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409 lines
7.0 KiB
409 lines
7.0 KiB
package binarydist
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import (
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"bytes"
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"encoding/binary"
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"io"
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"io/ioutil"
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)
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func swap(a []int, i, j int) { a[i], a[j] = a[j], a[i] }
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func split(I, V []int, start, length, h int) {
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var i, j, k, x, jj, kk int
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if length < 16 {
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for k = start; k < start+length; k += j {
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j = 1
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x = V[I[k]+h]
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for i = 1; k+i < start+length; i++ {
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if V[I[k+i]+h] < x {
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x = V[I[k+i]+h]
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j = 0
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}
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if V[I[k+i]+h] == x {
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swap(I, k+i, k+j)
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j++
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}
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}
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for i = 0; i < j; i++ {
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V[I[k+i]] = k + j - 1
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}
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if j == 1 {
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I[k] = -1
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}
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}
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return
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}
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x = V[I[start+length/2]+h]
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jj = 0
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kk = 0
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for i = start; i < start+length; i++ {
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if V[I[i]+h] < x {
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jj++
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}
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if V[I[i]+h] == x {
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kk++
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}
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}
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jj += start
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kk += jj
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i = start
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j = 0
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k = 0
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for i < jj {
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if V[I[i]+h] < x {
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i++
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} else if V[I[i]+h] == x {
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swap(I, i, jj+j)
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j++
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} else {
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swap(I, i, kk+k)
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k++
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}
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}
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for jj+j < kk {
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if V[I[jj+j]+h] == x {
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j++
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} else {
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swap(I, jj+j, kk+k)
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k++
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}
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}
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if jj > start {
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split(I, V, start, jj-start, h)
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}
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for i = 0; i < kk-jj; i++ {
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V[I[jj+i]] = kk - 1
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}
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if jj == kk-1 {
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I[jj] = -1
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}
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if start+length > kk {
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split(I, V, kk, start+length-kk, h)
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}
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}
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func qsufsort(obuf []byte) []int {
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var buckets [256]int
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var i, h int
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I := make([]int, len(obuf)+1)
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V := make([]int, len(obuf)+1)
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for _, c := range obuf {
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buckets[c]++
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}
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for i = 1; i < 256; i++ {
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buckets[i] += buckets[i-1]
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}
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copy(buckets[1:], buckets[:])
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buckets[0] = 0
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for i, c := range obuf {
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buckets[c]++
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I[buckets[c]] = i
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}
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I[0] = len(obuf)
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for i, c := range obuf {
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V[i] = buckets[c]
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}
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V[len(obuf)] = 0
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for i = 1; i < 256; i++ {
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if buckets[i] == buckets[i-1]+1 {
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I[buckets[i]] = -1
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}
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}
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I[0] = -1
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for h = 1; I[0] != -(len(obuf) + 1); h += h {
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var n int
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for i = 0; i < len(obuf)+1; {
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if I[i] < 0 {
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n -= I[i]
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i -= I[i]
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} else {
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if n != 0 {
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I[i-n] = -n
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}
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n = V[I[i]] + 1 - i
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split(I, V, i, n, h)
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i += n
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n = 0
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}
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}
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if n != 0 {
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I[i-n] = -n
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}
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}
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for i = 0; i < len(obuf)+1; i++ {
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I[V[i]] = i
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}
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return I
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}
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func matchlen(a, b []byte) (i int) {
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for i < len(a) && i < len(b) && a[i] == b[i] {
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i++
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}
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return i
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}
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func search(I []int, obuf, nbuf []byte, st, en int) (pos, n int) {
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if en-st < 2 {
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x := matchlen(obuf[I[st]:], nbuf)
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y := matchlen(obuf[I[en]:], nbuf)
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if x > y {
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return I[st], x
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} else {
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return I[en], y
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}
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}
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x := st + (en-st)/2
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if bytes.Compare(obuf[I[x]:], nbuf) < 0 {
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return search(I, obuf, nbuf, x, en)
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} else {
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return search(I, obuf, nbuf, st, x)
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}
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panic("unreached")
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}
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// Diff computes the difference between old and new, according to the bsdiff
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// algorithm, and writes the result to patch.
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func Diff(old, new io.Reader, patch io.Writer) error {
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obuf, err := ioutil.ReadAll(old)
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if err != nil {
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return err
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}
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nbuf, err := ioutil.ReadAll(new)
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if err != nil {
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return err
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}
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pbuf, err := diffBytes(obuf, nbuf)
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if err != nil {
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return err
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}
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_, err = patch.Write(pbuf)
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return err
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}
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func diffBytes(obuf, nbuf []byte) ([]byte, error) {
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var patch seekBuffer
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err := diff(obuf, nbuf, &patch)
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if err != nil {
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return nil, err
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}
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return patch.buf, nil
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}
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func diff(obuf, nbuf []byte, patch io.WriteSeeker) error {
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var lenf int
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I := qsufsort(obuf)
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db := make([]byte, len(nbuf))
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eb := make([]byte, len(nbuf))
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var dblen, eblen int
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var hdr header
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hdr.Magic = magic
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hdr.NewSize = int64(len(nbuf))
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err := binary.Write(patch, signMagLittleEndian{}, &hdr)
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if err != nil {
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return err
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}
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// Compute the differences, writing ctrl as we go
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pfbz2, err := newBzip2Writer(patch)
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if err != nil {
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return err
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}
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var scan, pos, length int
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var lastscan, lastpos, lastoffset int
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for scan < len(nbuf) {
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var oldscore int
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scan += length
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for scsc := scan; scan < len(nbuf); scan++ {
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pos, length = search(I, obuf, nbuf[scan:], 0, len(obuf))
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for ; scsc < scan+length; scsc++ {
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if scsc+lastoffset < len(obuf) &&
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obuf[scsc+lastoffset] == nbuf[scsc] {
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oldscore++
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}
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}
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if (length == oldscore && length != 0) || length > oldscore+8 {
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break
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}
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if scan+lastoffset < len(obuf) && obuf[scan+lastoffset] == nbuf[scan] {
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oldscore--
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}
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}
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if length != oldscore || scan == len(nbuf) {
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var s, Sf int
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lenf = 0
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for i := 0; lastscan+i < scan && lastpos+i < len(obuf); {
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if obuf[lastpos+i] == nbuf[lastscan+i] {
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s++
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}
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i++
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if s*2-i > Sf*2-lenf {
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Sf = s
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lenf = i
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}
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}
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lenb := 0
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if scan < len(nbuf) {
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var s, Sb int
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for i := 1; (scan >= lastscan+i) && (pos >= i); i++ {
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if obuf[pos-i] == nbuf[scan-i] {
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s++
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}
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if s*2-i > Sb*2-lenb {
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Sb = s
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lenb = i
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}
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}
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}
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if lastscan+lenf > scan-lenb {
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overlap := (lastscan + lenf) - (scan - lenb)
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s := 0
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Ss := 0
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lens := 0
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for i := 0; i < overlap; i++ {
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if nbuf[lastscan+lenf-overlap+i] == obuf[lastpos+lenf-overlap+i] {
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s++
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}
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if nbuf[scan-lenb+i] == obuf[pos-lenb+i] {
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s--
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}
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if s > Ss {
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Ss = s
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lens = i + 1
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}
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}
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lenf += lens - overlap
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lenb -= lens
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}
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for i := 0; i < lenf; i++ {
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db[dblen+i] = nbuf[lastscan+i] - obuf[lastpos+i]
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}
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for i := 0; i < (scan-lenb)-(lastscan+lenf); i++ {
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eb[eblen+i] = nbuf[lastscan+lenf+i]
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}
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dblen += lenf
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eblen += (scan - lenb) - (lastscan + lenf)
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err = binary.Write(pfbz2, signMagLittleEndian{}, int64(lenf))
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if err != nil {
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pfbz2.Close()
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return err
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}
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val := (scan - lenb) - (lastscan + lenf)
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err = binary.Write(pfbz2, signMagLittleEndian{}, int64(val))
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if err != nil {
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pfbz2.Close()
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return err
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}
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val = (pos - lenb) - (lastpos + lenf)
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err = binary.Write(pfbz2, signMagLittleEndian{}, int64(val))
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if err != nil {
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pfbz2.Close()
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return err
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}
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lastscan = scan - lenb
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lastpos = pos - lenb
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lastoffset = pos - scan
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}
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}
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err = pfbz2.Close()
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if err != nil {
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return err
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}
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// Compute size of compressed ctrl data
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l64, err := patch.Seek(0, 1)
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if err != nil {
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return err
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}
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hdr.CtrlLen = int64(l64 - 32)
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// Write compressed diff data
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pfbz2, err = newBzip2Writer(patch)
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if err != nil {
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return err
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}
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n, err := pfbz2.Write(db[:dblen])
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if err != nil {
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pfbz2.Close()
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return err
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}
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if n != dblen {
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pfbz2.Close()
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return io.ErrShortWrite
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}
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err = pfbz2.Close()
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if err != nil {
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return err
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}
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// Compute size of compressed diff data
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n64, err := patch.Seek(0, 1)
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if err != nil {
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return err
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}
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hdr.DiffLen = n64 - l64
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// Write compressed extra data
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pfbz2, err = newBzip2Writer(patch)
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if err != nil {
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return err
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}
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n, err = pfbz2.Write(eb[:eblen])
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if err != nil {
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pfbz2.Close()
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return err
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}
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if n != eblen {
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pfbz2.Close()
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return io.ErrShortWrite
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}
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err = pfbz2.Close()
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if err != nil {
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return err
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}
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// Seek to the beginning, write the header, and close the file
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_, err = patch.Seek(0, 0)
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if err != nil {
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return err
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}
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err = binary.Write(patch, signMagLittleEndian{}, &hdr)
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if err != nil {
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return err
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}
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return nil
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}
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