vochain/processarchive: swap filepath.Walk for os.ReadDir

filepath.Walk is mainly useful for many levels of directories,
but the archive data directory is entirely flat.
Plus, filepath.Walk stats every file that it walks over.

This is a bit simpler to understand and also less indented.

vochain/processarchive/processarchive.go

@@ -127,28 +127,33 @@ func BuildIndex(datadir string) (*Index, error) {
 		Entities: make(map[string][]*IndexProcess),
 	}
 	count := 0
-	if err := filepath.Walk(datadir, func(path string, info os.FileInfo, err error) error {
-		if len(info.Name()) == 64 {
-			content, err := os.ReadFile(path)
-			if err != nil {
-				return err
-			}
-			if content == nil {
-				log.Warnf("archive file %s is empty", path)
-				return nil
-			}
-			count++
-			p := &Process{}
-			if err := json.Unmarshal(content, p); err != nil {
-				return err
-			}
-			eid := fmt.Sprintf("%x", p.ProcessInfo.EntityID)
-			i.Entities[eid] = append(i.Entities[eid], &IndexProcess{ProcessID: p.ProcessInfo.ID})
-		}
-		return nil
-	}); err != nil {
+	entries, err := os.ReadDir(datadir)
+	if err != nil {
 		return nil, err
 	}
+	for _, entry := range entries {
+		name := entry.Name()
+		path := filepath.Join(datadir, name)
+		if len(entry.Name()) != 64 {
+			log.Warnf("archive file %s has an invalid name", path)
+			continue
+		}
+		content, err := os.ReadFile(filepath.Join(datadir, name))
+		if err != nil {
+			return nil, err
+		}
+		if content == nil {
+			log.Warnf("archive file %s is empty", path)
+			continue
+		}
+		count++
+		p := &Process{}
+		if err := json.Unmarshal(content, p); err != nil {
+			return nil, err
+		}
+		eid := fmt.Sprintf("%x", p.ProcessInfo.EntityID)
+		i.Entities[eid] = append(i.Entities[eid], &IndexProcess{ProcessID: p.ProcessInfo.ID})
+	}
 	indexData, err := json.MarshalIndent(i, " ", " ")
 	if err != nil {
 		return nil, err