From 4371f98346b0a50c0a77e93948fe5e21d9346d06 Mon Sep 17 00:00:00 2001
From: Pieter Wuille <pieter@wuille.net>
Date: Thu, 11 May 2023 03:05:35 -0400
Subject: [PATCH] Abstract out verify logic for fe_add_int

---
 src/field.h            |  7 ++++++-
 src/field_10x26_impl.h | 10 +---------
 src/field_5x52_impl.h  | 10 +---------
 src/field_impl.h       | 10 ++++++++++
 4 files changed, 18 insertions(+), 19 deletions(-)

diff --git a/src/field.h b/src/field.h
index c20638e45e..a515f38095 100644
--- a/src/field.h
+++ b/src/field.h
@@ -99,6 +99,7 @@ static const secp256k1_fe secp256k1_const_beta = SECP256K1_FE_CONST(
 #  define secp256k1_fe_inv_var secp256k1_fe_impl_inv_var
 #  define secp256k1_fe_get_bounds secp256k1_fe_impl_get_bounds
 #  define secp256k1_fe_half secp256k1_fe_impl_half
+#  define secp256k1_fe_add_int secp256k1_fe_impl_add_int
 #endif /* !defined(VERIFY) */
 
 /** Normalize a field element.
@@ -213,7 +214,11 @@ static void secp256k1_fe_get_b32(unsigned char *r, const secp256k1_fe *a);
  */
 static void secp256k1_fe_negate(secp256k1_fe *r, const secp256k1_fe *a, int m);
 
-/** Adds a small integer (up to 0x7FFF) to r. The resulting magnitude increases by one. */
+/** Add a small integer to a field element.
+ *
+ * Performs {r += a}. The magnitude of r increases by 1, and normalized is cleared.
+ * a must be in range [0,0xFFFF].
+ */
 static void secp256k1_fe_add_int(secp256k1_fe *r, int a);
 
 /** Multiply a field element with a small integer.
diff --git a/src/field_10x26_impl.h b/src/field_10x26_impl.h
index ec53165e88..80f32aa460 100644
--- a/src/field_10x26_impl.h
+++ b/src/field_10x26_impl.h
@@ -389,16 +389,8 @@ SECP256K1_INLINE static void secp256k1_fe_impl_add(secp256k1_fe *r, const secp25
     r->n[9] += a->n[9];
 }
 
-SECP256K1_INLINE static void secp256k1_fe_add_int(secp256k1_fe *r, int a) {
-    secp256k1_fe_verify(r);
-    VERIFY_CHECK(a >= 0);
-    VERIFY_CHECK(a <= 0x7FFF);
+SECP256K1_INLINE static void secp256k1_fe_impl_add_int(secp256k1_fe *r, int a) {
     r->n[0] += a;
-#ifdef VERIFY
-    r->magnitude += 1;
-    r->normalized = 0;
-    secp256k1_fe_verify(r);
-#endif
 }
 
 #if defined(USE_EXTERNAL_ASM)
diff --git a/src/field_5x52_impl.h b/src/field_5x52_impl.h
index 06a2e379ab..a9a436dec0 100644
--- a/src/field_5x52_impl.h
+++ b/src/field_5x52_impl.h
@@ -334,16 +334,8 @@ SECP256K1_INLINE static void secp256k1_fe_impl_mul_int(secp256k1_fe *r, int a) {
     r->n[4] *= a;
 }
 
-SECP256K1_INLINE static void secp256k1_fe_add_int(secp256k1_fe *r, int a) {
-    secp256k1_fe_verify(r);
-    VERIFY_CHECK(a >= 0);
-    VERIFY_CHECK(a <= 0x7FFF);
+SECP256K1_INLINE static void secp256k1_fe_impl_add_int(secp256k1_fe *r, int a) {
     r->n[0] += a;
-#ifdef VERIFY
-    r->magnitude += 1;
-    r->normalized = 0;
-    secp256k1_fe_verify(r);
-#endif
 }
 
 SECP256K1_INLINE static void secp256k1_fe_impl_add(secp256k1_fe *r, const secp256k1_fe *a) {
diff --git a/src/field_impl.h b/src/field_impl.h
index 8dbc765f73..0d46b313d5 100644
--- a/src/field_impl.h
+++ b/src/field_impl.h
@@ -220,6 +220,16 @@ SECP256K1_INLINE static void secp256k1_fe_set_int(secp256k1_fe *r, int a) {
     secp256k1_fe_verify(r);
 }
 
+static void secp256k1_fe_impl_add_int(secp256k1_fe *r, int a);
+SECP256K1_INLINE static void secp256k1_fe_add_int(secp256k1_fe *r, int a) {
+    VERIFY_CHECK(0 <= a && a <= 0x7FFF);
+    secp256k1_fe_verify(r);
+    secp256k1_fe_impl_add_int(r, a);
+    r->magnitude += 1;
+    r->normalized = 0;
+    secp256k1_fe_verify(r);
+}
+
 static void secp256k1_fe_impl_clear(secp256k1_fe *a);
 SECP256K1_INLINE static void secp256k1_fe_clear(secp256k1_fe *a) {
     a->magnitude = 0;