# 授权持久化(C/C++)

## 场景介绍

应用通过Picker获取临时授权，临时授权在应用退出后或者设备重启后会清除，如果应用重启或者设备重启后需要直接访问之前已访问过的文件，则对文件进行[持久化授权](file-persistPermission.md#场景介绍)。FileShare提供了支持基于URI的文件及目录授于持久化权限、权限激活、权限查询等方法。

## 接口说明

接口的详细介绍请参见[API参考](../reference/apis-core-file-kit/file_share.md)。

| 接口名称 | 描述 |
| -------- | -------- |
| OH_FileShare_PersistPermission(const FileShare_PolicyInfo *policies, unsigned int policyNum, FileShare_PolicyErrorResult **result, unsigned int *resultNum) | 对所选择的多个文件或目录URI持久化授权。 |
| OH_FileShare_RevokePermission(const FileShare_PolicyInfo *policies, unsigned int policyNum, FileShare_PolicyErrorResult **result, unsigned int *resultNum) | 对所选择的多个文件或目录URI取消持久化授权。 |
| OH_FileShare_ActivatePermission(const FileShare_PolicyInfo *policies, unsigned int policyNum, FileShare_PolicyErrorResult **result, unsigned int *resultNum) | 使能多个已经永久授权过的文件或目录URI。 |
| OH_FileShare_DeactivatePermission(const FileShare_PolicyInfo *policies, unsigned int policyNum, FileShare_PolicyErrorResult **result, unsigned int *resultNum) | 取消使能授权过的多个文件或目录URI。 |
| OH_FileShare_CheckPersistentPermission(const FileShare_PolicyInfo *policies, unsigned int policyNum, bool **result, unsigned int *resultNum) | 校验所选择的多个文件或目录URI的持久化权限结果。 |
| OH_FileShare_ReleasePolicyErrorResult(FileShare_PolicyErrorResult *errorResult, unsigned int resultNum) | 释放FileShare_PolicyErrorResult内存。 |

## 约束与限制

- 使用文件分享的相关接口，需确认设备具有以下系统能力：SystemCapability.FileManagement.AppFileService.FolderAuthorization。

- 在调用文件分享的相关接口前，需要申请权限："ohos.permission.FILE_ACCESS_PERSIST"，申请方式请参考[访问控制-申请应用权限](../security/AccessToken/determine-application-mode.md)。

## 开发步骤

以下步骤描述了如何使用`FileShare`提供的Native API接口。

**添加动态链接库**

CMakeLists.txt中添加以下lib。

```txt
target_link_libraries(sample PUBLIC libohfileshare.so)
```

**头文件**

```c++
#include <filemanagement/fileshare/oh_file_share.h>
#include <iostream>
```
1. 创建FileShare_PolicyInfo实例,调用OH_FileShare_PersistPermission接口，设置URI的持久化授权，接口入参policyNum最大上限为500。
    ```c++
    static const uint32_t POLICY_NUM = 2;
    char strTestPath1[] = "file://com.example.fileshare/data/storage/el2/base/files/test1.txt";
    char strTestPath2[] = "file://com.example.fileshare/data/storage/el2/base/files/test2.txt";
    FileShare_PolicyInfo policy[POLICY_NUM] = {
        {strTestPath1, static_cast<unsigned int>(strlen(strTestPath1)), FileShare_OperationMode::READ_MODE},
        {strTestPath2, static_cast<unsigned int>(strlen(strTestPath2)), FileShare_OperationMode::WRITE_MODE}};
    FileShare_PolicyErrorResult* result = nullptr;
    uint32_t resultNum = 0;
    auto ret = OH_FileShare_PersistPermission(policy, POLICY_NUM, &result, &resultNum);
    if (ret != ERR_OK) {
        if (ret == ERR_EPERM && result != nullptr) {
            for(uint32_t i = 0; i < resultNum; i++) {
                std::cout << "error uri: " <<  result[i].uri << std::endl;
                std::cout << "error code: " <<  result[i].code << std::endl;
                std::cout << "error message: " << result[i].message << std::endl;
            }
        }
    }
    OH_FileShare_ReleasePolicyErrorResult(result, resultNum);
    ```
2. 调用OH_FileShare_ActivatePermission接口，激活启用已授权过的URI，接口入参policyNum最大上限为500。
    ```c++
    auto ret = OH_FileShare_ActivatePermission(policy, POLICY_NUM, &result, &resultNum);
    if (ret != ERR_OK) {
        if (ret == ERR_EPERM && result != nullptr) {
            for(uint32_t i = 0; i < resultNum; i++) {
                std::cout << "error uri: " <<  result[i].uri << std::endl;
                std::cout << "error code: " <<  result[i].code << std::endl;
                std::cout << "error message: " << result[i].message << std::endl;
            }
        }
    }
    OH_FileShare_ReleasePolicyErrorResult(result, resultNum);
    ```
3. 调用OH_FileShare_DeactivatePermission接口，停止已启用授权过URI的访问权限，接口入参policyNum最大上限为500。
    ```c++
    auto ret = OH_FileShare_DeactivatePermission(policy, POLICY_NUM, &result, &resultNum);
    if (ret != ERR_OK) {
        if (ret == ERR_EPERM && result != nullptr) {
            for(uint32_t i = 0; i < resultNum; i++) {
                std::cout << "error uri: " <<  result[i].uri << std::endl;
                std::cout << "error code: " <<  result[i].code << std::endl;
                std::cout << "error message: " << result[i].message << std::endl;
            }
        }
    }
    OH_FileShare_ReleasePolicyErrorResult(result, resultNum);
    ```
4. 调用OH_FileShare_RevokePermission接口，撤销已经授权的URI持久化权限，接口入参policyNum最大上限为500。
    ```c++
    auto ret = OH_FileShare_RevokePermission(policy, POLICY_NUM, &result, &resultNum);
    if (ret != ERR_OK) {
        if (ret == ERR_EPERM && result != nullptr) {
            for(uint32_t i = 0; i < resultNum; i++) {
                std::cout << "error uri: " <<  result[i].uri << std::endl;
                std::cout << "error code: " <<  result[i].code << std::endl;
                std::cout << "error message: " << result[i].message << std::endl;
            }
        }
    }
    OH_FileShare_ReleasePolicyErrorResult(result, resultNum);
    ```
5. 调用OH_FileShare_CheckPersistentPermission接口，检查URI持久化权限，接口入参policyNum最大上限为500。
    ```c++
    bool *result = nullptr;
    auto ret = OH_FileShare_CheckPersistentPermission(policy, POLICY_NUM, &result, &resultNum);
    if (result != nullptr && resultNum > 0) {
        for(uint32_t i = 0; i < resultNum && resultNum <= POLICY_NUM; i++) {
            std::cout << "uri: " <<  policy[i].uri << std::endl;
            std::cout << "result: " <<  result[i] << std::endl;
        }
    }
    std::cout << "retCode: " <<  ret << std::endl;
    free(result);
    ```