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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>
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<THEAD>
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<P ALIGN=LEFT>Method</P>
</TH>
<TH WIDTH=75%>
<P ALIGN=LEFT>Description</P>
</TH>
</TR>
</THEAD>
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<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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