40 lines
1.6 KiB
Markdown
40 lines
1.6 KiB
Markdown
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# Patch bay
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The patch bay (or simply bay) allows [channels](../channels/) to be registered
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with their name so they are visible to all parts of the emulator and provides a
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way to run callbacks when the channels update their values.
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The name follows from the [patch bay](https://en.wikipedia.org/wiki/Patch_panel)
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used to connect audio channels:
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## Registering channels
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Channels are registered with `bay_register()`, using the channel name as a
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unique identifier. It is an error to register multiple channels with the same
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name.
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The register step sets the channel callback function, so the bay can detect
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which channel become dirty and act upon them.
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## Callbacks
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After registering a channel in the bay, multiple callbacks can be registered
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with `bay_add_cb()` and will be called in same order they were added.
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The callbacks are executed in the propagation phase, when `bay_propagate()` is
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called. There are two types of callbacks: *dirty* and *emit*.
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All dirty callbacks are called first, for all the channels that are dirty.
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Executing the dirty callbacks may cause other channels to become dirty too,
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which will be added to the list of dirty channels. Channels that are already
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dirty cannot be modified, so we prevent an infinite updating loop.
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Then the emit callbacks are called for each dirty channel in the same way. The
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emit callbacks are generally used to write the values of the channels in the
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output traces. These callbacks cannot cause any new channel to become dirty.
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Finally, all channels are flushed by calling `chan_flush()`, clearing the dirty
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flag and leaving them ready for the next input event.
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