Image class.
</P>
<P>The Blob class supports value assignment while preserving any
outstanding earlier versions of the object. Since assignment is via a
pointer internally, Blob is efficient enough to be stored directly in
an STL container or any other data structure which requires
assignment. In particular, by storing a Blob in an <A HREF="http://www.sgi.com/tech/stl/AssociativeContainer.html">associative
container</A> (such as STL's '<A HREF="http://www.sgi.com/tech/stl/Map.html"><I>map</I></A>')
it is possible to create simple indexed in-memory "database"
of Blobs.
</P>
<P>Magick++ currently uses Blob to contain encoded images (e.g. JPEG)
as well as ICC and IPTC profiles. Since Blob is a general-purpose
class, it may be used for other purposes as well.
</P>
<P STYLE="margin-bottom: 0cm">The methods Blob provides are shown in
the following table: <BR><BR>
</P>
<P ALIGN=CENTER STYLE="margin-bottom: 0cm"><B>Blob Methods</B></P>
<TABLE WIDTH=100% BORDER=1 CELLPADDING=2 CELLSPACING=2>
<TR>
<TD>
<P ALIGN=CENTER><B>Method</B></P>
</TD>
<TD>
<P ALIGN=CENTER><B>Return Type</B></P>
</TD>
<TD>
<P ALIGN=CENTER><B>Signature(s)</B></P>
</TD>
<TD>
<P ALIGN=CENTER><B>Description</B></P>
</TD>
</TR>
<TR>
<TD ROWSPAN=3>
<P><A NAME="Blob"></A><FONT SIZE=2>Blob</FONT></P>
</TD>
<TD ROWSPAN=3 BGCOLOR="#666666">
<P><FONT SIZE=2> </FONT></P>
</TD>
<TD>
<P><FONT SIZE=2>void</FONT></P>
</TD>
<TD>
<P><FONT SIZE=2>Default constructor</FONT></P>
</TD>
</TR>
<TR>
<TD>
<P><FONT SIZE=2>const void* data_, size_t length_</FONT></P>
</TD>
<TD>
<P><FONT SIZE=2>Construct object with data, making a copy of the
supplied data</FONT></P>
</TD>
</TR>
<TR>
<TD>
<P><FONT SIZE=2>const Blob& blob_</FONT></P>
</TD>
<TD>
<P><FONT SIZE=2>Copy constructor (reference counted)</FONT></P>
</TD>
</TR>
<TR>
<TD>
<P><A NAME="operator="></A><FONT SIZE=2>operator=</FONT></P>
</TD>
<TD>
<P><FONT SIZE=2>Blob</FONT></P>
</TD>
<TD>
<P><FONT SIZE=2>const Blob& blob_</FONT></P>
</TD>
<TD>
<P><FONT SIZE=2>Assignment operator (reference counted)</FONT></P>
</TD>
</TR>
<TR>
<TD>
<P><A NAME="update"></A><FONT SIZE=2>update</FONT></P>
</TD>
<TD>
<P><FONT SIZE=2>void</FONT></P>
</TD>
<TD>
<P><FONT SIZE=2>const void* data_, size_t length_</FONT></P>
</TD>
<TD>
<P><FONT SIZE=2>Update object contents, making a copy of the
supplied data. Any existing data in the object is deallocated.</FONT></P>
</TD>
</TR>
<TR>
<TD>
<P><A NAME="data"></A><FONT SIZE=2>data</FONT></P>
</TD>
<TD>
<P><FONT SIZE=2>const void*</FONT></P>
</TD>
<TD>
<P><FONT SIZE=2>void</FONT></P>
</TD>
<TD>
<P><FONT SIZE=2>Obtain pointer to data</FONT></P>
</TD>
</TR>
<TR>
<TD>
<P><A NAME="length"></A><FONT SIZE=2>length</FONT></P>
</TD>
<TD>
<P><FONT SIZE=2>size_t</FONT></P>
</TD>
<TD>
<P><FONT SIZE=2>void</FONT></P>
</TD>
<TD>
<P><FONT SIZE=2>Obtain data length</FONT></P>
</TD>
</TR>
<TR>
<TD>
<P><A NAME="updateNoCopy"></A><FONT SIZE=2>updateNoCopy</FONT></P>
</TD>
<TD>
<P><FONT SIZE=2>void</FONT></P>
</TD>
<TD>
<P><FONT SIZE=2>void* data_, size_t length_, Blob::Allocator
allocator_ = Blob::NewAllocator</FONT></P>
</TD>
<TD>
<P><FONT SIZE=2>Update object contents, using supplied pointer
directly (no copy) Any existing data in the object is
deallocated. The user must ensure that the pointer supplied
is not deleted or otherwise modified after it has been supplied to
this method. The optional allocator_ parameter allows the user to
specify if the C (MallocAllocator) or C++ (NewAllocator) memory
allocation system was used to allocate the memory. The default is
to use the C++ memory allocator.</FONT></P>
</TD>
</TR>
</TABLE>
<P><BR><BR>
</P>
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