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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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	<TITLE>binaryXHR module</TITLE>
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<H1 CLASS="western">binaryXHR module</H1>
<TABLE WIDTH=50% CELLPADDING=2 CELLSPACING=2>
	<TR>
		<TD>
			<HR>
			<P>The <A HREF="../../src/lib/binaryXHR.js">binaryXHR Javascript
			module</A> implements a set of functions and classes that can be
			used to retrieve binary files using the <A HREF="http://en.wikipedia.org/wiki/XMLHttpRequest">XMLHttpRequest</A>
			API.</P>
			<HR>
		</TD>
	</TR>
</TABLE>
<P CLASS="heading-2-western">Overview</P>
<P>This module provides two functions, 
<A HREF="#FetchBinaryURL">FetchBinaryURL</A> and
<A HREF="#FetchBinaryURLAsync">FetchBinaryURLAsync</a>, 
that are wrappers around the 
<A HREF="http://en.wikipedia.org/wiki/XMLHttpRequest">XMLHttpRequest</A> API
and return an object of type 
<A HREF="#BinaryFile">BinaryFile</A>. 
The first one implements a
straight load, while the second one initiates an asynchronous
operation handled by a callback function.</P>
<P>The <A HREF="#BinaryFile">BinaryFile</A> class implements the methods needed to access the
elements of the binary files, such as strings, integers and real
numbers. 
</P>
<P>Both the functions and the class internally handle the differences
between different Web Browsers, so the user of this module does not
need to worry about them.</P>
<A NAME="FetchBinaryURL">
<P CLASS="heading-2-western">Function FetchBinaryURL</P>
</A>
<P>Load a binary file.</P>
<P>Arguments:</P>
<UL>
	<LI><P>url:string - URL from where to load the binary file.</P>
</UL>
<P>Output:</P>
<UL>
	<LI><P>An object of type BinaryFile.</P>
</UL>
<A NAME="FetchBinaryURLAsync">
<P CLASS="heading-2-western">Function FetchBinaryURLAsync</P>
</A>
<P>Initiate an asynchronous binary load.</P>
<P>Arguments:</P>
<UL>
	<LI><P>url:string - URL from where to load the binary file.</P>
	<LI><P>callback:function(obj) - Pointer to the function that will
	be called when the binary file has been loaded. He function will be
	given a single argument; an object of type <A HREF="#BinaryFile">BinaryFile</A>.</P>
</UL>
<P>Output:</P>
<UL>
	<LI><P>A reference to the <A HREF="http://www.w3.org/TR/XMLHttpRequest/">XMLHttpRequest</A> object.
	       It may be used to verify the status of the load or to implement timeouts.<BR>
               The callback function will receive the loaded binary file.</P>
</UL>
<A NAME="BinaryFile">
<P CLASS="heading-2-western">Class BinaryFile</P>
</A>
<P>This class implements the methods needed to access the content of
the binary file.</P>
<DIV ALIGN=RIGHT>
	<TABLE WIDTH=90% BORDER=1>
		<COL WIDTH=25%>
		<COL WIDTH=75%>
		<THEAD>
			<TR VALIGN=TOP>
				<TH WIDTH=25%>
					<P ALIGN=LEFT>Method</P>
				</TH>
				<TH WIDTH=75%>
					<P ALIGN=LEFT>Description</P>
				</TH>
			</TR>
		</THEAD>
		<TBODY>
			<TR VALIGN=TOP>
				<TD WIDTH=25%>
					<P>getLength()</P>
				</TD>
				<TD WIDTH=75%>
					<P>Return the number of bytes held by the object.</P>
				</TD>
			</TR>
			<TR VALIGN=TOP>
				<TD WIDTH=25%>
					<P>getByteAt(idx)</P>
				</TD>
				<TD WIDTH=75%>
					<P>Return an 8 bit unsigned integer from offset <I>idx</I>.</P>
				</TD>
			</TR>
			<TR VALIGN=TOP>
				<TD WIDTH=25%>
					<P>getShortAt(idx)</P>
				</TD>
				<TD WIDTH=75%>
					<P>Return a 16 bit little endian unsigned integer from offset
					idx. 
					</P>
				</TD>
			</TR>
			<TR VALIGN=TOP>
				<TD WIDTH=25%>
					<P>getLongAt(idx)</P>
				</TD>
				<TD WIDTH=75%>
					<P>Return a 32 bit little endian unsigned integer from offset
					idx.</P>
				</TD>
			</TR>
			<TR VALIGN=TOP>
				<TD WIDTH=25%>
					<P>getDoubleAt(idx)</P>
				</TD>
				<TD WIDTH=75%>
					<P>Return a double float (64 bit little endian) from offset idx.</P>
				</TD>
			</TR>
			<TR VALIGN=TOP>
				<TD WIDTH=25%>
					<P>getFastDoubleAt(idx)</P>
				</TD>
				<TD WIDTH=75%>
					<P>Return a low resolution (20 bit mantissa) double flat
					obtained from the high 32 bits of the original little endian
					double float from offset idx.</P>
				</TD>
			</TR>
			<TR VALIGN=TOP>
				<TD WIDTH=25%>
					<P>getCharAt(idx)</P>
				</TD>
				<TD WIDTH=75%>
					<P>Get a character from offset idx.</P>
				</TD>
			</TR>
			<TR VALIGN=TOP>
				<TD WIDTH=25%>
					<P>getCStringAt(idx,maxlen)</P>
				</TD>
				<TD WIDTH=75%>
					<P>Get a zero terminated string of limited size from offset idx.
					 
					</P>
				</TD>
			</TR>
			<TR VALIGN=TOP>
				<TD WIDTH=25%>
					<P>getStringAt(idx,len)</P>
				</TD>
				<TD WIDTH=75%>
					<P>Get a fixed length string from offset idx.</P>
				</TD>
			</TR>
		</TBODY>
	</TABLE>
</DIV>
<A NAME="InvalidBinaryFile">
<P CLASS="heading-2-western">Exception class InvalidBinaryFile</P>
</A>
<P>This is a helper exception class that can be thrown while loading the binary file.</P>
<P><BR></P>
<TABLE WIDTH=50%>
	<TR>
		<TD>
			<HR>
			<P>This module is part of the <A HREF="http://javascript.sourceforge.net/">javascriptRRD
			package</A> hosted at <A HREF="http://javascript.sourceforge.net/">http://javascript.sourceforge.net</A>.
			<BR>It is licensed under the <A HREF="http://www.opensource.org/licenses/mit-license.php">MIT
			licanse</A>. 
		</P>
			<HR>
		</TD>
	</TR>
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