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Downloading Objects

Terakhir diperbarui:2022-01-23 14:17:46

    Overview

    This document provides an overview of APIs and SDK code samples related to object downloads.

    Simple operations

    API Operation Description
    GET Object Downloading an object Downloads an object to the local file system.

    Advanced APIs (Recommended)

    Downloading an object (checkpoint restart)

    Description

    The multipart download API automatically downloads data concurrently with Range according to the object size. The part size is 1,048,576 (1 MB) by default and can be adjusted via the part_size parameter.

    Method prototype

    cos_status_t *cos_resumable_download_file(cos_request_options_t *options,
                                            cos_string_t *bucket,
                                            cos_string_t *object,
                                            cos_string_t *filepath,
                                            cos_table_t *headers,
                                            cos_table_t *params,
                                            cos_resumable_clt_params_t *clt_params,
                                            cos_progress_callback progress_callback);
    

    Parameter description

    Parameter Description Type
    options COS request options Struct
    bucket Bucket name in the format: BucketName-APPID String
    object Object name String
    filepath The local file name of the object String
    headers Headers attached to the COS request Struct
    params Parameters for the COS request Struct
    clt_params Control parameters for the download operation Struct
    part_size Part size in bytes. If you specify the part size to be below 4,194,304 (4 MB), the system will divide your data based on the part size 4,194,304 (4 MB). Int
    thread_num Number of threads, that is, size of the thread pool. Default: 1 Int
    enable_checkpoint Indicates whether to enable checkpoint restart Int
    checkpoint_path Indicates the file path for which the upload progress is saved when checkpoint restart is enabled. Default: <filepath>.cp, where filepath is the local file name of the object String
    progress_callback Callback function for the download progress Function

    Response

    Response Parameter Description Type
    code Error code Int
    error_code Error code content String
    error_msg Error code description String
    req_id Request message ID String

    Sample

    #include "cos_http_io.h"
    #include "cos_api.h"
    #include "cos_log.h"
    // `endpoint` is the COS access domain name. For more information, see https://intl.cloud.tencent.com/document/product/436/6224.
    static char TEST_COS_ENDPOINT[] = "cos.ap-guangzhou.myqcloud.com";
    // A developer-owned secret ID/key used for the project. It can be obtained at https://console.intl.cloud.tencent.com/cam/capi.
    static char *TEST_ACCESS_KEY_ID;                // Your SecretId
    static char *TEST_ACCESS_KEY_SECRET;            // Your SecretKey
    // A unique user-level resource identifier for COS access. It can be obtained at https://console.intl.cloud.tencent.com/cam/capi.
    static char TEST_APPID[] = "<APPID>";    // Your APPID
    // COS bucket name, in the format of [bucket]-[appid], for example `mybucket-1253666666`. It can be obtained at https://console.intl.cloud.tencent.com/cos5/bucket.
    static char TEST_BUCKET_NAME[] = "<bucketname-appid>";
    static char TEST_DOWNLOAD_NAME4[] = "multipart_download.dat";
    static char TEST_MULTIPART_OBJECT4[] = "multipart4.dat";
    void log_status(cos_status_t *s)
    {
      cos_warn_log("status->code: %d", s->code);
      if (s->error_code) cos_warn_log("status->error_code: %s", s->error_code);
      if (s->error_msg) cos_warn_log("status->error_msg: %s", s->error_msg);
      if (s->req_id) cos_warn_log("status->req_id: %s", s->req_id);
    }
    void init_test_config(cos_config_t *config, int is_cname)
    {
      cos_str_set(&config->endpoint, TEST_COS_ENDPOINT);
      cos_str_set(&config->access_key_id, TEST_ACCESS_KEY_ID);
      cos_str_set(&config->access_key_secret, TEST_ACCESS_KEY_SECRET);
      cos_str_set(&config->appid, TEST_APPID);
      config->is_cname = is_cname;
    }
    void init_test_request_options(cos_request_options_t *options, int is_cname)
    {
      options->config = cos_config_create(options->pool);
      init_test_config(options->config, is_cname);
      options->ctl = cos_http_controller_create(options->pool, 0);
    }
    void test_resumable()
    {
      cos_pool_t *p = NULL;
      int is_cname = 0;
      cos_status_t *s = NULL;
      cos_request_options_t *options = NULL;
      cos_string_t bucket;
      cos_string_t object;
      cos_string_t filepath;
      cos_resumable_clt_params_t *clt_params;
    
      cos_pool_create(&p, NULL);
      options = cos_request_options_create(p);
      init_test_request_options(options, is_cname);
      cos_str_set(&bucket, TEST_BUCKET_NAME);
      cos_str_set(&object, TEST_MULTIPART_OBJECT4);
      cos_str_set(&filepath, TEST_DOWNLOAD_NAME4);
       clt_params = cos_create_resumable_clt_params_content(p, 5*1024*1024, 3, COS_FALSE, NULL);
      s = cos_resumable_download_file(options, &bucket, &object, &filepath, NULL, NULL, clt_params, NULL);
      log_status(s);
       cos_pool_destroy(p);
    }
    int main(int argc, char *argv[])
    {
      // Get SecretId and SecretKey from environment variables
      TEST_ACCESS_KEY_ID     = getenv("COS_SECRETID");
      TEST_ACCESS_KEY_SECRET = getenv("COS_SECRETKEY");
        if (cos_http_io_initialize(NULL, 0) != COSE_OK) {
         exit(1);
      }
       // Set the log level. Default value: `COS_LOG_WARN`
      cos_log_set_level(COS_LOG_WARN);
       // Set log output. Default value: `stderr`
      cos_log_set_output(NULL);
       test_resumable();
       cos_http_io_deinitialize();
       return 0;
    }
    

    Batch downloading files (downloading a COS directory)

    Description

    This API is used to download a COS directory and the files in it to the local disk.

    Sample

    #include "cos_http_io.h"
    #include "cos_api.h"
    #include "cos_log.h"
    // `endpoint` is the COS access domain name. For more information, see https://intl.cloud.tencent.com/document/product/436/6224.
    static char TEST_COS_ENDPOINT[] = "cos.ap-guangzhou.myqcloud.com";
    // A developer-owned secret ID/key used for the project. It can be obtained at https://console.intl.cloud.tencent.com/cam/capi.
    static char *TEST_ACCESS_KEY_ID;                // Your SecretId
    static char *TEST_ACCESS_KEY_SECRET;            // Your SecretKey
    // A unique user-level resource identifier for COS access. It can be obtained at https://console.intl.cloud.tencent.com/cam/capi.
    static char TEST_APPID[] = "<APPID>";    // Your APPID
    // COS bucket name, in the format of [bucket]-[appid], for example `mybucket-1253666666`. It can be obtained at https://console.intl.cloud.tencent.com/cos5/bucket.
    static char TEST_BUCKET_NAME[] = "<bucketname-appid>";
    void log_status(cos_status_t *s)
    {
      cos_warn_log("status->code: %d", s->code);
      if (s->error_code) cos_warn_log("status->error_code: %s", s->error_code);
      if (s->error_msg) cos_warn_log("status->error_msg: %s", s->error_msg);
      if (s->req_id) cos_warn_log("status->req_id: %s", s->req_id);
    }
    void init_test_config(cos_config_t *config, int is_cname)
    {
      cos_str_set(&config->endpoint, TEST_COS_ENDPOINT);
      cos_str_set(&config->access_key_id, TEST_ACCESS_KEY_ID);
      cos_str_set(&config->access_key_secret, TEST_ACCESS_KEY_SECRET);
      cos_str_set(&config->appid, TEST_APPID);
      config->is_cname = is_cname;
    }
    void init_test_request_options(cos_request_options_t *options, int is_cname)
    {
      options->config = cos_config_create(options->pool);
      init_test_config(options->config, is_cname);
      options->ctl = cos_http_controller_create(options->pool, 0);
    }
    void test_download_directory()
    {
      cos_pool_t *p = NULL;
      int is_cname = 0;
      cos_status_t *s = NULL;
      cos_request_options_t *options = NULL;
      cos_string_t bucket;
      cos_string_t file_name;
      cos_string_t suffix = cos_string("/");
      cos_table_t *resp_headers;
      cos_table_t *headers = NULL;
      cos_table_t *params = NULL;
      int is_truncated = 1;
      cos_string_t marker;
      apr_status_t status;
       // Initialize the request options
      cos_pool_create(&p, NULL);
      options = cos_request_options_create(p);
      init_test_request_options(options, is_cname);
      cos_str_set(&bucket, TEST_BUCKET_NAME);
       //list object (get bucket)
      cos_list_object_params_t *list_params = NULL;
      list_params = cos_create_list_object_params(p);
      cos_str_set(&list_params->prefix, "folder/");   // Use your own directory name
      cos_str_set(&marker, "");
      while (is_truncated) {
          list_params->marker = marker;
          s = cos_list_object(options, &bucket, list_params, &resp_headers);
          log_status(s);
          if (!cos_status_is_ok(s)) {
              printf("list object failed, req_id:%s\n", s->req_id);
              break;
          }
          cos_list_object_content_t *content = NULL;
          cos_list_for_each_entry(cos_list_object_content_t, content, &list_params->object_list, node) {
              cos_str_set(&file_name, content->key.data);
              if (cos_ends_with(&content->key, &suffix)) {
                  // If you need to create the directory first, you can modify the 0x0755 permission as desired. For details, see the definition in `apr_file_info.h`.
                  status = apr_dir_make(content->key.data, 0x0755, options->pool);
                  if (status != APR_SUCCESS && !APR_STATUS_IS_EEXIST(status)) {
                      printf("mkdir: %s failed, status: %d\n", content->key.data, status);
                  }
              } else {
                  // Download the object to a local directory, which is the current program running directory by default
                  s = cos_get_object_to_file(options, &bucket, &content->key, headers, params, &file_name, &resp_headers);
                  if (!cos_status_is_ok(s)) {
                      printf("get object[%s] failed, req_id:%s\n", content->key.data, s->req_id);
                  }
              }
          }
          is_truncated = list_params->truncated;
          marker = list_params->next_marker;
      }
       // Destroy the memory pool.
      cos_pool_destroy(p);
    }
    int main(int argc, char *argv[])
    {
      // Get SecretId and SecretKey from environment variables
      TEST_ACCESS_KEY_ID     = getenv("COS_SECRETID");
      TEST_ACCESS_KEY_SECRET = getenv("COS_SECRETKEY");
        if (cos_http_io_initialize(NULL, 0) != COSE_OK) {
         exit(1);
      }
       // Set the log level. Default value: `COS_LOG_WARN`
      cos_log_set_level(COS_LOG_WARN);
       // Set log output. Default value: `stderr`
      cos_log_set_output(NULL);
       test_download_directory();
       cos_http_io_deinitialize();
       return 0;
    }
    

    Simple Operations

    Downloading an object

    Description

    This API is used to download an object to the local file system. This operation requires that you have read permission for the object, or that the object has public read permission enabled.

    Method prototype

    cos_status_t *cos_get_object_to_file(const cos_request_options_t *options,
                                       const cos_string_t *bucket, 
                                       const cos_string_t *object,
                                       cos_table_t *headers, 
                                       cos_table_t *params,
                                       cos_string_t *filename, 
                                       cos_table_t **resp_headers);
    

    Parameter description

    Parameter Description Type
    options COS request options Struct
    bucket Bucket name in the format: BucketName-APPID String
    object Object name String
    headers Additional headers of a COS request Struct
    params Parameters for the COS request operation Struct
    filename Filename of the local object before it is uploaded to COS String
    resp_headers Returns the HTTP response headers Struct

    Response description

    Response Parameter Description Type
    code Error code Int
    error_code Error code content String
    error_msg Error code description String
    req_id Request message ID String

    Sample: simple download

    #include "cos_http_io.h"
    #include "cos_api.h"
    #include "cos_log.h"
    // `endpoint` is the COS access domain name. For more information, see https://intl.cloud.tencent.com/document/product/436/6224.
    static char TEST_COS_ENDPOINT[] = "cos.ap-guangzhou.myqcloud.com";
    // A developer-owned secret ID/key used for the project. It can be obtained at https://console.intl.cloud.tencent.com/cam/capi.
    static char *TEST_ACCESS_KEY_ID;                // Your SecretId
    static char *TEST_ACCESS_KEY_SECRET;            // Your SecretKey
    // A unique user-level resource identifier for COS access. It can be obtained at https://console.intl.cloud.tencent.com/cam/capi.
    static char TEST_APPID[] = "<APPID>";    // Your APPID
    // COS bucket name, in the format of [bucket]-[appid], for example `mybucket-1253666666`. It can be obtained at https://console.intl.cloud.tencent.com/cos5/bucket.
    static char TEST_BUCKET_NAME[] = "<bucketname-appid>";
    // A unique identifier of an object stored in COS. For more information about objects and object keys, please see https://intl.cloud.tencent.com/document/product/436/13324.
    static char TEST_OBJECT_NAME1[] = "1.txt";
    static char TEST_DOWNLOAD_NAME[] = "download_test3.dat";
    void log_status(cos_status_t *s)
    {
      cos_warn_log("status->code: %d", s->code);
      if (s->error_code) cos_warn_log("status->error_code: %s", s->error_code);
      if (s->error_msg) cos_warn_log("status->error_msg: %s", s->error_msg);
      if (s->req_id) cos_warn_log("status->req_id: %s", s->req_id);
    }
    void init_test_config(cos_config_t *config, int is_cname)
    {
      cos_str_set(&config->endpoint, TEST_COS_ENDPOINT);
      cos_str_set(&config->access_key_id, TEST_ACCESS_KEY_ID);
      cos_str_set(&config->access_key_secret, TEST_ACCESS_KEY_SECRET);
      cos_str_set(&config->appid, TEST_APPID);
      config->is_cname = is_cname;
    }
    void init_test_request_options(cos_request_options_t *options, int is_cname)
    {
      options->config = cos_config_create(options->pool);
      init_test_config(options->config, is_cname);
      options->ctl = cos_http_controller_create(options->pool, 0);
    }
    void test_download_object()
    {
      cos_pool_t *p = NULL;
      int is_cname = 0;
      cos_status_t *s = NULL;
      cos_request_options_t *options = NULL;
      cos_string_t bucket;
      cos_string_t object;
      cos_string_t file;
      cos_table_t *resp_headers = NULL;
       // Create a memory pool
      cos_pool_create(&p, NULL);
       // Initialize the request options
      options = cos_request_options_create(p);
      init_test_request_options(options, is_cname);
      cos_str_set(&bucket, TEST_BUCKET_NAME);
       // Get the object
      cos_str_set(&file, TEST_DOWNLOAD_NAME);
      cos_str_set(&object, TEST_OBJECT_NAME1);
      s = cos_get_object_to_file(options, &bucket, &object, NULL, NULL, &file, &resp_headers);
      if (cos_status_is_ok(s)) {
          printf("get object succeeded\n");
      } else {
          printf("get object failed\n");
      }
       // Destroy the memory pool.
      cos_pool_destroy(p); 
    }
    int main(int argc, char *argv[])
    {
      // Get SecretId and SecretKey from environment variables
      TEST_ACCESS_KEY_ID     = getenv("COS_SECRETID");
      TEST_ACCESS_KEY_SECRET = getenv("COS_SECRETKEY");
        if (cos_http_io_initialize(NULL, 0) != COSE_OK) {
         exit(1);
      }
       // Set the log level. Default value: `COS_LOG_WARN`
      cos_log_set_level(COS_LOG_WARN);
       // Set log output. Default value: `stderr`
      cos_log_set_output(NULL);
       test_download_object();
       cos_http_io_deinitialize();
       return 0;
    }
    
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