pkg/index: Support xxHash

go.mod

@@ -2,4 +2,7 @@ module github.com/the-maldridge/dumbsync
 
 go 1.20
 
-require github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510 // indirect
+require (
+	github.com/cespare/xxhash/v2 v2.3.0 // indirect
+	github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510 // indirect
+)

go.sum

@@ -1,2 +1,4 @@
+github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
+github.com/cespare/xxhash/v2 v2.3.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
 github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510 h1:El6M4kTTCOh6aBiKaUGG7oYTSPP8MxqL4YI3kZKwcP4=
 github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510/go.mod h1:pupxD2MaaD3pAXIBCelhxNneeOaAeabZDe5s4K6zSpQ=

pkg/index/index.go

@@ -4,11 +4,15 @@ import (
 	"bytes"
 	"crypto/md5"
 	"errors"
+	"hash"
 	"io"
 	"io/fs"
 	"log"
 	"os"
+	"strings"
 	"sync"
+
+	"github.com/cespare/xxhash/v2"
 )
 
 // IndexPath walks the directory structure below basepath and
@@ -21,7 +25,15 @@ func (i *Indexer) IndexPath(basepath string) (*Index, error) {
 	i.basepath = basepath
 	i.idx = &Index{Files: make(map[string][]byte), Mutex: new(sync.Mutex)}
 	i.idx.fs = os.DirFS(i.basepath)
-	i.idx.HashType = MD5
+
+	switch strings.ToUpper(os.Getenv("DUMBSYNC_HASH")) {
+	case "MD5":
+		i.idx.HashType = MD5
+	case "XX":
+		i.idx.HashType = XXHash
+	default:
+		i.idx.HashType = MD5
+	}
 
 	if err := fs.WalkDir(i.idx.fs, ".", i.walkDir); err != nil {
 		return new(Index), err
@@ -55,7 +67,13 @@ func (i *Indexer) handleFile(path string, d fs.DirEntry) {
 	}
 	defer f.Close()
 
-	h := md5.New()
+	var h hash.Hash
+	switch i.idx.HashType {
+	case MD5:
+		h = md5.New()
+	case XXHash:
+		h = xxhash.New()
+	}
 	if _, err := io.Copy(h, f); err != nil {
 		return
 	}

pkg/index/type.go

@@ -31,4 +31,9 @@ const (
 	// MD5 is a basic hash type.  Not great, not bad, just a basic
 	// hash type.
 	MD5 HashType = iota
+
+	// XXHash is a very fast non-crypto hash.  It is great for
+	// detecting file differences but is not as resistant to
+	// tampering.
+	XXHash
 )