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