snapshot of https://github.com/go-gitea/gitea.git (main, 2026-09-15; blobs > 131072B omitted)

modules/util/filename.go

@@ -0,0 +1,54 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package util
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+// FileNameJoinFields joins the fields by separator "-" as a safe filename,
+// the last field is used as extname (no sep is added before it).
+// This function does its best to avoid the filename exceeding the max filename length (255 bytes on Linux),
+// Each field needs at least about 3 bytes, if the caller passes too many fields (e.g.: 100 fields),
+// then it's unavoidable, just do not write such code in real world.
+func FileNameJoinFields(fields ...any) string {
+	// linux max filename length is 255, we leave some space for the separators and extname
+	const maxFilenameLen = 210
+	return fileNameJoinFields(maxFilenameLen, fields...)
+}
+
+func fileNameJoinFields(stemNameLimit int, fields ...any) string {
+	// stemNameLimit is just a suggested limit, when adding more fields, the length might still exceed a little
+	sb := strings.Builder{}
+	for i, f := range fields {
+		var field string
+		switch v := f.(type) {
+		case string:
+			field = v
+		case int64:
+			field = strconv.FormatInt(v, 10)
+		default:
+			field = fmt.Sprint(v)
+		}
+		field = PathNameValidator().InvalidChars.ReplaceAllString(field, "_")
+		if i < len(fields)-1 {
+			field = strings.ReplaceAll(strings.ReplaceAll(field, ".", "_"), "-", "_")
+			estimatedRemainingLen := (len(fields) - 1 - i) * 3
+			estimatedLimit := stemNameLimit - estimatedRemainingLen
+			if sb.Len()+len(field) > estimatedLimit {
+				field = TruncateStringBytes(field, estimatedLimit-sb.Len()-2) + "__"
+			}
+			sb.WriteString(field)
+			if i < len(fields)-2 {
+				sb.WriteString("-")
+			}
+		} else {
+			// last field is extname, no need to do more processing
+			sb.WriteString(field)
+		}
+	}
+	return sb.String()
+}