Abstract out verify logic for fe_is_odd

sipa · May 11, 2023 · c5e788d · c5e788d
1 parent d3f3fe8
commit c5e788d
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Showing 4 changed files with 15 additions and 11 deletions.
diff --git a/src/field.h b/src/field.h
@@ -83,6 +83,7 @@ static const secp256k1_fe secp256k1_const_beta = SECP256K1_FE_CONST(
 #  define secp256k1_fe_set_int secp256k1_fe_impl_set_int
 #  define secp256k1_fe_clear secp256k1_fe_impl_clear
 #  define secp256k1_fe_is_zero secp256k1_fe_impl_is_zero
+#  define secp256k1_fe_is_odd secp256k1_fe_impl_is_odd
 #endif /* !defined(VERIFY) */
 
 /** Normalize a field element.
@@ -142,7 +143,11 @@ static void secp256k1_fe_clear(secp256k1_fe *a);
  */
 static int secp256k1_fe_is_zero(const secp256k1_fe *a);
 
-/** Check the "oddness" of a field element. Requires the input to be normalized. */
+/** Determine whether a (mod p) is odd.
+ *
+ * On input, a must be a valid normalized field element.
+ * Returns (int(a) mod p) & 1.
+ */
 static int secp256k1_fe_is_odd(const secp256k1_fe *a);
 
 /** Compare two field elements. Requires magnitude-1 inputs. */

diff --git a/src/field_10x26_impl.h b/src/field_10x26_impl.h
@@ -274,11 +274,7 @@ SECP256K1_INLINE static int secp256k1_fe_impl_is_zero(const secp256k1_fe *a) {
     return (t[0] | t[1] | t[2] | t[3] | t[4] | t[5] | t[6] | t[7] | t[8] | t[9]) == 0;
 }
 
-SECP256K1_INLINE static int secp256k1_fe_is_odd(const secp256k1_fe *a) {
-#ifdef VERIFY
-    VERIFY_CHECK(a->normalized);
-    secp256k1_fe_verify(a);
-#endif
+SECP256K1_INLINE static int secp256k1_fe_impl_is_odd(const secp256k1_fe *a) {
     return a->n[0] & 1;
 }
 

diff --git a/src/field_5x52_impl.h b/src/field_5x52_impl.h
@@ -220,11 +220,7 @@ SECP256K1_INLINE static int secp256k1_fe_impl_is_zero(const secp256k1_fe *a) {
     return (t[0] | t[1] | t[2] | t[3] | t[4]) == 0;
 }
 
-SECP256K1_INLINE static int secp256k1_fe_is_odd(const secp256k1_fe *a) {
-#ifdef VERIFY
-    VERIFY_CHECK(a->normalized);
-    secp256k1_fe_verify(a);
-#endif
+SECP256K1_INLINE static int secp256k1_fe_impl_is_odd(const secp256k1_fe *a) {
     return a->n[0] & 1;
 }
 

diff --git a/src/field_impl.h b/src/field_impl.h
@@ -209,6 +209,13 @@ SECP256K1_INLINE static int secp256k1_fe_is_zero(const secp256k1_fe *a) {
     VERIFY_CHECK(a->normalized);
     return secp256k1_fe_impl_is_zero(a);
 }
+
+static int secp256k1_fe_impl_is_odd(const secp256k1_fe *a);
+SECP256K1_INLINE static int secp256k1_fe_is_odd(const secp256k1_fe *a) {
+    secp256k1_fe_verify(a);
+    VERIFY_CHECK(a->normalized);
+    return secp256k1_fe_impl_is_odd(a);
+}
 #endif /* defined(VERIFY) */
 
 #endif /* SECP256K1_FIELD_IMPL_H */