1 files changed, 145 insertions, 0 deletions

diff --git a/pyecsca/misc/cfg.py b/pyecsca/misc/cfg.py
new file mode 100644
index 0000000..b1c4007
--- /dev/null
+++ b/pyecsca/misc/cfg.py
@@ -0,0 +1,145 @@
+from copy import deepcopy
+from contextvars import ContextVar, Token
+
+from public import public
+
+
+@public
+class ECConfig(object):
+    """Configuration for the :py:mod:`pyecsca.ec` package."""
+    _no_inverse_action: str = "error"
+    _non_residue_action: str = "error"
+    _unsatisfied_formula_assumption_action: str = "error"
+    _unsatisfied_coordinate_assumption_action: str = "error"
+    _mod_implementation: str = "gmp"
+
+    @property
+    def no_inverse_action(self) -> str:
+        """
+        The action to take when a non-invertible element is to be inverted. One of:
+
+         - `"error"`: Raise :py:class:`pyecsca.ec.error.NonInvertibleError`.
+         - `"warning"`: Raise :py:class:`pyecsca.ec.error.NonInvertibleWarning`.
+         - `"ignore"`: Ignore the event and compute as if nothing happened."""
+        return self._no_inverse_action
+
+    @no_inverse_action.setter
+    def no_inverse_action(self, value: str):
+        if value not in ("error", "warning", "ignore"):
+            raise ValueError("Action has to be one of 'error', 'warning', 'ignore'.")
+        self._no_inverse_action = value
+
+    @property
+    def non_residue_action(self) -> str:
+        """
+        The action to take when a the square-root of a non-residue is to be computed. One of:
+
+         - `"error"`: Raise :py:class:`pyecsca.ec.error.NonResidueError`.
+         - `"warning"`: Raise :py:class:`pyecsca.ec.error.NonResidueWarning`.
+         - `"ignore"`: Ignore the event and compute as if nothing happened."""
+        return self._non_residue_action
+
+    @non_residue_action.setter
+    def non_residue_action(self, value: str):
+        if value not in ("error", "warning", "ignore"):
+            raise ValueError("Action has to be one of 'error', 'warning', 'ignore'.")
+        self._non_residue_action = value
+
+    @property
+    def unsatisfied_formula_assumption_action(self) -> str:
+        """
+        The action to take when a formula assumption is unsatisfied during execution.
+        This works for assumption that can be ignored without a fatal error,
+        which are those that are not used to compute a value of an undefined parameter.
+        For example, things of the form `Z1 = 1`.
+        One of:
+
+         - `"error"`: Raise :py:class:`pyecsca.ec.error.UnsatisfiedAssumptionError`.
+         - `"warning"`: Raise :py:class:`pyecsca.ec.error.UnsatisfiedAssumptionWarning`.
+         - `"ignore"`: Ignore the event and compute as if nothing happened.
+        """
+        return self._unsatisfied_formula_assumption_action
+
+    @unsatisfied_formula_assumption_action.setter
+    def unsatisfied_formula_assumption_action(self, value: str):
+        if value not in ("error", "warning", "ignore"):
+            raise ValueError("Action has to be one of 'error', 'warning', 'ignore'.")
+        self._unsatisfied_formula_assumption_action = value
+
+    @property
+    def unsatisfied_coordinate_assumption_action(self) -> str:
+        """
+        The action to take when a coordinate assumption is unsatisfied during curve creation.
+        This works for assumption that can be ignored without a fatal error,
+        which are those that are not used to compute a value of an undefined parameter.
+        For example, things of the form `a = -1`.
+        One of:
+
+         - `"error"`: Raise :py:class:`pyecsca.ec.error.UnsatisfiedAssumptionError`.
+         - `"warning"`: Raise :py:class:`pyecsca.ec.error.UnsatisfiedAssumptionWarning`.
+         - `"ignore"`: Ignore the event and compute as if nothing happened.
+        """
+        return self._unsatisfied_coordinate_assumption_action
+
+    @unsatisfied_coordinate_assumption_action.setter
+    def unsatisfied_coordinate_assumption_action(self, value: str):
+        if value not in ("error", "warning", "ignore"):
+            raise ValueError("Action has to be one of 'error', 'warning', 'ignore'.")
+        self._unsatisfied_coordinate_assumption_action = value
+
+    @property
+    def mod_implementation(self) -> str:
+        """
+        The selected :py:class:`pyecsca.ec.mod.Mod` implementation. One of:
+
+         - `"gmp"`: Requires the GMP library and `gmpy2` package.
+         - `"python"`: Doesn't require anything.
+        """
+        return self._mod_implementation
+
+    @mod_implementation.setter
+    def mod_implementation(self, value: str):
+        if value not in ("python", "gmp"):
+            raise ValueError(f"Bad Mod implementaiton, can be one of 'python' or 'gmp'.")
+        self._mod_implementation = value
+
+
+@public
+class Config(object):
+    """A runtime configuration for the library."""
+    ec: ECConfig
+    """Configuration for the :py:mod:`pyecsca.ec` package."""
+
+    def __init__(self):
+        self.ec = ECConfig()
+
+
+_config: ContextVar[Config] = ContextVar("config", default=Config())
+
+
+@public
+def getconfig() -> Config:
+    return _config.get()
+
+
+@public
+def setconfig(cfg: Config) -> Token:
+    return _config.set(cfg)
+
+
+@public
+def resetconfig(token: Token):
+    _config.reset(token)
+
+
+@public
+class TemporaryConfig(object):
+    def __init__(self):
+        self.new_config = deepcopy(getconfig())
+
+    def __enter__(self) -> Config:
+        self.token = setconfig(self.new_config)
+        return self.new_config
+
+    def __exit__(self, t, v, tb):
+        resetconfig(self.token)
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