mirror of
https://github.com/fadden/6502bench.git
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137 lines
4.7 KiB
HTML
137 lines
4.7 KiB
HTML
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<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="utf-8"/>
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<meta name="viewport" content="width=device-width, initial-scale=1"/>
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<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.6.0/jquery.min.js"
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integrity="sha384-vtXRMe3mGCbOeY7l30aIg8H9p3GdeSe4IFlP6G8JMa7o7lXvnz3GFKzPxzJdPfGK" crossorigin="anonymous"></script>
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<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css"/>
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<link rel="stylesheet" href="/main.css"/>
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<title>Inline Data - SourceGen Tutorial</title>
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</head>
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<body>
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<div id="masthead">
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<!-- START: /masthead-incl.html -->
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<script>$("#masthead").load("/masthead-incl.html");</script>
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<!-- END: /masthead-incl.html -->
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</div>
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<div id="topnav">
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<!-- START: /topnav-incl.html active:#topnav-sgtutorial -->
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<script>
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// Load global topnav content, and mark current page active.
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$("#topnav").load("/topnav-incl.html", function() {
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$("#topnav-sgtutorial").addClass("active");
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});
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</script>
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<!-- END: /topnav-incl.html -->
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</div>
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<div id="sidenav">
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<!-- START: /sidenav-incl.html active:#sidenav-inline-data -->
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<script>
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// Load local sidenav content, and mark current page active.
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$("#sidenav").load("sidenav-incl.html", function() {
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$("#sidenav-inline-data").addClass("active");
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});
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</script>
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<!-- END: /sidenav-incl.html -->
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</div>
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<div id="main">
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<h2>Inline Data</h2>
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<div class="grid-container">
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<div class="grid-item-image">
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<img src="images/t2-206b.png" alt="t2-206b"/>
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</div>
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<div class="grid-item-text">
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<p>Consider the code at address $206B. It's a <code>JSR</code> followed by some
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ASCII text, then a $00 byte, and then what might be code.</p>
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</div>
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</div>
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<div class="grid-container">
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<div class="grid-item-image">
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<img src="images/t2-20ab-1.png" alt="t2-20ab-1"/>
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<br/>
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...
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<br/>
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<img src="images/t2-20ab-2.png" alt="t2-20ab-2"/>
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</div>
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<div class="grid-item-text">
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<p>Double-click on the <code>JSR</code> opcode
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to jump to $20AB to see the function. It pulls the
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call address off the stack, and uses it as a pointer. When it encounters
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a zero byte, it breaks out of the loop, pushes the adjusted pointer
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value back onto the stack, and returns.</p>
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</div>
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</div>
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<div class="grid-container">
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<div class="grid-item-text">
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<p>This is an example of "inline data", where a function uses the return
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address to get a pointer to data. The return address is adjusted to
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point past the inline data before returning (technically, it points at
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the very last byte of the inline data, because
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<code>RTS</code> jumps to address + 1).</p>
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</div>
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</div>
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<div class="grid-container">
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<div class="grid-item-image">
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<img src="images/t2-inline-tag.png" alt="t2-inline-tag"/>
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</div>
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<div class="grid-item-text">
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<p>To format the data, we first need to tell SourceGen that there's data
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in line with the code. Select the line at address $206E, then
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shift-click the line at address $2077. Use
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<samp>Actions > Tag Bytes As Inline Data</samp>
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(<kbd class="key">Ctrl+H</kbd><kbd class="key">Ctrl+I</kbd>).</p>
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</div>
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</div>
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<div class="grid-container">
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<div class="grid-item-image">
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<img src="images/t2-inline-after.png" alt="t2-inline-after"/>
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</div>
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<div class="grid-item-text">
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<p>The data turns to single-byte values, and we now see the code
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continuing at address $2078. We can format the data as a string by
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using <samp>Actions > Edit Operand</samp>,
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setting the Character Encoding to <samp>Low or High ASCII</samp>,
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and selecting <samp>null-terminated strings</samp>.</p>
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</div>
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</div>
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<div class="grid-container">
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<div class="grid-item-text">
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<p>That's pretty straightforward, but this could quickly become tedious if
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there were a lot of these. SourceGen allows you to define scripts to
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automate common formatting tasks. This is covered in the "Extension
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Scripts" tutorial.</p>
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</div>
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</div>
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</div> <!-- #main -->
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<div id="prevnext">
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<a href="#" class="btn-previous">« Previous</a>
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<a href="#" class="btn-next">Next »</a>
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</div>
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<div id="footer">
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<!-- START: /footer-incl.html -->
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<script>$("#footer").load("/footer-incl.html");</script>
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<!-- END: /footer-incl.html -->
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</div>
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</body>
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</html>
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