[PATCH v2 10/20] rv/rvgen: use class constant for init marker

Replace hardcoded string literal and magic number with a class
constant for the initial state marker in DOT file parsing. The
previous implementation used the magic string "__init_" directly
in the code along with a hardcoded length of 7 for substring
extraction, which made the code less maintainable and harder to
understand.

This change introduces a class constant init_marker to serve as
a single source of truth for the initial state prefix. The code
now uses startswith() for clearer intent and calculates the
substring position dynamically using len(), eliminating the magic
number. If the marker value needs to change in the future, only
the constant definition requires updating rather than multiple
locations in the code.

The refactoring improves code readability and maintainability
while preserving the exact same runtime behavior.

Signed-off-by: Wander Lairson Costa <redacted>
Reviewed-by: Gabriele Monaco <gmonaco@redhat.com>
Reviewed-by: Gabriele Monaco <gmonaco@redhat.com>
---
 tools/verification/rvgen/rvgen/automata.py | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/verification/rvgen/rvgen/automata.py b/tools/verification/rvgen/rvgen/automata.py
index 38035d59cdd51..035d0e8c12c9a 100644
--- a/tools/verification/rvgen/rvgen/automata.py
+++ b/tools/verification/rvgen/rvgen/automata.py

@@ -25,6 +25,7 @@ class Automata:
     """
 
     invalid_state_str = "INVALID_STATE"
+    init_marker = "__init_"
 
     def __init__(self, file_path, model_name=None):
         self.__dot_path = file_path

@@ -96,8 +97,8 @@ class Automata:
 
             #  "enabled_fired"}; -> enabled_fired
             state = raw_state.replace('"', '').replace('};', '').replace(',', '_')
-            if state[0:7] == "__init_":
-                initial_state = state[7:]
+            if state.startswith(self.init_marker):
+                initial_state = state[len(self.init_marker):]
             else:
                 states.append(state)
                 if "doublecircle" in self.__dot_lines[cursor]:

-- 
2.52.0