fix: Move mapping closer to enum

Author: tmathern

src/c2pa/c2pa.py

@@ -123,6 +123,19 @@ class C2paSigningAlg(enum.IntEnum):
     ED25519 = 6
 
 
+# Mapping from C2paSigningAlg enum to string representation,
+# as the enum value currently maps by default to an integer value.
+_ALG_MAPPING = {
+    C2paSigningAlg.ES256: b"es256",
+    C2paSigningAlg.ES384: b"es384",
+    C2paSigningAlg.ES512: b"es512",
+    C2paSigningAlg.PS256: b"ps256",
+    C2paSigningAlg.PS384: b"ps384",
+    C2paSigningAlg.PS512: b"ps512",
+    C2paSigningAlg.ED25519: b"ed25519",
+}
+
+
 # Define callback types
 ReadCallback = ctypes.CFUNCTYPE(
     ctypes.c_ssize_t,
@@ -205,18 +218,6 @@ class C2paSignerInfo(ctypes.Structure):
         ("ta_url", ctypes.c_char_p),
     ]
 
-    # Mapping from C2paSigningAlg enum to string representation,
-    # as the enum value currently maps by default to an integer value.
-    _ALG_MAPPING = {
-        C2paSigningAlg.ES256: b"es256",
-        C2paSigningAlg.ES384: b"es384",
-        C2paSigningAlg.ES512: b"es512",
-        C2paSigningAlg.PS256: b"ps256",
-        C2paSigningAlg.PS384: b"ps384",
-        C2paSigningAlg.PS512: b"ps512",
-        C2paSigningAlg.ED25519: b"ed25519",
-    }
-
     def __init__(self, alg=None, sign_cert=None, private_key=None, ta_url=None):
         """Initialize C2paSignerInfo with optional parameters.
 
@@ -231,7 +232,7 @@ def __init__(self, alg=None, sign_cert=None, private_key=None, ta_url=None):
         if alg is not None:
             if isinstance(alg, C2paSigningAlg):
                 # Convert enum to string representation
-                alg_str = self._ALG_MAPPING.get(alg)
+                alg_str = _ALG_MAPPING.get(alg)
                 if alg_str is None:
                     raise ValueError(f"Unsupported signing algorithm: {alg}")
                 alg = alg_str