init: v1.0.0

utils/padding/p7.go

@@ -0,0 +1,41 @@
+package padding
+
+import "fmt"
+
+type P7Padding struct {
+}
+
+func (P7Padding) Pad(src []byte, blockSize int) (dst []byte) {
+	if blockSize < MIN_BLOCK_SIZE || blockSize > MAX_BLOCK_SIZE {
+		panic("blocksize error")
+	}
+	// if blocksize == 2^n, then paddingsize = -len(src) & (blocksize - 1)
+	paddingSize := byte(blockSize - (len(src) % blockSize))
+	for i := 0; i < int(paddingSize); i++ {
+		src = append(src, paddingSize)
+	}
+	return src
+}
+
+func (P7Padding) Unpad(src []byte, blockSize int) (dst []byte, err error) {
+	if blockSize < MIN_BLOCK_SIZE || blockSize > MAX_BLOCK_SIZE {
+		panic("blocksize error")
+	}
+
+	if len(src) == 0 {
+		return src, nil
+	}
+	paddingSize := int(uint(src[len(src)-1]))
+
+	if paddingSize > len(src) || paddingSize == 0 {
+		return src, fmt.Errorf("unpadding error")
+	}
+
+	for i := len(src) - paddingSize; i < len(src)-1; i++ {
+		if int(src[i]) != paddingSize {
+			return src, fmt.Errorf("unpadding error")
+		}
+	}
+
+	return src[:len(src)-paddingSize], nil
+}