Downloading an Object - Resumable (SDK for C)

Updated on 2025-05-16 GMT+08:00

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Function

Downloading large files often fails due to an unstable network or program breakdown. It is a waste of resources to download files again. Moreover, the restarted download may still fail due to an unstable network. To resolve such issues, the resumable download API splits the file to be downloaded into multiple parts and downloads them separately. The download result of each part is recorded in a checkpoint file in real time. Only when all parts are downloaded is a message indicating the download is successful returned. If any parts fail to be downloaded, a message is returned telling you to call the API again to download the failed parts. Since the checkpoint file contains the progress of all parts, it helps you avoid downloading all parts in re-downloads, so that you can enjoy a cost-effective, efficient download.

You can use download_file to perform a resumable download.

Restrictions

To download an object, you must be the bucket owner or have the required permission (obs:object:GetObject in IAM or GetObject in a bucket policy). For details, see Introduction to OBS Access Control, IAM Custom Policies, and Configuring an Object Policy.
The mapping between OBS regions and endpoints must comply with what is listed in Regions and Endpoints.
The API for resumable download, which is implemented based on partial download, is an encapsulated and enhanced version of partial download.
By resuming a failed download from where it failed, this API helps save resources. In addition, parts can be downloaded concurrently, which helps speed up the download. During the download process, you do not need to take care of internal service details, such as the creation and deletion of checkpoint files, division of objects, or concurrent downloads of parts.

Method

void download_file(const obs_options *options, char *key, char* version_id, 
    obs_get_conditions *get_conditions,
    server_side_encryption_params *encryption_params,
    obs_download_file_configuration * download_file_config,
    obs_download_file_response_handler *handler, void *callback_data);

Request Parameters

**Table 1** List of request parameters
Parameter	Type	Mandatory (Yes/No)	Description
options	const obs_options*	Yes	Explanation: The context of the requested bucket. Refer to Configuring option (SDK for C) to set the AK, SK, endpoint, bucket, timeout, and temporary credentials through obs_options. Restrictions: None
key	char *	Yes	Explanation: Object name. An object name is a complete path that does not contain the bucket name. For example, if the access path is examplebucket.obs.ap-southeast-1.myhuaweicloud.com/folder/test.txt, the object name is folder/test.txt. Restrictions: The name of each object in a bucket must be unique. Value range: The value can contain 1 to 1,024 characters. Default value: None
version_id	char *	Yes	Explanation: Object version ID. Restrictions: None Value range: None Default value: None
download_file_config	obs_download_file_configuration *	Yes	Explanation: Configuration description of the file to be downloaded. Restrictions: None
get_conditions	obs_get_conditions *	Yes	Explanation: Sets filter conditions of the object and read range. Restrictions: None
encryption_params	server_side_encryption_params *	No	Explanation: Decryption settings of the downloaded object. Restrictions: None
handler	obs_download_file_response_handler *	Yes	Explanation: A callback structure where all members are pointers to callback functions, used to set the callback functions that handle response data. You can set a callback function to copy the response data from the server to your custom callback_data. Restrictions: None
callback_data	void *	No	Explanation: Custom callback data. Restrictions: None Value range: None Default value: None

**Table 2** obs_options
Parameter	Type	Mandatory (Yes/No)	Description
bucket_options	obs_bucket_context	Yes	Explanation: Bucket settings. Restrictions: None
request_options	obs_http_request_option	Yes	Explanation: Request-related settings. Restrictions: None
temp_auth	temp_auth_configure*	No	Explanation: The structure used to calculate a temporary signature. Set it to NULL if it is not used. Restrictions: None

**Table 3** obs_bucket_context
Parameter	Type	Mandatory (Yes/No)	Description
host_name	char *	Yes	Explanation: The requested host name, used as an address for connecting to OBS. It is the domain name (the endpoint) of the server where the requested resource is stored. Example: host_name = "obs.ap-southeast-1.myhuaweicloud.com"; Restrictions: The value does not need to contain http:// or https:// as a prefix, which is controlled using obs_protocol. Value range: To view the endpoints available for OBS, see Regions and Endpoints. Default value: None
bucket_name	char *	Yes	Explanation: Bucket name. Restrictions: A bucket name must be unique across all accounts and regions. A bucket name: Must be 3 to 63 characters long and start with a digit or letter. Lowercase letters, digits, hyphens (-), and periods (.) are allowed. Cannot be formatted as an IP address. Cannot start or end with a hyphen (-) or period (.). Cannot contain two consecutive periods (..), for example, my..bucket. Cannot contain a period (.) and a hyphen (-) adjacent to each other, for example, my-.bucket or my.-bucket. If you repeatedly create buckets with the same name in the same region, no error will be reported and the bucket attributes comply with those set in the first creation request. Value range: None Default value: None
useCname	bool	No	Explanation: Whether to use a custom domain name to access OBS. Restrictions: None Value range: true: A custom domain name is used. false: A custom domain name is not used. Default value: false
protocol	obs_protocol	No	Explanation: Whether to use the HTTP or HTTPS protocol. Restrictions: None Value range: For details, see obs_protocol. Default value: OBS_PROTOCOL_HTTPS (HTTPS is used by default.)
access_key	char *	Yes	Explanation: Access key ID (AK). Restrictions: None Value range: For details, see Creating Access Keys. Value range: None
secret_access_key	char *	Yes	Explanation: Secret access key (SK). Restrictions: None Value range: For details, see Creating Access Keys. Value range: None
storage_class	obs_storage_class	No	Explanation: Bucket storage class that can be specified at bucket creation. Restrictions: None Value range: For details, see obs_storage_class. Default value: OBS_STORAGE_CLASS_STANDARD (Standard storage class)
token	char *	No	Explanation: The security token in temporary credentials. Restrictions: None Value range: For details, see Creating Access Keys. Value range: None
epid	char *	No	Explanation: Enterprise project ID that can be specified during bucket creation. If you have enabled EPS, you can obtain the project ID from the EPS console. Restrictions: The value needs to be represented as a UUID. This parameter is not required if EPS is not enabled. Example: 9892d768-2d13-450f-aac7-ed0e44c2585f Default value: None
bucket_type	obs_bucket_type	No	Explanation: Whether a bucket is an object bucket or a parallel file system. Restrictions: None Value range: For details, see obs_bucket_type. Default value: OBS_BUCKET_OBJECT (object bucket)
bucket_list_type	obs_bucket_list_type	No	Explanation: Whether to list all buckets, object buckets, or parallel file systems. Restrictions: None Value range: For details, see obs_bucket_list_type.

**Table 4** obs_storage_class
Value	Description
OBS_STORAGE_CLASS_STANDARD	Standard storage class. This class features low access latency and high throughput and is used for storing massive, frequently accessed (multiple times a month) or small objects (< 1 MB) requiring quick response.
OBS_STORAGE_CLASS_STANDARD_IA	Infrequent Access storage class. Used for storing data that is semi-frequently accessed (fewer than 12 times a year) but becomes instantly available when needed.
OBS_STORAGE_CLASS_GLACIER	Archive storage class. Used for storing rarely accessed (once a year) data.

**Table 5** obs_http_request_option
Parameter	Type	Mandatory (Yes/No)	Description
connect_time	int	Yes	Explanation: Timeout period for establishing an HTTP/HTTPS connection, in ms. Restrictions: None Value range: [10000, 60000] Default value: 60000
max_connected_time	int	Yes	Explanation: Timeout period (in seconds) of a request. Restrictions: None Value range: None Default value: 0 (There is never automatic disconnection.)
proxy_auth	char*	No	Explanation: Proxy authentication information, in the format username:password Restrictions: None Value range: None Default value: None
proxy_host	char*	No	Explanation: IP address or host name of the proxy server. Restrictions: None Value range: None Default value: None

**Table 6** obs_protocol
Value	Description
OBS_PROTOCOL_HTTPS	HTTPS is used for access.
OBS_PROTOCOL_HTTP	HTTP is used for access.

**Table 7** obs_bucket_type
Value	Description
OBS_BUCKET_OBJECT	Object bucket
OBS_BUCKET_PFS	Parallel file system

**Table 8** obs_bucket_list_type
Value	Description
OBS_BUCKET_LIST_ALL	Lists all buckets.
OBS_BUCKET_LIST_OBJECT	Lists all object buckets.
OBS_BUCKET_LIST_PFS	Lists all parallel file systems.

**Table 9** temp_auth_configure
Parameter	Type	Mandatory (Yes/No)	Description
expires	long long int	Yes	Explanation: Validity period of the temporary credentials, in seconds. Restrictions: None Value range: [0-630720000] Default value: None
temp_auth_callback	void(temp_auth_callback)(char temp_auth_url, uint64_t temp_auth_url_len, chartemp_auth_headers, uint64_t temp_auth_headers_len, voidcallback_data)	Yes	Explanation: The pointer to the custom callback function, which is used to record the temporary URL and involved signature header to the custom callback data. Restrictions: None
callback_data	void *	Yes	Explanation: Custom callback data. Restrictions: None Value range: None Default value: None

**Table 10** temp_auth_callback
Parameter	Type	Mandatory (Yes/No)	Description
temp_auth_url	char *	Yes	Explanation: Temporary URL. OBS allows you to construct a URL for a specific operation. In such a URL, you use Query parameters to provide authentication information including the user AK, signature, and validity period. Anyone who has the URL can perform the specified operation. After receiving a request made using such a URL, OBS treats the requester as the user who issued the URL and processes the request. For example, if you construct a pre-signed URL for downloading an object and provide it to various users, they can use the URL to download the object without authentication, but they must do so within the validity period specified by the Expires parameter. Restrictions: None Value range: None Default value: None
temp_auth_url_len	uint64_t	Yes	Explanation: Length of the temporary URL. Restrictions: None Value range: None Default value: None
temp_auth_headers	char *	Yes	Explanation: Headers for temporary authentication. Restrictions: None Value range: None Default value: None
temp_auth_headers_len	uint64_t	Yes	Explanation: Number of temporary authentication headers. Restrictions: None Value range: None Default value: None
callback_data	void *	Yes	Explanation: Custom callback data. Restrictions: None Value range: None Default value: None

**Table 11** obs_get_conditions
Parameter	Type	Mandatory (Yes/No)	Description
start_byte	uint64_t	No	Explanation: Start position for object download. Restrictions: None Value range: 0 (included) to the object length minus 1 (not included), in bytes Default value: 0 (indicating that the download starts from the first byte of the object)
byte_count	uint64_t	No	Explanation: Specifies the length to be downloaded. Restrictions: Value: an integer greater than 0 If the sum of start_byte and byte_count is greater than the object length minus 1, the object length minus 1 is used. The unit is byte. Value range: None Default value: None
download_limit	uint64_t	No	Explanation: Bandwidth limit for single connection requests. Restrictions: None Value range: 819200 to 838860800, in bit/s Default value: None
if_modified_since	int64_t	No	Explanation: The request succeeds if the object has been modified since the specified time; otherwise, an error is returned. Restrictions: None Value range: None Default value: None
if_not_modified_since	int64_t	No	Explanation: The request succeeds if the object has not been modified since the specified time; otherwise, an error is returned. Restrictions: None Value range: None Default value: None
if_match_etag	char *	No	Explanation: Preset ETag. If the ETag of the object to be downloaded or copied is the same as the preset ETag, the request succeeds. Otherwise, an error is returned. Restrictions: None Value range: The value must contain 32 characters. Default value: None
if_not_match_etag	char *	No	Explanation: Preset ETag. If the ETag of the object to be downloaded or copied is different from the preset ETag, the request succeeds. Otherwise, an error is returned. Restrictions: None Value range: The value must contain 32 characters. Default value: None
image_process_config	image_process_configure *	No	Explanation: Image processing parameters. Restrictions: None

**Table 12** image_process_configure
Parameter	Type	Mandatory (Yes/No)	Description
image_process_mode	image_process_mode_type	No	Explanation: Image processing parameters. Restrictions: None Value range: For details, see image_process_mode_type.
cmds_stylename	char *	No	Explanation: Image processing parameters. Restrictions: None Value range: None Default value: None

**Table 13** image_process_mode_type
Value	Description
obs_image_process_invalid_mode	Default invalid value.
obs_image_process_cmd	Image processing parameters start with image.
obs_image_process_style	Image processing parameters start with style.

**Table 14** server_side_encryption_params
Parameter	Type	Mandatory (Yes/No)	Description
encryption_type	obs_encryption_type	No	Explanation: Encryption type. Restrictions: None Value range: For details, see obs_encryption_type.
kms_server_side_encryption	char *	No	Explanation: Indicates that SSE-KMS is used for server-side encryption. Restrictions: None Value range: kms AES256 Default value: None
kms_key_id	char *	No	Explanation: Key ID. If the SSE-KMS encryption is used with a specified key, the key ID is required. Restrictions: This header can only be used when you specify kms for the kms_server_side_encryption header. Value range: To obtain the key ID, see Viewing a CMK. Default value: If you specify kms for encryption but do not specify a key ID, the default master key will be used. If there is not a default master key, OBS will create one and use it.
ssec_customer_algorithm	char *	No	Explanation: Indicates the algorithm used to encrypt an object. Restrictions: The header is used only in SSE-C mode. Value range: AES256 (AES256 encryption algorithm) Default value: None
ssec_customer_key	char *	No	Explanation: Indicates the key used to encrypt an object. Restrictions: The header is used only in SSE-C mode. Value range: Base64-encoded 256-bit key Default value: None
des_ssec_customer_algorithm	char *	No	Explanation: Indicates the algorithm used to decrypt a source object. Restrictions: The header is used only in SSE-C mode. Value range: None Default value: None
des_ssec_customer_key	char *	No	Explanation: Indicates the key used to decrypt the source object. Restrictions: The header is used only in SSE-C mode. Value range: None Default value: None

**Table 15** obs_encryption_type
Value	Description
OBS_ENCRYPTION_KMS	Use the KMS encryption.
OBS_ENCRYPTION_SSEC	Use the SSE-C encryption.

**Table 16** obs_download_file_configuration
Parameter	Type	Mandatory (Yes/No)	Description
downLoad_file	char *	Yes	Explanation: Local path to which the object is downloaded. Restrictions: None Value range: None Default value: None
part_size	uint64_t	No	Explanation: Part size, in bytes Restrictions: None Value range: None Default value: None
check_point_file	char *	No	Explanation: Path of the file that records the upload progress. This parameter is effective only in the resumable mode. Restrictions: If the value of this parameter is left blank, the file will be in the same directory as the local file to be uploaded. This parameter is valid only when enable_check_point is set to 1. Value range: None Default value: None
enable_check_point	int	No	Explanation: Whether to enable the resumable mode Restrictions: None Value range: 0: The resumable mode is disabled. In this case, this API works as a multipart transmission API, and no checkpoint files are generated. 1: The resumable mode is enabled. Default value: 0: disabled
task_num	int	No	Explanation: Maximum number of parts that can be uploaded concurrently Use this parameter to configure how many concurrent tasks there can be in downloading a single object. Restrictions: None Value range: None Default value: 1

**Table 17** obs_download_file_response_handler
Parameter	Type	Mandatory (Yes/No)	Description
response_handler	obs_response_handler *	Yes	Explanation: Response callback function structure. Restrictions: None
download_file_callback	obs_download_file_callback *	Yes	Explanation: The pointer to the callback function, where the callback parameters can be recorded in callback_data (custom callback data). Restrictions: None

**Table 18** obs_download_file_callback
Parameter	Type	Mandatory (Yes/No)	Description
status	obs_status	Yes	Explanation: Request status Restrictions: None Value range: For details, see obs_status.
result_message	char *	Yes	Explanation: Download result. Restrictions: None Value range: None Default value: None
callback_data	void *	Yes	Explanation: The pointer to the custom callback data. Restrictions: None Value range: None Default value: None

**Table 19** obs_response_handler
Parameter	Type	Mandatory (Yes/No)	Description
properties_callback	obs_response_properties_callback *	Yes	Explanation: The pointer to the response callback function. The content of properties in the callback can be recorded in callback_data (custom callback data). Restrictions: None
complete_callback	obs_response_complete_callback *	Yes	Explanation: The pointer to the completion callback function. The content of obs_status and obs_error_details in the callback can be recorded in callback_data (custom callback data). Restrictions: None

**Table 20** obs_response_properties_callback
Parameter	Type	Mandatory (Yes/No)	Description
properties	const obs_response_properties*	Yes	Explanation: Parameters in the response headers. You are advised to record them to callback_data (custom callback data). Restrictions: None
callback_data	void *	Yes	Explanation: The pointer to the custom callback data. Restrictions: None Value range: None Default value: None

**Table 21** obs_response_complete_callback
Parameter	Type	Mandatory (Yes/No)	Description
status	obs_status	Yes	Explanation: Internal request status code of the SDK. Restrictions: None Value range: For details, see obs_status.
error_details	const obs_error_details*	Yes	Explanation: The pointer to the response callback function. The content of properties in the callback can be recorded in callback_data (custom callback data). Restrictions: None
callback_data	void *	Yes	Explanation: The pointer to the custom callback data. Restrictions: None Value range: None Default value: None

**Table 22** obs_response_properties
Parameter	Type	Mandatory (Yes/No)	Description
request_id	const char *	No	Explanation: The value created by OBS to uniquely identify the request. OBS uses this value to locate the fault. Restrictions: None Value range: None Default value: None
request_id2	const char *	No	Explanation: A special symbol that helps troubleshoot. Restrictions: None Value range: None Default value: None
content_type	const char *	No	Explanation: MIME type of the object. MIME type is a standard way of describing a data type and is used by the browser to decide how to display data. Restrictions: None Value range: None Default value: None
content_length	uint64_t	No	Explanation: The size (in bytes) of the response body. Restrictions: None Value range: None Default value: None
server	const char *	No	Explanation: Server header in an HTTP request. Restrictions: None Value range: None Default value: None
etag	const char *	No	Explanation: Base64-encoded, 128-bit MD5 value of an object. It uniquely identifies the content of an object and can be used to check the object integrity. For example, if the ETag is A when an object is uploaded and is B when the object is downloaded, it indicates that the object content has been changed. The ETag reflects changes to the contents of the object, not its metadata. An object created by an upload or copy operation has a unique ETag. Restrictions: If an object is encrypted using server-side encryption, the ETag is not the MD5 value of the object. Value range: The value must contain 32 characters. Default value: None
expiration	const char *	No	Explanation: Expiration details of the object. Restrictions: None Value range: An integer greater than 0, in days. Default value: None
website_redirect_location	const char *	No	Explanation: Indicates where an object request is redirected. If the bucket that contains the object is configured with Website settings, this parameter can be set in the object metadata so that the request for the object can be redirected to another object in the same bucket or an external URL after the website returns a 301 redirect response. To another object in the same bucket: x-obs-website-redirect-location:/anotherPage.html To an external URL: x-obs-website-redirect-location:http://www.example.com/ OBS obtains the specified value from the header and stores it in the object metadata WebsiteRedirectLocation. Restrictions: The value must start with a slash (/), http://, or https:// and cannot exceed 2 KB. OBS only supports redirection of objects that are in the root directory. Value range: None Default value: None
version_id	const char *	No	Explanation: Object version ID. Restrictions: If the object has no version ID, the value is NULL. Value range: The value must contain 32 characters. Default value: None
meta_data_count	int	No	Explanation: Number of elements in the meta_data array. Restrictions: None Value range: None Default value: None
meta_data	const obs_name_value *	No	Explanation: Custom metadata of the object. You can add custom metadata headers that start with x-obs-meta- for easy object management. When you retrieve or query the metadata of the object, the added custom metadata headers will be returned in the response. Restrictions: None Value range: None Default value: None
use_server_side_encryption	char	No	Explanation: If server-side encryption is enabled, this parameter is set to '\1'. Restrictions: None Value range: None Default value: None
allow_origin	const char *	No	Explanation: Returned if the request origin meets the CORS configured on the server. Restrictions: None Value range: The value that complies with the CORS Default value: None
allow_headers	const char *	No	Explanation: Returned if the request headers meet the CORS configured on the server. Restrictions: At most one asterisk () is allowed. Spaces, ampersands (&), colons (:), less-than signs (<), and full-width characters are not allowed. Value range: The value that complies with the CORS Default value*: None
max_age	const char *	No	Explanation: MaxAgeSeconds in the CORS rules of the bucket. It specifies the time your client can cache the response for a cross-origin request. Restrictions: Each CORS rule can contain at most one MaxAgeSeconds. Value range: An integer greater than or equal to 0, in seconds. Default value: 3000
allow_methods	const char *	No	Explanation: Indicates that methods in the rule are included in the response if Access-Control-Request-Method in the request meets the CORS configuration requirements when CORS is configured for buckets. Restrictions: None Value range: GET PUT HEAD POST DELETE Value range: None
expose_headers	const char *	No	Explanation: ExposeHeader in the CORS rules of the bucket. It specifies additional headers allowed in the response by a CORS rule. These headers provide extra information to clients. By default, a browser can access only headers Content-Length and Content-Type. If the browser needs to access other headers, you need to configure them as additional headers. Restrictions: Spaces, asterisks (), ampersands (&), colons (:), less-than signs (<), and full-width characters are not allowed. Value range: None Default value*: None
storage_class	const char *	No	Explanation: Object storage class. Restrictions: This header is returned only when the storage class of an object is not Standard. Value range: WARM (Infrequent Access storage class) COLD (Archive storage class) Default value: None
server_side_encryption	const char *	No	Explanation: The encryption method used by the server. Example: x-obs-server-side-encryption:kms Restrictions: This header is included in a response if SSE-KMS is used. Value range: kms (SSE-KMS encryption) obs (SSE-OBS encryption) Default value: None
kms_key_id	const char *	No	Explanation: Key ID. If the SSE-KMS encryption is used with a specified key, the key ID is required. Restrictions: This header can only be used when you specify kms for the server_side_encryption header. Value range: To obtain the key ID, see Viewing a CMK. Default value: If you specify kms for encryption but do not specify a key ID, the default master key will be used. If there is not a default master key, OBS will create one and use it.
customer_algorithm	const char *	No	Explanation: Indicates a decryption algorithm. This header is included in a response if SSE-C is used. Restrictions: None Value range: AES256 (AES256 decryption algorithm) Default value: None
customer_key_md5	const char *	No	Explanation: Indicates the MD5 value of a key used to decrypt objects. This header is included in a response if SSE-C is used. Restrictions: Base64-encoded MD5 value of the key, for example, 4XvB3tbNTN+tIEVa0/fGaQ== Value range: Base64-encoded MD5 value of the key ID. Default value: None
bucket_location	const char *	No	Explanation: Indicates the region where the bucket resides. Restrictions: None Value range: None Default value: None
obs_version	const char *	No	Explanation: OBS version of the bucket. Restrictions: None Value range: 3.0: bucket of the latest version --: bucket of an earlier version Default value: None
restore	const char *	No	Explanation: Restoration status of an object. Examples: ongoing-request="true" (the object is being restored); ongoing-request="false", expiry-date="Wed, 7 Nov 2012 00:00:00 GMT" (the object has been restored) expiry-date indicates when the restored object will expire. Restrictions: For an Archive object that is being restored or has been restored, this header is returned. Value range: None Default value: None
obs_object_type	const char *	No	Explanation: Type of the object. Restrictions: This header is returned only when the object is not a Normal object. Value range: Appendable Default value: None
obs_next_append_position	const char *	No	Explanation: Indicates the position to be provided for the next request. Restrictions: This header is returned only when the object is an Appendable object. Value range: None Default value: None
obs_head_epid	const char *	No	Explanation: Enterprise project ID for the current bucket. Users who have enabled the enterprise project function can obtain the ID from the enterprise project service. Restrictions: The value is a UUID. This parameter is not required if you have not enabled an enterprise project. Value range: None Default value: None
reserved_indicator	const char *	No	Explanation: A special symbol that helps troubleshoot. Restrictions: None Value range: None Default value: None

**Table 23** obs_error_details
Parameter	Type	Description
message	const char*	Explanation: Error details in the XML error response body. Restrictions: None Value range: See Error Codes. Default value: None
resource	const char*	Explanation: Bucket or object related to the error. Restrictions: None Value range: None Default value: None
further_details	const char*	Explanation: The value of the FurtherDetails element in the XML error response body. Restrictions: None Value range: None Default value: None
extra_details_count	int	Explanation: The number of other elements in the XML error response body. Restrictions: None Value range: None Default value: None
extra_details	obs_name_value*	Explanation: Values of other elements in the XML error response body. Restrictions: None
error_headers_count	int	Explanation: Number of headers in error_headers. Restrictions: None Value range: None Default value: None
error_headers	char**	Explanation: All response headers that contain the error. Restrictions: None Value range: None Default value: None

**Table 24** obs_name_value
Parameter	Type	Mandatory (Yes/No)	Description
name	char *	No	Explanation: Key of a property. Restrictions: None Value range: None Default value: None
value	char *	No	Explanation: Property value. Restrictions: None Value range: None Default value: None

**Table 25** obs_status
Value	Description
OBS_STATUS_OK	The request is successful.
OBS_STATUS_InitCurlFailed	Failed to initialize curl.
OBS_STATUS_InternalError	Internal error.
OBS_STATUS_OutOfMemory	The local memory is insufficient.
OBS_STATUS_FailedToIInitializeRequest	Failed to initialize the request.
OBS_STATUS_ConnectionFailed	Network connection failed.
OBS_STATUS_XmlParseFailure	Failed to parse the XML file.
OBS_STATUS_NameLookupError	Domain name resolution failed.
OBS_STATUS_FailedToConnect	Failed to connect to the server.
OBS_STATUS_PartialFile	Network transmission.
OBS_STATUS_InvalidParameter	Invalid parameter.
OBS_STATUS_NoToken	The current number of concurrent tasks exceeds the maximum number (1000 by default). Use the set_online_request_max_count function to adjust the maximum number of concurrent tasks.
OBS_STATUS_OpenFileFailed	Failed to open the file.
OBS_STATUS_AccessDenied	The request is rejected.
OBS_STATUS_MalformedPolicy	The format of the request policy is incorrect.
OBS_STATUS_MalformedXML	The XML request format is incorrect.
OBS_STATUS_MethodNotAllowed	The request method is not allowed.
OBS_STATUS_SignatureDoesNotMatch	The signatures do not match. Check whether the AK, SK, and token are correct.
OBS_STATUS_ServiceUnavailable	Server exception.
OBS_STATUS_SlowDown	The request frequency is too high.

Code Examples: Resumable Download

This example calls download_file to perform the resumable download.

     
      
        
        #include "eSDKOBS.h"
#include <stdio.h>
#include <sys/stat.h>
// The response callback function. The content of properties in the callback can be recorded in callback_data (custom callback data).
obs_status response_properties_callback(const obs_response_properties *properties, void *callback_data);
// The completion callback function. The content of obs_status and obs_error_details in the callback can be recorded in callback_data (custom callback data).
void response_complete_callback(obs_status status, const obs_error_details *error, void *callback_data);
void downloadFileResultCallback(obs_status status,
    char *resultMsg,
    int partCountReturn,
    obs_download_file_part_info * downloadInfoList,
    void *callbackData);
int main()
{
    // The following code shows how to use download_file to perform the resumable download:
    // Call the obs_initialize method at the program entry to initialize global resources such as the network and memory.
    obs_initialize(OBS_INIT_ALL); 
    obs_options options;
    // Create and initialize options, including the access domain name (host_name), access keys (access_key_id and access_key_secret), bucket name (bucket_name), and bucket storage class (storage_class).
    init_obs_options(&options);
    // Enter the endpoint corresponding to the bucket for host_name. CN-Hong Kong is used here as an example. Replace it with the one in your actual situation.
    options.bucket_options.host_name = "obs.ap-southeast-1.myhuaweicloud.com";
    // Hard-coded or plaintext AK and SK are risky. For security purposes, encrypt your AK and SK and store them in the configuration file or environment variables.
    // In this example, the AK and SK are stored in environment variables for identity authentication. Before running the code in this example, configure local environment variables ACCESS_KEY_ID and SECRET_ACCESS_KEY.
    options.bucket_options.access_key = getenv("ACCESS_KEY_ID");
    options.bucket_options.secret_access_key = getenv("SECRET_ACCESS_KEY");
    // Specify the bucket name, for example, example-bucket-name.
    char * bucketName = "example-bucket-name";
    options.bucket_options.bucket_name = bucketName;
    // Set the object to be downloaded.
    char* key = "example_get_file_test";
    // Set the name of the local file to which the object is downloaded.
    char *file_name = "./example_get_file_test";
    // Initialize getConditions.
    obs_get_conditions getConditions;
    memset(&getConditions, 0, sizeof(obs_get_conditions));
    init_get_properties(&getConditions);
    // Object information in the resumable download
    obs_download_file_configuration downloadFileConfig;
    memset(&downloadFileConfig, 0, sizeof(obs_download_file_configuration));
    // Size of the object parts
    uint64_t downloadSliceSize = 5L * 1024 * 1024;
    downloadFileConfig.check_point_file = NULL;
    downloadFileConfig.enable_check_point = 1;
    downloadFileConfig.part_size = downloadSliceSize;
    downloadFileConfig.task_num = 10;
    downloadFileConfig.downLoad_file = file_name;
    // Set the response callback function.
    obs_download_file_response_handler Handler =
    {
        {&response_properties_callback, &response_complete_callback},
        &downloadFileResultCallback
    };
    char* versionId = NULL;
    server_side_encryption_params* sse = NULL;
    initialize_break_point_lock();
    obs_status ret_status = OBS_STATUS_BUTT;
    download_file(&options, key, versionId, &getConditions, sse, &downloadFileConfig,
        &Handler, &ret_status);
    deinitialize_break_point_lock();
    if (OBS_STATUS_OK == ret_status) {
        printf("test download file successfully. \n");
    }
    else
    {
        printf("test download file failed(%s).\n", obs_get_status_name(ret_status));
    }
    // Release the allocated global resources.
    obs_deinitialize();
}
// The response callback function. The content of properties in the callback can be recorded in callback_data (custom callback data).
obs_status response_properties_callback(const obs_response_properties *properties, void *callback_data)
{
    if (properties == NULL)
    {
        printf("error! obs_response_properties is null!");
        if (callback_data != NULL)
        {
            obs_sever_callback_data *data = (obs_sever_callback_data *)callback_data;
            printf("server_callback buf is %s, len is %llu",
                data->buffer, data->buffer_len);
            return OBS_STATUS_OK;
        }
        else {
            printf("error! obs_sever_callback_data is null!");
            return OBS_STATUS_OK;
        }
    }
    // Print the response.
#define print_nonnull(name, field)                                 \
    do {                                                           \
        if (properties-> field) {                                  \
            printf("%s: %s\n", name, properties->field);          \
        }                                                          \
    } while (0)
    print_nonnull("request_id", request_id);
    print_nonnull("request_id2", request_id2);
    print_nonnull("content_type", content_type);
    if (properties->content_length) {
        printf("content_length: %llu\n", properties->content_length);
    }
    print_nonnull("server", server);
    print_nonnull("ETag", etag);
    print_nonnull("expiration", expiration);
    print_nonnull("website_redirect_location", website_redirect_location);
    print_nonnull("version_id", version_id);
    print_nonnull("allow_origin", allow_origin);
    print_nonnull("allow_headers", allow_headers);
    print_nonnull("max_age", max_age);
    print_nonnull("allow_methods", allow_methods);
    print_nonnull("expose_headers", expose_headers);
    print_nonnull("storage_class", storage_class);
    print_nonnull("server_side_encryption", server_side_encryption);
    print_nonnull("kms_key_id", kms_key_id);
    print_nonnull("customer_algorithm", customer_algorithm);
    print_nonnull("customer_key_md5", customer_key_md5);
    print_nonnull("bucket_location", bucket_location);
    print_nonnull("obs_version", obs_version);
    print_nonnull("restore", restore);
    print_nonnull("obs_object_type", obs_object_type);
    print_nonnull("obs_next_append_position", obs_next_append_position);
    print_nonnull("obs_head_epid", obs_head_epid);
    print_nonnull("reserved_indicator", reserved_indicator);
    int i;
    for (i = 0; i < properties->meta_data_count; i++) {
        printf("x-obs-meta-%s: %s\n", properties->meta_data[i].name,
            properties->meta_data[i].value);
    }
    return OBS_STATUS_OK;
}
void print_error_details(const obs_error_details *error) {
    if (error && error->message) {
        printf("Error Message: \n   %s\n", error->message);
    }
    if (error && error->resource) {
        printf("Error Resource: \n  %s\n", error->resource);
    }
    if (error && error->further_details) {
        printf("Error further_details: \n   %s\n", error->further_details);
    }
    if (error && error->extra_details_count) {
        int i;
        for (i = 0; i < error->extra_details_count; i++) {
            printf("Error Extra Detail(%d):\n   %s:%s\n", i, error->extra_details[i].name,
                error->extra_details[i].value);
        }
    }
    if (error && error->error_headers_count) {
        int i;
        for (i = 0; i < error->error_headers_count; i++) {
            const char *errorHeader = error->error_headers[i];
            printf("Error Headers(%d):\n    %s\n", i, errorHeader == NULL ? "NULL Header" : errorHeader);
        }
    }
}
// The completion callback function. The content of obs_status and obs_error_details in the callback can be recorded in callback_data (custom callback data).
void response_complete_callback(obs_status status, const obs_error_details *error, void *callback_data)
{
    if (callback_data) {
        obs_status *data =
            (obs_status *)callback_data;
        *data = status;
    }
    else {
        printf("Callback_data is NULL");
    }
    print_error_details(error);
}
//downloadFileResultCallback is used as an example here. The printf statements can be replaced with custom logging print statements.
void downloadFileResultCallback(obs_status status,
    char *resultMsg,
    int partCountReturn,
    obs_download_file_part_info * downloadInfoList,
    void *callbackData)
{
    int i = 0;
    obs_download_file_part_info * pstDownloadInfoList = downloadInfoList;
    printf("status return is %d(%s)\n", status, obs_get_status_name(status));
    printf("%s", resultMsg);
    printf("partCount[%d]\n", partCountReturn);
    for (i = 0; i < partCountReturn; i++)
    {
        printf("partNum[%d],startByte[%llu],partSize[%llu],status[%d]\n",
            pstDownloadInfoList->part_num,
            pstDownloadInfoList->start_byte,
            pstDownloadInfoList->part_size,
            pstDownloadInfoList->status_return);
        pstDownloadInfoList++;
    }
    if (callbackData) {
        obs_status* retStatus = (obs_status*)callbackData;
        (*retStatus) = status;
    }
}

       

     
    