Update the chunker

vendor/github.com/restic/chunker/.travis.yml

@@ -1,18 +1,20 @@
 language: go
 sudo: false
 
-go:
-  - 1.6.4
-  - 1.7.4
-  - tip
-
-os:
-  - linux
-  - osx
+matrix:
+  include:
+    - os: linux
+      go: "1.9.x"
+    - os: linux
+      go: "1.10.x"
+    - os: linux
+      go: "tip"
+    - os: osx
+      go: "1.10.x"
 
 install:
   - go get -t ./...
-  - go get -u github.com/golang/lint/golint
+  - go get -u golang.org/x/lint/golint
   - go get -u golang.org/x/tools/cmd/goimports
 
 script:

vendor/github.com/restic/chunker/README.md

@@ -1,5 +1,5 @@
 [![GoDoc](https://godoc.org/github.com/restic/chunker?status.svg)](http://godoc.org/github.com/restic/chunker)
-[![Build Status](https://travis-ci.org/restic/chunker.svg?branch=master)](https://travis-ci.org/restic/chunker)
+[![Build Status](https://travis-ci.com/restic/chunker.svg?branch=master)](https://travis-ci.com/restic/chunker)
 
 The package `chunker` implements content-defined-chunking (CDC) based on a
 rolling Rabin Hash. The library is part of the [restic backup

vendor/github.com/restic/chunker/chunker.go

@@ -47,7 +47,7 @@ type Chunk struct {
 
 type chunkerState struct {
 	window [windowSize]byte
-	wpos   int
+	wpos   uint
 
 	buf  []byte
 	bpos uint
@@ -225,6 +225,12 @@ func (c *Chunker) Next(data []byte) (Chunk, error) {
 	tabout := c.tables.out
 	tabmod := c.tables.mod
 	polShift := c.polShift
+	// go guarantees the expected behavior for bit shifts even for shift counts
+	// larger than the value width. Bounding the value of polShift allows the compiler
+	// to optimize the code for 'digest >> polShift'
+	if polShift > 53-8 {
+		return Chunk{}, errors.New("the polynomial must have a degree less than or equal 53")
+	}
 	minSize := c.MinSize
 	maxSize := c.MaxSize
 	buf := c.buf
@@ -291,10 +297,12 @@ func (c *Chunker) Next(data []byte) (Chunk, error) {
 		wpos := c.wpos
 		for _, b := range buf[c.bpos:c.bmax] {
 			// slide(b)
+			// limit wpos before to elide array bound checks
+			wpos = wpos % windowSize
 			out := win[wpos]
 			win[wpos] = b
 			digest ^= uint64(tabout[out])
-			wpos = (wpos + 1) % windowSize
+			wpos++
 
 			// updateDigest
 			index := byte(digest >> polShift)
@@ -331,7 +339,7 @@ func (c *Chunker) Next(data []byte) (Chunk, error) {
 		}
 		c.digest = digest
 		c.window = win
-		c.wpos = wpos
+		c.wpos = wpos % windowSize
 
 		steps := c.bmax - c.bpos
 		if steps > 0 {

vendor/github.com/restic/chunker/go.mod

@@ -0,0 +1 @@
+module github.com/restic/chunker

vendor/github.com/restic/chunker/polynomials.go

@@ -94,7 +94,6 @@ func (x Pol) Deg() int {
 	}
 
 	if uint64(x)&0x2 > 0 {
-		x >>= 1
 		r |= 1
 	}