This topic describes how to download an object to the local memory.
Examples
The following code provides an example on how to download a specified object to the local memory:
#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 located in the China (Hangzhou) region, set the endpoint to https://oss-cn-hangzhou.aliyuncs.com. */
const char *endpoint = "yourEndpoint";
/* The AccessKey pair of an Alibaba Cloud account has permissions on all API operations. Using these credentials to perform operations in Object Storage Service (OSS) is a high-risk operation. We recommend that you use a RAM user to call API operations or perform routine O&M. To create a RAM user, log on to the RAM console. */
const char *access_key_id = "yourAccessKeyId";
const char *access_key_secret = "yourAccessKeySecret";
/* Specify the bucket name. Example: examplebucket. */
const char *bucket_name = "examplebucket";
/* Specify the full path of the object. The full path of the object cannot contain the bucket name. Example: exampledir/exampleobject.txt. */
const char *object_name = "exampledir/exampleobject.txt";
void init_options(oss_request_options_t *options)
{
options->config = oss_config_create(options->pool);
/* Use a char* string to initialize the aos_string_t data type. */
aos_str_set(&options->config->endpoint, endpoint);
aos_str_set(&options->config->access_key_id, access_key_id);
aos_str_set(&options->config->access_key_secret, access_key_secret);
/* Specify whether to use CNAME. A value of 0 indicates that CNAME is not used. */
options->config->is_cname = 0;
/* Configure network 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 in main() to initialize global resources such as networks and memory. */
if (aos_http_io_initialize(NULL, 0) != AOSE_OK) {
exit(1);
}
/* Create a memory pool to manage memory. aos_pool_t is equivalent to apr_pool_t. The code used to create a memory pool is included in the APR library. */
aos_pool_t *pool;
/* Create a memory pool. The value of the second parameter is NULL. This value indicates that the pool does not inherit other memory pools. */
aos_pool_create(&pool, NULL);
/* Create and initialize options. This parameter includes global configuration information such as endpoint, access_key_id, access_key_secret, is_cname, and curl. */
oss_request_options_t *oss_client_options;
/* Allocate the memory resources in the memory pool to the options. */
oss_client_options = oss_request_options_create(pool);
/* Initialize 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);
/* Download the object to the local 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");
/* Copy the downloaded content to the buffer. */
len = aos_buf_list_len(&buffer);
buf = aos_pcalloc(pool, len + 1);
buf[len] = '\0';
aos_list_for_each_entry(aos_buf_t, content, &buffer, node) {
size = aos_buf_size(content);
memcpy(buf + pos, content->pos, size);
pos += size;
}
}
else {
printf("get object to buffer failed\n");
}
/* Release the memory pool. This operation releases the memory resources allocated for the request. */
aos_pool_destroy(pool);
/* Release the allocated global resources. */
aos_http_io_deinitialize();
return 0;
}