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|
package xdelta
import (
"io"
"math/rand"
)
const (
blocksize = 16380 // A factor of 7
)
func WriteRstreams(seed, offset, len int64,
first, second io.WriteCloser) {
go writeOne(seed, 0, len, first)
go writeOne(seed, offset, len, second)
}
func writeOne(seed, offset, len int64, stream io.WriteCloser) error {
if offset != 0 {
// Fill with other random data until the offset
if err := writeRand(rand.New(rand.NewSource(^seed)), offset, stream); err != nil {
return err
}
}
if err := writeRand(rand.New(rand.NewSource(seed)),
len - offset, stream); err != nil {
return err
}
return stream.Close()
}
func writeRand(r *rand.Rand, len int64, s io.Writer) error {
blk := make([]byte, blocksize)
for len > 0 {
fillRand(r, blk)
c := blocksize
if len < blocksize {
c = int(len)
}
if _, err := s.Write(blk[0:c]); err != nil {
return err
}
len -= int64(c)
}
return nil
}
func fillRand(r *rand.Rand, blk []byte) {
for p := 0; p < blocksize; {
v := r.Int63()
for i := 7; i != 0; i-- {
blk[p] = byte(v)
p++
v >>= 8
}
}
}
|
