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55 lines
2.0 KiB
Markdown
55 lines
2.0 KiB
Markdown
# fsm
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This module implements a Finite State Machine (FSM).
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The FSM is composed of states and transitions between them.
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These need to be specified by the client.
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## Usage
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Have a look at `fsm_test.v` for usage examples.
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On each `run()`, all the possible transitions from the current state are evaluated.
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The first transition for the current state, whose condition evaluates to true is
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taken (the condition is specified by a transition callback function).
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In a successful transition, the current state changes to the new one.
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When that happens:
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* the client-specified `on_exit()` handler from the current state is called.
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* the client-specified `on_entry()` handler of the new state is called.
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After all transitions are checked, and thus the state is changed, the client-specified
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`on_run()` handler of the now current state is called.
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## Plot States and Transitions
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This module includes a tool for generating dot diagrams from .v source code,
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that defines a FSM. The tool is located in [fsm_graph.v](tools/fsm_graph.v).
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Here is an example of how to generate a .dot file with the graph and transitions:
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```bash
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v run vlib/datatypes/fsm/tools/fsm_graph.v -f vlib/datatypes/fsm/fsm_test.v > graph.dot
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```
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You can convert the generated .dot file to a PNG file with Graphviz's `dot`
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conversion tool:
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```bash
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v run vlib/datatypes/fsm/tools/fsm_graph.v -f vlib/datatypes/fsm/fsm_test.v > graph.dot
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dot -Tpng graph.dot > graph.png
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xdg-open graph.png
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```
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You can also visualise it with Graphviz (the `dot` command)
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& ImageMagick (the `display` command):
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```bash
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v run vlib/datatypes/fsm/tools/fsm_graph.v -f vlib/datatypes/fsm/fsm_test.v | dot -Tpng | display
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```
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To view the .dot file, you can also use any of the
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[Graphviz Graphical Interfaces](https://graphviz.org/resources/#graphical-interfaces)
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and `xdot` in particular:
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```bash
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v run vlib/datatypes/fsm/tools/fsm_graph.v -f vlib/datatypes/fsm/fsm_test.v | xdot -
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```
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In all of the above examples, you can replace `vlib/datatypes/fsm/fsm_test.v`
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with the path to your own .v code that imports and uses `fsm`.
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