mirror of https://github.com/restic/restic.git
Update chunker
This commit is contained in:
Alexander Neumann
parent
4dac6d45fd
commit
9e24238cdd
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@ -40,7 +40,7 @@
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{
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"importpath": "github.com/restic/chunker",
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"repository": "https://github.com/restic/chunker",
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"revision": "16c849a106e0a50d658e8f5e49a01f6728f4f92c",
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"revision": "d1a97fa6e55ab338a8ceb769d72f856a56e9379a",
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"branch": "master"
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},
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{
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@ -33,12 +33,12 @@ type tables struct {
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// cache precomputed tables, these are read-only anyway
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var cache struct {
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entries map[Pol]*tables
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entries map[Pol]tables
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sync.Mutex
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}
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func init() {
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cache.entries = make(map[Pol]*tables)
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cache.entries = make(map[Pol]tables)
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}
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// Chunk is one content-dependent chunk of bytes whose end was cut when the
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@ -50,17 +50,7 @@ type Chunk struct {
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Data []byte
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}
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// Chunker splits content with Rabin Fingerprints.
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type Chunker struct {
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MinSize, MaxSize uint
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pol Pol
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polShift uint
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tables *tables
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rd io.Reader
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closed bool
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type chunkerState struct {
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window [windowSize]byte
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wpos int
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@ -77,15 +67,37 @@ type Chunker struct {
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digest uint64
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}
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type chunkerConfig struct {
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MinSize, MaxSize uint
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pol Pol
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polShift uint
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tables tables
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tablesInitialized bool
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rd io.Reader
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closed bool
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}
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// Chunker splits content with Rabin Fingerprints.
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type Chunker struct {
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chunkerConfig
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chunkerState
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}
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// New returns a new Chunker based on polynomial p that reads from rd
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// with bufsize and pass all data to hash along the way.
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func New(rd io.Reader, pol Pol) *Chunker {
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c := &Chunker{
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chunkerState: chunkerState{
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buf: make([]byte, chunkerBufSize),
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},
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chunkerConfig: chunkerConfig{
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pol: pol,
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rd: rd,
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MinSize: MinSize,
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MaxSize: MaxSize,
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},
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}
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c.reset()
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@ -96,11 +108,15 @@ func New(rd io.Reader, pol Pol) *Chunker {
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// Reset reinitializes the chunker with a new reader and polynomial.
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func (c *Chunker) Reset(rd io.Reader, pol Pol) {
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*c = Chunker{
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chunkerState: chunkerState{
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buf: c.buf,
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},
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chunkerConfig: chunkerConfig{
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pol: pol,
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rd: rd,
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MinSize: c.MinSize,
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MaxSize: c.MaxSize,
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MinSize: MinSize,
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MaxSize: MaxSize,
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},
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}
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c.reset()
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@ -118,7 +134,7 @@ func (c *Chunker) reset() {
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c.digest = 0
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c.wpos = 0
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c.count = 0
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c.slide(1)
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c.digest = c.slide(c.digest, 1)
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c.start = c.pos
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// do not start a new chunk unless at least MinSize bytes have been read
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@ -133,6 +149,8 @@ func (c *Chunker) fillTables() {
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return
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}
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c.tablesInitialized = true
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// test if the tables are cached for this polynomial
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cache.Lock()
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defer cache.Unlock()
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@ -141,10 +159,6 @@ func (c *Chunker) fillTables() {
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return
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}
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// else create a new entry
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c.tables = &tables{}
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cache.entries[c.pol] = c.tables
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// calculate table for sliding out bytes. The byte to slide out is used as
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// the index for the table, the value contains the following:
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// out_table[b] = Hash(b || 0 || ... || 0)
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@ -178,6 +192,8 @@ func (c *Chunker) fillTables() {
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// enough to reduce modulo Polynomial
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c.tables.mod[b] = Pol(uint64(b)<<uint(k)).Mod(c.pol) | (Pol(b) << uint(k))
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}
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cache.entries[c.pol] = c.tables
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}
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// Next returns the position and length of the next chunk of data. If an error
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@ -186,13 +202,19 @@ func (c *Chunker) fillTables() {
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// subsequent calls yield an io.EOF error.
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func (c *Chunker) Next(data []byte) (Chunk, error) {
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data = data[:0]
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if c.tables == nil {
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return Chunk{}, errors.New("polynomial is not set")
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if !c.tablesInitialized {
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return Chunk{}, errors.New("tables for polynomial computation not initialized")
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}
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tabout := c.tables.out
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tabmod := c.tables.mod
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polShift := c.polShift
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minSize := c.MinSize
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maxSize := c.MaxSize
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buf := c.buf
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for {
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if c.bpos >= c.bmax {
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n, err := io.ReadFull(c.rd, c.buf[:])
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n, err := io.ReadFull(c.rd, buf[:])
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if err == io.ErrUnexpectedEOF {
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err = nil
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@ -230,7 +252,7 @@ func (c *Chunker) Next(data []byte) (Chunk, error) {
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n := c.bmax - c.bpos
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if c.pre > uint(n) {
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c.pre -= uint(n)
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data = append(data, c.buf[c.bpos:c.bmax]...)
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data = append(data, buf[c.bpos:c.bmax]...)
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c.count += uint(n)
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c.pos += uint(n)
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@ -239,7 +261,7 @@ func (c *Chunker) Next(data []byte) (Chunk, error) {
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continue
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}
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data = append(data, c.buf[c.bpos:c.bpos+c.pre]...)
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data = append(data, buf[c.bpos:c.bpos+c.pre]...)
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c.bpos += c.pre
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c.count += c.pre
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@ -248,37 +270,41 @@ func (c *Chunker) Next(data []byte) (Chunk, error) {
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}
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add := c.count
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for _, b := range c.buf[c.bpos:c.bmax] {
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// inline c.slide(b) and append(b) to increase performance
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out := c.window[c.wpos]
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c.window[c.wpos] = b
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c.digest ^= uint64(c.tables.out[out])
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c.wpos = (c.wpos + 1) % windowSize
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digest := c.digest
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win := c.window
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wpos := c.wpos
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for _, b := range buf[c.bpos:c.bmax] {
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// slide(b)
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out := win[wpos]
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win[wpos] = b
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digest ^= uint64(tabout[out])
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wpos = (wpos + 1) % windowSize
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// c.append(b)
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index := c.digest >> c.polShift
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c.digest <<= 8
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c.digest |= uint64(b)
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// updateDigest
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index := byte(digest >> polShift)
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digest <<= 8
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digest |= uint64(b)
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c.digest ^= uint64(c.tables.mod[index])
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// end inline
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digest ^= uint64(tabmod[index])
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// end manual inline
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add++
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if add < c.MinSize {
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if add < minSize {
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continue
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}
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if (c.digest&splitmask) == 0 || add >= MaxSize {
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if (digest&splitmask) == 0 || add >= maxSize {
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i := add - c.count - 1
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data = append(data, c.buf[c.bpos:c.bpos+uint(i)+1]...)
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c.count = add
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c.pos += uint(i) + 1
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c.bpos += uint(i) + 1
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c.buf = buf
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chunk := Chunk{
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Start: c.start,
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Length: c.count,
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Cut: c.digest,
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Cut: digest,
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Data: data,
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}
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@ -287,6 +313,9 @@ func (c *Chunker) Next(data []byte) (Chunk, error) {
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return chunk, nil
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}
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}
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c.digest = digest
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c.window = win
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c.wpos = wpos
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steps := c.bmax - c.bpos
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if steps > 0 {
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@ -298,21 +327,23 @@ func (c *Chunker) Next(data []byte) (Chunk, error) {
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}
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}
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func (c *Chunker) append(b byte) {
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index := c.digest >> c.polShift
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c.digest <<= 8
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c.digest |= uint64(b)
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func updateDigest(digest uint64, polShift uint, tab tables, b byte) (newDigest uint64) {
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index := digest >> polShift
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digest <<= 8
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digest |= uint64(b)
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c.digest ^= uint64(c.tables.mod[index])
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digest ^= uint64(tab.mod[index])
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return digest
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}
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func (c *Chunker) slide(b byte) {
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func (c *Chunker) slide(digest uint64, b byte) (newDigest uint64) {
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out := c.window[c.wpos]
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c.window[c.wpos] = b
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c.digest ^= uint64(c.tables.out[out])
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digest ^= uint64(c.tables.out[out])
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c.wpos = (c.wpos + 1) % windowSize
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c.append(b)
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digest = updateDigest(digest, c.polShift, c.tables, b)
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return digest
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}
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func appendByte(hash Pol, b byte, pol Pol) Pol {
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