Performing a Partial Download

When only partial data of an object is required, you can use range-based download. If the specified range is from 0 to 1,000, data from byte 0 to byte 1,000, 1,001 bytes in total, are returned. If the specified range is invalid, data of the whole object is returned.

static OBSClient *client;
NSString *endPoint = @"https://your-endpoint";
// Hard-coded or plaintext AK and SK are risky. For security purposes, encrypt your AK and SK before storing them in the configuration file or environment variables. In this example, the AK and SK are stored in environment variables. Before running the code in this example, configure environment variables AccessKeyID and SecretAccessKey.
// Obtain an AK/SK pair on the management console. For details, see https://support.huaweicloud.com/intl/en-us/usermanual-ca/ca_01_0003.html.
char* ak_env = getenv("AccessKeyID");
char* sk_env = getenv("SecretAccessKey");
if (ak_env == NULL || sk_env == NULL) {
    NSLog(@"Error: AccessKeyID or SecretAccessKey environment variable not set");
    return;
}
NSString *AK = [NSString stringWithUTF8String:ak_env];
NSString *SK = [NSString stringWithUTF8String:sk_env];
    
// Initialize identity authentication.
OBSStaticCredentialProvider *credentialProvider = [[OBSStaticCredentialProvider alloc] initWithAccessKey:AK secretKey:SK];
    
//Initialize service configuration.
OBSServiceConfiguration *conf = [[OBSServiceConfiguration alloc] initWithURLString:endPoint credentialProvider:credentialProvider];
    
// Initialize an instance of OBSClient.
client = [[OBSClient alloc] initWithConfiguration:conf];
    
// Streaming download
OBSGetObjectToDataRequest *request = [[OBSGetObjectToDataRequest alloc]initWithBucketName:@"bucketname" objectKey:@"objectname"];
    
// Set the start and end positions of the download range to 0 and 10000 respectively.
request.range = @"bytes=0-1000";
    
//Query the download progress.
request.downloadProgressBlock = ^(int64_t bytesWritten, int64_t totalBytesWritten, int64_t totalBytesExpectedToWrite) {
    NSLog(@"%0.1f%%", (totalBytesExpectedToWrite > 0) ? (float)(totalBytesWritten)*100/(float)totalBytesExpectedToWrite : 0);
};
    
// Receive downloaded data.
__block NSMutableData *objectData = [NSMutableData new];
request.onReceiveDataBlock = ^(NSData *data) {
    [objectData appendData:data];
};
    
// Download result
[client getObject:request completionHandler:^(OBSGetObjectResponse *response, NSError *error){
    NSLog(@"%@",response);
}] ;

• If the specified range is invalid (because the start or end position is set to a negative integer or the range is longer than the object length), data of the whole object will be returned.