58 lines
1.0 KiB
Go
58 lines
1.0 KiB
Go
package util
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import (
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"io"
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)
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// SaltXOR xors bits of data with salt
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// repeating salt if necessary.
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func SaltXOR(data, salt []byte) []byte {
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return SaltXOROffset(data, salt, 0)
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}
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// SaltXOROffset xors bits of data with salt starting from off byte
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// repeating salt if necessary.
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func SaltXOROffset(data, salt []byte, off int) (result []byte) {
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result = make([]byte, len(data))
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ls := len(salt)
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if ls == 0 {
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copy(result, data)
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return
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}
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for i := range result {
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result[i] = data[i] ^ salt[(i+off)%ls]
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}
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return
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}
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type saltWriter struct {
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w io.Writer
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off int
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salt []byte
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}
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// NewSaltingWriter returns io.Writer instance that applies
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// salt to written data and write the result to w.
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func NewSaltingWriter(w io.Writer, salt []byte) io.Writer {
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if len(salt) == 0 {
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return w
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}
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return &saltWriter{
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w: w,
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salt: salt,
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}
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}
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func (w *saltWriter) Write(data []byte) (int, error) {
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if dataLen := len(data); dataLen > 0 {
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data = SaltXOROffset(data, w.salt, w.off)
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w.off += dataLen
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}
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return w.w.Write(data)
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}
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