feat(签章标识): 规范签章标识与导入合并

ofdgo_sign_id.go

@@ -0,0 +1,43 @@
+// Copyright 2025-2026 肖其顿 (XIAO QI DUN)
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ofdgo
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+// signatureIDSequence 签名及签章注释共用的编号上限，与文档图元编号相互独立
+type signatureIDSequence uint64
+
+// observe 记录已有签章标识的编号上限，其他命名形式保持不变
+// 入参: id 已有标识
+func (s *signatureIDSequence) observe(id string) {
+	n, err := strconv.ParseUint(strings.TrimPrefix(id, "s"), 10, 64)
+	if err == nil && n > uint64(*s) {
+		*s = signatureIDSequence(n)
+	}
+}
+
+// next 分配采用sNNN格式的签章标识
+// 返回: string 新标识, error 编号耗尽错误
+func (s *signatureIDSequence) next() (string, error) {
+	if uint64(*s) == ^uint64(0) {
+		return "", fmt.Errorf("signature ID exhausted")
+	}
+	*s++
+	return "s" + strconv.FormatUint(uint64(*s), 10), nil
+}