Object Storage Service:Download progress bar (C SDK)

Notes

• In this topic, the public endpoint of the China (Hangzhou) region is used. If you want to access OSS from other Alibaba Cloud services in the same region as OSS, use an internal endpoint. For more information about OSS regions and endpoints, 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 Initialization.

Limits

The oss_get_object_from_file and oss_get_object_from_buffer methods do not support the progress bar feature.

Example code

The following code shows how to display download progress using a progress bar.

#include "oss_api.h"
#include "aos_http_io.h"
/* Set yourEndpoint to the Endpoint of the region where the bucket is located. For example, for China (Hangzhou), set the Endpoint to https://oss-cn-hangzhou.aliyuncs.com. */
const char *endpoint = "yourEndpoint";

/* Specify the bucket name. Example: examplebucket. */
const char *bucket_name = "examplebucket";
/* Specify the full path of the object. The full path cannot contain the bucket name. Example: exampledir/exampleobject.txt. */
const char *object_name = "example.txt";
/* Specify the name of the file to download to your local machine. */
const char *download_filename = "1.txt";
/* Set yourRegion to the region where the bucket is located. For example, for China (Hangzhou), set the Region to cn-hangzhou. */
const char *region = "yourRegion";
void init_options(oss_request_options_t *options)
{
    options->config = oss_config_create(options->pool);
    /* Initialize the aos_string_t type with a char* string. */
    aos_str_set(&options->config->endpoint, endpoint);
    /* Obtain access credentials from environment variables. Before you run this code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are set. */    
    aos_str_set(&options->config->access_key_id, getenv("OSS_ACCESS_KEY_ID"));
    aos_str_set(&options->config->access_key_secret, getenv("OSS_ACCESS_KEY_SECRET"));
    // Configure the following two parameters.
    aos_str_set(&options->config->region, region);
    options->config->signature_version = 4;
    /* Specify whether a CNAME is used. 0 indicates that a CNAME is not used. */
    options->config->is_cname = 0;
    /* Set network parameters, such as the timeout period. */
    options->ctl = aos_http_controller_create(options->pool, 0);
}
void percentage(int64_t consumed_bytes, int64_t total_bytes) 
{
    assert(total_bytes >= consumed_bytes);
    printf("%%%" APR_INT64_T_FMT "\n", consumed_bytes * 100 / total_bytes);
}
int main(int argc, char *argv[])
{
    /* At the program entry point, call the aos_http_io_initialize method to initialize global resources, such as the network and memory. */
    if (aos_http_io_initialize(NULL, 0) != AOSE_OK) {
        exit(1);
    }
    /* The memory pool (pool) for memory management is equivalent to apr_pool_t. The implementation code is in the apr library. */
    aos_pool_t *pool;
    /* Create a new memory pool. The second parameter is NULL, which indicates that the new pool does not inherit from other memory pools. */
    aos_pool_create(&pool, NULL);
    /* Create and initialize options. This parameter includes global configurations, such as endpoint, access_key_id, access_key_secret, is_cname, and curl. */
    oss_request_options_t *oss_client_options;
    /* Allocate memory for options in the memory pool. */
    oss_client_options = oss_request_options_create(pool);
    /* Initialize the client options oss_client_options. */
    init_options(oss_client_options);
    /* Initialize the parameters. */
    aos_string_t bucket;
    aos_string_t object;
    aos_string_t file;    
    aos_status_t *resp_status = NULL; 
    aos_str_set(&bucket, bucket_name);
    aos_str_set(&object, object_name);  
    /* Download the file with a progress bar. */
    aos_pool_create(&pool, NULL);
    oss_client_options = oss_request_options_create(pool);
    init_options(oss_client_options);
    aos_str_set(&file, download_filename);
    resp_status = oss_do_get_object_to_file(oss_client_options, &bucket, &object, NULL, NULL, &file, percentage, NULL);
    if (aos_status_is_ok(resp_status)) {
        printf("get object to file succeeded\n");
    } else {
        printf("get object to file failed\n");
    }
    /* Release the memory pool. This releases the memory allocated for resources during the request. */
    aos_pool_destroy(pool);
    /* Release the previously allocated global resources. */
    aos_http_io_deinitialize();
    return 0;
}

References

For the complete sample code that shows how to use a progress bar for file downloads, see the GitHub example.