You can use range download to download a specified range of data from an object.
Usage notes
In this topic, the public endpoint of the China (Hangzhou) region is used. If you want to access OSS by using other Alibaba Cloud services in the same region as OSS, use an internal endpoint. For more information about the regions and endpoints supported by OSS, see Regions and endpoints.
In this topic, an OSSClient instance is created by using an OSS endpoint. If you want to create an OSSClient instance by using custom domain names or Security Token Service (STS), see Create an OSSClient instance.
To perform range download, you must have the
oss:GetObjectpermission. For more information, see Common examples of RAM policies.
Specify a valid range to download
The following sample code provides an example on how to specify a valid range to download data:
#include <alibabacloud/oss/OssClient.h>
using namespace AlibabaCloud::OSS;
int main(void)
{
/* Initialize information about the account that is used to access OSS. */
/* Specify the endpoint of the region in which the bucket is located. For example, if the bucket is located in the China (Hangzhou) region, set the endpoint to https://oss-cn-hangzhou.aliyuncs.com. */
std::string Endpoint = "https://oss-cn-hangzhou.aliyuncs.com";
/* Specify the name of the bucket. Example: examplebucket. */
std::string BucketName = "examplebucket";
/* Specify the full path of the object. Do not include the bucket name in the full path of the object. Example: exampledir/exampleobject.txt. */
std::string ObjectName = "exampledir/exampleobject.txt";
/* Initialize resources such as network resources. */
InitializeSdk();
ClientConfiguration conf;
/* Obtain access credentials from environment variables. Before you run the sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are configured. */
auto credentialsProvider = std::make_shared<EnvironmentVariableCredentialsProvider>();
OssClient client(Endpoint, credentialsProvider, conf);
/* Query the object. */
GetObjectRequest request(BucketName, ObjectName);
/* Specify the download range. */
request.setRange(0, 1);
auto outcome = client.GetObject(request);
if (!outcome.isSuccess ()) {
/* Handle exceptions. */
std::cout << "getObject fail" <<
",code:" << outcome.error().Code() <<
",message:" << outcome.error().Message() <<
",requestId:" << outcome.error().RequestId() << std::endl;
return -1;
}
/* Release resources such as network resources. */
ShutdownSdk();
return 0;
}Specify an invalid range to download data
For an object whose size is 1,000 bytes, the valid range is from byte 0 to byte 999. If the specified range is not within the range of byte 0 to byte 999, the range does not take effect. In this case, OSS returns HTTP status code 200 and the data of the entire object. The following examples show invalid requests and the returned results:
If you set Range: bytes to 500-2000, the value at the end of the range is invalid. In this case, OSS returns HTTP status code 200 and the data of the entire object.
If you set Range: bytes to 1000-2000, the value at the start of the range is invalid. In this case, OSS returns HTTP status code 200 and the data of the entire object.
Specify standard behaviors to download data by range
If you add x-oss-range-behavior:standard to the request header, the download behavior is modified when the specified range is not within the valid range. For an object whose size is 1,000 bytes:
If you set Range: bytes to 500-2000, the value at the end of the range is invalid. In this case, OSS returns HTTP status code 206 and the data that is within the range of byte 500 to byte 999.
If you set Range: bytes to 1000-2000, the value at the start of the range is invalid. In this case, OSS returns HTTP status code 416 and the InvalidRange error code.
The following sample code provides an example on how to specify standard behaviors to download data by range:
#include <alibabacloud/oss/OssClient.h>
using namespace AlibabaCloud::OSS;
int main(void)
{
/* Initialize information about the account that is used to access OSS. */
/* Specify the endpoint of the region in which the bucket is located. For example, if the bucket is located in the China (Hangzhou) region, set the endpoint to https://oss-cn-hangzhou.aliyuncs.com. */
std::string Endpoint = "https://oss-cn-hangzhou.aliyuncs.com";
/* Specify the name of the bucket. Example: examplebucket. */
std::string BucketName = "examplebucket";
/* Specify an object whose size is 1,000 bytes. */
/* Specify the full path of the object. Do not include the bucket name in the full path. Example: exampledir/exampleobject.txt. */
std::string ObjectName = "yourObjectName";
/* Initialize resources such as network resources. */
InitializeSdk();
ClientConfiguration conf;
/* Obtain access credentials from environment variables. Before you run the sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are configured. */
auto credentialsProvider = std::make_shared<EnvironmentVariableCredentialsProvider>();
OssClient client(Endpoint, credentialsProvider, conf);
/* Query the object. */
GetObjectRequest request(BucketName, ObjectName);
/* Specify the download range. */
/* If the value at the end of the range is invalid, the data range from byte 500 to byte 999 and HTTP status code 206 are returned. */
request.setRange(500, 2000, true);
auto outcome = client.GetObject(request);
/* If the value at the start of the range is invalid, exceptions are thrown. HTTP status code 416 and the InvalidRange error message are returned. */
request.setRange(1000, 2000, true);
outcome = client.GetObject(request);
if (!outcome.isSuccess ()) {
/* Handle exceptions. */
std::cout << "getObject fail" <<
",code:" << outcome.error().Code() <<
",message:" << outcome.error().Message() <<
",requestId:" << outcome.error().RequestId() << std::endl;
return -1;
}
/* Release resources such as network resources. */
ShutdownSdk();
return 0;
}References
For more information about the API operation that you can call to perform range download, see GetObject.