Add method to load PrivateKey

- from hex string
- from wif format
- from file path

load.go

@@ -0,0 +1,21 @@
+package crypto
+
+import (
+	"crypto/ecdsa"
+	"encoding/hex"
+	"io/ioutil"
+
+	"github.com/pkg/errors"
+)
+
+func LoadPrivateKey(val string) (*ecdsa.PrivateKey, error) {
+	if data, err := ioutil.ReadFile(val); err == nil {
+		return UnmarshalPrivateKey(data)
+	} else if data, err = hex.DecodeString(val); err == nil {
+		return UnmarshalPrivateKey(data)
+	} else if key, err := WIFDecode(val); err == nil {
+		return key, nil
+	}
+
+	return nil, errors.Errorf("unknown key format (%q), expect: hex-string, wif or file-path", val)
+}

load_test.go

@@ -0,0 +1,86 @@
+package crypto
+
+import (
+	"crypto/x509"
+	"encoding/hex"
+	"io/ioutil"
+	"os"
+	"testing"
+
+	"github.com/nspcc-dev/neofs-crypto/test"
+	"github.com/stretchr/testify/require"
+)
+
+func Test_LoadPrivateKey_FromWIF(t *testing.T) {
+	for i := 0; i < 10; i++ {
+		expected := test.DecodeKey(i)
+
+		wif, err := WIFEncode(expected)
+		require.NoError(t, err)
+
+		actual, err := LoadPrivateKey(wif)
+		require.NoError(t, err)
+
+		require.Equal(t, expected, actual)
+	}
+}
+
+func Test_LoadPrivateKey_FromHexString(t *testing.T) {
+	for i := 0; i < 10; i++ {
+		expected := test.DecodeKey(i)
+
+		hs := hex.EncodeToString(expected.D.Bytes())
+
+		actual, err := LoadPrivateKey(hs)
+		require.NoError(t, err)
+
+		require.Equal(t, expected, actual)
+	}
+}
+
+func Test_LoadPrivateKey_FromFile(t *testing.T) {
+	for i := 0; i < 10; i++ {
+		expected := test.DecodeKey(i)
+
+		file, err := ioutil.TempFile("", "_marshaled.key")
+		require.NoError(t, err)
+
+		defer func() {
+			require.NoError(t, file.Close())
+			require.NoError(t, os.Remove(file.Name()))
+		}()
+
+		data, err := x509.MarshalECPrivateKey(expected)
+		require.NoError(t, err)
+
+		_, err = file.Write(data)
+		require.NoError(t, err)
+
+		actual, err := LoadPrivateKey(file.Name())
+		require.NoError(t, err)
+
+		require.Equal(t, expected, actual)
+	}
+}
+
+func Test_LoadPrivateKey_FromCompressedFormatFile(t *testing.T) {
+	for i := 0; i < 10; i++ {
+		expected := test.DecodeKey(i)
+
+		file, err := ioutil.TempFile("", "_compressed.key")
+		require.NoError(t, err)
+
+		defer func() {
+			require.NoError(t, file.Close())
+			require.NoError(t, os.Remove(file.Name()))
+		}()
+
+		_, err = file.Write(expected.D.Bytes())
+		require.NoError(t, err)
+
+		actual, err := LoadPrivateKey(file.Name())
+		require.NoError(t, err)
+
+		require.Equal(t, expected, actual)
+	}
+}