From 92feebd2728d3fd5b07c8a0a43ab63ccc6ce0c31 Mon Sep 17 00:00:00 2001
From: Dave Collins <davec@conformal.com>
Date: Sat, 21 Mar 2020 02:22:53 -0500
Subject: [PATCH] secp256k1: Make field value set int take uint16.

This modifies the SetInt method on a field value to take a uint16
instead of a uint in order to make it impossible to misuse it since it
has a precondition of a max value of 2^26 - 1.  In practice, the code
currently only ever calls it with 0 and 1, but in order to prepare for
exporting the type, it's nicer to prevent the potential misuse.
---
 dcrec/secp256k1/field.go      |  2 +-
 dcrec/secp256k1/field_test.go | 20 ++++++++------------
 2 files changed, 9 insertions(+), 13 deletions(-)

diff --git a/dcrec/secp256k1/field.go b/dcrec/secp256k1/field.go
index 2f28fe36..b54d778d 100644
--- a/dcrec/secp256k1/field.go
+++ b/dcrec/secp256k1/field.go
@@ -171,7 +171,7 @@ func (f *fieldVal) Set(val *fieldVal) *fieldVal {
 //
 // The field value is returned to support chaining.  This enables syntax such
 // as f := new(fieldVal).SetInt(2).Mul(f2) so that f = 2 * f2.
-func (f *fieldVal) SetInt(ui uint) *fieldVal {
+func (f *fieldVal) SetInt(ui uint16) *fieldVal {
 	f.Zero()
 	f.n[0] = uint32(ui)
 	return f
diff --git a/dcrec/secp256k1/field_test.go b/dcrec/secp256k1/field_test.go
index 28ca0bbc..9ded85ad 100644
--- a/dcrec/secp256k1/field_test.go
+++ b/dcrec/secp256k1/field_test.go
@@ -54,24 +54,20 @@ func randIntAndFieldVal(t *testing.T, rng *rand.Rand) (*big.Int, *fieldVal) {
 func TestFieldSetInt(t *testing.T) {
 	tests := []struct {
 		name     string     // test description
-		in       uint       // test value
+		in       uint16     // test value
 		expected [10]uint32 // expected raw ints
 	}{{
+		name:     "one",
+		in:       1,
+		expected: [10]uint32{1, 0, 0, 0, 0, 0, 0, 0, 0, 0},
+	}, {
 		name:     "five",
 		in:       5,
 		expected: [10]uint32{5, 0, 0, 0, 0, 0, 0, 0, 0, 0},
 	}, {
-		name:     "2^26",
-		in:       67108864,
-		expected: [10]uint32{67108864, 0, 0, 0, 0, 0, 0, 0, 0, 0},
-	}, {
-		name:     "2^26 + 1",
-		in:       67108865,
-		expected: [10]uint32{67108865, 0, 0, 0, 0, 0, 0, 0, 0, 0},
-	}, {
-		name:     "2^32 - 1",
-		in:       4294967295,
-		expected: [10]uint32{4294967295, 0, 0, 0, 0, 0, 0, 0, 0, 0},
+		name:     "2^16 - 1",
+		in:       65535,
+		expected: [10]uint32{65535, 0, 0, 0, 0, 0, 0, 0, 0, 0},
 	}}
 
 	for _, test := range tests {