1
0
mirror of https://github.com/fadden/6502bench.git synced 2024-09-10 13:54:52 +00:00
6502bench/docs/sgtutorial/inline-data.html

137 lines
4.7 KiB
HTML
Raw Normal View History

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8"/>
<meta name="viewport" content="width=device-width, initial-scale=1"/>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.6.0/jquery.min.js"
integrity="sha384-vtXRMe3mGCbOeY7l30aIg8H9p3GdeSe4IFlP6G8JMa7o7lXvnz3GFKzPxzJdPfGK" crossorigin="anonymous"></script>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css"/>
<link rel="stylesheet" href="/main.css"/>
<title>Inline Data - SourceGen Tutorial</title>
</head>
<body>
<div id="masthead">
<!-- START: /masthead-incl.html -->
<script>$("#masthead").load("/masthead-incl.html");</script>
<!-- END: /masthead-incl.html -->
</div>
<div id="topnav">
<!-- START: /topnav-incl.html active:#topnav-sgtutorial -->
<script>
// Load global topnav content, and mark current page active.
$("#topnav").load("/topnav-incl.html", function() {
$("#topnav-sgtutorial").addClass("active");
});
</script>
<!-- END: /topnav-incl.html -->
</div>
<div id="sidenav">
<!-- START: sidenav-incl.html active:#sidenav-inline-data -->
<script>
// Load local sidenav content, and mark current page active.
$("#sidenav").load("sidenav-incl.html", function() {
$("#sidenav-inline-data").addClass("active");
});
</script>
<!-- END: sidenav-incl.html -->
</div>
<div id="main">
<h2>Inline Data</h2>
<div class="grid-container">
<div class="grid-item-image">
<img src="images/t2-206b.png" alt="t2-206b"/>
</div>
<div class="grid-item-text">
<p>Consider the code at address $206B. It's a <code>JSR</code> followed by some
ASCII text, then a $00 byte, and then what might be code.</p>
</div>
</div>
<div class="grid-container">
<div class="grid-item-image">
<img src="images/t2-20ab-1.png" alt="t2-20ab-1"/>
<br/>
...
<br/>
<img src="images/t2-20ab-2.png" alt="t2-20ab-2"/>
</div>
<div class="grid-item-text">
<p>Double-click on the <code>JSR</code> opcode
to jump to $20AB to see the function. It pulls the
call address off the stack, and uses it as a pointer. When it encounters
a zero byte, it breaks out of the loop, pushes the adjusted pointer
value back onto the stack, and returns.</p>
</div>
</div>
<div class="grid-container">
<div class="grid-item-text">
<p>This is an example of "inline data", where a function uses the return
address to get a pointer to data. The return address is adjusted to
point past the inline data before returning (technically, it points at
the very last byte of the inline data, because
<code>RTS</code> jumps to address + 1).</p>
</div>
</div>
<div class="grid-container">
<div class="grid-item-image">
<img src="images/t2-inline-tag.png" alt="t2-inline-tag"/>
</div>
<div class="grid-item-text">
<p>To format the data, we first need to tell SourceGen that there's data
in line with the code. Select the line at address $206E, then
shift-click the line at address $2077. Use
<samp>Actions &gt; Tag Bytes As Inline Data</samp>
(<kbd class="key">Ctrl+H</kbd><kbd class="key">Ctrl+I</kbd>).</p>
</div>
</div>
<div class="grid-container">
<div class="grid-item-image">
<img src="images/t2-inline-after.png" alt="t2-inline-after"/>
</div>
<div class="grid-item-text">
<p>The data turns to single-byte values, and we now see the code
continuing at address $2078. We can format the data as a string by
using <samp>Actions &gt; Edit Operand</samp>,
setting the Character Encoding to <samp>Low or High ASCII</samp>,
and selecting <samp>null-terminated strings</samp>.</p>
</div>
</div>
<div class="grid-container">
<div class="grid-item-text">
<p>That's pretty straightforward, but this could quickly become tedious if
there were a lot of these. SourceGen allows you to define scripts to
automate common formatting tasks. This is covered in the "Extension
Scripts" tutorial.</p>
</div>
</div>
</div> <!-- #main -->
<div id="prevnext">
<a href="#" class="btn-previous">&laquo; Previous</a>
<a href="#" class="btn-next">Next &raquo;</a>
</div>
<div id="footer">
<!-- START: /footer-incl.html -->
<script>$("#footer").load("/footer-incl.html");</script>
<!-- END: /footer-incl.html -->
</div>
</body>
</html>