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Objects

Objects represent items stored within a container. These are subject to the permissions of the container being the most relaxed possible permissions that can be applied to an object. It is possible using Session/Bearer Tokens to restrict permissions further on objects within a container however

Please note actions on objects are restricted by the permissions on the container AND the permissions of the token used to access the functions.

Uploading Objects#

you will need#

Attributes#

Attributes are key value pairs (string:string) that are attached to the metadata of objects. You can specify anything as an attribute, however there are a couple of reserved ones

var attributes []*object.Attribute
timeStampAttr := new(object.Attribute)timeStampAttr.SetKey(object.AttributeTimestamp) // AttributeTimestamp key is like a 'created at' attributetimeStampAttr.SetValue(strconv.FormatInt(time.Now().Unix(), 10))
fileNameAttr := new(object.Attribute)fileNameAttr.SetKey(object.AttributeFileName) // AttributeFileName key is the filename to be associated with the object. fileNameAttr.SetValue(path.Base(filepath)) //path.Base(filepath) returns the last element of a file path (usually the filename)
expirationEpochAttr := new(object.Attribute)expirationEpochAttr.SetKey("__NEOFS__EXPIRATION_EPOCH") // Reserved case for when the life of the object should expire expirationEpochAttr.SetValue(strconv.Itoa(epoch)) //The epoch at which the object will expire
attributes = append(attributes, []*object.Attribute{timeStampAttr, fileNameAttr, expirationEpochAttr}...)
note

If you have set the FileName attribute, you can also refer to the object by its filename, i.e https://http.testnet.fs.neo.org/CONTAINER_ID/upload.png when its uploaded, (see acl permissions)

Session Token#

See tokens for how to create a session token

Upload#

This example demonstrates how to upload binary data using an io.Reader defined by the developer

var objectID oid.IDo := object.New()o.SetContainerID(&containerID)o.SetOwnerID(ownerID)o.SetAttributes(attr...)
objWriter, err := cli.ObjectPutInit(ctx, client.PrmObjectPutInit{})//you probably have either a session or bearer token depending on your permissions. If the container is yours, use a session tokenif sessionToken != nil {    objWriter.WithinSession(*sessionToken)}if bearerToken != nil {    objWriter.WithBearerToken(*bearerToken)}if !objWriter.WriteHeader(*o) {    return objectID, errors.New("could not write object header")}buf := make([]byte, 1024*1024) // 1 MiBfor {    // update progress bar    _, err := (*reader).Read(buf) //could be a file reader for instance .. reader *io.Reader    if !objWriter.WritePayloadChunk(buf) {        break    }    if errors.Is(err, io.EOF) {        break    }}res, err := objWriter.Close()if err != nil {    return objectID, err}    res.ReadStoredObjectID(&objectID)}//the object ID is stored in response.ID()

Depending on your container's permissions you should now be able to view the file you uploaded at:

https://http.testnet.fs.neo.org/CONTAINER_ID/OBJECT_ID

Listing the content of a container#

Once you have uploaded objects to a container, you will want to list them out. Listing is a special case of searching within a container. To search for specific objects, you add filters to the search. By setting the only filter as a root filter, it will list everything within the container

var filters = object.SearchFilters{}filters.AddRootFilter()search := client.PrmObjectSearch{}if sessionToken != nil {    search.WithinSession(*sessionToken)}if bearerToken != nil {    search.WithBearerToken(*bearerToken)}search.SetFilters(filters)search.InContainer(containerID)
var list []oid.IDsearchInit, err := cli.ObjectSearchInit(ctx,search)if err != nil {    return list, err}
err = searchInit.Iterate(func(id oid.ID) bool {    list = append(list, id)    return true})fmt.Printf("list objects %+v\n", list)

Retrieve an Object#

Once you have the ID of an object, you can download it.

You will need#

  • an io.Writer to write the data to a file such as a file writer
  • an object address, which is made up of a container ID and an object ID

To generate an object address from the string forms of a containerID and an objectID:

contID := cid.New()contID.Parse(containerID)objID := obj.NewID()objID.Parse(objectID)

Then use an io.Writer to save the content back to somewhere such as a local file

dstObject := &object.Object{}getParms := client.PrmObjectGet{}getParms.ByID(objID)getParms.FromContainer(contID)if sessionToken != nil {    getParms.WithinSession(*sessionToken)}if bearerToken != nil {    getParms.WithBearerToken(*bearerToken)}objReader, err := cli.ObjectGetInit(ctx, getParms)if err != nil {    return dstObject, err}if !objReader.ReadHeader(dstObject) {    _, err = objReader.Close()    return dstObject, err}buf := make([]byte, 1024) // 1 MiBfor {    if _, writerErr := (*writer).Write(buf); writerErr != nil {        return nil, errors.New("error writing to buffer: " + writerErr.Error())    }    if _, ok := objReader.ReadChunk(buf); !ok {        break    }    fmt.Printf("* %v\r\n", string(buf))    // get total size from object header and update progress bar based on n bytes received    if errors.Is(err, io.EOF) {        break    }}return dstObject, err

Retrieving an objects HEAD/metadata#

Sometimes you want information about an object, without actually downloading the entire object, for instance the size of an object

From a container, you can find out storage policies, owners and any other meta information about the container itself. This is very similar to retrieving the object

h := client.PrmObjectHead{}h.ByID(objectID)if sessionToken != nil {    h.WithinSession(*sessionToken)}if bearerToken != nil {    h.WithBearerToken(*bearerToken)}h.FromContainer(containerID)var o = &object.Object{}head, err := cli.ObjectHead(ctx, h)if err != nil {    return o, err}response := head.ReadHeader(o)if !response {    return o, errors.New("could not read the object header. Did not exist")}return o, nil

Deleting Objects#

You may wish to delete an object for a container 

del := client.PrmObjectDelete{}if sessionToken != nil {    del.WithinSession(*sessionToken)}if bearerToken != nil {    del.WithBearerToken(*bearerToken)}del.ByID(objectID)del.FromContainer(containerID)deleteResponse, err := cli.ObjectDelete(ctx, del)return deleteResponse, err

Questions about objects#

  • Can you update the attributes of an existing object
  • Can you determine the original uploader of an object