Querying Assets (C/C++)

Available APIs

You can use OH_Asset_Query to query asset information.

The following table describes the attributes for querying an asset.

NOTE

In the following table, the attributes starting with ASSET_TAG_DATA_LABEL are custom asset attributes reserved. These attributes are not encrypted. Therefore, do not put personal data in these attributes.

Constraints

The assets queried are transmitted to the service through an IPC channel. Due to the limitation of the IPC buffer size, the maximum number of assets to be queried at a time cannot exceed 40.

Example

Querying the Plaintext of an Asset

Query the plaintext of asset demo_alias.

For details about how to query the plaintext of an asset in a group, see Querying the Plaintext of an Asset in a Group.

1. Add the dynamic library in the CMake script.

   target_link_libraries(entry PUBLIC libasset_ndk.z.so)
   

2. Add an asset. “`c #include

#include “asset/asset_api.h”

void QueryAsset() { static const char *ALIAS = “demo_alias”; Asset_Blob alias = { (uint32_t)(strlen(ALIAS)), (uint8_t *)ALIAS }; Asset_Attr attr[] = { { .tag = ASSET_TAG_ALIAS, .value.blob = alias }, // Specify the alias of the asset to query. { .tag = ASSET_TAG_RETURN_TYPE, .value.u32 = ASSET_RETURN_ALL }, // Return all asset information, including the attributes and asset plaintext. };

  Asset_ResultSet resultSet = {0};
  int32_t ret = OH_Asset_Query(attr, sizeof(attr) / sizeof(attr[0]), &resultSet);
  if (ret == ASSET_SUCCESS) {
     // Parse the resultSet.
     for (uint32_t i = 0; i < resultSet.count; i++) {
           // Parse the secret: the data is secret->blob.data, the size is secret->blob.size.
           Asset_Attr *secret = OH_Asset_ParseAttr(resultSet.results + i, ASSET_TAG_SECRET);
     }
  }
  OH_Asset_FreeResultSet(&resultSet);

}

### Querying Attributes of an Asset

Query attributes of asset **demo_alias**.

For details about how to query the attributes of an asset in a group, see [Querying the Attributes of an Asset in a Group](asset-native-group-access-control.md#querying-the-attributes-of-an-asset-in-a-group).

1. Add the dynamic library in the CMake script.
   ```txt
   target_link_libraries(entry PUBLIC libasset_ndk.z.so)

1. Add an asset. “`c #include

#include “asset/asset_api.h”

void QueryAttributes() { static const char *ALIAS = “demo_alias”; Asset_Blob alias = { (uint32_t)(strlen(ALIAS)), (uint8_t *)ALIAS }; Asset_Attr attr[] = { { .tag = ASSET_TAG_ALIAS, .value.blob = alias }, // Specify the alias of the asset to query. { .tag = ASSET_TAG_RETURN_TYPE, .value.u32 = ASSET_RETURN_ATTRIBUTES }, // Return only the asset attributes, that is, the result does not include the asset plaintext. };

  Asset_ResultSet resultSet = {0};
  int32_t ret = OH_Asset_Query(attr, sizeof(attr) / sizeof(attr[0]), &resultSet);
  if (ret == ASSET_SUCCESS) {
     // Parse the result.
     for (uint32_t i = 0; i < resultSet.count; i++) {
     // Parse the data label: the data is label->blob.data, the size is label->blob.size.
           Asset_Attr *label = OH_Asset_ParseAttr(resultSet.results + i, ASSET_TAG_DATA_LABEL_NORMAL_1);
     }
  }
  OH_Asset_FreeResultSet(&resultSet);

}

### Querying Attributes of Assets

Query attributes of assets with the tag of **demo_label** and return a total of 10 records sorted by **DATA_LABEL_NORMAL_1** starting from the fifth record that matches the search criteria.

1. Add the dynamic library in the CMake script.
   ```txt
   target_link_libraries(entry PUBLIC libasset_ndk.z.so)

1. Add an asset. “`c #include

#include “asset/asset_api.h”

void BatchQuery() { static const char *LABEL = “demo_label”; Asset_Blob label = { (uint32_t)(strlen(LABEL)), (uint8_t *)LABEL };

  Asset_Attr attr[] = {
     { .tag = ASSET_TAG_RETURN_TYPE, .value.u32 = ASSET_RETURN_ATTRIBUTES },
     { .tag = ASSET_TAG_DATA_LABEL_NORMAL_1, .value.blob = label },
     { .tag = ASSET_TAG_RETURN_OFFSET, .value.u32 = 5 },
     { .tag = ASSET_TAG_RETURN_LIMIT, .value.u32 = 10 },
     { .tag = ASSET_TAG_RETURN_ORDERED_BY, .value.u32 = ASSET_TAG_DATA_LABEL_NORMAL_1 },
  };

  Asset_ResultSet resultSet = { 0 };
  int32_t ret = OH_Asset_Query(attr, sizeof(attr) / sizeof(attr[0]), &resultSet);
  if (ret == ASSET_SUCCESS) {
     // Parse the result.
     for (uint32_t i = 0; i < resultSet.count; i++) {
           // Parse the data alias: the data is alias->blob.data, the size is alias->blob.size.
           Asset_Attr *alias = OH_Asset_ParseAttr(resultSet.results + i, ASSET_TAG_ALIAS);
     }
  }
  OH_Asset_FreeResultSet(&resultSet);

} “`

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