X-Git-Url: http://www.git.cypherpunks.ru/?a=blobdiff_plain;f=gost3413%2Fpadding.go;fp=gost3413%2Fpadding.go;h=f0941418527e643df24ce2e6ae47ddec878f79e3;hb=c07494bbd559b9d00f391e28cfd070e18afe9900;hp=0000000000000000000000000000000000000000;hpb=107600dede989f0cc479b5a72c5f97e174307154;p=gogost.git

diff --git a/gost3413/padding.go b/gost3413/padding.go
new file mode 100644
index 0000000..f094141
--- /dev/null
+++ b/gost3413/padding.go
@@ -0,0 +1,48 @@
+// GoGOST -- Pure Go GOST cryptographic functions library
+// Copyright (C) 2015-2019 Sergey Matveev <stargrave@stargrave.org>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, version 3 of the License.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+// GOST R 34.13-2015 padding methods.
+package gost3413
+
+func PadSize(dataSize, blockSize int) int {
+	if dataSize < blockSize {
+		return blockSize - dataSize
+	}
+	if dataSize%blockSize == 0 {
+		return 0
+	}
+	return blockSize - dataSize%blockSize
+}
+
+func Pad1(data []byte, blockSize int) []byte {
+	padSize := PadSize(len(data), blockSize)
+	if padSize == 0 {
+		return data
+	}
+	return append(data, make([]byte, padSize)...)
+}
+
+func Pad2(data []byte, blockSize int) []byte {
+	pad := make([]byte, 1+PadSize(len(data)+1, blockSize))
+	pad[0] = byte(0x80)
+	return append(data, pad...)
+}
+
+func Pad3(data []byte, blockSize int) []byte {
+	if PadSize(len(data), blockSize) == 0 {
+		return data
+	}
+	return Pad2(data, blockSize)
+}