add decimal and test case

math/big/decimal_benchmark_test.go

+// Copyright 2019 PingCAP, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package hessian
+
+import "testing"
+
+func BenchmarkRound(b *testing.B) {
+	b.StopTimer()
+	var roundTo BigDecimal
+	tests := []struct {
+		input    string
+		scale    int
+		inputDec BigDecimal
+	}{
+		{input: "123456789.987654321", scale: 1},
+		{input: "15.1", scale: 0},
+		{input: "15.5", scale: 0},
+		{input: "15.9", scale: 0},
+		{input: "-15.1", scale: 0},
+		{input: "-15.5", scale: 0},
+		{input: "-15.9", scale: 0},
+		{input: "15.1", scale: 1},
+		{input: "-15.1", scale: 1},
+		{input: "15.17", scale: 1},
+		{input: "15.4", scale: -1},
+		{input: "-15.4", scale: -1},
+		{input: "5.4", scale: -1},
+		{input: ".999", scale: 0},
+		{input: "999999999", scale: -9},
+	}
+
+	for i := 0; i < len(tests); i++ {
+		tests[i].inputDec.FromString([]byte(tests[i].input))
+	}
+
+	b.StartTimer()
+	for n := 0; n < b.N; n++ {
+		for i := 0; i < len(tests); i++ {
+			tests[i].inputDec.Round(&roundTo, tests[i].scale, ModeHalfEven)
+		}
+		for i := 0; i < len(tests); i++ {
+			tests[i].inputDec.Round(&roundTo, tests[i].scale, ModeTruncate)
+		}
+		for i := 0; i < len(tests); i++ {
+			tests[i].inputDec.Round(&roundTo, tests[i].scale, modeCeiling)
+		}
+	}
+}