2021-01-21 13:40:28 +01:00
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</head><body>
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<p><span class="h1">Internals: I/O</span>
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<br/><br/>
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2021-05-17 19:04:42 +02:00
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Retro provides three words for interacting with I/O. These are:
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<br/><br/>
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<tt class='indentedcode'>io:enumerate returns the number of attached devices</tt>
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<tt class='indentedcode'>io:query returns information about a device</tt>
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<tt class='indentedcode'>io:invoke invokes an interaction with a device</tt>
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<br/><br/>
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As an example, with an implementation providing an output source,
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a block storage system, and keyboard:
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<br/><br/>
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<tt class='indentedcode'>io:enumerate will return `3` since there are three</tt>
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<tt class='indentedcode'> i/o devices</tt>
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<tt class='indentedcode'>#0 io:query will return 0 0, since the first device</tt>
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<tt class='indentedcode'> is a screen (device class 0) with a version</tt>
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<tt class='indentedcode'> of 0</tt>
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<tt class='indentedcode'>#1 io:query will return 1 3, since the second device is</tt>
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<tt class='indentedcode'> block storage (device class 3), with a version</tt>
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<tt class='indentedcode'> of 1</tt>
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<tt class='indentedcode'>#2 io:query will return 0 1, since the last device is a</tt>
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<tt class='indentedcode'> keyboard (device class 1), with a version</tt>
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<tt class='indentedcode'> of 0</tt>
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<br/><br/>
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In this case, some interactions can be defined:
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<br/><br/>
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<tt class='indentedcode'>:c:put #0 io:invoke ;</tt>
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<tt class='indentedcode'>:c:get #2 io:invoke ;</tt>
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<br/><br/>
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Setup the stack, push the device handle, and then use <span class="tt">io:invoke</span>
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to invoke the interaction.
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<br/><br/>
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2021-05-17 19:04:42 +02:00
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A Retro system requires one I/O device (a generic output for a
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single character). This must be the first device, and must have
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a device class and handle of 0.
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<br/><br/>
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All other devices are optional and can be specified in any
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order.
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<br/><br/>
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</p>
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</body></html>
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