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Checking Whether Objects Exist

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

    Overview

    This document provides an overview of the API and sample code for quickly checking whether an object exists in a bucket.
    API
    Operation
    Description
    Querying object metadata
    Queries the metadata of an object

    Checking Whether an Object Exists

    Description

    This API is used to check whether an object exists in a bucket. It actually calls the HEAD Object API to perform the action.

    Method prototype

    cos_status_t *cos_check_object_exist(const cos_request_options_t *options,
    const cos_string_t *bucket,
    const cos_string_t *object,
    cos_table_t *headers,
    cos_object_exist_status_e *object_exist,
    cos_table_t **resp_headers);

    Parameter description

    Parameter
    Description
    Type
    options
    COS request options
    Struct
    bucket
    Bucket name in the format of BucketName-APPID
    String
    object
    Object name
    String
    headers
    Additional headers of a COS request
    Struct
    object_exist
    Whether an object exists. Enumerated values: exist, non exist, unknown (no explicit state is obtained)
    Enum
    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

    #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";
    
    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_check_object_exist()
    {
    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_table_t *resp_headers;
    cos_table_t *headers = NULL;
    cos_object_exist_status_e object_exist;
    
    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_OBJECT_NAME1);
    
    // Check whether an object exists
    s = cos_check_object_exist(options, &bucket, &object, headers, &object_exist, &resp_headers);
    if (object_exist == COS_OBJECT_NON_EXIST) {
    printf("object: %.*s non exist.\\n", object.len, object.data);
    } else if (object_exist == COS_OBJECT_EXIST) {
    printf("object: %.*s exist.\\n", object.len, object.data);
    } else {
    printf("object: %.*s unknown status.\\n", object.len, object.data);
    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_check_object_exist();
    
    cos_http_io_deinitialize();
    
    return 0;
    }
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