Object Storage Service:Range download (C SDK)

#include "oss_api.h"
#include "aos_http_io.h"
/* Specify the endpoint of the region in which the bucket is located. For example, if the bucket is in the China (Hangzhou) region, 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. Do not include the bucket name in the full path. Example: exampledir/exampleobject.txt. */
const char *object_name = "exampledir/exampleobject.txt";
/* Specify the region in which the bucket is located. For example, if the bucket is in the China (Hangzhou) region, 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 running this sample code, make sure 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 two additional parameters.
    aos_str_set(&options->config->region, region);
    options->config->signature_version = 4;
    /* Specify whether to use a CNAME. A value of 0 indicates that a CNAME is not used. */
    options->config->is_cname = 0;
    /* Set network-related parameters, such as the timeout period. */
    options->ctl = aos_http_controller_create(options->pool, 0);
}
int main(int argc, char *argv[])
{
    /* Call the aos_http_io_initialize method at the program entry point to initialize global resources, such as the network and memory. */
    if (aos_http_io_initialize(NULL, 0) != AOSE_OK) {
        exit(1);
    }
    /* The memory pool for memory management, which 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 pool does not inherit from other memory pools. */
    aos_pool_create(&pool, NULL);
    /* Create and initialize options. This parameter includes global configuration information, such as the 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_list_t buffer;
    aos_buf_t *content = NULL;
    aos_table_t *params = NULL;
    aos_table_t *headers = NULL;
    aos_table_t *resp_headers = NULL; 
    aos_status_t *resp_status = NULL; 
    char *buf = NULL;
    int64_t len = 0;
    int64_t size = 0;
    int64_t pos = 0;
    aos_str_set(&bucket, bucket_name);
    aos_str_set(&object, object_name);
    aos_list_init(&buffer);
    headers = aos_table_make(pool, 1);
    /* Set the Range header to download bytes 20 to 100. */
    apr_table_set(headers, "Range", "bytes=20-100");
    /* Download the object to memory. */
    resp_status = oss_get_object_to_buffer(oss_client_options, &bucket, &object, headers, params, &buffer, &resp_headers);
    if (aos_status_is_ok(resp_status)) {
        printf("get object to buffer succeeded\n");
        /* Get the buffer length. */
        aos_list_for_each_entry(aos_buf_t, content, &buffer, node) {
            len += aos_buf_size(content);
        }
        buf = aos_pcalloc(pool, (apr_size_t)(len + 1));
        buf[len] = '\0';
        /* Copy the buffer content to memory. */
        aos_list_for_each_entry(aos_buf_t, content, &buffer, node) {
            size = aos_buf_size(content);
            memcpy(buf + pos, content->pos, (size_t)size);
            pos += size;
        }
    }
    else {
        printf("get object to buffer 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;
}