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Downloading Objects

Terakhir diperbarui:2024-02-01 18:01:21

    Overview

    This document provides an overview of APIs and SDK code samples related to object downloads.
    Simple operations
    API
    Operation
    Description
    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://www.tencentcloud.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.tencentcloud.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.tencentcloud.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.tencentcloud.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://www.tencentcloud.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.tencentcloud.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.tencentcloud.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.tencentcloud.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://www.tencentcloud.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.tencentcloud.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.tencentcloud.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.tencentcloud.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://www.tencentcloud.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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