libs/common: Refactor libs/common 4 (#4237)

* libs/common: Refactor libs/common 4

- move byte function out of cmn to its own pkg
- move tempfile out of cmn to its own pkg
- move throttletimer to its own pkg

ref #4147

Signed-off-by: Marko Baricevic <marbar3778@yahoo.com>

* add changelog entry

* fix linting issues

libs/bytes/bytes.go

@@ -0,0 +1,62 @@
+package bytes
+
+import (
+	"encoding/hex"
+	"fmt"
+	"strings"
+)
+
+// The main purpose of HexBytes is to enable HEX-encoding for json/encoding.
+type HexBytes []byte
+
+// Marshal needed for protobuf compatibility
+func (bz HexBytes) Marshal() ([]byte, error) {
+	return bz, nil
+}
+
+// Unmarshal needed for protobuf compatibility
+func (bz *HexBytes) Unmarshal(data []byte) error {
+	*bz = data
+	return nil
+}
+
+// This is the point of Bytes.
+func (bz HexBytes) MarshalJSON() ([]byte, error) {
+	s := strings.ToUpper(hex.EncodeToString(bz))
+	jbz := make([]byte, len(s)+2)
+	jbz[0] = '"'
+	copy(jbz[1:], []byte(s))
+	jbz[len(jbz)-1] = '"'
+	return jbz, nil
+}
+
+// This is the point of Bytes.
+func (bz *HexBytes) UnmarshalJSON(data []byte) error {
+	if len(data) < 2 || data[0] != '"' || data[len(data)-1] != '"' {
+		return fmt.Errorf("invalid hex string: %s", data)
+	}
+	bz2, err := hex.DecodeString(string(data[1 : len(data)-1]))
+	if err != nil {
+		return err
+	}
+	*bz = bz2
+	return nil
+}
+
+// Allow it to fulfill various interfaces in light-client, etc...
+func (bz HexBytes) Bytes() []byte {
+	return bz
+}
+
+func (bz HexBytes) String() string {
+	return strings.ToUpper(hex.EncodeToString(bz))
+}
+
+func (bz HexBytes) Format(s fmt.State, verb rune) {
+	switch verb {
+	case 'p':
+		s.Write([]byte(fmt.Sprintf("%p", bz)))
+	default:
+		s.Write([]byte(fmt.Sprintf("%X", []byte(bz))))
+	}
+}

libs/bytes/bytes_test.go

@@ -0,0 +1,66 @@
+package bytes
+
+import (
+	"encoding/json"
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// This is a trivial test for protobuf compatibility.
+func TestMarshal(t *testing.T) {
+	bz := []byte("hello world")
+	dataB := HexBytes(bz)
+	bz2, err := dataB.Marshal()
+	assert.Nil(t, err)
+	assert.Equal(t, bz, bz2)
+
+	var dataB2 HexBytes
+	err = (&dataB2).Unmarshal(bz)
+	assert.Nil(t, err)
+	assert.Equal(t, dataB, dataB2)
+}
+
+// Test that the hex encoding works.
+func TestJSONMarshal(t *testing.T) {
+
+	type TestStruct struct {
+		B1 []byte
+		B2 HexBytes
+	}
+
+	cases := []struct {
+		input    []byte
+		expected string
+	}{
+		{[]byte(``), `{"B1":"","B2":""}`},
+		{[]byte(`a`), `{"B1":"YQ==","B2":"61"}`},
+		{[]byte(`abc`), `{"B1":"YWJj","B2":"616263"}`},
+	}
+
+	for i, tc := range cases {
+		tc := tc
+		t.Run(fmt.Sprintf("Case %d", i), func(t *testing.T) {
+			ts := TestStruct{B1: tc.input, B2: tc.input}
+
+			// Test that it marshals correctly to JSON.
+			jsonBytes, err := json.Marshal(ts)
+			if err != nil {
+				t.Fatal(err)
+			}
+			assert.Equal(t, string(jsonBytes), tc.expected)
+
+			// TODO do fuzz testing to ensure that unmarshal fails
+
+			// Test that unmarshaling works correctly.
+			ts2 := TestStruct{}
+			err = json.Unmarshal(jsonBytes, &ts2)
+			if err != nil {
+				t.Fatal(err)
+			}
+			assert.Equal(t, ts2.B1, tc.input)
+			assert.Equal(t, ts2.B2, HexBytes(tc.input))
+		})
+	}
+}

libs/bytes/byteslice.go

@@ -0,0 +1,10 @@
+package bytes
+
+// Fingerprint returns the first 6 bytes of a byte slice.
+// If the slice is less than 6 bytes, the fingerprint
+// contains trailing zeroes.
+func Fingerprint(slice []byte) []byte {
+	fingerprint := make([]byte, 6)
+	copy(fingerprint, slice)
+	return fingerprint
+}