From b0744c2b2122bdd98898bab25e38bf2fdfb87529 Mon Sep 17 00:00:00 2001
From: Roman Khimov <roman@nspcc.ru>
Date: Wed, 1 Jun 2022 11:26:36 +0300
Subject: [PATCH] util: optimize MarshalJSON allocations
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name                  old time/op    new time/op    delta
Uint256MarshalJSON-8     230ns ± 6%      83ns ±13%  -63.78%  (p=0.000 n=8+10)

name                  old alloc/op   new alloc/op   delta
Uint256MarshalJSON-8      320B ± 0%       80B ± 0%  -75.00%  (p=0.000 n=10+10)

name                  old allocs/op  new allocs/op  delta
Uint256MarshalJSON-8      5.00 ± 0%      1.00 ± 0%  -80.00%  (p=0.000 n=10+10)
---
 pkg/util/bench_test.go | 13 +++++++++++++
 pkg/util/uint160.go    |  7 ++++++-
 pkg/util/uint256.go    |  7 ++++++-
 3 files changed, 25 insertions(+), 2 deletions(-)
 create mode 100644 pkg/util/bench_test.go

diff --git a/pkg/util/bench_test.go b/pkg/util/bench_test.go
new file mode 100644
index 000000000..916d5b41e
--- /dev/null
+++ b/pkg/util/bench_test.go
@@ -0,0 +1,13 @@
+package util
+
+import (
+	"testing"
+)
+
+func BenchmarkUint256MarshalJSON(b *testing.B) {
+	v := Uint256{0x01, 0x02, 0x03}
+
+	for i := 0; i < b.N; i++ {
+		_, _ = v.MarshalJSON()
+	}
+}
diff --git a/pkg/util/uint160.go b/pkg/util/uint160.go
index 3ac8d0eec..2f107e05e 100644
--- a/pkg/util/uint160.go
+++ b/pkg/util/uint160.go
@@ -132,7 +132,12 @@ func (u *Uint160) UnmarshalJSON(data []byte) (err error) {
 
 // MarshalJSON implements the json marshaller interface.
 func (u Uint160) MarshalJSON() ([]byte, error) {
-	return []byte(`"0x` + u.StringLE() + `"`), nil
+	r := make([]byte, 3+Uint160Size*2+1)
+	copy(r, `"0x`)
+	r[len(r)-1] = '"'
+	slice.Reverse(u[:]) // u is a copy, so we can mangle it in any way.
+	hex.Encode(r[3:], u[:])
+	return r, nil
 }
 
 // UnmarshalYAML implements the YAML Unmarshaler interface.
diff --git a/pkg/util/uint256.go b/pkg/util/uint256.go
index 303ba5221..8886a261d 100644
--- a/pkg/util/uint256.go
+++ b/pkg/util/uint256.go
@@ -109,7 +109,12 @@ func (u *Uint256) UnmarshalJSON(data []byte) (err error) {
 
 // MarshalJSON implements the json marshaller interface.
 func (u Uint256) MarshalJSON() ([]byte, error) {
-	return []byte(`"0x` + u.StringLE() + `"`), nil
+	r := make([]byte, 3+Uint256Size*2+1)
+	copy(r, `"0x`)
+	r[len(r)-1] = '"'
+	slice.Reverse(u[:]) // u is a copy, so we can mangle it in any way.
+	hex.Encode(r[3:], u[:])
+	return r, nil
 }
 
 // CompareTo compares two Uint256 with each other. Possible output: 1, -1, 0