Faster and leaner comparisons in fileset

files/set_anal.go

@@ -0,0 +1,44 @@
+//+build anal
+
+package files
+
+import (
+	"crypto/md5"
+
+	"github.com/calmh/syncthing/scanner"
+)
+
+type key struct {
+	Name     string
+	Version  uint64
+	Modified int64
+	Hash     [md5.Size]byte
+}
+
+func keyFor(f scanner.File) key {
+	h := md5.New()
+	for _, b := range f.Blocks {
+		h.Write(b.Hash)
+	}
+	return key{
+		Name:     f.Name,
+		Version:  f.Version,
+		Modified: f.Modified,
+		Hash:     md5.Sum(nil),
+	}
+}
+
+func (a key) newerThan(b key) bool {
+	if a.Version != b.Version {
+		return a.Version > b.Version
+	}
+	if a.Modified != b.Modified {
+		return a.Modified > b.Modified
+	}
+	for i := 0; i < md5.Size; i++ {
+		if a.Hash[i] != b.Hash[i] {
+			return a.Hash[i] > b.Hash[i]
+		}
+	}
+	return false
+}