diff --git a/frameworks/native/backup_ext/src/untar_file.cpp b/frameworks/native/backup_ext/src/untar_file.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..f6567ca6634ff7c0540f8deec04a12b741191d64
--- /dev/null
+++ b/frameworks/native/backup_ext/src/untar_file.cpp
@@ -0,0 +1,91 @@
+/*
+ * Copyright (c) 2023 Huawei Device Co., Ltd.
+ * 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.
+ */
+
+#include "untar_file.h"
+namespace OHOS::FileManagement::Backup {
+
+string UntarFile::GenRealPath(const string &rootPath, const string &realName)
+{
+    if (rootPath.empty() || realName.empty()) {
+        return "";
+    }
+    string realPath(rootPath);
+    size_t len = realPath.length();
+    if (realPath[len - 1] == '/') {
+        realPath = realPath.substr(0, len - 1);
+    }
+    realPath.append((realName[0] == '/') ? realName : ("/" + realName));
+    return realPath;
+}
+
+int UntarFile::CreateDir(string &path, mode_t mode)
+{
+    size_t len = path.length();
+    if (path[len - 1] == '/') {
+        path[len - 1] = '\0';
+    }
+    int ret = access(path.c_str(), F_OK);
+    if (ret != 0) {
+        HILOGE("%{public}s does not exist, err = %{public}d", path.c_str(), errno);
+        ret = mkdir(path.c_str(), mode);
+        if (ret != 0) {
+            HILOGE("Failed to mkdir %{public}s, err = %{public}d", path.c_str(), errno);
+        }
+    }
+    return ret;
+}
+
+FILE *UntarFile::CreateFile(string &filePath, mode_t mode, char fileType)
+{
+    string fileMode = "wb+";
+    if (fileType == SPLIT_END_TYPE || fileType == SPLIT_CONTINUE_TYPE) {
+        fileMode = "ab+";
+    }
+    FILE *f = fopen(filePath.c_str(), fileMode.c_str());
+    if (f != nullptr) {
+        return f;
+    }
+
+    HILOGE("Failed to open file %{public}s, err = %{public}d", filePath.c_str(), errno);
+    size_t pos = filePath.rfind('/');
+    if (pos == string::npos) {
+        return nullptr;
+    }
+
+    string path = filePath.substr(0, pos);
+    if (ForceCreateDirectory(path)) {
+        f = fopen(filePath.c_str(), "wb+");
+        if (f == nullptr) {
+            HILOGE("Failed to open file %{public}s, err = %{public}d", filePath.c_str(), errno);
+        }
+    }
+
+    return f;
+}
+
+int UntarFile::CreateSoftlink(const string &oldPath, const string &newPath)
+{
+    int ret = unlink(newPath.c_str());
+    if (ret != 0) {
+        HILOGE("Failed to unlink, err = %{public}d", errno);
+    }
+    ret = symlink(oldPath.c_str(), newPath.c_str());
+    if (ret != 0) {
+        HILOGE("Failed to symlink, err = %{public}d", errno);
+    }
+    return ret;
+}
+
+} // namespace OHOS::FileManagement::Backup
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